ArticleLiterature Review

A guideline for leaf senescence analyses: From quantification to physiological and molecular investigations

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Abstract

Leaf senescence is not a chaotic breakdown but a dynamic process following a precise timetable. It enables plants to economize with their resources and control their own viability and integrity. The onset as well as the progression of leaf senescence are coordinated by a complex genetic network that continuously integrates developmental and environmental signals such as biotic and abiotic stresses. Therefore, studying senescence requires an integrative and multi-scale analysis of the dynamic changes occurring in plant physiology and metabolism. In addition to providing an automated and standardized method to quantify leaf senescence at the macroscopic scale, we also propose an analytic framework to investigate senescence at physiological, biochemical, and molecular levels throughout the plant life cycle. We have developed protocols and suggested methods for studying different key processes involved in senescence, including photosynthetic capacities, membrane degradation, redox status, and genetic regulation. All methods presented in this review were conducted on Arabidopsis thaliana Columbia-0 and results are compared with senescence-related mutants. This guideline includes experimental design, protocols, recommendations, and the automated tools for leaf senescence analyses that could also be applied to other species.

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... An automated colorimetric assay was performed and H 2 O 2 levels were estimated as described by Bresson et al. (2018). Chlorophyll was extracted from 20 leaves per developmental stage. ...
... The leaves were subsequently frozen in liquid nitrogen and then vacuum-dried. Once the dry weights had been measured, chlorophyll extraction in 80% acetone in phosphate buffer proceeded as described in Bresson et al. (2018). ...
... H 2 O 2 was quantified from 20 leaves per developmental stage exactly as described in Bresson et al. (2018). A stock solution was prepared containing 0.4 mg 5(6)-carboxy-2ʹ,7ʹ-dichlorofluorescin diacetate solved in 400 μl dimethyl sulfoxide, diluted 1:1 with distilled water. ...
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The lifespan of plants is restricted by environmental and genetic components. Following the transition to reproductive growth, leaf senescence ceases cellular life in monocarpic plants to remobilize nutrients to storage organs. We initially observed altered leaf to seed ratios, faster senescence progression, altered leaf nitrogen recovery after transient nitrogen removal and ultimately enhanced nitrogen remobilization from the leaves in two methylation mutants (ros1 and the triple dmr1/2 cmt3 knockout). Analysis of the DNA methylome in wild type Col-0 leaves identified an initial moderate decline of cytosine methylation with progressing leaf senescence, predominantly in the CG context. Late senescence was associated with moderate de novo methylation of cytosines, primarily in the CHH context. Relatively few differentially methylated regions, including one in the ROS1 promoter linked to the down-regulation of ROS1, were present, but these were unrelated to known senescence-associated genes. Differential methylation patterns were identified in transcription factor binding sites, such as the W-boxes that are targeted by WRKYs. Methylation in artificial binding sites impaired transcription factor binding in vitro. However, it remains unclear how the moderate methylome changes during leaf senescence are linked with up-regulated genes during senescence.
... pWRKY53::GUS lines in Col-0 and rev5 background, and pREV::GUS plants in rev9 knock-out mutant [25,36] were used to quantify promoter activity in planta. Plants were grown on standard soil (9:1 soil and sand) under controlled conditions: in long days (16 h day; 8 h night), low light (~70-80 μE m −2 s −1 at plant height) and an ambient temperature of 21˚C (see [49] for details). Three independent experiments were done for developmental analysis, including senescence and plant productivity quantification. ...
... Leaf blades were scanned for measurements of area using the ImageJ software (1.47v, Rasband, Bethesda, Maryland, USA). The maximum rate of leaf expansion (R max ) was determined as for [49]. Specific leaf area (SLA) was calculated as the ratio of total leaf area to leaf DM. ...
... Senescence was quantified in leaves using ChlF imaging (Imaging-PAM; Maxi version; ver. 2-46i, Heinz Walz GmbH; see [49,51]). The maximum quantum yield of photosystem II (PSII) was estimated by the ratio of variable to maximal ChlF (F v /F m , also called photosynthetic efficiency) on dark-adapted plants, after 15-20 min. ...
