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Selenium as an anti-oxidant and pro-oxidant in ryegrass
Abstract
Selenium is an essential element for antioxidation reactions in human and animals. In order to study its biological role in
higher plants, ryegrass (Lolium perenne) was cultivated in a soil without Se or amended with increasing dosages of H2SeO4 (0.1, 1.0, 10.0 and 30.0 mg Se kg−1). Ryegrass was harvested twice and the yields were analyzed for antioxidative systems and growth parameters. Selenium exerted
dual effects: At low concentrations it acted as an antioxidant, inhibiting lipid peroxidation, whereas at higher concentrations,
it was a pro-oxidant, enhancing the accumulation of lipid peroxidation products. The antioxidative effect was associated with
an increase in glutathione peroxidase (GSH-Px) activity, but not with superoxide dismutase (SOD) and αα-tocopherol, which
was the only tocopherol detected. In the second yield, the diminished lipid peroxidation due to a proper Se addition coincided
with promoted plant growth. The oxidative stress found at the Se addition level ≥ 10 mg kg−1 resulted in drastic yield losses. This result indicates that the toxicity of Se can be attributed, in addition to metabolic
disturbances, to its pro-oxidative effects. Neither the growth-promoting nor the toxic effect of Se could be explained by
the changes in the total chlorophyll concentration.
... Mostofa et al. (2017) showed that Na 2 SeO 4 caused an increase in GPX and GST activities in rice plants. Numerous other studies conducted on peanuts (Wang et al., 2016), ryegrass (Hartikainen et al., 2000), white clover (Wang et al., 2011), and oilseed rape (Hasanuzzaman et al., 2011) have shown the same results. Some studies have shown a positive correlation between GPX activity and Se concentration, suggesting that GPX is a Se-dependent enzyme in higher plants (Hartikainen et al., 2000;Š tolfa et al., 2017). ...
... Numerous other studies conducted on peanuts (Wang et al., 2016), ryegrass (Hartikainen et al., 2000), white clover (Wang et al., 2011), and oilseed rape (Hasanuzzaman et al., 2011) have shown the same results. Some studies have shown a positive correlation between GPX activity and Se concentration, suggesting that GPX is a Se-dependent enzyme in higher plants (Hartikainen et al., 2000;Š tolfa et al., 2017). ...
... The intensity of changes associated with the redox potential of the cell mostly depends on Se concentration. So, when Se is present at low concentrations it may act as an antioxidant, but at higher concentrations, it may act as a pro-oxidant (Hartikainen et al., 2000). As such, Se interferes with the antioxidant defence system and largely with the AsA-GSH cycle, evident from numerous previous studies (Huang et al., 2018;Kaur et al., 2014a;Mostofa et al., 2017) and ours. ...
Biofortification aims to increase selenium (Se) concentration and bioavailability in edible parts of crops such as wheat (Triticum aestivum L.), resulting in increased concentration of Se in plants and/or soil. Higher Se concentrations can disturb protein structure and consequently influence glutathione (GSH) metabolism in plants which can affect antioxidative and other detoxification pathways. The aim of this study was to elucidate the impact of five different concentrations of selenate and selenite (0.4, 4, 20, 40 and 400 mg kg−1) on the ascorbate-glutathione cycle in wheat shoots and roots and to determine biochemical and molecular tissue-specific responses. Content of investigated metabolites, activities of detoxification enzymes and expression of their genes depended both on the chemical form and concentration of the applied Se, as well as on the type of plant tissue. The most pronounced changes in the expression level of genes involved in GSH metabolism were visible in wheat shoots at the highest concentrations of both forms of Se. Obtained results can serve as a basis for further research on Se toxicity and detoxification mechanisms in wheat. New insights into the Se impact on GSH metabolism could contribute to the further development of biofortification strategies.
... Second, POD and CAT further convert them into completely non-toxic O 2 − and H 2 O, thereby reducing the accumulation of ROS [26]. Lin et al. [12] believed that the significant decrease in Cd stress that they observed in rice seedlings under Se treatment was mainly attributed to the fact that Se application decreased the Cd-induced increase in SOD and POD activities but elevated depressed CAT activity. ...
... This result is consistent with the present experiment. The decrease in POD and SOD activities under Se treatment may be due to the significant increase in CAT activity on the one hand and the removal of some oxidized free radicals in non-enzymatic form on the other hand [26]. Non-enzymatic antioxidants are able to scavenge free radicals by breaking the free radical chain reaction. ...
The enrichment of cadmium (Cd) is an important factor threatening crop growth and food safety. However, it is unclear whether exogenous selenium (Se) can simultaneously achieve Cd reduction and promote the growth of peppers. This study used Yuefeng 750 and Hongtianhu 101 as materials and investigated the interaction effects of different Se-Cd concentrations (Cd = 2 and 5 μM; Se = 0, 0.5, and 2 μM) on the uptake and transport of Cd and Se, resistance physiology, and growth and development of pepper seedlings in a hydroponic experiment. The organ Cd content was significantly increased in pepper seedlings, inhibiting their growth and aggravating their physiological stress under Cd application. However, the growth and photosynthetic capacity of peppers were promoted after Se application under Cd stress. The superoxide anion (O2⁻), hydrogen peroxide (H2O2), malondialdehyde (MDA), and abscisic acid (ABA) contents and indole-3-acetic acid oxidase (IAAO) activity in the leaves showed a significantly progressive decline, while the proline (Pro), ascorbic acid (ASA), and trans zeatin riboside (ZR) contents showed a significant rising trend. Thus, the growth, development, and dry matter accumulation of peppers were enhanced by reducing Cd stress. Meanwhile, the application of exogenous Se significantly improved the accumulation of Se in seedlings. In addition, compared to Hongtianhu 101, the Yuefeng 750 cultivars had a greater Cd and Se enrichment capacity. The cultivation of Cd-excluding cultivars combined with exogenous Se addition can be used as a recommended solution to reduce Cd toxicity and achieve Cd reduction and Se enrichment in peppers under Cd pollution.
... It also leads to the stimulation of photosynthetic pigment creation, net photosynthetic ratio, gas exchange, and the production of secondary metabolites during the process of photosynthesis [2,6,7]. High levels of Se may cause adverse effects and act as a pro-oxidant, which promotes the formation of lipid peroxidation byproducts and subsequently leads to significant reductions in crop yields [8,9]. Therefore, Se's application in plant nutrition and physiology remains an interesting topic. ...
... In this study, SeNP foliar application at 0.5 to 2.5 mg L −1 obviously enhanced activities of POD, SOD, and GSH-Px and increased the contents of chlorophyll and carotenoids in F. dibotrys (Figures 5 and 6). Reports suggested that in the presence of Se, external H 2 O 2 was primarily removed by GSH-Px [8]. Regardless of the role of GSH-Px in this study, the increasing activities of POD at 0.5 to 2.5 mg L −1 SeNP treatments clearly show its participation in alleviating lipid peroxidation to quench H 2 O 2 . ...
Fagopyrum dibotrys is a herbal plant. Selenium (Se) is a beneficial element for plants; selenium nanoparticles (SeNPs) are gaining importance in food and agriculture due to their low toxicity and high activity. This study revealed that foliar application of SeNPs enhanced superoxide dismutase, glutathione peroxidase, and peroxisome activities and significantly enhanced the flavonoid compound content in F. dibotrys. SeNPs with a concentration of 5.0 mg L⁻¹ also promoted the growth of F. dibotrys. The foliar application of SeNPs could be absorbed by pores in leaves of F. dibotrys and mainly transformed to selenomethionine (32.5–43.2%) and selenocysteine (23.4–38.4%) in leaves and tubers of F. dibotrys. Consequently, this study offers a profound understanding of plants’ uptake and biotransformation of SeNPs. Furthermore, the findings of this study have suggested that SeNPs can be applied to improve the quantity and quality of the herbal plant of F. dibotrys.
... Additionally, Se can promote photosynthesis (Gupta and Gupta, 2017), postpone senescence (Xue et al., 2001), and boost plant production at low concentrations (Germ et al., 2005). Other crops treated with selenium, such as B. juncea (Yusuf et al., 2016), Lolium perenne (Hartikainen et al., 2000), S. tuberosum (Turakainen et al., 2004), and Lens culinaris (Lyons et al., 2009), exhibited similar outcomes (Ekanayake et al., 2015). Brassinosteroids (BRs) represent a novel group of polyhydroxy steroidal hormones identified in plants, serving as intrinsic signals governing plant growth and expansion (Vidya Vardhini, 2017). ...
... In line with earlier research, our findings showed that supplementing wheat with low dosages of Se increased its growth, leaf area, and chlorophyll content (Naz et al., 2015;Yusuf et al., 2016). Comparable results have been noted for ryegrass, lettuce, wheat, and B. juncea, among other plant species (Hartikainen et al., 2000;Ramos et al., 2010;Naz et al., 2015;Boldrin et al., 2016;Yusuf et al., 2016). Furthermore, as suggested by Xie et al. (2011), the transcriptional impacts of brassinosteroids (BR) and their influence on biomass could prove instrumental in enhancing agricultural yields and resilience. ...
In the current investigation, the combination of selenium (Se) and epibrassinolide (EBL) exhibited a promising alleviative response against the concurrent stress of heat and drought in wheat plants. The compromised growth and photosynthetic performance of wheat plants under the combined stress of heat and drought were substantially improved with the treatment involving Se and EBL. This improvement was facilitated through the expression of Q9FIE3 and O04939 proteins, along with enhanced antioxidant activities. The heightened levels of antioxidant enzymes and the accumulation of osmoprotectant proline helped mitigate the overaccumulation of reactive oxygen species (ROS), including electrolyte leakage, H2O2 accumulation, and lipid peroxidation, thus conferring tolerance against the combined stress of heat and drought. Studies have demonstrated that Se and EBL can assist wheat plants in recuperating from the adverse effects of heat and drought. As such, they are essential components of sustainable farming methods that aim to increase crop productivity.
... GSH-Px, with the assistance of GSH, acts as a potent scavenger of hydroperoxides [12]. Additionally, research by Hartikainen and Hussain has shown that the addition of exogenous selenium can increase antioxidant enzyme activity in plants, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), assisting in the removal of ROS [33,34]. Nevertheless, with the escalation of selenium spray concentration, there was a gradual rise in the level of hydrogen peroxide, superoxide anion, and malondialdehyde in the leaves (Figure 2). ...
... This stress is produced by the spraying of high concentrations of selenium, which subsequently leads to high absorption of selenium into the plant's body. According to the text, selenium acts on plants in two ways, depending on how concentrated it is, as reported by Hartikainen [33]. During pot experiments, lower doses of selenium were found to enhance the growth of ryegrass seedlings, whereas higher doses displayed a pro-oxidant impact, leading to reduced yields and the onset of metabolic disorders. ...
Drought stress can impact the physiological and biochemical properties of crops. However, selenium (Se) can effectively alleviate the abiotic stress experienced by plants. This study aims to investigate how applying selenium to tomato leaves affects their antioxidant system and photosynthetic traits when subjected to drought conditions. The experiment used four different foliar selenium concentrations and three different irrigation levels. The investigation scrutinized the effects of foliar spraying employing different selenium concentrations on the antioxidant system, osmotic adjustment substances, photosynthetic performance, and growth indices of tomatoes under drought stress. The findings indicated that drought stress led to cellular oxidative damage, significantly elevating peroxide, MDA, proline, and soluble sugar content (p < 0.001). Under severe drought stress, malondialdehyde (MDA) and proline levels increased by 21.2% and 110.0% respectively, compared to well-watered conditions. Concurrently, the net photosynthetic rate exhibited a reduction of 26.0% and dry matter accumulation decreased by 35.5%. However, after spraying with a low concentration of selenium, selenium reduced oxidative damage and malondialdehyde content by reducing the content of peroxide in leaves, restoring photosynthesis, and promoting the normal growth of tomato. Compared to the control group, spraying with 2.5 mg·L⁻¹ selenium resulted in a 21.5% reduction in MDA content, a 111.8% increase in net photosynthetic rate, and a 29.0% increase in dry matter accumulation. When subjected to drought stress conditions, foliar spraying of low concentrations of selenium (2.5 mg·L⁻¹) can effectively reduce oxidative damage caused by drought stress and alleviate growth constraints in tomatoes. In addition, treatments with high selenium concentrations exhibited specific toxic effects. These findings offer valuable insights into the mechanisms governing selenium-induced drought tolerance in tomatoes, thus advancing our comprehension of standard tomato production practices.
... Recently it has been shown that selenium has the ability to regulate the water status of plants under conditions of drought (Kuznetsov et al., 2003). Hartikainen et al. (2000) reported about growth promoting effect of selenium in ryegrass. Senescence stress is partly counteracted with enhanced antioxidation which is associated with an increase glutathione peroxidase (GSH-Px) activity. ...
... Higher ETS activity reflected increased GSH-Px activity in mitochondria (Smrkolj et al., 2006a). It was evidenced Hartikainen et al., 2000;Xue et al., 2001) that selenium exposure increased GSH-Px activity in ryegrass and lettuce. However, selenium did not affect respiratory potential in F. esculentum and F. tataricum (Breznik et al., 2005a), foliarly treated with selenium. ...
Selenium is of metabolic importance in cyanobacteria and in some plants, being involved in their antioxidative processes. Selenium is widely distributed on the Earth’s surface and available for plants in at least small traces. Cultivation of plants enriched with selenium could be an effective way of producing selenium rich foodstuffs and thereby increase health benefits. The essentiality of selenium to higher plants is still under debate. Selenium can increase the tolerance of plants to UV-induced oxidative stress, delay senescence, and promote the growth of ageing seedlings. Recently it has been shown that selenium has the ability to regulate the water status of plants under conditions of drought. The distribution and speciation of selenium in plants and the effect of selenium alone and in combination with some other environmental parameters is discussed.
... A stimulatory effect of foliar application of Se on growth has been reported for ryegrass (Hartikainen et al., 2000), lettuce (Xue et al., 2001), potato (Turakainen et al., 2004), soybean (Djanaguiraman et al., 2005) and green tea leaves (Hu et al., 2003). Selenium can also delay senescence and promote the growth of aging seedlings (Xue et al., 2001). ...
... Most probably the first positive effect of selenium on plant growth was reported by Singh et al. (1980), who showed that the application of selenium stimulated growth and dry matter yield of Brassica juncea. In this work, similarly with that observed for lettuce, ryegrass (Hartikainen et al., 1997;Hartikainen et al., 2000) and soybean (Djanaguiraman et al., 2005), selenium increased shoot dry weight in barley plants. Drought stress reduced growth activity of barley (Tables 1), as is observed by other plants species (Ramesh, 1999;Liu and Stützel, 2004;Degu et al., 2008). ...
This paper reports the effects of selenium (Se) application on some physiological characteristics of barley (Hordeum vulgare L. cv. Rihane-03) exposed to drought stress. Foliar application to barley at 30 g selenium ha-1, as sodium selenate, increased significantly shoot dry weight and relative water content in well-watered plants. A remarkable reduction in dry weight of water-stressed plants was associated with significant decrease in maximal efficiency of PSII (Fv/Fm), stomatal conductance (gs) and net CO2 assimilation rate (A). Activity of antioxidant enzymes was increased by drought stress significantly. Amounts of malondialdehyde (MDA) and hydrogen peroxide (H2O2) remained unchanged in Se-supplemented water-deficit plants obviously because of an efficient scavenging following significant enhancement of catalase (CAT) and glutathione peroxidase (GSH-Px) activities. These results indicate that an application of selenium was favorable for biomass accumulation of barley plants under well-watered conditions. However, it did not significantly affect dry matter accumulation under drought stress, but Se-supplemented water-deficit plants exhibited better protection from oxidative damage because of higher CAT and GSH-Px activities and lower level of lipid peroxidation. These results suggest that selenium application can improve antioxidant defense system under drought stress conditions, and it may be recommended for arid and semiarid regions.
... Jiang et al., [44] found the same trend in another study in which the application of high doses of selenium significantly reduced the root and stem growth of maize plants. This phenomenon has been observed in other crops, such as ryegrass seedlings, whose growth was stimulated at low doses of selenium and inhibited at high doses [45]. However, selenium can also cause (eco)toxicity in high rate, as observed in soils in selenium-containing regions of the world [46]. ...
Selenium-enriched sweet maize is an important product to alleviate selenium deficiency in the human body. In this study, the effects of the basal application of selenium fertilizer on the selenium content and yield of maize were analyzed in a 2-year field trial using a two-factor, five-level, split-area experimental combination design with a different selenium fertilizer application rate (150–750 kg ha⁻¹) and depth (1–20 cm). It was found that the selenium application rate and depth significantly affected dry matter mass, selenium content, and selenium accumulation in maize. In particular, the Se3D4 treatment combination (a selenium application rate of 450 kg ha⁻¹ and depth of 15 cm) performed the best in increasing the selenium content and yield of the maize grain. The 2-year data showed that the selenium content of maize grain under Se3D4 treatment reached 3.59 mg kg⁻¹ and 3.24 mg kg⁻¹, which were 13.63 and 13.70 folds as the control, respectively, and the yield reached 6.28 t ha⁻¹ and 6.07 t ha⁻¹, which were 24.35% and 33.30% higher than the control, respectively. Therefore, by optimizing the application rate and depth of selenium fertilizer, the selenium content and yield of maize can be significantly increased. The results of this study provide a theoretical basis for the precise application of selenium fertilizer in the biofortification of sweet maize.
... Plants have a fundamental role in Se transfer in the human food chain. In relevant studies, it has been determined that Se plays an antioxidant role, has beneficial effects on plants at low concentrations, promotes plant growth, reduces UV-induced oxidative damage, and improves the recovery of chlorophyll under mild stress conditions, delays senescence, provides resistance to drought and can increase pollen viability (Hartikainen et al., 2000;Combs, 2001;Seppanen et al., 2003;Yao et al., 2009;Hassanuzzaman et al., 2010). ...
... Superoxide anion (μg g − 1 FW, O 2 ⋅− ) level in fresh materials was monitored as previously discussed by (Hartikainen et al., 2000). To detect the Hydroxyl radicals (μmol g − 1 FW, ⋅ OH) in the fresh leaf tissues, the protocol of (Halliwell et al., 1987) was applied. ...
Sustainable agriculture is a major theme of the Food and Agriculture Organization (FAO) Strategic Framework 2022–2031. Using microbial-based regulators is a sustainable organic approach to accomplish food safety. Normally, drought is a menace to most crops' agricultural production, but for leafy green vegetables the matter is more frustrating due to grade standards. Despite breakthroughs in boosting crop tolerance to drought stress, the quest for leafy greens remains restricted. The current report is to study the ability of biologically-produced gibberellin by Fusarium oxysporum in alleviating water stress in leafy vegetable spinach, Spinacia oleracea. Endophytic Fusarium oxysporum demonstrated high gibberellin production by 200±5.9 mg L−1. Water stress (100, 75, 50, 25 % field capacity, FC) generated mild to severe abnormal growth and physiological dynamics. Foliar-applied biological gibberellin (BG) motivated plant yield and quality by boosting various phenotypic and physiological features in terms of plant height, biomass, and number of leaves accompanied by thicker epicuticular wax, balanced water status, higher photosynthetic pigment, increased osmoprotectants. BG shoulders a role in upgrading plant liveness via exacerbating antioxidants (anthocyanin, ascorbic acids, total antioxidants, and flavonoids) joined with activation of secondary metabolizing enzyme phenylalanine ammonia-lyase PAL, fulfilling consumer demand standards for spinach as well as lowering the content of phenolics and its oxidizing enzyme polyphenol oxidas (PPO, browning causer). Catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were instigated thus maintaining electrolyte leakage, cellular O2·−, ·OH, H2O2, malondialdehyde, and lipid peroxidation at baseline levels. BG appears to reduce nitrative toxicity via enhancing nitrate reductase (NR) activity. BG foliar spray increased spinach's resilience to dehydration and its capacity to produce an adequate upgraded yield while cultivated with reduced water regimes or even exposed to drought.
... Additionally, researches have shown that trace amounts of Se can enhance plant growth, delay senescence, and regulate water content under drought conditions by reducing ROS levels and increasing activity of antioxidant enzymes [51,29]. Se can also boost crop yield by participating in the formation of compounds such as selenoproteins and selenoenzymes and reactions like glutathione peroxidase (GSH-Px) enzyme activity, which enhance antioxidative enzyme activity [23,52]. Furthermore, Se NPs improve plant growth and development by increasing stomatal conductance, net photosynthetic rate, PSII potential activity, transpiration rate, actual photochemical e ciency, effective photochemical e ciency, and electron transport rate [53]. ...
Background: Dracocephalum kotschyi Boiss., a perennial medicinal and aromatic plant endemic to Iran, is renowned for its diverse biological and medicinal properties. This study aimed to evaluate the influence of foliar application of selenium nanoparticles (Se NPs) and sodium selenite (Na 2 SeO 3 ) on the growth, yield, physiological and biochemical characteristics, and essential oil (EO) of D. kotschyi . The experiment included seven treatments: a control (distilled water) and foliar spray of 50, 100, and 200 mg L ⁻¹ of both Se NPs and Na 2 SeO 3 separately. Results: Se NPs were found to be more effective than Na 2 SeO 3 in improving plant growth and yield. Specifically, a 200 mg L ⁻¹ Se NPs treatment led to the highest plant height, fresh weight of plant, dry weight of leaf, and relative water content. Elevated Se concentrations were associated with a decrease in chlorophyll level. Both Se NPs and Na 2 SeO 3 treatments increased hydrogen peroxide levels, and the activity of catalase and ascorbate peroxidase. The phenylalanine ammonia-lyase activity increased with Se NPs up to 50 mg L ⁻¹ and Na 2 SeO 3 up to 100 mg L ⁻¹ . Application of 200 mg L ⁻¹ Na 2 SeO 3 resulted in the highest total phenol content and antioxidant activity. Although spraying 100 mg L ⁻¹ Se NPs led to the highest EO content, the EO yield peaked with 200 mg L ⁻¹ Se NPs. Notably, the application of 200 mg L ⁻¹ Se NPs reduced the level of neral, while 200 mg L ⁻¹ Na 2 SeO 3 decreased both geranial and neral levels. Conversely, levels of α -pinene and geranyl acetate increased with Se application. Conclusions: The results revealed that Se NPs was more effective than the Na 2 SeO 3 for improving plant growth and yield. Overall, the 200 mg L ⁻¹ Se NPs treatment was the most effective in improving growth, yield attributes, and EO yield of D. kotschyi.
... APX activity was measured by the decrease in absorbance at a wavelength of 290 nm related to the oxidation of ascorbate with hydrogen peroxide and calculated using an extinction coefficient of 2.8 mM −1 cm −1 [74]. GPX activity was assessed by the decrease in reduced glutathione due to its oxidation by hydrogen peroxide [75]. POD activity was determined by spectrophotometry using guaiacol and hydrogen peroxide as substrates and calculated using an extinction coefficient of 26.6 mM −1 cm −1 (at 470 nm) [76]. ...
Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.
... Although Se has an antioxidative function in trace amounts, this effect of Se appeared to be reduced or reversed at higher concentrations. In addition to several other damages, the pro-oxidant nature of Se contributing to Se toxicity was also reported [22]. Following this study, TBAR level was also increased two-to three-fold when polished and finished wheat were treated with 100 µM selenite in a survey conducted by Labanowska et al. [23]. ...
Wheat seedlings were hydroponically grown in Hoagland solution containing various levels of Se. Tolerance response to Se toxicity was investigated by determining the level of thiobarbituric acid reactive substance (TBARS), proline and chlorophyll content, the growth parameters, and the activity of antioxidant enzymes. The toxic level of Se treatment significantly retarded the seedling growth. A substantial amount of proline accumulation was also observed in response to toxic Se concentration, but it was more pronounced in putative-sensitive cultivars. Chlorophyll content significantly decreased in Se-intoxicated seedlings and increased at the lowest Se dose in both cultivars. Severe and mild chlorosis was observed in putative-sensitive and tolerant cultivars at the highest Se level. Alterations in the activities of glutathione reductase (GR, 1.6.4.2), glutathione S transferase (GST, 2.5.1.18), guaiacol peroxidase (GPX, 1.11.1.7), catalase (CAT, 1.11.1.6), and ascorbate peroxidase (APX, 1.11.1.11) and superoxide dismutase (SOD, EC 1.15.1.1) were determined. TBAR level did not significantly increase in putative tolerant cultivars as an indicator of membrane lipid peroxidation. However, a significant increase was observed in putative-sensitive cultivars in response to higher selenium concentrations. In higher Se treatment groups, CAT and GST activities significantly increased in putative Se tolerant cultivars. However, excluding SOD, the activity of all the studied enzymes was increased considerably in putative-sensitive cultivars in a dose-dependent manner. Higher antioxidant enzyme activities and a substantial amount of proline accumulation did not significantly contribute to overcoming Se phytotoxicity in wheat seedlings grown in media supplemented with toxic selenium levels.
... The activity of glutathione peroxidase (GPX) was assayed by the method modified by Hartikainen et al. [35]. In brief, the samples were extracted with phosphate buffer (pH 7). ...
Water deficit stress significantly reduces grain yield in bread wheat, requiring improved tolerance in cultivars. Despite recent breeding advancements, enhancing tolerance remains crucial. Plant growth-promoting bacteria (PGPB) and silicon (Si) independently boost drought resistance through different mechanisms, but their combined effects are understudied. This research explored the combined impacts of silicon dioxide nanoparticles (SiO2 NPs) and native PGPB on wheat's morphophysiological and nutritional responses under water deficit stress. The study tested various SiO2 NPs concentrations (control, soil application of 100 and 200 mgkg⁻¹, and foliar application of 200 mgkg⁻¹) and PGPB strains (no bacterium, Pseudomonas fluorescens p-187, and Pseudomonas putida p-168). Results showed that SiO2 NPs significantly improved wheat tolerance to water stress, increasing shoot dry weight by 4.40 g/pot with 100 mgkg⁻¹ SiO2NPs and Pseudomonas fluorescens p-187 compared to the control, and root dry weight by 1.05 g pot⁻¹ with foliar application of 200 mgkg⁻¹ SiO2 NPs and Pseudomonas putida p-168. SiO2 NPs and PGPB also boosted N, P, K, and Si concentrations in wheat shoots, reduced malondialdehyde content, and increased superoxide dismutase and glutathione peroxidase activities. The best performance was achieved with 200 mgkg⁻¹ SiO2 NPs and Pseudomonas fluorescens p-187. The study confirms that combining SiO2 NPs sources with PGPB effectively enhances wheat's drought tolerance. This synergistic approach offers an environmentally sustainable strategy to bolster crop resilience against water deficit stress, ensuring better wheat yield in drought-prone conditions.
... However, relatively high Se concentrations can decrease plant GPX activity, and plants may exhibit pro-oxidative properties [107]. According to the literature, the antioxidant properties of Se are associated with its beneficial effects on GPX activity [108]. The application of Se or selenites can enhance GPX activity [109]. ...
Human activities, such as mining, industrialization, industrial waste emissions, and agricultural practices, have caused heavy metals to become widespread and excessively accumulated in soil. The high concentrations of heavy metals in soil can be toxic to plants, severely affecting crop yield and quality. Moreover, these heavy metals can also enter the food chain, affecting animals and humans and leading to various serious illnesses. Selenium (Se) is not only an essential element for animals and humans but is also beneficial for plants, as it promotes their ability to respond actively to biotic and abiotic stresses. The global issue of Se deficiency in diets has made plants the primary source for human Se supplementation. This paper comprehensively reviews the effects of heavy metal stress on plant growth and development, physiological responses of plants to such stress, and the intracellular transport processes of heavy metals within plants. It particularly focuses on the mechanisms by which Se alleviates heavy metal stress in plants. Additionally, the study delves into how Se significantly enhances plant tolerance mechanisms against typical heavy metals, such as cadmium (Cd), lead (Pb), and mercury (Hg). This integrative research not only expands the boundaries of research in the field of plant heavy metal stress and Se application but also provides new perspectives and solutions for understanding and addressing complex environmental heavy metal pollution issues. By integrating these aspects, this paper not only fills existing gaps in the literature but also offers comprehensive scientific basis and strategic recommendations for environmental protection and sustainable agriculture development.
... When Se is abundant, it promotes oxidation leading to cellular damage and reduced yield and even pose a threat to the environment (Wu 2004). On the other hand, at low concentrations of Se, it can improve the nutritional quality of plants, such as total amino acids, vitamin C and flavonoids (Wen 2021), stimulate plant growth and act as an antioxidant (Hartikainen et al. 2000;Jiang et al. 2021). The threshold between toxic and beneficial concentrations of Se depends on the plant species and the form in which Se is provided. ...
Elevating the selenium concentration in fruit has the potential to enhance the average dietary selenium intake in humans. The application of selenium fertilizer through a spraying method has been found to be an effective approach for producing selenium-enriched fruit. While kiwifruit (Actinidia chinensis) is known for its ability to accumulate selenium, the ‘Hongyang’ variety grown in Sichuan, China has been observed to have low selenium content. The tree was treated by spraying the leaves with water solution containing 10, 25, 50 and 100 mg per litre in the form of sodium selenite (Na2SeO3) in the flowering period. The total Se and organic Se content, and the effects of different concentrations of Na2SeO3 on antioxidant activity in peels, pulps and seeds of fruits were investigated. The findings indicated that kiwifruit has the ability to transform exogenously absorbed inorganic selenium into organic selenium. The organic selenium content in the pulps treated with 50 mg L⁻¹ sodium selenite was 9.04 times higher than in the control treatment. Furthermore, protein-Se was identified as the main component of organic selenium, comprising 48.04–51.15% of the pulps. The protein-Se is the primary component of organic Se, which the proportion in pulps was 48.04–51.15%. The application of 50 and 100 mg L⁻¹ sodium selenite via foliar spraying resulted in a notable enhancement of ferric reducing/antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) values across all tissues. A significant positive correlation between FRAP value and organic Se content in pulps, and a significant relationship between ORAC values and protein-Se and polysaccharide-Se content of kiwifruit tissue showed regression equation. In general, the optimum Se application is 50 mg L⁻¹, and some areas with a severe selenium deficiency can apply 100 mg L⁻¹ selenite. It might serve as a source of selenium in dietary supplements or as an ingredient for the formulation of nutraceuticals.
... Hartikainen et al. [49] reported that selenium has dual effects on the body: a low concentration of selenium acts as an antioxidant to inhibit lipid peroxidation, while a high concentration of selenium is a pro-oxidant, which promotes the production and accumulation of membrane lipid peroxidation products. The accumulation of MDA also indicates that plants are damaged by the peroxidation of ROS [50], and the application of selenium alleviates the harmful effects of leaf senescence in rice [51]. ...
Selenium is an essential trace element in the human body. However, its intake is generally low. Therefore, the production and utilisation of selenium-enriched foods is currently a research hotspot. In this study, the effects of low (0.2 mg·kg⁻¹), medium (1.0 mg·kg⁻¹), and high (5.0 mg·kg⁻¹) concentrations of selenium on the physiological and biochemical characteristics of rice were investigated to develop selenium-enriched rice. High concentrations of selenium have been found to inhibit the growth, physiology, and biochemistry of rice, while low concentrations of selenium promote its growth. The height of mature rice plants exposed to high concentrations of selenium was reduced by 7.20% compared with the height of control rice. Selenium decreased the proline content of rice during the growth period except in mature rice treated with medium and high concentrations of selenium. Excluding high concentrations, selenium treatment increased the soluble sugar content of rice from the tillering to the mature stages. The peroxidase activity of rice at the heading stage treated with medium levels of selenium was significantly higher than that of the control rice, while the superoxide dismutase activity of rice exposed to selenium was significantly enhanced at the mature stage. The malondialdehyde levels of mature rice treated with medium and high levels of selenium were significantly lower than those of the control rice. The selenium content of each plant part was significantly correlated with the soil selenium level. An increase in the soil selenium level facilitated the production of selenium-enriched rice.