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In annual plants, tight coordination of successive developmental events is of primary importance to optimize performance under fluctuating environmental conditions. The recent finding of the genetic interaction of WRKY53 , a key senescence-related gene with REVOLUTA , a master regulator of early leaf patterning, raises the question of how early and late developmental events are connected. Here, we investigated the developmental and metabolic consequences of an alteration of the REVOLUTA and WRKY53 gene expression, from seedling to fruiting. Our results show that REVOLUTA critically controls late developmental phases and reproduction while inversely WRKY53 determines vegetative growth at early developmental stages. We further show that these regulators of distinct developmental phases frequently, but not continuously, interact throughout ontogeny and demonstrated that their genetic interaction is mediated by the salicylic acid (SA). Moreover, we showed that REVOLUTA and WRKY53 are keys regulatory nodes of development and plant immunity thought their role in SA metabolic pathways, which also highlights the role of REV in pathogen defence. Together, our findings demonstrate how late and early developmental events are tightly intertwined by molecular hubs. These hubs interact with each other throughout ontogeny, and participate in the interplay between plant development and immunity.
... However, a large proportion of these genes in crop plants (close to one-third) appear to be associated with senescence, based on transcriptomic analyses (Podzimska-Sroka et al., 2015). Senescence is an active process driven by different signals such as hormones, sugars, reactive oxygen species (ROS), and calcium (Bresson et al., 2018). Several families of transcription factors regulate this process, particularly NAC and WRKY transcription, based initially on their induction at the onset of senescence (Guo et al., 2004;Lin and Wu, 2004;Buchanan-Wollaston et al., 2005;Balazadeh et al., 2008;Liu et al., 2010;Breeze et al., 2011;Li et al., 2012). ...
... In PROM-ANAC087 lines, no significant difference was observed compared to wild-type plants (Figure 4C). On the other hand, some studies report that photosynthesis is gradually inactivated during senescence and accompanied by degradation of chlorophyll and also anthocyanin accumulation (Bresson et al., 2018). Thus, the results in this work show that ANAC087 expression is related to the process of leaf senescence, since OE-ANAC087 lines showed higher anthocyanin accumulation and senescence rate relative to control plants. ...
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CmNACP1 mRNA has been shown to move long distance through the phloem in Cucurbita maxima (pumpkin) and through a graft junction. Whereas the phloem transport of several different mRNAs has been documented in other systems as well, its function remains, for most of these RNAs, largely unknown. To gain insight into the possible role of these RNAs, we searched for the closest homologs of CmNACP1 in Arabidopsis, a model plant much more amenable for analysis. A phylogenetic approach using the predicted NAC domain indicated that ANAC059, ANAC092, ANAC079, ANAC100, ANAC046, and ANAC087 form a single clade with CmNACP1. In the present work, we analyzed the possible function of the ANAC087 gene in more detail. The promoter region of this gene directed expression in the vasculature, and also in trichomes, stem, apexes, and developing flowers which supports the notion that ANAC087 and CmNACP1 are orthologs. Overexpression of the ANAC087 gene induced increased branching in inflorescence stem, and also development of ectopic or aerial rosettes in T1 and T2 plants. Furthermore, overexpression of ANAC087 leads to accelerated leaf senescence in 44 days post-germination (dpg). Interestingly, a similar phenotype was observed in plants expressing the ANAC087 gene upstream region, also showing an increase in ANAC087 transcript levels. Finally, the results shown in this work indicate a role for ANAC087 in leaf senescence and also in rosette development.
... Chl a and Chl b are the two forms of pigments that predominate in higher plants. Differently involved in light assimilation, Chl a is linked to the photosystems energy-processing centres whereas Chl b is an accessory pigment for harvesting light energy and transmitting it to Chl a [31]. Concerning carotenoids (Car), they act first as collectors of light energy driving photosynthetic processes. ...
... The thiobarbituric acid reactive substances (TBARS) content was determined according to the method of [24] with modifications mainly based on [31,56]. Apple leaves were ground in liquid nitrogen with a mortar and pestle. ...