... Large amounts of ROS such as O 2 and H 2 O 2 generated by HMs stress could vastly reduce oxygen efficiency, exacerbating cell membrane damage and affecting crop production. ROS primarily scavenged by antioxidants including CAT, POD, and APX (Hartikainen et al. 2000). In wetlands with 100% WW concentration, SOD, CAT, POD, and APX activities slightly increased (Figure 3). ...
Water contamination with metals poses significant environmental challenges. The occurrence of
heavy metals (HMs) prompts modifications in plant structures, emphasizing the necessity of
employing focused safeguarding measures. Cadmium (Cd), lead (Pb), and chromium (Cr) emerge as
particularly menacing toxins due to their high accumulation potential. Increasing the availability of
organic acids is crucial for optimizing toxic metal removal via phytoremediation. This constructed
wetland system (CWs) was used to determine how oxalic acid (OA) treatments of textile wastewater
(WW) effluents affected morpho-physiological characteristics, antioxidant enzyme activity, oxidative
stress, and HM concentrations in Phragmites australis. Multiple treatments, comprising the application
of OA at a concentration of 10mM and WW at different dilutions (25%, 50%, 75%, and 100%), were
employed, with three replications of each treatment. WW stress decreased chlorophyll and carotenoid
content, and concurrently enhanced HMs adsorption and antioxidant enzyme activities. Furthermore,
the application of WW was found to elevate oxidative stress levels, whereas the presence of OA
concurrently mitigated this oxidative stress. Similarly, WW negatively affected soil-plant analysis
development (SPAD) and the total soluble proteins (SP) in both roots and shoots. Conversely, these
parameters showed improvement with OA treatments. P. australis showed the potential to enhance
HM accumulation under 100% WW stress. Specifically, there is an increase in root SP ranging from
9% to 39%, an increase in shoot SP from 6% to 91%, and an elevation in SPAD values from 4% to
64% compared to their respective treatments lacking OA inclusion. The OA addition resulted in
decreased EL contents in the root and shoot by 10%–19% and 13%–15%, MDA by 9%–14% and
9%–20%, and H2O2 by 14%–21% and 9%–17%, in comparison to the respective treatments without
OA. Interestingly, the findings further revealed that the augmentation of OA also contributed to an
increased accumulation of Cr, Cd, and Pb. Specifically, at 100% WW with OA (10mM), the
concentrations of Cr, Pb, and Cd in leaves rose by 164%, 447%, and 350%, in stems by 213%, 247%,
and 219%, and in roots by 155%, 238%, and 195%, respectively. The chelating agent oxalic acid
effectively alleviated plant toxicity induced by toxins. Overall, our findings demonstrate the
remarkable tolerance of P. australis to elevated concentrations of WW stress, positioning it as an
eco-friendly candidate for industrial effluent remediation. This plant exhibits efficacy in restoring
contaminants present in textile effluents, and notably, oxalic acid emerges as a promising agent for
the phytoextraction of HMs.
... The activity of glutathione peroxidase (GPX) was assayed by the method modi ed by Hartikainen et al. [35]. In brief, the samples were extracted with phosphate buffer (pH 7). ...
Water deficit stress significantly reduces grain yield in bread wheat, requiring improved tolerance in cultivars. Despite recent breeding advancements, enhancing tolerance remains crucial. Plant growth-promoting bacteria (PGPB) and silicon (Si) independently boost drought resistance through different mechanisms, but their combined effects are understudied. This research explored the combined impacts of silicon dioxide nanoparticles (SiO 2 NPs) and native PGPB on wheat's morphophysiological and nutritional responses under water deficit stress. The study tested various SiO 2 NP concentrations (control, soil application of 100 and 200 mg/kg, and foliar application of 200 mg/kg) and PGPB strains (no bacterium, Pseudomonas fluorescens p-187, and Pseudomonas putida p-168). Results showed that SiO 2 NPs significantly improved wheat tolerance to water stress, increasing shoot dry weight by 4.40 g/pot with 100 mg/kg Si-NPs and Pseudomonas fluorescens p-187 compared to the control, and root dry weight by 1.05 g/pot with foliar application of 200 mg/kg Si-NPs and Pseudomonas putida p-168. SiO 2 NPs and PGPB also boosted N, P, K, and Si concentrations in wheat shoots, reduced malondialdehyde content, and increased superoxide dismutase and glutathione peroxidase activities. The best performance was achieved with 200 mg/kg Si-NPs and Pseudomonas fluorescens p-187. The study confirms that combining Si sources with PGPB effectively enhances wheat's drought tolerance. This synergistic approach offers an environmentally sustainable strategy to bolster crop resilience against water deficit stress, ensuring better wheat yield in drought-prone conditions.
... Application of selenium nanoparticles in low concentrations has been found to mitigate the effects of heat stress by enhancing plant development, chlorophyll content, and hydration (Haghighi et al. 2014). Additionally, plants can benefit from the antioxidative properties of selenium nanoparticles at low concentrations, whereas oxidative stress was brought on by selenium nanoparticles at high concentrations (Hartikainen et al. 2000;Hasanuzzaman et al. 2014). During times of heat stress, plants produce a number of molecular chaperones and heat shock proteins (Schulze et al. 2005). ...
Plant growth and productivity are greatly impacted by temperature stress, both high and low. These stresses impair biochemical, physiological, and molecular processes in the plant, eventually affecting plant growth, development, and productivity. Consequently, novel approaches are needed to overcome these problems and achieve sustainability. Nanotechnology is one such novel approach to improving crop production, by using nanoscale products. Nanoparticle size, nature, application mode, environmental conditions, rhizospheric and phyllospheric environments, and the species of plant make a significant impact on their action. With their easy soluble nature, smaller size, and excellent ability to penetrate plants, and their ability to cross cellular barriers, nanoparticles have become an increasingly popular agricultural tool. It has recently been observed that silver, silicon, titanium, and selenium nanoparticles can alter the physiological and biochemical response of plants in order to counteract high or low temperature stress. In this review, a description is provided of how nanoparticles are absorbed in different plant parts and how they are translocate along with the factors that influence their uptake and translocation. Also how plant response to nanoparticles in temperature stress and the various types of physiological, morphological, anatomical, biochemical and molecular modifications caused by nanoparticles. The review is going to provide researchers in agricultural sciences a glimpse into how to discover new nanoparticles to deal with heat stress.
... However, the specific physiological mechanism by which excess Se affects plants has yet to be fully understood. At high doses, Se acts as a pro-oxidant and can cause damage to plants [71]. At present, the mechanism of Se-Mn interaction is still unclear. ...
Zinc (Zn)- and iron (Fe)-regulating transport-like proteins (ZIPs) are a class of proteins crucial for metal uptake and transport in plants, particularly for Zn and Fe absorption and distribution. These proteins ensure the balance of trace elements essential for plant growth, development, and metabolic activities. However, the role of the rice (Oryza sativa) OsZIP gene family in manganese (Mn) and selenium (Se) transport remains underexplored. This research conducted an all-sided analysis of the rice OsZIPs and identified 16 OsZIP sequences. Phylogenetic analysis categorized the OsZIPs predominantly within the three subfamilies. The expression levels of OsZIPs in rice root and leaf subjected to Mn and Se toxicity stress were examined through quantitative real-time PCR (qRT–PCR). The findings revealed significant differential expression of many OsZIPs under these conditions, indicating a potential regulating effect in the response of rice to Mn and Se toxicity. This work lays a foundation for further functional studies of OsZIPs, enhancing our understanding of the response mechanisms of rice to Mn and Se toxicity and their roles in growth, development, and environmental adaptation.
... Selenium (Se) is a beneficial element for plants (Feng et al. 2021b), and there is increasing interest in using Se to remediate heavy metal-polluted soil (Feng et al. 2021a(Feng et al. , 2013. Numerous studies have shown that Se acted as an antioxidant or an uptake inhibitor (Djanaguiraman et al. 2005;Hartikainen et al. 2000), counteracting the toxic effects of various metal(loid)s, reducing uptake various metal(loid)s of plant, including arsenic (As) (Singh et al. 2018), cadmium (Cd) (Ismael et al. 2018), lead (Pb), chromium (Cr) (Fargašová et al. 2006), mercury (Hg), manganese (Mn), aluminum (Al) (Feng et al. 2011), and antimony (Sb) (Dai et al. 2022;Feng et al. 2021b;Huang et al. 2018aHuang et al. , 2018bTang et al. 2017). Additionally, previous research has summed up different heavy metal toxicity alleviation mechanism by Se, which included the following: the coprecipitation of Se and heavy metals, reduction of the bioavailability of metal(loid)s by Se, the regulation of the root morphology by Se, the stimulation of increased metal(loid)s sequestration by Se in root iron plaques, cell walls, or vacuoles, and the regulation of uptake and transport pathways by Se (Feng et al. 2021a). ...
Many studies have focused their attention on strategies to improve soil phytoremediation efficiency. In this study, a pot experiment was carried out to investigate whether Se and Bacillus proteolyticus SES promote Cu-Cd-Cr uptake by ryegrass. To explore the effect mechanism of Se and Bacillus proteolyticus SES, rhizosphere soil physiochemical properties and rhizosphere soil bacterial properties were determined further. The findings showed that Se and Bacillus proteolyticus SES reduced 23.04% Cu, 36.85% Cd, and 9.85% Cr from the rhizosphere soil of ryegrass. Further analysis revealed that soil pH, organic matter, soil enzyme activities, and soil microbial properties were changed with Se and Bacillus proteolyticus SES application. Notably, rhizosphere key taxa (Bacteroidetes, Actinobacteria, Firmicutes, Patescibacteria, Verrucomicrobia, Chloroflexi, etc.) were significantly enriched in rhizosphere soil of ryegrass, and those taxa abundance were positively correlated with soil heavy metal contents (P < 0.01). Our study also demonstrated that in terms of explaining variations of soil Cu-Cd-Cr content under Se and Bacillus proteolyticus SES treatment, soil enzyme activities (catalase and acid phosphatase) and soil microbe properties showed 42.5% and 12.2% contributions value, respectively. Overall, our study provided solid evidence again that Se and Bacillus proteolyticus SES facilitated phytoextraction of soil Cu-Cd-Cr, and elucidated the effect of soil key microorganism and chemical factor.
Graphical Abstract
... Depending upon its concentrations, selenium has dual role i.e.it enhances plant growth by acting as an antioxidant in low quantities, and it reduces plant yield when present in high concentration. 5 Moreover, Se reduces the photo oxidative stress and activates defense mechanisms in potato chloroplasts. 6 Electro microscopic studies revealed that the growth of lettuce plant increases and higher quantities of starch accumulated when lettuce plants were provided with selenium doses. ...
Purpose: Heavy metal accumulation in environment is potentially creating problems to life especially to plants. Two selenium resistant bacteria, Bacillus pumils strain CrK08 and Bacillus licheniformis strain AsK03 were checked for their role in growth promotion of Zea mays in pot experiment under selenium stress. Methods: The two bacterial strains Bacillus pumils strain CrK08 and Bacillus licheniformis strain AsK03 were assessed for their ability to promote plant in pot experiment and growth parameters were measured. Results: Both strains significantly promoted root length (13%) in control and (51%) in autoclaved soil. Number of roots was reduced to 28% and 35% in control and autoclave soil respectively. Fresh weight and dry weight were reduced up to 2%, 1% and 28% and 25% in control and autoclave soil plants. In treated plants fresh weight was 35% and 16 % high than non-treated plants. Strains also produced an increase in soluble protein content. Indole acetic acid (IAA) content was enhanced to 10% and 65% while acid phosphatase activity was 13.3% and 50% lower in inoculated plants than respective controls. Peroxidase content reduced up to 2%. Selenium content in control plants was high as compared to treated plants. Conclusion: On the whole these strains promote plant growth under Se stress (17mg/kg) in soil.
... Plants uptake Se from soil where it exists in both organic (Se-amino acids) and inorganic (selenite, selenides and selenate) forms with various oxidation states (− 2 to +6). Among these, the selenate (SeO 4 2-) is less adsorbed to oxide surfaces than selenite (SeO 3 2-), which makes it the most bioavailable, mobile and water-soluble Se species in oxicsoils (Hartikainen et al., 2000). At low pH or anoxic conditions, SeO 4 2is readily converted to SeO 3 2-, which may be further reduced to insoluble forms of Se i.e., selenides (Se 2-) and elemental Se (Se o ) under intense reducing conditions (Winkel et al., 2015). ...
... The reason may be that Se could indiscriminately replace sulfur to form selenoamino acids and bind to proteins, reducing resulting in the lower stress response of plants. Additionally, it may also be due to the activity of GSH-Px significantly increased under Se treatment, GSH-Px as a scavenger of H 2 O 2 and MDA, promoted the scavenging of the production of H 2 O 2 , and enhanced the O 2 − spontaneous disproportionation (proportion imbalance), that is, only lower O 2 − content were produced, thereby reducing the demand for SOD enzymes, and the demand for CAT and POD enzymes to scavenge and decompose H 2 O 2 was also reduced (Hartikainen et al. 2000). In addition, our research showed that the contents of O 2 − , MDA, Pro and the activities of antioxidant enzymes (CAT, POD and SOD) of pepper seedlings significantly increased under the higher Se concentration, which was an important physiological and biochemical manifestation of Se excess leading to toxicity. ...
Mixed salt stress significantly inhibits pepper germination and seedling growth, but it is unclear whether the negative effect can be mitigated by selenium (Se) addition.
Four pepper varieties with large differences in salt tolerance were used as materials in this study. Based on the significant stress of mixed salts, the concentration of sodium selenite was set to 0, 5, 10, 20, 40, 80, and 120 µmol L− 1, respectively. Various parameters related to seed germination, seedling growth and development, as well as internal physiological indicators were measured, and the alleviating effects of sodium selenite on salt stress was comprehensively evaluated by fuzzy membership function method.
The results showed that with the increase of sodium selenite concentration, the germination rate, relative salt damage mitigation rate, root fresh weight, fresh weight above ground, root length, hypocotyl length, and seedling activity index all showed an initial increase followed by a decrease, while the contents of superoxide anion radical (O2−), malondialdehyde (MDA), proline (Pro) and the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) decreased first and then increased. On the whole, the total weighted values of membership function values of each index of the four varieties increased first and then decreased with the increase of sodium selenite concentration. The addition of appropriate concentration of exogenous sodium selenite (10–20 µmol L− 1) significantly improved seed germination of pepper, meanwhile, it alleviated the effect of salt stress and promoted root and above ground growth by significantly reducing the content of O2− and MDA.
The appropriate concentration of exogenous Se could promote the growth and development of pepper seedlings and ensure the cultivation of strong seedlings by promoting the early and rapid germination of seeds and reducing the degree of stress.
... Se nanoparticles, when applied to plants at low concentrations, reduced the harmful impacts of heat stress by increasing water absorption, chlorophyll levels, and plant development (Haghighi et al., 2014). Se nanoparticles at weakly concentrated have antioxidative effects on plants, while Se nanoparticles at high concentrations cause oxidative stress (Hartikainen et al., 2000;Hasanpour et al., 2015). The plant's response to the stress of being exposed to high temperatures was to produce several heat shock proteins and molecular chaperones (Anten, 2005). ...
... Our results showed that GSSG gradually accumulated after Se treatment, thus reduced oxidized glutathione (GSSG) to GSH under GR catalyze, which also promoted ROS elimination. Additionally,Hartikainen et al. proposed that selenium at an appropriate concentration is an antioxidant for ryegrass, but too high concentration of selenium is a prooxidant for ryegrass[40]. In this study, the activities of antioxidant enzymes such as SOD, POD, CAT, and glutathione metabolism related enzymes such as GSH, GR, and GSSG in the rice leaves showed a trend of rst increasing and then decreasing with the increase of selenium concentration under three selenium source treatments and different selenium application methods, and the effect was more signi cant under the medium concentration treatment of SeMet and NS. ...
Background: Selenium (Se) is an essential trace element that has various beneficial effects for human healthy. However, the effects of different selenium sources, treatment methods and concentrations on growth and development, photosynthetic characteristics and antioxidant capacity are still unclear in rice.
Results: In this study, three concentrations of three different selenium sources were performed in rice using two treatment methods, respectively. The results showed that selenium treatment can increase the plant height, the 1000 grain weight, the Se content of rice grain, and increased the organic selenium content of rice grain, especially. All the selenium treatments improved the photosynthetic indexes including net photosynthetic rate, transpiration rate, and stomatal conductance, decreased inter-cellular CO2 concentration. The activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and glutathione reductase (GR), as well as the content of GSSG (Glutathione oxidized) were increased at different levels after Se treatments, while GSH (Glutathione) decreased. Totally, 32 DEGs related to selenium absorption/endocytosis (including six heat shock 70 kDa protein, one ACD), transport (including four ABC transporters, one SULTR, one LAST, one Inorganic phosphate transporter, one GlpT, one PHO, one PPT) and metabolism (including NAS1, NAS2, APS5, 3MST2, PPCS1, SAMDC and 8 protein kinases), 6 DEGs related to glutathione metabolic pathway (including one G6PD, four GSTs and one GSS), 69 transcription factors (including 19 AP2/ERF-ERFs, 9 MYBs, 9 WRKYs, 8 HSFs, 6 bHLHs, 5 GRASs, 4 NACs,3 B3-ARFs, 3 C2H2s and 3 bZIPs) were identified by RNA-Seq.
Conclusion: Our study indicated that exogenous selenium treatments could increase the 1000 grain weight, the Se content and the organic selenium content of rice grain by improving photosynthetic traits and antioxidant enzyme activities, especially sodium selenite. The expressions of the genes related to selenium metabolism indicated that foliar spraying can faster induce the response of Se treatment in rice than root irrigation. The results will provide an insight into the selenium enrichment of rice.
... At low concentrations, it acts as an antioxidant, inhibiting lipid peroxidation, because Se is involved in the antioxidant defense systems. It is a key component of selenoproteins such as thioredoxin reductase (TR) and the glutathione peroxidase family (GPx), which have reactive oxygen species (ROS) scavenging activity [307]. ...
Free radicals (FRs) are unstable molecules that cause reactive stress (RS), an imbalance between reactive oxygen and nitrogen species in the body and its ability to neutralize them. These species are generated by both internal and external factors and can damage cellular lipids, proteins, and DNA. Antioxidants prevent or slow down the oxidation process by interrupting the transfer of electrons between substances and reactive agents. This is particularly important at the cellular level because oxidation reactions lead to the formation of FR and contribute to various diseases. As we age, RS accumulates and leads to organ dysfunction and age-related disorders. Polyphenols; vitamins A, C, and E; and selenoproteins possess antioxidant properties and may have a role in preventing and treating certain human diseases associated with RS. In this review, we explore the current evidence on the potential benefits of dietary supplementation and investigate the intricate connection between SIRT1, a crucial regulator of aging and longevity; the transcription factor NRF2; and polyphenols, vitamins, and selenium. Finally, we discuss the positive effects of antioxidant molecules, such as reducing RS, and their potential in slowing down several diseases.
... At low concentrations, Se enhances photosynthesis and increases the accumulation of carbohydrates and secondary metabolites [39]. It is also involved in antioxidant defense, enhancing the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione peroxidase [40,41]. Increased stress tolerance following Se application has been observed in various plant species and stress conditions, such as cold, drought, desiccation or heavy metals [37]. ...
Among various methods stimulating biological progress, double haploid (DH) technology, which utilizes the process of microspore embryogenesis (ME), is potentially the most effective. However, the process depends on complex interactions between many genetic, physiological and environmental variables, and in many cases, e.g., winter wheat, does not operate with the efficiency required for commercial use. Stress associated with low-temperature treatment, isolation and transfer to in vitro culture has been shown to disturb redox homeostasis and generate relatively high levels of reactive oxygen species (ROS), affecting microspore vitality. The aim of this study was to investigate whether controlled plant growth, specific tiller pre-treatment and culture conditions could improve the potential of microspores to cope with stress and effectively induce ME. To understand the mechanism of the stress response, hydrogen peroxide levels, total activity and the content of the most important low-molecular-weight antioxidants (glutathione and ascorbate), as well as the content of selected macro- (Mg, Ca, NA, K) and micronutrients (Mn, Zn, Fe, Cu, Mo) were determined. These analyses, combined with the cytological characteristics of the microspore suspensions, allowed us to demonstrate that an increased microspore vitality and stronger response to ME induction were associated with higher stress resistance based on more efficient ROS scavenging and nutrient management. It was shown that a modified procedure, combining a low temperature with mannitol and sodium selenate tiller pre-treatment, reduced oxidative stress and improved the effectiveness of ME in winter wheat lines.
... Evidências demonstram que o tratamento de sementes, com uso de soluções contendo Se, mostra-se eficaz para melhorar a tolerância de plantas a diversos estresses ambientais, entre eles o de Cd (NAWAZ et al., 2013). Estudos comprovam que o Se pode aumentar a tolerância das plantas à deficiência hídrica (HASANUZZAMAN; FUJITA, 2011;AHMAD et al., 2015b), aos metais pesados (KUMAR et al., 2012;GHORABA et al., 2015;PANDEY;GUPTA, 2015) como Cd (FILEK, 2008(FILEK, , 2010) e a outros fatores ambientais, podendo reduzir os danos causados por vários estresses e conferir diversos benefícios fisiológicos aos vegetais incluindo aumentos no crescimento (HARTIKAINEN et al., 2000). ...
O cádmio (Cd) é considerado como um dos poluentes agrícolas mais difundidos e prejudiciais, e devido sua alta mobilidade e fácil absorção pelas plantas, provoca, principalmente, a inibição do crescimento destas. Dentre as alternativas que visam solucionar os problemas induzidos pela contaminação com Cd em plantas, está o uso de atenuadores como o selênio (Se) que é considerado um elemento benéfico, podendo aumentar sua tolerância aos diversos estresses bióticos e abióticos. Nesse sentido, o objetivo do trabalho foi avaliar o efeito do selênio, no tratamento de sementes, sobre o desempenho inicial e a osmorregulação de plântulas de milho, em condições de estresse por cadmio. Utilizou-se sementes de milho híbrido (K9606 VIP 3) tratadas com selenito de sódio nas concentrações de 0,0; 1,5; 3,0 e 5,0 mg L-1 de Se e submetidas a diferentes dosagens de Cd (0,0; 1,3; 3,0 e 4,5 mg L-1). Foram avaliados: comprimento da raiz (CR); comprimento da parte aérea (CPA); matéria seca da raiz (MSR), matéria seca da parte aérea (MSPA); matéria seca total (MST) e as concentrações de carboidratos solúveis totais (CST), sacarose e prolina em folhas e raízes de milho. O delineamento experimental foi inteiramente casualizado em esquema fatorial 4 × 4, com quatro repetições, compostas por 25 subamostras cada. A presença de Cd reduziu o CR, CPA, MSR, MST e CST, provocando acréscimo nos teores de prolina e sacarose nas raízes e folhas. Em geral, o pré-tratamento com Se antes da exposição ao Cd promoveu aumento no CR, CPA, na produção de MSR e MSPA, com mitigação acentuada dos efeitos deletérios induzido pelo Cd, através de incrementos na prolina, sacarose e CST nas folhas, principalmente, na dose de 5 mg L-1 de Se.
... Moreover, selenium is able to increase the plant's antioxidant defense system (Hasanuzzaman and Fujita, 2011). In several horticultural species, it has been shown to retard fruit ripening and plant senescence (Hartikainen et al. 2000;Zhu et al. 2016;Zhu et al. 2017), this might reduce post-harvest loss. The same results were previously reported by (Hawrylak et al. 2010) on cucumber, (Hajiboland et al. 2015;Dawood et al. 2020) on wheat and (Tufail, et al. 2023) on lettuce. ...
The current study aimed to investigate the effects of inoculate application with arbuscular mycorrhizal fungi (AMF), Azospirillum brasilense bacteria (AZSB) and Azotobacter chrococcum bacteria (AZBB) individually or in combination with selenium spraying at rates 0, 25, 50 and 100 ppm as well as their interaction on vegetative growth, herb yield, chemical composition of leaf and volatile oil productivity of French basil (Ocimum basilicum L.) plants grown in salinity affected soil in sandy new reclamation land. A field trial was conducted in two successive seasons (2021 and 2022) at a private farm located at Sanur Village, Biba Bistrict, Beni-Suef Governorate, Egypt. The obtained results indicated that inoculated basil plants with the three microorganisms (AMF, AZSB, and AZBB) or/and spraying selenium at different concentrations significantly enhanced all vegetative growth parameters, herb yield, leaf main pigments and mineral composition, volatile oil content, and volatile oil yield. Also, the companies application of microorganisms and selenium application was superior to using each one individually. The highest values of investigated parameters were found in plants that were inoculated with AMF and sprayed with selenium at 50 or 100 ppm. Whereas there were no significant variations between the two higher selenium concentrations. Consequently, we recommended that inoculating French basil plants with AMF and selenium spraying at 50 ppm in the form of sodium selenite could be an effective method of enhancing the growth, yield, and oil productivity of plants grown in similar conditions.
... Moreover, selenium is able to increase the plant's antioxidant defense system (Hasanuzzaman and Fujita, 2011). In several horticultural species, it has been shown to retard fruit ripening and plant senescence (Hartikainen et al. 2000;Zhu et al. 2016;Zhu et al. 2017), this might reduce post-harvest loss. The same results were previously reported by (Hawrylak et al. 2010) on cucumber, (Hajiboland et al. 2015;Dawood et al. 2020) on wheat and (Tufail, et al. 2023) on lettuce. ...
... The application of Se strengthens the antioxidative level through increasing tocopherol and superoxide dismutase (SOD) levels (Xue et al., 2001). Senescence probably slows down by antioxidation, which correlated with the increasing of glutathione peroxidase activity delay (Hartikainen et al., 2000). Many other studies showed that Se significantly improved the activity of CAT (Yao et al., 2011;Malik et al., 2012). ...
Anise is one of the plants with therapeutic potential, which is classified among the most important
medicinal plants with interesting biological effects. Its components could be perceived so as “natural” and “safe”
alternatives to antibiotics as well as they are applied in different industries such as food and cosmetic purposes.
Selenium (Se) is an essential micronutrient, however, its importance to improve oil yield and quality of anise
has not been adequately investigated, specifically under drought. Therefore, two successive seasons were
conducted to investigate the effect of selenium foliar application upon anise plants under drought stress.
Selenium was applied at three different concentrations (0.0 1.0 and 2.0 mM denoted Se0, Se1 and Se2,
respectively) along with two levels of crop evapotranspiration (ET): Full irrigation, 100% of ET (FI) and 60%
of ET (DI). The promotive effect of combinations of DI × Se1 or Se2 (for Fv/Fm, RWC%, and MSI% in the
first season) and DI × Se2 (for Fv/Fm, and MSI% in the second season) were as similar as FI × Se2. Compared
to the counterpart control treatment (DI × Se0), the highest increases in total free amino acids (31.5 and
31.6%), total soluble sugars (84.2 and 86.4%) and free proline content (84.2 and 86.4%) were recorded with
application of DI × Se2 practice in both seasons, respectively. Under DI, Se2 recorded the maximum values of root length, shoot fresh weight and shoot dry weight in the second season. Under drought, the increases in seed
yield due to application of Se1 and Se2 amounted to 1.72 and 1.62 folds in the 1st season and 1.50 and 1.43 folds
in 2nd one, respectively. The most effective practice for improving IWUE was Se1× DI in both seasons, followed
by Se2 × DI. Based on the chromatographical detection, the maximum values of Anethole were recorded with
FI × Se2 while L-Linalool has greatly increased with DI × Se2. In conclusion, the growers in arid and semi-arid
zones are advised to use selenium (2.0 mM) in anise fertilization to mitigate the adverse impacts of drought,
and keeping crop yield and quality.
... Selenium (Se) has long been recognized as an essential micronutrient for animal and human nutrition, but the essentiality of Se to higher plants is still under debate (Terry et al., 2000;Germ et al., 2007). Growth stimulating effect of trace amounts of Se has been frequently reported in some plant species such as ryegrass (Hartikainen et al., 2000), lettuce (Xue et al., 2001), potato (Seppänen et al., 2003) and different varieties of Brassica oleracea (Hajiboland and Amjad 2007). At proper levels it also delays some of the effects of senescence (Djanaguiraman et al., 2005). ...
Selenium (Se) is a beneficial element for higher plants and its positive effect on plants growth and performance has been reported. Effect of Se under non-stress conditions especially during reproductive phase has not been attracted enough attention. In this work effect of Se supplementation at 0, 10 and 20 μg Se plant-1 was studied in canola (Brassica napus’RGS’) plants during vegetative and reproductive phase of growth under greenhouse conditions. Selenium addition resulted in a significant enhancement of dry matter production of vegetative parts as well as pod and seed dry weight. In addition, Se supplementation caused a considerable acceleration of reproductive events. In vegetative plants, higher photosynthesis rate, carbohydrates and protein content in the leaves was observed in Se treated plants compared with control. Our results suggested beneficial effect of Se on canola seed yield that may also contribute in improving nutritional value of canola for livestock and human.
... vitamin C content, total amino acid and polyphenol content, were significantly improved after treatment with selenium. By increasing the amount of selenium in plants a defensive role against external stress factors (UV-B radiation), a growth promoting response manifested as a decrease in lipid peroxidation, an increase in glutathione peroxidase activity and the enhanced growth of senescent ryegrass (Hartikainen et al., 2000) and lettuce (Xue et al., 2001) were confirmed. Seppänen et al. (2003) cited positive effects of selenium on photooxidative stress tolerance in selenium enriched potato. ...
Cultivated plants generally are a poor source of dietary selenium (< 0.1 mg/kg wet weight). In this work the influence of sodium selenate on selenium distribution in the chicory (Cichorium intybus L.) cultivars ‘Anivip’ and ‘Monivip’ was studied in an aeroponic system in a greenhouse. The plants roots were moistened every fifteen minutes with a Resh nutrient solution with added selenium (10 mg L-1) in the form of sodium selenate. The content of total selenium in chicory roots and leaves was studied after different periods of time and different temperatures of exposure to the selenium enriched nutrient solution. In two separate experiments chicory was treated with selenium enriched nutrient solution for 40 days at 10 ºC in the slow growing phase, and for 5, 7 and 10 days at 20 ºC in the developmental phase at the beginning of formation of the flower stem. The concentration in leaves increased with time during plant growth, and in Se treated groups was 370 and 139 mg kg-1 in ‘Anivip’ and 460 and 205 mg kg-1 in ‘Monivip’ leaves after 40 and 10 days of exposure, respectively. A smaller increase in selenium content was obtained in roots, namely to 73 and 46 mg kg-1 in ‘Anivip’ roots and to 87 and 46 mg kg-1 in ‘Monivip’ roots after 40 and 10 days of exposure, respectively. All results are expressed on a lyophilised matter basis. In long and short term treatment, the selenium content in ‘Monivip’ cultivar was higher than in ‘Anivip’. No visible toxic effects on the chicory plants were observed.