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Essential oils (EOs) are actively investigated as an alternative to numerous synthetic bio-cide products. Due to their large spectra of biological activities, the impact of EOs on non-target organisms should be characterized for biopesticide development purposes. In this study the potential phytotoxicity of Cinnamomum cassia EO (CEO) on apple trees (Malus domestica) were investigated in terms of oxidative burst (glutathione redox state) and damage (malondialdehyde). At 2%, CEO concentration the reduced glutathione leaf content drops from 269.6 ± 45.8 to 143 ± 28.4 nmol g −1 FW, after 30 min, illustrating a rapid and strong oxidative burst. Regarding oxidative damage, malondialdehyde increased significantly 24 h post application to 10.7 ± 3.05 nmol g −1 FW. Plant defence induction was previously suspected after trans-cinnamaldehyde (CEO main compound) application. Therefore, the elicitor potential was investigated by qRT-PCR, on the expression level of 29 genes related to major defence pathways (PR protein, secondary metabolism, oxidative stress, parietal modification). Multivariate analysis and increased expression levels suggest induction of systemic resistance. Hence, the present research illustrates the dose-dependent phytotoxicity of CEO in terms of lipid peroxidation. Transcriptional data illustrates the elicitor properties of CEO. These findings can help to design pest management strategies considering both their risks (phyto-toxicity) and benefits (defence activation combined with direct biocide properties).
... Unfortunately, observing the expression of SAGs on the stand or landscape scale is unattainable. Since leaf senescence consists of multiple steps and requires an integrative and multi-scale analysis, assessing the best proxy for detecting temporal trends in leaf senescence therefore becomes of crucial importance (Bresson et al., 2017;Gill et al., 2015;Keskitalo et al., 2005). Examples in the literature, of such proxies include visual coloration assessments, chlorophyll measurements, remote sensing observations of standard indices and coloration analysis through phenocams (Maleki et al., 2020;Piao et al., 2019;Qiu et al., 2020). ...
... The leaves from each tree were measured approximately on the same moment of the day; and using the same side of the leaf. Due to its curvilinear relationship, the CCI acts as a proxy for chlorophyll concentrations and senescence (Bresson et al., 2017;Michelson et al., 2018). ...
Article
Accurate estimations of phenophases in deciduous trees are important to understand forest ecosystems and their feedback on the climate. In particular, the timing of leaf senescence is of fundamental importance to trees’ nutrient stoichiometry and drought tolerance and therefore to trees’ vigor and fecundity. Nevertheless, there is no integrated view on the significance, and direction, of seasonal trends in leaf senescence, especially for years characterized by extreme weather events. Difficulties in the acquisition and analyses of hierarchical data can account for this. We collected four years of chlorophyll content index (CCI) measurements in thirty-eight individuals of four deciduous tree species (Betula pendula, Fagus sylvatica, Populus tremula and Quercus robur) in Belgium, Norway and Spain, and analyzed these data using generalized additive models for location, scale and shape (GAMLSS). As a result, (I) the phenological strategy and seasonal trend of leaf senescence in these tree species could be clarified for exceptionally dry and warm years, and (II) the daily average (air) temperature, global radiation, and vapor pressure deficit could be established as main drivers behind the variation in the timing of the senescence transition date. Our results show that the onset of the re-organization phase in the leaf senescence, which we approximated and defined as local minima in the second derivative of a CCI graph, was in all species mainly negatively affected by the average temperature, global radiation and vapor pressure deficit. All together the variables explained 89 to 98% of the variability in the leaf senescence timing. An additional finding is that the generalized beta type 2 and generalized gamma distributions are well suited to model the chlorophyll content index, while the senescence transition date can be modeled using the normal-exponential-student-t, generalized gamma and zero-inflated Box-Cox Cole and Green distributions for beech, oak and birch, and poplar, respectively.
... The protocol described by Bresson et al. (2018) was used. Ground frozen green leaf samples (25 mg) were homogenized with 0.5 ml 0.1% trichloroacetic acid (TCA) in technical duplicate. ...
... Both fractions were vortexed, incubated at 95 • C for 30 min and cooled quickly in an ice bath. Following centrifugation, A440, A532 and A600 nm were recorded, and malondialdehyde equivalents as well as total anthocyanin content were calculated with equations provided by Bresson et al. (2018). ...
Article
Reactive species causing oxidative stress are unavoidable by-products of various plant metabolic processes, such as photosynthesis, respiration or photorespiration. In leaves, flavonoids scavenge reactive species produced during photosynthesis and protect plant cells against deleterious oxidative damages. Their biosynthesis and accumulation are therefore under tight regulation at the cellular level. Glycosylation has emerged as an essential biochemical reaction in the homeostasis of various specialized metabolites such as flavonoids. This article provides a functional characterization of the Populus tremula x P. alba (poplar) UGT72A2 coding for a UDP-glycosyltransferase that is localized in the chloroplasts. Compared to the wild type, transgenic poplar lines with decreased expression of UGT72A2 are characterized by reduced growth and oxidative damages in leaves, as evidenced by necrosis, higher content of glutathione and lipid peroxidation products as well as diminished soluble peroxidase activity and NADPH to NADP+ ratio under standard growing conditions. They furthermore display lower pools of phenolics, anthocyanins and total flavonoids but higher proanthocyanidins content. Promoter analysis revealed the presence of cis-elements involved in photomorphogenesis, chloroplast biogenesis and flavonoid biosynthesis. UGT72A2 is regulated by the poplar MYB119, a transcription factor known to regulate the flavonoid biosynthesis pathway. Phylogenetic analysis and molecular docking suggest that UGT72A2 could glycosylate flavonoids, however the actual substrate(s) was(ere) not consistently evidenced with in vitro assays nor analyses of glycosylated products in leaves of transgenic poplar overexpressing or downregulated for UGT72A2. This article provides elements highlighting the importance of flavonoid glycosylation regarding protection against oxidative stress in poplar leaves and raises new questions about the link between this biochemical reaction and regulation of the redox homeostasis system.
... Senescence is a precisely arranged series of dynamic processes designed to allow plants to remobilize resources (Bresson, Bieker, Riester, Doll, & Zentgraf, 2018;Jagadish et al., 2015). Detoxification through anthocyanin accumulation and activity remains persistent throughout this process, since it stabilizes mitochondrial activity (He & Monica Giusti, 2010;Zimmermann, Heinlein, Orendi, & Zentgraf, 2006). ...
... Detoxification through anthocyanin accumulation and activity remains persistent throughout this process, since it stabilizes mitochondrial activity (He & Monica Giusti, 2010;Zimmermann, Heinlein, Orendi, & Zentgraf, 2006). This is important because senescence relies on the existence of viable mitochondria (Bresson et al., 2018;Keech et al., 2007;Ruberti et al., 2014), as such it is conceivable that senescence drives increased respiration. Regardless of the precise dynamics between senescence and respiration, it can be concluded that increasing the capacity of a plant to stay green during heat stress will balance net carbon gain (Figure 1). ...
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Impaired carbon metabolism and reproductive development constrain crop productivity during heat stress. Reproductive development is energy intensive and its requirement for respiratory substrates rises as associated metabolism increases with temperature. Understanding how these processes are integrated and the extent to which they contribute to the maintenance of yield during and following periods of elevated temperatures is important for developing climate resilient crops. Recent studies are beginning to demonstrate links between processes underlying carbon dynamics and reproduction during heat stress, consequently a summation of research that has been reported thus far and an evaluation of purported associations is needed to guide and stimulate future research. To this end, we review recent studies relating to source‐sink dynamics, non‐foliar photosynthesis and net carbon gain as pivotal in understanding how to improve reproductive development and crop productivity during heat stress. Rapid and precise phenotyping during narrow phenological windows will be important for understanding mechanisms underlying these processes, thus we discuss the development of relevant high throughput phenotyping approaches that will allow for more informed decision making regarding future crop improvement. This article is protected by copyright. All rights reserved.
... The initiation of senescence typically coincides with the decline in the growth rate, which in Arabidopsis is concomitant with the transition to flowering (Thomas, 2013). During this developmental phase in Arabidopsis, the increase in intracellular H 2 O 2 concentrations is coupled with the temporal decrease in the activity of two key H 2 O 2 -scavenging enzymes, CATALASE2 (CAT2) and ASCORBATE PEROXIDASE1 (APX1; Ye et al., 2000;Zimmermann et al., 2006;Bresson et al., 2017). ...
... During this phase, the bulk of photoassimilates and available nutrient are being exported to sink tissues before the cytoplasm and nucleus degrade. The loss of Chl and other macromolecules can lead to the accumulation of ROS, further promoting senescence (Foyer and Noctor, 2009;Chen et al., 2012;Khanna-Chopra, 2012;Jajic et al., 2015;Bresson et al., 2017). Thus, the regulation of the oxidative load during senescence is critical to allow a timely and efficient sink to source nutrient mobilization under favorable conditions, and for reducing the risk of excessive oxidative damage and loss of organic material under stress conditions (Foyer and Noctor, 2005). ...