... In plants, Se functions as an antioxidant (Hartikainen, 2000). Plants take up Se from the soil primarily as selenate (SeO 4 2-) or selenite (SeO 3 2-) (Ellis and Salt, 2003). ...
Effect of selenium (Se) was studied in soybean (Glycine max (L.) Merr.) cv. Olna in Ljubljana, Slovenia. Se was added to plants as foliary spraying. Quantum yield of photosystem II (PSII) and respiratory potential measured as ETS activity of mitochondria were measured two times in the growing season. Respiratory potential was higher in young plants compared to mature plants. Se induced the lowering of respiratory potential. Addition of Se had no effect on quantum yield of photosystem II.
... A high concentration of nano-Se significantly stimulated the organogenesis and the growth of root system in tobacco callus cultures, which was completely inhibited by selenate 34 . According to Hartikainen et al. 71 , the improvement in ryegrass plant growth is believed to be due to the effect of SeNPs on preventing the initiation of growth promoter biosynthesis and/or its disruption. Alternatively, it may be due to a synergistic effect on the stimulatory action of the promoter by converting the inactive form to its promoter. ...
Sulfur (S) is an essential microelement for plants. Based on the chemical similarity between Se and S, selenium may affects sulphur uptake by plants. This work aimed at investigating the effect of foliar spray with sodium selenate, gum arabic coated selenium nanoparticles (GA-SeNPs ≈ 48.22 nm) and sodium sulfate on red kidney bean (Phaseolus vulgaris L.) plants. Each treatment was used at 0.0, 1, 5, 10 and 50 µM, alone or combination of sodium sulfate with either Se or nano-Se, each at 0.5, 2.5 and 5 µM concentrations. The effect of foliar spray on vegetative growth, seed quality, and some metabolic constituents of red kidney bean (Phaseolus vulgaris L.) plants were investigated. Selenium nanoparticles have been synthesized through the green route using gum arabic (as a stabilizing and coating agent. Foliar application of different concentrations of Se, nano-Se, Na2SO4 up to 10 μM and their interaction were effective in increasing the growth criteria (i.e. shoot and root lengths, plant fresh and dry weights, number of leaves and photosynthetic area (cm² plant⁻¹).There was also a significant increase in photosynthetic pigment contents, yield (i.e., 100-seed weight), total carbohydrate, crude proteins and mineral contents in both leaf as compared to their untreated control plants. Furthermore, interaction between sodium sulfate with nano-Se or Se, each at 5 µM significantly increased the vegetative growth, 100-seed weight, and pigment contents in leaves and improved the nutritional value and quality of red kidney bean seeds.
... In an experiment by Bocchini et al. (2018) Se-biofortified (CSe) maize plants showed improved water stress tolerance by increasing aerial biomass by 13% as compared to untreated (-Se) plants grown under water limiting conditions. Response of exogenous Se application on plants varies based on its concentrations applied as at lower rates, Se stimulated growth of ryegrass seedlings in pot experiments, while at high doses it acted as pro-oxidant reducing yields and induced metabolic disturbances (Hartikainen et al. 2000). At present, the effect of Se on wheat yield under drought stress is still controversial mainly due to different concentrations and methods used as presented in Table 21.1. ...
Drought is among the most dangerous consequences of climate change. It poses a substantial threat to agriculture, which reduces crop yields and impedes the realization of land’s full potential around the globe. This review article is divided into two sections: the effect of water stress on the physiological and biochemical features of crop plants and the amelioration of this effect by selenium treatment. In the first section, physiological and biochemical drought responses of crop plants are discussed. Drought stress has a detrimental effect on plant growth characteristics such as plant height, number of leaves and tillers per plant, and dry weight of various plant parts. This is as a result of decreased relative water content (RWC), which closes stomata and consequently decreases transpiration rate, stomatal conductance, and photosynthesis. In the second section, physiological and biochemical alterations generated by selenium (Se) in plants under drought stress are reviewed. Selenium’s antioxidant properties enable it to mitigate the negative effects of drought-induced stress on plants. The accumulation of metabolites is accompanied by the activation of catalase, superoxide dismutase, ascorbate peroxidase, and glutathione peroxidase. By promoting the accumulation of osmolytes, Se plays a crucial function in the maintenance of water relations such as leaf water potential and RWC. Osmotic adjustment increases drought tolerance by allowing cell expansion, plant development, and stomata to remain partially open, as well as by maintaining stomatal conductivity, photosynthesis, and transpiration. Therefore, Se improves the quality of grains by promoting the absorption and translocation of many micro- and macroelements whose uptake was reduced under drought.
In this study, we aimed to determine the optimal concentration of selenium (Se) required to increase the bioactive compound content, growth, antioxidant capacity, and photosynthetic parameters in Agastache rugosa. We investigated the effects of various concentrations of Se (0, 2.5, 5, 10, 20, and 40 µmol mol− 1) on the growth, chlorophyll contents, total carotenoid contents, photosynthetic characteristics, antioxidant enzyme activities, and bioactive compound contents in A. rugosa plants. High Se concentrations, particularly 20 and 40 µmol mol− 1, significantly enhanced almost all plant growth parameters, including the flower branch number, flower fresh weight (FW), leaf area, stem length, shoot FW, stem FW, root dry weight (DW), flower DW, shoot DW, and overall plant DW. Total chlorophyll and chlorophyll a contents were significantly increased with 20 µmol mol− 1 Se, and the total carotenoid contents were significantly increased with 5, 10, 20, and 40 µmol mol− 1 of Se compared to those in the untreated treatment. Additionally, net photosynthetic rate was significantly increased after 20 and 40 µmol mol− 1 Se treatments. Furthermore, total flavonoid and phenolic contents and antioxidant enzyme activities (superoxide dismutase, 2,2-diphenyl-1-picrylhydrazyl radical-scavenging, peroxidase, and catalase) were significantly elevated after high-concentration Se treatments. Specifically, rosmarinic acid and acacetin 1 contents peaked with 20 µmol mol− 1 Se, whereas tilianin and acacetin contents were significantly higher in the 10 µmol mol− 1 Se treatment group than in the untreated group. Acacetin 2 and 3 contents were the highest after 20 µmol mol− 1 Se treatment. Overall, our findings suggest that Se, particularly at 20 and 40 µmol mol− 1, positively influences the growth, photosynthetic characteristics, bioactive compound content, and antioxidant enzyme activity in A. rugosa plants, thereby enhancing the plant productivity and quality.
Human recombinant epidermal growth factor (EGF) promotes cell proliferation
as well as skin remodeling and healing. However, it’s unclear if EGF is
stable in in vitro cell culture medium treatment conditions. Since EGF’s instability
in aqueous solutions has resulted in different kinds of challenges, novel
treatment approaches that preserve EGF’s stability and usefulness have been
developed. The current study examined the effects of the antioxidants sodium
selenite (Se), disodium ethylenediaminetetraacetic acid dihydrate (EDTA),
zinc chloride (Zn), and ascorbic acid (AA) on the stability of EGF in cell culture
using Dulbecco’s Modified Eagle Medium (DMEM) and Roswell Park
Memorial Institute 1640 medium (RPMI), as well as their ability to scavenge
free radicals. In vitro, DMEM and RPMI serum free medium with 2.5 μM of
EDTA, Se, AA, and Zn antioxidants were used separately at 37˚C for three
days to examine the stability of EGF. The stability of EGF was evaluated using
reversed phase high-performance liquid chromatography (RP-HPLC). Cells
were cultivated for 3 days to further estimate the impact of antioxidants on
cell cytotoxicity and proliferation using the MTT assay with NIH-3T3, L929,
TF-1, and Sp2/0-Ag14 cell types. The antioxidants EDTA, Se, AA, and Zn at
an extracellular concentration of 2.5 μM improved EGF stability in both
DMEM and RPMI medium while having no effect on the proliferation of NIH-
3T3, L929, TF-1, and SP2/0-Ag14 cells.
Open Access to Publication: https://www.scirp.org/journal/paperinformation?paperid=141142
Selenium (Se) is a key mineral element beneficial for normal plant development. However, the importance of Se in altering nitrate reductase (NR) and nitrite reductase (NiR) activities to enhance grain storage protein abundance and mineral contents remains unclear. In this study, we assessed the positive responses of Se with various NO3− and NH4+ fertilizers on nutrient accumulation and storage proteins of wheat. Se (Na2SeO4) was applied as a foliar spray (75 mg Se L−1) and via fertigation (40 g Se ha−1) at grain filling stage (80 days after sowing) alongside three splits of the recommended level of different nitrogen (N) fertilizer sources (urea, calcium ammonium nitrate [CAN], nitrophos (NP) and ammonium sulfate [AS]). Foliar Se application combined with urea fertilization significantly increased NR and NiR activities in cv. Anaj-17 compared to urea application without Se. Storage protein fractions including albumin, globulin, prolamin, and glutelin were also higher with foliar Se supplementation + urea application compared to AS or CAN fertilization. Mineral accumulation in wheat grains was significantly enhanced, with increased concentrations of Se, iron (Fe), zinc (Zn), and potassium (K) observed following foliar Se application in cv. Anaj-17. Foliar Se spraying notably boosted mineral concentrations, particularly grain Se levels while the combination of various N fertilizers with Se supplementation resulted in marked variations. Moreover, photosynthetic rate (A), transpiration rate (E), stomatal conductance (Ci) and substomatal conductance (gs) were higher in cv. Anaj-17 than Ujala-16 when treated with foliar Se + urea fertilizer. While Se application had some influence on yield attributes, significant variations were observed in response to different N fertilizers. The yield attributes were affected to some extent by Se application while these characteristics varied significantly in response to different N fertilizers. In conclusion, Se supplementation as a foliar spray combined with urea as an N fertilizer considerably increased wheat grain protein fractions by boosting N metabolism enzymatic activities (NR and NiR) and increased mineral accumulation, thereby improving the nutritional value of wheat.
Nanotechnology is believed to accelerate our fight to sustain and enhance crop productivity for the ever-increasing world population. It has been reckoned as one of the safest and most cost-efficient techniques to boost crop productivity in the future. The ever-increasing state-of-the-art availability of various nanomaterials has allowed us to pursue their beneficial properties in agronomy. Nanotechnology will help minimize the dependency on chemical fertilizers and existing crop production techniques that have already been exploited to their maximum potential. Therefore, in the present context, it could well be realized that agriculture will be driven by nanotechnology in the future.
This book focuses on the application of nanotechnology for enhancing crop production through the application of nanofertilizers or nanocomposites. Several avenues of nanotechnology are beneficial in improving crop productivity in a sustainable manner, which has been presented in a comprehensive way. The book also delves into the mechanistic view of nanoparticle functioning and its role in stress alleviation. In addition, the book presents some recent insights into the application of nanotechnology for post-harvest management, stress tolerance and usage as nanobiosensors.
Broadly, the book will encompass the following advances in the field, distinguishing it from other published volumes. The salient features include:
· Role of nanoparticles in improving abiotic stress tolerance in plants.
· Role of nanoparticles in protection against pathogens and pests.
· Mechanism of nanoparticle-induced plant responses.
· Synthesis and modification of nanoparticles to enhance their biological efficacy.
· Prospects of nanofertilizers, nanoformulations, nanopesticides, etc., and their beneficial attributes.
This book, therefore, presents this emerging topic and the most recent innovations in this field for postgraduate students, researchers and faculty members working in the fields of plant science, microbiology, biotechnology, agricultural sciences, etc.
Raziskan je bil vpliv okoljskega sončnega sevanja z in brez UV-B dela spektra ter foliarnega gnojenja z raztopino selenata na pridelek bučnic buče golice (Cucurbita pepo L.) Pridelek semen na enoto površine je bil večji, ko je bil s filtriranjem UV-B sevanja odstranjen vpliv tega dela spektra na rastline, v primerjavi z vplivi celotnega sončnega spektra. Na osnovi rezultatov se ugotavlja, da je manjši pridelek v razmerah celotnega sončnega spektra odvisen od antioksidativnih poškodb, ki jih povzroča UV-B sevanje, saj je foliarno tretiranje z raztopino selenata zmanjšalo negativen vpliv tega sevanja.
The combined effect of selenium (Se) foliar spraying and drought was studied for 3 months in two cultivars of potato; Bard and Adora in Ljubljana, Slovenia. Four combinations of treatments were conducted: well-watered plants with and without Se foliar spraying, and drought exposed plants with and without Se foliar spraying. Net photosynthesis, transpiration rate, quantum yield of photosystem II (PSII), and respiration potential measured by electron transport system activity were monitored throughout the period. After three months of treatment, leaf water potential, the number and size of leaf stomata, and tuber yield were determined. Several impacts of drought and Se application and their combinations were established, and the responses shown to be cultivar-specific. Net photosynthesis, transpiration rate, effective quantum yield of PSII, and respiratory potential were lower in drought exposed plants. Se lowered respiratory potential in the leaves in cv. Bard. The mass of the tubers in cv. Adora, and photosynthesis in cvs. Bard and Adora were lower in Se treated plants. Se treatment did not significantly affect the number and size of leaf stomata in the cultivars.
Arsenic (As), a toxic metalloid and human carcinogen, has caused severe soil pollution around the world. Pteris vittata is the first known As hyperaccumulator and has been widely and successfully used to remediate As-contaminated soils. Mineral nutrients are crucial for As transfer in soil and As uptake, translocation, detoxification and accumulation in P. vittata. In addition, rhizosphere microbes also play a role in As mobilization, transformation, and plant As uptake. This review summarizes the effects of water status, nutrient elements (phosphorus, sulfur, selenium and calcium), and rhizosphere microbes on the efficiency of phytoextraction of As by P. vittata, providing insights into improvement of phytoremediation in future.
Cadmium (Cd) contamination in paddy soil significantly threatens food safety and demands immediate attention in modern agriculture. The uptake of Cd by plant roots, facilitated by transporters involved in nutrient uptake, contributes to its accumulation in rice grains. To mitigate Cd accumulation in rice crops, reducing its bioavailability and controlling plant uptake is crucial. Various strategies, including the application of biochar and selenium (Se), have been proposed to address Cd toxicity in contaminated soils. Biochar and Se have effectively reduced Cd toxicity in rice crops through mechanisms such as Cd immobilization and sequestration in vacuoles. This review provides a comprehensive overview of past methods, such as chemical stabilization, and novel approaches, including biochar amendment, biochar modification, and Se-assisted Cd immobilization, in current research on Cd toxicity and its mitigation. Additionally, we examine the fate of Cd in paddy fields, Cd transport processes from soil to grains, and the adverse effects of Cd stress on rice plant growth, physiology, yield, and human health. The overall objective of this review is to enhance understanding of the environmental risks associated with Cd in rice ecosystems and the remediation effects of biochar and Se.
The effect of Se-fertilization on the chemical composition and anti-oxidative properties of ryegrass and lettuce was studied in a pot experiment. The addition of Se enhanced its relative incorporation in soluble and insoluble proteins and diminished it in free amino acids. It also affected the anti-oxidative systems of the plants. The glutathione peroxidase (GSH-Px) activity found in both plant species increased with increasing Se-fertilization, whereas the superoxide dismutase (SOD) activity as well as the concentration of vitamin E decreased. This may indicate that the synthesis of SOD and vitamin E was reduced because the requirement of these anti-oxidants was diminished by antioxidative function of Se.