Article
Age-dependent changes in reactive oxygen species (ROS) levels are critical in leaf senescence. While H2O2-reducing enzymes such as catalases and cytosolic ASCORBATE PEROXIDASE1 (APX1) tightly control the oxidative load during senescence, their regulation and function are not specific to senescence. Previously, we identified the role of ASCORBATE PEROXIDASE6 (APX6) during seed maturation in Arabidopsis (Arabidopsis thaliana). Here, we show that APX6 is a bona fide senescence-associated gene. APX6 expression is specifically induced in aging leaves and in response to senescence-promoting stimuli such as abscisic acid (ABA), extended darkness, and osmotic stress. apx6 mutants showed early developmental senescence and increased sensitivity to dark stress. Reduced APX activity, increased H2O2 level, and altered redox state of the ascorbate pool in mature pre-senescing green leaves of the apx6 mutants correlated with the early onset of senescence. Using transient expression assays in Nicotiana benthamiana leaves, we unraveled the age-dependent post-transcriptional regulation of APX6. We then identified the coding sequence of APX6 as a potential target of miR398, which is a key regulator of copper redistribution. Furthermore, we showed that mutants of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7), the master regulator of copper homeostasis and miR398 expression, have a higher APX6 level compared with the wild type, which further increased under copper deficiency. Our study suggests that APX6 is a modulator of ROS/redox homeostasis and signaling in aging leaves that plays an important role in developmental- and stress-induced senescence programs.
... Additionally, MYB transcription factor, OsMYB102, involved in the regulation of leaf senescence, through the downregulated ABA biosynthesis and signaling response 20 . Intrinsically, the initiation of senescence is the consequence of integrated signals, including endogenous and environmental signals 4 . The developmental senescence, which was a coordinated physiological process and being induced by the endogenous factors 21 , has been studied in a large variety of plants using high-throughput method, such as Arabidopsis 22 , wheat 23 , maize 24 , Gossypium hirsutum L. 25 , tobacco 26 , sorghum 27 , soybean leaves 28 , sunflower 29 , Lonicera macranthoides leaves 30 , grape berry 31 , pear 32 , and so on. ...
... The developmental senescence, which was a coordinated physiological process and being induced by the endogenous factors 21 , has been studied in a large variety of plants using high-throughput method, such as Arabidopsis 22 , wheat 23 , maize 24 , Gossypium hirsutum L. 25 , tobacco 26 , sorghum 27 , soybean leaves 28 , sunflower 29 , Lonicera macranthoides leaves 30 , grape berry 31 , pear 32 , and so on. On the other hand, when confronted with uncomfortable external factors, plants were inclined to start an 'escape' or protective strategy, to decrease canopy size and ensure the optimal survival for next generation 4,33 , which resulted in premature senescence. In recent studies, it has been proved that a wide variety of abiotic and biotic stresses, such as drought 34 , heat 35 , salt 36 , would trigger premature senescence 2 . ...
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Senescence is a degenerative process triggered by intricate and coordinated regulatory networks, and the mechanisms of age-dependent senescence and stress-induced premature senescence still remain largely elusive. Thus we selected leaf samples of developmental senescence (DS) and premature senescence (PS) to reveal the regulatory divergence. Senescent leaves were confirmed by yellowing symptom and physiological measurement. A total of 1171 and 309 genes (DEGs) were significantly expressed respectively in the whole process of DS and PS. Up-regulated DEGs in PS were mostly related to ion transport, while the down-regulated DEGs were mainly associated with oxidoreductase activity and sesquiterpenoid and triterpenoid biosynthesis. In DS, photosynthesis, precursor metabolites and energy, protein processing in endoplasmic reticulum, flavonoid biosynthesis were notable. Moreover, we found the vital pathways shared by DS and PS, of which the DEGs were analyzed further via protein–protein interaction (PPI) network analysis to explore the alteration responding to two types of senescence. In addition, plant hormone transduction pathway was mapped by related DEGs, suggesting that ABA and ethylene signaling played pivotal roles in formulating the distinction of DS and PS. Finally, we conducted a model containing oxidative stress and ABA signaling as two hub points, which highlighted the major difference and predicted the possible mechanism under DS and PS. This work gained new insight into molecular divergence of developmental senescence and premature senescence and would provide reference on potential mechanism initiating and motivating senescence for further study.
... In addition, the RGB model of digital color images has also been used to determine plant adaptability and degree of damage under biological or abiotic stresses [21]. Particularly when plant leaves display obvious senescence and color change after a long period of severe adversity and climate change, the RGB model is used to analyze the color depth of leaves and area size of different colors, as well as their proportion [22]. ...
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The crop leaf color is tightly connected with its meteorological environment. Color gradation skewness-distribution (CGSD) parameters can describe the information of leaf color more accurately, systematically, and comprehensively from five dimensions. We took photographs of pepper growing in the greenhouse at a fixed time every day and observed the meteorological factors. The results showed that the CGSD parameters were significantly correlated with meteorological factors, especially with the accumulated temperature, which showed the strongest correlation. Since the relationship between canopy leaf color and accumulated temperature is nonlinear, the piecewise inversion models were constructed by taking the stationary point of the high-order response model of Gskewness to accumulated temperature as the point of demarcation. The rate of outliers had decreased by 57.72%; moreover, the overall inversion accuracy had increased by 3.31% compared with the linear model directly constructed by the stepwise regression. It was observed that the pepper in the greenhouse had a different response to the same meteorological environmental stimulus before and after the stationary point. This study will provide a new method for constructing crop growth models in future research.
... In this experiment, the MDA accumulation of transgenic tomatoes after drought and NaCl treatment was relatively less, and the relative conductivity was significantly lower than that of the wild-type, which significantly alleviated the degree of oxidative damage and increased the responsiveness of transgenic tomatoes to drought and salt. MDA is a final product of unsaturated fatty acid peroxidation in phospholipids (Bokhorst et al., 2010;Bresson et al., 2018). Its content can reflect lipid peroxidation or cell membrane damage in plant tissues, affecting protein synthesis (Khan et al., 2021b). ...
Article
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The homeodomain-leucine zipper protein HAT belongs to the homeodomain leucine zipper subfamily (HD-Zip) and is important for regulating plant growth and development and stress tolerance. To investigate the role of HAT5 in tolerance to drought, salt, and low temperature stress, we selected a HAT gene from Pyrus sinkiangensis Yü (Pyrus sinkiangensis T.T. Yu). The sequences were analyzed using ioinformatics, and the overexpressed tomato lines were obtained using molecular biology techniques. The phenotypes, physiological, and biochemical indexes of the wild-type and transgenic tomato lines were observed under different stress conditions. We found that the gene had the highest homology with PbrHAT5. Under drought and NaCl stress, osmotic regulatory substances (especially proline) were significantly accumulated, and antioxidant enzyme activities were enhanced. The malondialdehyde level and relative electrical conductivity of transgenic tomatoes under low temperature (freezing) stress were significantly higher than those of wild-type tomatoes. The reactive oxygen species scavenging system was unbalanced. This study found that PsHAT5 improved the tolerance of tomatoes to drought and salt stress by regulating proline metabolism and oxidative stress ability, reducing the production of reactive oxygen species, and maintaining normal cell metabolism. In conclusion, the PsHAT5 transcription factor has great potential in crop resistance breeding, which lays a theoretical foundation for future excavation of effective resistance genes of the HD-Zip family and experimental field studies.
... Taken together, these results reveal that TgNAP represses TgPOD12 and TgPOD17 transcription through binding to the core-binding motif. . Different from leaf senescence, the molecular mechanisms of flower or petal senescence are much less studied and remain largely elusive (Woo et al., 2013;Bresson et al., 2018). Previous reports have indicated that NAC TF family is prominent among plant leaf senescence-associated transcriptional regulators. ...
Article
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Petal senescence is a crucial determinant for ornamental quality and economic value of floral crops. Salicylic acid (SA) and reactive oxygen species (ROS) are two prominent factors involved in plant senescence regulation. In this study, tulip TgNAP (NAC-like, activated by APETALA3/PISTILLATA), was characterized as positively regulating tulip petal senescence through dually regulating SA biosynthesis and ROS detoxification pathways. TgNAP was up-regulated in senescing petals of tulip while exogenous SA and H2O2 treatments substantially promoted petal senescence in tulip. Silencing of TgNAP by VIGS assay delayed SA and H2O2-induced petal senescence in tulip, whereas overexpression of TgNAP promoted the senescence process in Arabidopsis (Arabidopsis thaliana) plants. Additionally, inhibition of SA biosynthesis prolonged the lifespan of TgNAP-silenced petal discs. Further evidence indicated that TgNAP activates the transcriptions of two key SA biosynthetic genes ISOCHORISMATE SYNTHASE 1 (TgICS1) and PHENYLALANINE AMMONIA-LYASE 1 (TgPAL1)) through directly binding to their promoter regions. Meanwhile, TgNAP repressed ROS scavenging by directly inhibiting PEROXIDASE 12 (POD12) and POD17 expression. Taken together, these results indicate that TgNAP enhances SA biosynthesis and ROS accumulation to positively regulate petal senescence in tulip.