This study describes the O2 uptake characteristics of intact roots of Brachypodium pinnatum. In the presence of 25 mM salicylhydroxamic acid (SHAM), concentrations of KCN below 3.5 ?M had no effect on the rate of root respiration, whereas in the absence of 25 mM SHAM a significant inhibition of approx. 18% was observed. This indicates that an O2-consuming reaction, not associated with the cytochrome pathway, the alternative pathway or the “residual component”, operates in the absence of any inhibitors in roots of B. pinnatum. We demonstrate here that this fourth O2-consuming reaction is mediated by a peroxidase. A peroxidase which catalyzed O2 reduction in the presence of NADH was readily washed from the roots of B. pinnatum. This peroxidase was stimulated by 5 mM SHAM, whereas ascorbic acid, catalase, catechol, gentisic acid, low concentrations potassium cyanide (3.5 µM), sodium azide, sodium sulfide, superoxide dismutase and high concentrations SHAM (25 mM) inhibited this reaction. Except for high concentrations of SHAM and concentrations of KCN higher than approx. 3.5 µM, these effectors could not be used to inhibit the peroxidase-mediated O2 uptake in intact roots of B. pinnatum. Concentrations of SHAM below 10 mM stimulated O2 uptake up to 15% of the control rate, depending on concentration, whereas 25 mM SHAM inhibited O2 uptake by 35%. The stimulation at low concentrations resulted from a SHAM-stimulated peroxidase activity, whereas 25 mM SHAM completely inhibited both the peroxidase-mediated O2 uptake and the activity of the alternative pathway. A method is presented for determining the relative contributions of each of the four O2-consuming reactions, i.e. the cytochrome pathway, the alternative pathway, the “residual component” and the peroxidase-mediated O2 uptake. The peroxidase-mediated O2 uptake contributed 21% to the total rate of oxygen uptake in roots of B. pinnatum, the cytochrome pathway contributed 41%, the alternative pathway 14% and the “residual component” 24%.
Selenium (Se) is able to defend human and animal cells against UV(B) stress. Higher plants are gener-ally considered not to require Se but to have a low tolerance to it. However, recently it has been dem-onstrated that Se is able to protect also plants against UV-induced oxidative stress and even to pro-mote the growth of plants subjected to high-energy light. In the present study the effects of Se on anti-oxidative enzymes possibly associated with this synergistic effect were investigated. Ryegrass and lettuce were grown in soil supplemented with Se at 0, 0.1 or 1.0 mg kg -1 under normal light or sub-jected to UV episodes. Lipid peroxidation and the changes of antioxidative enzymes were measured at two growing stages. The positive synergistic effect of the lower Se dosage and UV was found to be at least partly associated with the antioxidative role of Se through increased glutathione peroxidase (GSH-Px) and catalase (CAT) activity, whereas ascorbate peroxidase (APX) responded negatively to both factors. The contribution of the other enzymes studied seemed to be plant-specific: glutathione S-transferase (GST) increased in both ryegrass assays and superoxide dismutase (SOD) in the first let-tuce assay. At the higher addition level Se acted as a pro-oxidant and diminished fresh weight yields. UV irradiation alleviated the toxicity coincidently with increase of CAT in ryegrass and SOD in let-tuce.
Selenium which occurs in proteins as the amino acid, selenocysteine, is essential for numerous biological processes and for human health. A prominent 75Se-labeled protein detected in human T-cells migrated as a 15-kDa band by SDS-polyacrylamide gel electrophoresis. This protein subunit was purified and subjected to tryptic digestion and peptide sequence analyses. Sequences of tryptic peptides derived from the protein corresponded to a human placental gene sequence containing an open reading frame of 162 residues and a readthrough in-frame TGA codon. Three different peptide sequences of the 15-kDa protein corresponded to a nucleotide sequence located downstream of this codon, suggesting that the T-cell 15-kDa selenoprotein contains a selenocysteine residue encoded by TGA. Post-translational processing of the N-terminal portion of the predicted gene product to give the 15-kDa protein was suggested on the basis of molecular mass, amino acid analysis, and immunoblot assays of the purified protein. The 3'-untranslated region (UTR) of the gene encoding the 15-kDa protein contained a sequence that is very similar to the canonical selenocysteine-inserting sequence element. Computer analysis of transcript map data bases indicated that this gene was located on human chromosome 1. Its coding sequence showed no homology to known protein-encoding genes. The 15-kDa protein gene was expressed as mRNA in a wide range of tissues, with increased levels in the thyroid, parathyroid, and prostate-derived cells as evidenced by searches of partial cDNA sequences in public data bases. Genes corresponding to the 15-kDa selenocysteine-containing protein were found in mice and rats, while the corresponding genes in Caenorhabditis elegans and Brugia malayi contained a cysteine codon in place of TGA. The discovery of a new human selenoprotein provides an additional example of the role of selenium in mammalian systems.
To determine glutathione peroxidase reliably, some factors of potential pitfall have to be considered, for example, enzymatic side reactions of substrates (especially when crude tissue samples are assayed), high and variable spontaneous reaction rates of substrates, and the peculiar kinetics of the enzyme itself. With the best documented example, the enzyme of bovine red blood cells, ping-pong kinetics with infinite limiting maximum velocities, and Michaelis constants have been established. This means that the generally recommended conditions for determination of enzyme activity––that is, “saturating” concentrations of all substrates, cannot possibly be fulfilled. In consequence, compromises are inevitable in the choice of substrate concentration for the assay and in the definition of the unit of activity. Fixed-time assay measuring H2O2 consumption and continuous monitoring of Glutathione disulfide (GSSG) formation are cited here. The main differences between the assay procedure described and those proposed by others are listed in the chapter. To compare the results obtained by different procedures, appropriate empirical converting factors are also given.
Human placenta thioredoxin reductase (HP-TR) in the presence of NADPH-catalyzed reduction of (15S)-hydroperoxy-(5Z),(8Z),11(Z),13(E)-eicosatetraenoic acid ((15S)-HPETE) into the corresponding alcohol ((15S)-HETE). Incubation of 50 nM HP-TR and 0.5 mM NADPH with 300 microM 15-HPETE for 5 min resulted in formation of 16.5 microM 15-HETE. After 60 min, 74.7 microM 15-HPETE was reduced. The rate of the reduction of 15-HPETE by the HP-TR/NADPH peroxidase system was increased 8-fold by the presence of 2.5 microM selenocystine, a diselenide amino acid. In this case, 15-HPETE was catalytically reduced by the selenol amino acid, selenocysteine, generated from the diselenide by the HP-TR/NADPH system. To a smaller extent, selenodiglutathione or human thioredoxin also potentiated the reduction of 15-HPETE by HP-TR. Hydrogen peroxide and 15-HPETE were reduced at approximately the same rate by HP-TR, thioredoxin, and selenocystine. In contrast, t-butyl hydroperoxide was reduced at a 10-fold lower rate. Our data suggest two novel pathways for the reduction and detoxification of lipid hydroperoxides, hydrogen peroxide, and organic hydroperoxides, i.e. the human thioredoxin reductase-dependent pathway and a coupled reduction in the presence of selenols or selenide resulting from the reduction of selenocystine or selenodiglutathione.
We report the isolation and characterization of a new selenoprotein from a human lung adenocarcinoma cell line, NCI-H441. Cells were grown in RPMI-1640 medium containing 10% (vol/vol) fetal bovine serum and 0.1 microM [75Se]selenite. A 75Se-labeled protein was isolated from sonic extracts of the cells by chromatography on DE-23, phenyl-Sepharose, heparin-agarose, and butyl-Sepharose. The protein, a homodimer of 57-kDa subunits, was shown to contain selenium in the form of selenocysteine; hydrolysis of the protein alkylated with either iodoacetate or 3-bromopropionate yielded Se-carboxymethyl-selenocysteine or Se-carboxyethyl-selenocysteine, respectively. The selenoprotein showed two isoelectric points at pH 5.2 and pH 5.3. It was distinguished from selenoprotein P by N-glycosidase assay and by the periodate-dansylhydrazine test, which indicated no detectable amounts of glycosyl groups on the protein. The selenoprotein contains FAD as a prosthetic group and catalyzes NADPH-dependent reduction of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), and reduction of insulin in the presence of thioredoxin (Trx). The specific activity was determined to be 31 units/mg by DTNB assay. Apparent Km values for DTNB, Escherichia coli Trx, and rat Trx were 116, 34, and 3.7 microM, respectively. DTNB reduction was inhibited by 0.2 mM arsenite. Although the subunit composition and catalytic properties are similar to those of mammalian thioredoxin reductase (TR), the human lung selenoprotein failed to react with anti-rat liver TR polyclonal antibody in immunoblot assays. The selenocysteine-containing TR from the adenocarcinoma cells may be a variant form distinct from rat liver TR.
The iodothyronine deiodinases are a family of selenoproteins that metabolize thyroxine and other thyroid hormones to active
and inactive metabolites in a number of tissues including brain. Using primary cultures of rat astroglial cells as a model
system, we demonstrate that the mRNA for the type II iodothyronine deiodinase (DII) selenoenzyme is rapidly and markedly induced
by forskolin and 8-bromo-cAMP. The induction of DII activity, however, was significantly impaired by culturing cells in selenium-deficient
medium for 7 days. Under such conditions, the addition of selenium resulted in a rapid increase in cAMP-induced DII activity
that was dose-dependent, with maximal effects noted within 2 h. Cycloheximide blocked this effect of selenium on restoring
cAMP-induced DII activity, whereas actinomycin D did not. These data demonstrate that the DII selenoenzyme is expressed in
cultured astrocytes and that the induction of DII activity by cAMP analogues appears to be mediated, at least in part, by
pretranslational mechanisms. Furthermore, selenium deprivation impairs the expression of DII activity at the level of translation.
The protective role of selenium (Se), given as a Se-rich yeast, selenomethionine or selenomethionine + vitamin E supplement, toward changes in lipid, peroxide, and fatty acid distribution in tissues of streptozotocin-induced diabetic rats, was investigated, after 24 wk of disease. Diabetes increased liver thiobarbituric acid-reactive substances and conjugated dienes; Se supplement completely corrected these changes. In kidney, as in heart, the peroxide levels were not significantly changed by diabetes. In diabetic rat liver, a significant drop in triglycerides and phospholipids (P < 0.05) was observed; this was modulated by Se + vitamin E supplementation. Se + vitamin E supplementation also inhibited the decrease in 18:2n-6 and the increase in 22:6n-3 observed in liver of diabetic rats, changes which reflect altered glycemic control. In kidney, heart, and aorta, diabetes produced some changes in lipid content and fatty acid distribution, especially an increase in heart triglycerides which was also corrected by the Se supplement. Se supplementation to diabetic rats also increased 18:0 ether-linked alcohol, 20:4 n-6, and 22:5 n-3 in cardiac lipids. In aorta, Se + vitamin E significantly increased 20:5 n-3. These polyunsaturated fatty acids are precursors, in situ, of prostaglandin I2 (PGI2) and PGI3 which may protect against cardiovascular dysfunction. In kidney, conversely, Se decreased 20:4 n-6, the precursor of thromboxane A2 implicated in diabetic glomerular injury. Thus Se, and more efficiently Se + Vitamin E supplementation, in experimental diabetes could play a role in controlling oxidative status and altered lipid metabolism in liver, thereby maintaining favorable fatty acid distribution in the major tissues affected by diabetic complications.
Selenomethionine and methionine were compared as substrates for in vitro aminoacylation, ribosome binding, and peptide bond formation with preparations from wheat germ. Selenomethionine paralleled methionine in all steps of the translation process except peptide bond formation. Peptide bond formation with the initiating species of tRNA(Met) demonstrated that selenomethionyl-tRNA(Met) was less effective as a substrate than was methionyl-tRNA(f) (Met). Participation of selenomethionine in the initiation process of translation could be expected to reduce the overall rate of protein synthesis and might aid in explaining selenium toxicity in selenium-sensitive plants.
Thalassiosira pseudonana Husedt (Hasle and Heimdal) clone 3H was grown in axenic culture in artificial seawater medium containing 10(-8) molar Na(2) (75)SeO(3). Biochemical distribution of radiolabeled Se was determined by solvent extraction techniques, gel filtration, and polyacrylamide gel electrophoresis. Of the total cellular Se, 51% was protein bound. Two soluble macromolecules of 21 and 29 kilodaltons contained (75)Se. These results are the first to provide evidence of specific Se-containing compounds in a photosynthetic organism. Glutathione peroxidase (GSH-Px) activity was measured in cell-free extracts and on nondenaturing polyacrylamide gels by a glutathione-reductase coupled assay. Two enzymes showing GSH-Px activity were present. One enzyme was active with H(2)O(2) and tert-butyl hydroperoxide (tBOOH); consistent with known Sedependent GSH-Pxs, but the other enzyme was only active with tBOOH. Co-migration of the H(2)O(2)-active GSH-Px and (75)Se on nondenaturing polyacrylamide gels provides evidence that T. pseudonana contains a Sedependent GSH-Px. The molecular weight of one of the (75)Se-labeled macromolecules is identical with the weight of previously characterized GSH-PX subunits. We conclude that the obligate requirement for Se in Thalassiosira pseudonana is due in part to the presence of the selenoenzyme glutathione peroxidase.
The original two supplementation levels of selenium in multinutrient fertilizers (Se 16 and 6 mg kg-1 fertilizer as sodium selenate; started in 1985) were reduced to one (6 mg kg-1 fertilizer) in 1991. The 16 mg supplementation level was intended for use in cereal production. Due to the lowering of the level of Se application, the Se content of spring cereals (spring wheat, oats and barley) has decreased more than that of any other food in the monitoring programme. The present level, 0.1 mg kg-1 for cereal grains, is about 40% of the concentrations common in 1990. The Se concentrations have decreased less in other foods than in cereals. The present Se concentrations in milk products, meat and liver are about 70, 60 and 50%, respectively, of the concentrations in 1990. The average daily human Se intake was 0.08 mg day-1 at an energy level of 10 MJ in 1994. Animal protein is the main source of Se. About 40% of the intake comes from meat, 24% from dairy products and eggs, and 11% from fish.
A type III iodothyronine deiodinase (D-III) that inactivates thyroid hormones has been recently cloned and identified as a selenoprotein in neonatal rat skin. However, selenium (Se) deficiency does not affect the D-III activity in the rat placenta and decreases the D-III in the rat brain only slightly. This study examines the effect of Se on the D-III activity in cultures of rat brain astrocytes. Astrocytes were depleted in Se by maintaining them in Se-free chemically defined medium for 7 days. These conditions decreased the activity of a recognized selenoprotein, glutathione peroxidase, 3-10-fold. D-III activity induced by 12-0-tetradecanoylphorbol-13-acetate (TPA) was also decreased 2-6-fold. Addition of 30 nM Se to the culture medium caused a rapid increase in TPA-induced D-III activity visible within 1 h. This Se effect was maximal at 3 h (4-fold increase) and dose-dependent. Se also increased the induction of D-III by acidic Fibroblast Growth Factor, 8-bromo-cAMP, T4, or retinoic acid. Cycloheximide ...
This paper presents an high-performance liquid chromatographic (HPLC) method for the determining of alpha-tocopherol in small samples of fresh plant material. Ryegrass was used as the test material. The samples of 5-100 mg are saponified for 30 min at 60 degrees C. After evaporating the n-hexane extract of the unsaponifiables and dissolving the residue in n-hexane, the sample is ready for the HPLC analysis. The HPLC system involves an amino column, n-hexane-isopropanol (99:1) flowing at the rate of 2 ml/min as the mobile phase and a fluorescence detector. The recovery of alpha-tocopherol added to ryegrass samples was 110 % when the quantification was based on an alpha-tocopherol standard run through the whole sample preparation procedure. The variation in the alpha-tocopherol contents was 11 % (coefficient of variation CV %) when 18 samples ranging 5-100 mg were analysed within one day. The day-to-day variation was only 4.6 % when samples of 50-100 mg were analysed. The results confirm that this simple, rapid and sensitive method is suitable both for routine analysis of fresh plant tissues and for plant physiological studies where live plants are to be monitored by repeated sampling.