... Therefore, plants use complex molecular mechanism with functional proteins such as proteases and regulatory proteins such as phosphatase, protein kinase, and transcription factors to supply energy when the plant needs to produce seeds and offspring of the next generation. The NAC and WRKY transcription factor families play important roles in senescence-related gene regulatory networks in Arabidopsis, rice, and wheat [47][48][49]. ...
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Background Plants use escape strategies including premature senescence and leaf reduction to cope in response to drought stress, which in turn reduces plant leaves and photosynthesis. This strategy allows the new generation (seeds) to survive under drought but, plants experience more yield loss during stress condition. The amount of damage caused by drought stress is compensated by the expression of genes involved in regulating leaf aging. Leaf senescence alters the expression of thousands of genes and ultimately affecting grain protein content, grain yield, and nitrogen utilization efficiency. Also, under drought stress, nitrogen in the soil will not become as much available and causes the beginning and acceleration of the senescence process of leaves. The main body of the abstract This review identified proteins signaling and functional proteins involved in senescence. Further, transcription factors and cell wall degradation enzymes (proteases) related to senescence during drought stress were surveyed. We discuss the regulatory pathways of genes as a result of the degradation of proteins during senescence process. Senescence is strongly influenced by plant hormones and environmental factors including the availability of nitrogen. During maturity or drought stress, reduced nitrogen uptake can cause nitrogen to be remobilized from leaves and stems to seeds, eventually leading to leaf senescence. Under these conditions, genes involved in chloroplast degradation and proteases show increased expression. The functional (proteases) and regulatory proteins such as protein kinases and phosphatases as well as transcription factors (AP2/ERF, NAC, WRKY, MYB, and bZIP) are involved in leaf senescence and drought stress. Short conclusion In this review, senescence-associated proteins involved in leaf senescence and regulatory and functional proteins in response to drought stress during grain filling were surveyed. The present study predicts on the role of nitrogen transporters, transcription factors and regulatory genes involved in the late stages of plant growth with the aim of understanding their mechanisms of action during grain filling stage. For a better understanding, the relevant evidence for the balance between grain filling and protein breakdown during grain filling in cereals is presented.
... These results indicate that the chlorophyll biosynthesis capacity is reduced under long-term MD. Moreover, chlorophyll degradation is an important part of nutrient recycling and redistribution during plant stress [59]. OsSGR encodes a new chloroplast protein senescence-related gene and regulates chlorophyll degradation in chloroplasts [60]. ...
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Magnesium (Mg) is an essential macronutrient for plant growth and development. Physiological and transcriptome analyses were conducted to elucidate the adaptive mechanisms to long-term Mg deficiency (MD) in banana seedlings at the 6-leaf stage. Banana seedlings were irrigated with a Mg-free nutrient solution for 42 days, and a mock control was treated with an optimum Mg supply. Leaf edge chlorosis was observed on the 9 th leaf, which gradually turned yellow from the edge to the interior region. Accordingly, the total chlorophyll content was reduced by 47.1%, 47.4%, and 53.8% in the interior, center and edge regions, respectively, and the net photosynthetic rate was significantly decreased in the 9 th leaf. Transcriptome analysis revealed that MD induced 9,314, 7,425 and 5,716 differentially expressed genes (DEGs) in the interior, center and edge regions, respectively. Of these, the chlorophyll metabolism pathway was preferentially enriched according to Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The expression levels of the five candidate genes in leaves were consistent with what is expected during chlorophyll metabolism. Our results suggest that changes in the expression of genes related to chlorophyll synthesis and decomposition result in the yellowing of banana seedling leaves, and these results are helpful for understanding the banana response mechanism to long-term MD.
... Transcription factors play a crucial role in plant leaf senescence [38,66]. Senescence-related gene regulatory networks in A. thaliana, rice, and wheat reveal the vital role of transcription factor families NAC and WRKY [67][68][69][70]. The senescence regulatory network in wheat contains differentially expressed transcription factors and is mainly enriched for NAC (61), MYB-associated (43), WRKY (27), and AP2/EREBP (16) genes. ...