The toxicity of selenium to animals and plants has been known and extensively documented since the 1930's, but it is only during the past 15 years that selenium has also been shown to be an essential micronutrient for animals and bacteria. Very little is known about the specific role or roles of selenium and, to date, there are only three enzyme-catalyzed reactions that have been shown to require the participation of a selenium-containing protein. These are the reactions catalyzed by (i) formate dehydrogenase of bacteria, (ii) glycine reductase of clostridia, and (iii) glutathione peroxidase of erythrocytes. The common denominator of these selenium-dependent processes is that they are all oxidation-reduction reactions. A fourth selenoprotein has been isolated from skeletal muscle of sheep but its catalytic function has not been identified. The form in which selenium occurs in these selenoproteins is unknown. The selenoprotein of clostridial glycine reductase contains selenium in a covalently bound form. Studies in progress indicate that this may be an organoselenium compound not previously detected in nature. Identification of the chemical nature of selenium in proteins participating in electron transport processes should enable us to determine its specific role and to understand the basic defects in certain cardiac and skeletal muscle degenerative diseases which are selenium-deficiency syndromes. The greater availability and ease of isolation of the selenoprotein of the bacterial glycine reductase system makes this the biological material of choice for studies on the mechanism of action of selenium. An added attractive feature of this system is that it can conserve the energy made available by the reductive deamination of glycine in a biologically useful form by synthesizing ATP.
Selenium (Se) has chemical properties similar to sulfur, but slight differences can lead to altered tertiary structure and dysfunction of proteins and enzymes, if selenocysteine is incorporated into proteins in place of cysteine.
In some areas of California with irrigation agriculture elevated Se concentration in drainage and shallow groundwaters caused bioaccumulation of Se in wetlands and Se toxicity to wildlife. Among higher plants Se accumulators are tolerant to high Se concentrations whereas non‐accumulators are Se‐sensitive. Algae show a requirement of Se for growth and development, but no Se essentiality has been demonstrated for higher plants, possibly with the exception of Se accumulators. Higher plants take up Se preferentially as selenate via the high affinity sulfate permease. Contents of Se in agricultural crops are usually below 1 mg kg ⁻¹ DW, and hence such crops are considered safe for human and animal consumption even when grown on moderately high Se soils. Sulfate salinity inhibits uptake of selenate by many plant species.
Assimilation of selenate by non‐accumulators leads to synthesis of selenocysteine and selenomethionine; Se‐cysteine is readily incorporated into proteins. High Se can interfere with S and N metabolism in non‐accumulators. In contrast, Se accumulators sequester Se mainly in non‐protein selenoamino acids. Among several selenoenzymes identified in bacteria and mammals, Se‐dependent glutathione peroxidase which catalyses the reduction of organic peroxides and H 2 O 2 has been demonstrated convincingly in algae; in higher plants, however, the experimental evidence regarding its occurrence is controversial. All organisms including higher plants contain Se‐cysteyl‐tRNAs that decode UGA. Selenocysteine is proposed to function as 21st proteinaceous amino acid and thus is suggested to have a biological role in higher plants.
Biogeochemical cycling of Se involves significant volatilization of methylated selenides such as dimethyl selenide to the atmosphere from higher plants as well as freshwater algae, but Se exchange between oceans and the atmosphere appears to proceed as net flux to the oceans.
Publisher Summary This chapter focuses on the diversity of glutathione peroxidases. Selenium was identified as a toxic factor for grazing animals in the first half of the twentieth century and since then has been considered hazardous. Only long after the identification of the first selenoenzymes in bacteria and mammals was a Recommended Dietary Allowance gradually established. In fact, the putative biological roles of the selenoenzymes, particularly those of the glutathione peroxidases (GPX), proved instrumental in the understanding of selenium deficiency syndromes in livestock and humans, although the emerging complexity of selenium enzymology still precludes definitive conclusions. The selenium-dependent peroxidases have long been considered a late achievement of evolution, as they were only detected in vertebrates. This view now has to be revised. Whether the common ancester of the GPX superfamily was a selenoprotein or a cysteine-containing homolog cannot be deduced from the available sequences. The only prokaryotic member of the superfamily detected so far, a cobalamine-binding protein of Escherichia coli , does not contain selenocysteine, and despite ongoing efforts, functionally active glutathione peroxidases have not yet been found in prokaryotes.
S ummary
Reactions involving free radicals are an inherent feature of plant senescence and appear to contribute to a process of oxidative deterioration that leads ultimately to cell death. Radical species derived from molecular oxygen are the primary mediators of this oxidative damage, but non‐radical excited states of oxygen, specifically singlet oxygen, may also be involved.
Several lines of evidence suggest that degradation of lipids in senescing membranes and the ensuing release of free fatty acids initiate oxidative deterioration by providing substrate for lipoxygenase. In some tissues, lipoxygenase activity increases with advancing senescence in a pattern that is consistent with its putative role in promoting oxidative damage. However, there are important exceptions to this which may be explained by the fact that the timing and extent of peroxidative reactions initiated by lipoxygenase are likely to be determined more by the availability of substrate for the enzyme than by changes in its activity. There are both membranous and cytosolic forms of lipoxygenase in senescing tissues, and peroxidation of membrane lipids appears to be initiated by the membranous enzyme once the appropriate fatty acid substrates, linoleic acid and linolenic acid, become available. Since lipid peroxidation is known to form alkoxy and peroxy radicals as well as singlet oxygen, these reactions in membrane bilayers are probably a major source of activated oxygen species in senescing tissues. Further‐more, there are indications that activated oxygen from the lipoxygenase reaction can become substrate for the cytosolic form of the enzyme which, in turn, may raise the titre of activated oxygen during senescence. Additional possible sources of increased free radical production in senescing tissues include peroxidase, which shows greatly increased activity with advancing age, leakage of electrons from electron transport systems to oxygen, in particular from the photosynthetic electron transport system, and decompartmentalization of iron, which would facilitate formation of the highly reactive hydroxyl radical from the less reactive superoxide anion.
A variety of macromolecules can be damaged by activated oxygen. Unsaturated fatty acids are especially prone to attack, and this implies that membranes are primary targets of free radical damage. The manifestations of this damage in senescing tissues range from altered membrane fluidity and phase properties to leakiness that can be attributed to a destabilized and highly perturbed membrane bilayer. There is also a progressive breakdown of cellular protein with advancing senescence. Free radicals can inactivate proteins by reacting with specific amino acid residues, and a number of in zitro studies have indicated that such alteration renders the proteins more prone to hydrolysis by proteases. Thus, although there is no direct evidence linking enhanced proteolysis during senescence to free radical damage, there is reason to believe that this may be a contributing factor.
Wounding of certain plant tissues also initiates a series of reactions that revolve around the breakdown of membrane lipids and their peroxidation. Indeed, as in the case of senescence, membrane deterioration follokving wounding appears to be facilitated by a self‐perpetuating wave of free radical production emanating from peroxidation within the lipid bilayer. There is also recent evidence for activation of an O 2 ⁻ ‐producing NADPH oxidase in plant tissues following fungal infection that may be analogous to the well‐characterized O 2 ⁻ ‐generating NADPH oxidase associated with the plasma membrane of polymorphonuclear leukocytes. This raises the interesting possibility that plants and animals share a common defence response to invading organisms.
C ontents
Summary
317
I.
Introduction
318
II.
Species of activated oxygen
319
III.
Sites of activated oxygen production
319
IV.
Free radical production during senescence
323
V.
Targets of free radical damage in senescing tissues
330
VI.
The role of free radicals in seed ageing
336
VII.
The role of free radicals in wounding
337
VIII.
Concluding remarks
338
Acknowledgement
338
References
338
The metabolism of hydrogen peroxide by the scavenging system was studied in Chlamydomonas grown in a selenium-lacking and a selenium-containing medium. In cells of the former, 40% of external hydrogen peroxide (H2O2) was scavenged by ascorbate peroxidase (AsAP; EC 1.11.1.11) and the residual H2O2 by catalase (EC 1.11.1.6). The enzymes involved in the ascorbate-glutathione cycle including AsAP. were localized in the chloroplast. In cells of the latter, glutathione peroxidase (GSHP; EC 1.11.1.9) functioned primarily in the removal of external H2O2. GSHP was located solely in the cytosol. The Chlamydomonas AsAP was relatively stable in ascorbate-depleted medium as compared with chloroplast AsAP of higher plants. No inactivation of the enzyme was found upon its incubation with hydroxyurea, an inhibitor of the chloroplast enzyme of higher plants. The enzyme showed higher specificity with pyrogallol than with ascorbate. The amino acid sequences in the N-terminal region of Chlamvdomonas AsAP showed no significant similarity to any other AsAP from higher plants and Euglena. The enzyme had a molecular mass of 34 kDa. The Km values of the enzyme for ascorbate and H2O2 were 5.2±0.3 and 25±3.4 μM, respectively. Hydrogen peroxide was generated at a rate of 6.1±0.8 μmol mg-1 chlorophyll h-1 in intact chloroplasts isolated from Chlamydomonas cells grown in the presence of Na-selenite, and it diffused from the organelles into the medium.
1. Different plant species show considerable variation in their selenium content. Primary indicators, also termed selenium accumulators, many of which are members of the genus Astragalus , are highly tolerant of selenium; they are known to contain tissue levels of several thousand µg selenium/g. Secondary indicators, tolerant to low concentrations of the element, may absorb up to 1000 µg selenium/g. Non‐accumulators are poisoned by selenium.
2. The toxicity of selenate (SeO 4 ‐ ) and selenite (SeO 3 ‐ ) to most plants can be attributed to a combination of three factors. Firstly, selenate and selenite are readily absorbed from the soil by roots and translocated to other parts of the plant. Secondly, metabolic reactions convert these anions into organic forms of selenium. Thirdly, the organic selenium metabolites, which act as analogues of essential sulphur compounds, interfere with cellular biochemical reactions.
3. Incorporation into proteins of the amino acid analogues selenocysteine and selenomethionine, in place of the equivalent sulphur amino acids, is considered to be the underlying cause of selenium toxicity. The physical and chemical differences between selenium and sulphur will result in small, but significant, changes in the biological properties of a selenium‐substituted protein.
4. Selenium‐tolerant accumulator plants differ in at least two respects from sensitive species. Large quantities of Se‐methylselenocysteine and selenocystathionine, two non‐protein selenoamino acids rarely detected in non‐accumulators, have been isolated from the tissues of selenium accumulators. In addition, selenium is kept from entering proteins so that the selenium levels in proteins of accumulator plants is significantly lower than the levels in selenium‐sensitive plants.
5. Exclusion of selenium from the proteins of accumulators is thought to be the basis of selenium tolerance. Discrimination against selenocysteine during protein synthesis seems to prevent incorporation of this selenoamino acid into proteins of accumulators. Furthermore, synthesis of Se‐methylselenocysteine and selenocystathionine, which results in diversion of selenium away from the synthesis of selenomethionine, will restrict the amount of this compound available for protein synthesis.
6. Selenium accumulation among unrelated plant genera is a striking example of convergent evolution. The possibility that accumulation of this element is associated with a nutritional requirement for selenium, although explored in the past, is still in need of further clarification.
Selenoproteins are involved in mechanisms of cell differentiation and defense. We investigated the expression of glutathione peroxidases, as well as other selenoproteins, in fetal human osteoblasts (hFOB-cells). Using 75-selenium metabolic labelling of viable hFOB-cells, we identified several selenoproteins in cell lysates of about 45-80 kDa and in the migration range of 14 kDa to 24 kDa. Cells expressed low mRNA levels of both cellular glutathione peroxidase and plasma glutathione peroxidase mRNA as analysed by Southern analysis of RT-PCR products. Basal cellular glutathione peroxidase enzyme activity in hFOB-cells (19.7 nmol NADPH oxidised per min and microg protein) was further increased 2.5-fold by the addition of 100 nM sodium selenite to the culture medium for 3 days. Furthermore, expression of selenoprotein P mRNA was demonstrated by RT-PCR. hFOB-cells did not show activities of the selenoproteins type I or type II 5'-deiodinase. In summary, we identified cellular glutathione peroxidase, plasma glutathione peroxidase and selenoprotein P among of a panel of several 75-selenium labelled proteins in human fetal osteoblasts. The expression of selenoproteins like glutathione peroxidases in hFOB-cells represents a new system of osteoblast antioxidative defense that may be relevant for the protection against hydrogen peroxide produced by osteoclasts during bone remodelling.
Oxidative stress in plants causes the induction of several enzymes, including superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2). The first two are responsible for converting superoxide to H2O2 and its subsequent reduction to H2O, and the third is involved in recycling of ascorbate. Glutathione peroxidases (GPXs, EC 1.11.1.9) are a family of key enzymes involved in scavenging oxyradicals in animals. Only recently, indications for the existence of this enzyme in plants were reported. Genes with significant sequence homology to one member of the animal GPX family, namely phospholipid hydroperoxide glutathione peroxidase (PHGPX), were isolated from several plants. Cit-SAP, the protein product encoded by the citrus csa gene, which is induced by salt-stress, is so far the only plant PHGPX that has been isolated and characterized. This protein differs from the animal PHGPX in its rate of enzymatic activity and in containing a Cys instead of selenocysteine (Sec) as its presumed catalytic residue. The physiological role of Cit-SAP and its homologs in other plants is not yet known.
Extracts from cultured plant cells of spinach, maize and sycamore and from Lemna plants contain detectable glutathione peroxidase activity, using either hydrogen peroxide or t-butyl hydroperoxide as substrates. Using extracts from cultured maize cells, two peaks of glutathione peroxidase activity could be resolved by a combination of gel filtration and ion exchange chromatography. One peak was eluted along with glutathione transferase activity; the second was distinct from both glutathione transferase and ascorbic acid peroxidase, and was active with both hydrogen peroxide and organic hydroperoxides. It seems likely that at least two enzymes with glutathione peroxidase activity exist in higher plant cells.
Diss. -- Helsingin yliopisto, 1997.
Selenocysteyl-tRNAs that decode UGA were previously identified in representatives of three of the five life kingdoms which were the monera, animal and protist kingdoms. In the present study, we show that these tRNAs also occur in representatives of the two remaining kingdoms, plants and fungi; i.e., selenocysteyl-tRNAs which code for UGA occur in Beta vulgaris, a higher plant, and in Gliocladium virens, a filamentous fungus. The fact that selenocysteyl-tRNAs are present in all five life kingdoms strongly suggests that UGA, in addition to dictating the cessation of protein synthesis, also codes for selenocysteine in the universal genetic code.
Selenocysteine is incorporated cotranslationally at UGA codons, normally read as stop codons, in several bacterial proteins and in the mammalian proteins glutathione peroxidase (GPX), selenoprotein P and Type I iodothyronine 5' deiodinase (5'DI). Previous analyses in bacteria have suggested that a stem-loop structure involving the UGA codon and adjacent sequences is necessary and sufficient for selenocysteine incorporation into formate dehydrogenase and glycine reductase. We used the recently cloned 5'DI to investigate selenoprotein synthesis in eukaryotes. We show that successful incorporation of selenocysteine into this enzyme requires a specific 3' untranslated (3'ut) segment of about 200 nucleotides, which is found in both rat and human 5'DI messenger RNAs. These sequences are not required for expression of a cysteine-mutant deiodinase. Although there is little primary sequence similarity between the 3'ut regions of these mRNAs and those encoding GPX, the 3'ut sequences of rat GPX can substitute for the 5'DI sequences in directing selenocysteine insertion. Computer analyses predict similar stem-loop structures in the 3'ut regions of the 5'DI and GPX mRNAs. Limited mutations in these structures reduce or eliminate their capacity to permit 5'DI translation. These results identify a 'selenocysteine-insertion sequence' motif in the 3'ut region of these mRNAs that is essential for successful translation of 5'DI, presumably GPX, and possibly other eukaryotic selenocysteine-containing proteins.
The selenite-induced glutathione peroxidase in Chlamydomonas reinhardtii has been purified about 323-fold with a 10% yield, as judged by PAGE. The native enzyme had an Mr of 67,000 and was composed of four identical subunits of Mr 17,000. Glutathione was the only electron donor, giving a specific activity of 193.6 mumol/min per mg of protein. L-Ascorbate, NADH, NADPH, pyrogallol, guaiacol and o-dianisidine did not donate electrons to the enzyme. In addition to H2O2, organic hydroperoxides were reduced by the enzyme. The Km values for glutathione and H2O2 were 3.7 mM and 0.24 mM respectively. The enzyme reaction proceeded by a Ping Pong Bi Bi mechanism. Cyanide and azide had no effect on the activity. The enzyme contained approx. 3.5 atoms of selenium per mol of protein. On immunoprecipitation, Chlamydomonas glutathione peroxidase was precipitated and its activity was inhibited about 90% by the antibody raised against bovine erythrocyte glutathione peroxidase. The antibody also cross-reacted with the subunits of Chlamydomonas glutathione peroxidase in Western blotting SDS/PAGE. In terms of enzymic, physico-chemical and immunological properties, the experimental results demonstrate clearly that Chlamydomonas glutathione peroxidase resembles other well-characterized glutathione peroxidases from animal sources that contain selenium.
Defence against oxidative damage by UV-generated free radicals in both guinea pig and human skin has been found to be mediated by the ubiquitous thioprotein, thioredoxin reductase. Human keratinocytes contain approximately 5% thioredoxin reductase in their total acidic protein fraction and also express membrane-associated enzyme activity in cells cultured in synthetic medium. The thioredoxin reductase/thioredoxin system has been shown to reduce superoxide anion radicals through hydrogen peroxide to water. However, both UVA and UVB radiation, below the minimal erythemal dose, generate a sufficiently high concentration of oxygen radicals to deactivate thioredoxin reductase considerably. In albino guinea pigs, enzyme deactivation was up to 70% for UVA and 66% for UVB (n = 10 animals/protocol). The application of sun blockers SPF4, SPF8 and SPF15 to albino guinea pig skin offered no significant protection for the deactivation of thioredoxin reductase by either UVA or UVB radiation. In the human population (n = 15), thioredoxin reductase was deactivated by 54% with UVA and 36% with UVB radiation, although the degree of enzyme inhibition depended on skin phototype (I-VI, Fitzpatrick Classification). SPF24 offered considerable protection for thioredoxin reductase against both UVA and UVB for skin types I and II. However, SPF24 yielded no significant protection with UVA for skin types III-VI, and enhanced the enzyme inhibition with UVB additively. These results indicate that UVB photo-oxidation of oxybenzone (the UVA filter in SPF24) may deactivate thioredoxin reductase in more pigmented members of the population by Michael addition of oxybenzone semiquinone to the thiolate active site of this enzyme.
Membrane-associated thioredoxin reductase (TR) has been discovered to reduce free radicals at the surface of the skin. An accurate bioassay for this enzyme has been developed by using a spin-labeled quaternary ammonium salt as a free radical substrate. Enzyme activity has been correlated with the surface area, and units of specific activity have been determined as the sequential decrease in nitroxide radical reduction per 3-mm punch biopsy per ten minutes. The TR activity in a random population of 30 healthy volunteers with different skin types (Fitzpatrick classification I through VI) could be correlated to the skin type. Ten patients with untreated vitiligo, two with piebaldism, three with albinism, and two with postinflammatory leukoderma were examined and the findings were compared with the expected rates for the individuals' skin types. The results from this survey on the human population support our previous molecular experiments on the control of melanin biosynthesis by TR in the epidermis.
The toxicity of selenium to animals and plants has been known and extensively documented since the 1930's, but it is only during the past 15 years that selenium has also been shown to be an essential micronutrient for animals and bacteria. Very little is known about the specific role or roles of selenium and, to date, there are only three enzyme-catalyzed reactions that have been shown to require the participation of a selenium-containing protein. These are the reactions catalyzed by (i) formate dehydrogenase of bacteria, (ii) glycine reductase of clostridia, and (iii) glutathione peroxidase of erythrocytes. The common denominator of these selenium-dependent processes is that they are all oxidation-reduction reactions. A fourth selenoprotein has been isolated from skeletal muscle of sheep but its catalytic function has not been identified. The form in which selenium occurs in these selenoproteins is unknown. The selenoprotein of clostridial glycine reductase contains selenium in a covalently bound form. Studies in progress indicate that this may be an organoselenium compound not previously detected in nature. Identification of the chemical nature of selenium in proteins participating in electron transport processes should enable us to determine its specific role and to understand the basic defects in certain cardiac and skeletal muscle degenerative diseases which are selenium-deficiency syndromes. The greater availability and ease of isolation of the selenoprotein of the bacterial glycine reductase system makes this the biological material of choice for studies on the mechanism of action of selenium. An added attractive feature of this system is that it can conserve the energy made available by the reductive deamination of glycine in a biologically useful form by synthesizing ATP.
The validity of 2 electrothermal atomic absorption spectrometric methods for determination of selenium in foods and diets was tested. By using 0.5% Ni(II) as a matrix modifier to prevent selenium losses during the ashing step, it was shown that selenium can be determined in samples containing greater than or equal to 1 microgram Se/g dry wt without organic extraction. The mean recovery tested, using NBS Bovine Liver, was 98%; recovery of added inorganic selenium in Bovine Liver matrix was 100%. In addition, this method gave values closest to the median value of all participating laboratories using hydride generation AAS or the spectrofluorometric method in a collaborative study on high selenium wheat, flour, and toast samples. For samples with concentrations less than 1 microgram Se/g dry wt, separation of selenium from interfering Fe and P ions by organic extraction was necessary. Using inorganic 75Se in meat and human milk matrixes, an ammonium pyrrolidine dithiocarbamate-methyl isobutyl ketone-extraction system with added Cu(II) as a matrix modifier yielded the best extraction recoveries, 97 and 98%, respectively. Accuracy and precision of the method were tested using several official and unofficial biological standard materials. The mean accuracy was within 4% of the certified or best values of the standard materials and the day-to-day variation was 9%. The Se/Fe or Se/P interference limits proved to be low enough not to affect selenium determinations in practically all foods or diets. The practical detection limit of the method was 3 ng Se/g dry wt for 1.0 g dry wt samples.(ABSTRACT TRUNCATED AT 250 WORDS)
Germinating barley grown on an artificial medium was exposed to 75Se-selenite for 8 d. Then the leaves were homogenized and proteins were separated by means of Sephadex G-150 filtration, followed by DEAE-Sepharose chromatography. Each fraction collected was assayed for total protein, radioactivity, and peroxidase activity. In barley leaves, three protein peaks (peaks no. I, II, and III) with peroxidase activity could be separated by Sephadex G 150 filtration. Each fraction was then further separated on DEAE-Sepharose chromatography. Thus, peaks I and II were resolved by DEAE-Sepharose into one major and two minor peaks of radioactivity. However, only the major peak showed peroxidase activity. Peak III was resolved from the gel filtration on the DEAE-sepharose into one major and four minor peaks of radioactivity. The major and three of the minor radioactivity peaks contained peroxidase activity. The protein fractions were separated by polyacrylamide gel electrophoresis. The molecular weights of separated proteins were estimated by means of molecular markers, and 75Se radioactivity was evaluated by autoradiography. Thus, gel filtration peak I contained four bands with mol wts of 128, 116, 100, and 89 kDa. Of these, the 89 kDa protein contained selenium. Peak II contained three protein bands with mol wts 79.4, 59.6, and 59.9. The 59.6 band was a selenoprotein. Peak III contained four protein bands (and some very weak bands). The four major bands had mol wts of 38.6, 31.6, 30.2, and 29.2 kDa. The last mentioned band was a selenoprotein.
A type III iodothyronine deiodinase (D-III) that inactivates thyroid hormones has been recently cloned and identified as a selenoprotein in neonatal rat skin. However, selenium (Se) deficiency does not affect the D-III activity in the rat placenta and decreases the D-III in the rat brain only slightly. This study examines the effect of Se on the D-III activity in cultures of rat brain astrocytes. Astrocytes were depleted in Se by maintaining them in Se-free chemically defined medium for 7 days. These conditions decreased the activity of a recognized selenoprotein, glutathione peroxidase, 3-10-fold. D-III activity induced by 12-0-tetradecanoylphorbol-13-acetate (TPA) was also decreased 2-6-fold. Addition of 30 nM Se to the culture medium caused a rapid increase in TPA-induced D-III activity visible within 1 h. This Se effect was maximal at 3 h (4-fold increase) and dose-dependent. Se also increased the induction of D-III by acidic Fibroblast Growth Factor, 8-bromo-cAMP, T4, or retinoic acid. Cycloheximide blocked the effect of Se on TPA-induced D-III activity, whereas actinomycin D did not. Thus the rapid effect of Se does not require messenger RNA synthesis but requires protein synthesis. We conclude that the D-III in astrocytes is probably a selenoprotein.
After labeling of rats in vivo with 75Se and protein separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis more than 25 Se-containing bands could be distinguished. Of those proteins which were detected only in certain compartments and might therefore have tissue-specific functions, two were chosen for detailed investigation. A 15 kDa-protein was found in the prostatic epithelium where it accounted for about two thirds of the protein-bound 75Se. It was mainly present in the cytosol but was not released into the prostatic secretion. After gel chromatography it was found in the fraction which contained proteins with molecular masses of about 300 kDa. Using two-dimensional electrophoresis a pI-value of about 4.5 was determined. In the testis a specific Se-containing 34 kDa-protein was observed which appeared after the onset of puberty. It was localized in the spermatid nuclei where it contained about 80% of the Se tracer present and was found to be bound to the DNA. After extraction it partly disintegrated into a 20 kDa-protein. Both compounds contain Se in the form of selenocysteine. The fact that their formation had priority over that of glutathione peroxidase during insufficient Se intake is an indication of their biological significance. Special interest in the prostatic epithelial selenoprotein derives from a possible inverse relationship between the Se status and the incidence of prostate cancer observed in epidemiological studies, whereas with the 34 kDa-selenoprotein its appearance during the condensation phase of the spermatid nuclei might suggest its participation in some processes of sperm maturation.
The nucleotide sequences of the open reading frames of cDNAs for selenoprotein W from skeletal muscle of rat, mouse, sheep, rhesus monkey and human are reported. Theoretical translation of the coding sequences indicated highly similar proteins of 88 (mouse and rat) or 87 (human, monkey and sheep) amino acids. In 73 of 88 positions the specified amino acids are identical for all five proteins. TGA encoding selenocysteine is the 13th codon of all the cDNAs. The mouse, rat and sheep open reading frames terminate with TGA but the human and rhesus monkey coding regions terminate with TAA. The encoded amino acid sequences are identical for the rat and mouse proteins, and for the human and monkey proteins. The similarity of the cDNAs continues in the 3' noncoding regions through the putative selenocysteine insertion sequence (SECIS) elements which are required for correct interpretation of the selenocysteine codon. The region between the SECIS elements and the polyadenylation signals showed much lower similarity. The cloned rat gene for selenoprotein W is 5000 bases long, with the 663 bases of the cDNA in six exons. The transcription start site was identified by nuclease protection assay to be 16 bases upstream of the longest cDNA clone. A canonical TATA box occurs 150 bases upstream, but the assay did not indicate the presence of longer mRNAs.
Selenium (Se) is an essential trace element and has been reported to decrease the incidence of some human cancers. We have investigated the effects of Se on thioredoxin reductase, a selenocysteine containing flavoenzyme, in HT-29 human colon cancer cells grown in serum-free medium. Sodium selenite and other Se containing compounds produced a time and concentration dependent increase in intracellular thioredoxin reductase activity and protein levels. Selenite was the most active of the Se compounds examined: 1 microM selenite produced a 28-fold increase in thioredoxin reductase activity by 1 day and 10 microM selenite over a 60-fold increase by 5 days. The activity of a related non-selenocysteine containing flavoenzyme glutathione reductase was not increased by selenite. Selenite, but not the other Se containing compounds inhibited cell growth at concentrations above 2 microM. The results show that Se can produce large increases in cell thioredoxin reductase activity.
Shoots, roots, and seeds of corn (Zea mays L., cv. Michigan 500), oats (Avena sativa L., cv. Au Sable), and peas (Pisum sativum L., cv. Wando) were analyzed for their superoxide dismutase content using a photochemical assay system consisting of methionine, riboflavin, and p-nitro blue tetrazolium. The enzyme is present in the shoots, roots, and seeds of the three species. On a dry weight basis, shoots contain more enzyme than roots. In seeds, the enzyme is present in both the embryo and the storage tissue. Electrophoresis indicated a total of 10 distinct forms of the enzyme. Corn contained seven of these forms and oats three. Peas contained one of the corn and two of the oat enzymes. Nine of the enzyme activities were eliminated with cyanide treatment suggesting that they may be cupro-zinc enzymes, whereas one was cyanide-resistant and may be a manganese enzyme. Some of the leaf superoxide dismutases were found primarily in mitochondria or chloroplasts. Peroxidases at high concentrations interfere with the assay. In test tube assays of crude extracts from seedlings, the interference was negligible. On gels, however, peroxidases may account for two of the 10 superoxide dismutase forms.
Selenomethionine and selenoethionine enhanced ethylene production in senescing flower tissue of Ipomoea tricolor Cav. and in auxin-treated pea (Pisum sativum L.) stem sections. This enhancement was fully inhibited by the aminoethoxy analog of rhizobitoxine. Methionine did not have a comparable promotive effect, and ethionine partly inhibited ethylene production. When [(14)C]methionine was applied to flower or pea stem tissue followed by treatment with unlabeled selenomethionine or selenoethionine, the specific radioactivity of the ethylene evolved was considerably reduced. The dilution of the specific radioactivity of ethylene by selenomethionine, and in pea stem sections also by selenoethionine, was greater than the dilution by nonradioactive methionine at the same concentration. These results indicate that both selenoamino acids serve as precursors of ethylene and that they are converted to ethylene more efficiently than is methionine.
Culture of the green alga Chlamydomonas reinhardtii in the medium containing sodium selenite caused the activity of ascorbate peroxidase to disappear and the appearance of glutathione peroxidase. The induced maximum activity of glutathione peroxidase reached 350 micromole (milligram chlorophyll hour)(-1) under assay conditions used. The enzymic properties of the selenite-induced glutathione peroxidase closely resembled those of animal glutathione peroxidase that contains selenium.
Schomburg D and Flohe L 1995 Diversity of glutathione peroxidases
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The antioxidative function of sel-enium in higher plants: II. Non-enzymatic mechanisms Piironen V and Hartikainen H 1997 A small scale HPLC method for the determination of α-tocopherol in fresh plant tissues
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Xue T, Hou S and Tan J 1993b The antioxidative function of sel-enium in higher plants: II. Non-enzymatic mechanisms. Chinese Sci. Bull. 38, 356–358. (in Chinese) Xue T, Piironen V and Hartikainen H 1997 A small scale HPLC method for the determination of α-tocopherol in fresh plant tissues. Agribiol. Res. 50, 265–270.
Mechanisms of oxygen activation in different compartments of plant cells
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- Steffen
Elstner E 1991 Mechanisms of oxygen activation in different compartments of plant cells. In: Active Oxygen/Oxidative Stress and
Plant Metabolism. Ed. E Pell and K L Steffen. Vol 6 pp 13-25.
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Effect of added selenite and selenate on the selenium content of rye grass (Lolium multiflorum) in different soils
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Yläranta T 1983. Effect of added selenite and selenate on the selenium content of rye grass (Lolium multiflorum) in different soils.
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