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Premature leaf senescence has a profound influence on crop yield and quality. Here, a stable premature senescence mutant (GSm) was obtained from the common wheat (Triticum aestivum L.) cultivar Chang 6878 by mutagenesis with ethyl methanesulfonate. The differences between the GSm mutant and its wild-type (WT) were analyzed in terms of yield characteristics, photosynthetic fluorescence indices, and senescence-related physiological parameters. RNA sequencing was used to reveal gene expression differences between GSm and WT. The results showed that the yield of GSm was considerably lower than that of WT. The net photosynthetic rate, transpiration rate, maximum quantum yield, non-photochemical quenching coefficient, photosynthetic electron transport rate, soluble protein, peroxidase activity, and catalase activity all remarkably decreased in flag leaves of GSm, whereas malondialdehyde content distinctively increased compared with those of WT. The analysis of differentially expressed genes indicated blockade of chlorophyll and carotenoid biosynthesis, accelerated degradation of chlorophyll, and diminished photosynthetic capacity in mutant leaves; brassinolide might facilitate chlorophyll breakdown and consequently accelerate leaf senescence. NAC genes positively regulated the senescence process. Compared with NAC genes, expression of WRKY and MYB genes was induced earlier in the mutant possibly due to increased levels of reactive oxygen species and plant hormones (e.g., brassinolide, salicylic acid, and jasmonic acid), thereby accelerating leaf senescence. Furthermore, the antioxidant system played a role in minimizing oxidative damage in the mutant. These results provides novel insight into the molecular mechanisms of premature leaf senescence in crops.
... Massive fluctuations in electrolytic leakage (EL) and malondialdehyde (MDA) content are common features of leaf senescence in plants [36]. To investigate Suc-induced leaf senescence, EL was studied in detached leaf discs treated with various concentrations of Suc. ...
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Sucrose (Suc) accumulation is one of the key indicators of leaf senescence onset, but little is known about its regulatory role. Here, we found that application of high (120–150 mM) and low levels (60 mM) of Suc to young leaf (YL) and fully expanded leaf (FEL) discs, respectively, decreased chlorophyll content and maximum photosynthetic efficiency. Electrolyte leakage and malondialdehyde levels increased at high Suc concentrations (90–120 mM in YL and 60 and 150 mM in FEL discs). In FEL discs, the senescence-associated gene NtSAG12 showed a gradual increase in expression with increased Suc application; in contrast, in YL discs, NtSAG12 was upregulated with low Suc treatment (60 mM) but downregulated at higher levels of Suc. In YL discs, trehalose-6-phosphate (T6P) accumulated at a low half-maximal effective concentration (EC50) of Suc (1.765 mM). However, T6P levels declined as trehalose 6 phosphate synthase (TPS) content decreased, resulting in the maximum velocity of sucrose non-fermenting-1-related protein kinase (SnRK) and hexokinase (HXK) occurring at higher level of Suc. We therefore speculated that senescence was induced by hexose accumulation. In FEL discs, the EC50 of T6P occurred at a low concentration of Suc (0.9488 mM); T6P levels progressively increased with higher TPS content, which inhibited SnRK activity with a dissociation constant (Kd) of 0.001475 U/g. This confirmed that the T6P–SnRK complex induced senescence in detached FEL discs.
... In contrast, photosynthesis-related marker genes CHLOROPHYLL A/B BINDING PROTEIN 3 (CAB3) and RUBISCO SMALL SUBUNIT 2B (RBCS2B), which are expressed in various regions of the mature leaf (Susek et al., 1993;Sawchuk et al., 2008), had broad expression domains with strongest expression in clusters 1 and 4, respectively ( Figure 3A). Interestingly, clusters 2 and 8 shared expression of stress-and senescence-related genes such as WRKY53 and ZAT12 (Davletova et al., 2005;Bresson et al., 2018;Zentgraf and Doll, 2019; Figure 3A and Supplemental Data Sets S22 and S28). This may indicate that senescence promotes a transcriptional convergence of epidermal pavement and mesophyll cells irrespective of cell type. ...
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Like other complex multicellular organisms, plants are composed of different cell types with specialized shapes and functions. For example, most laminar leaves consist of multiple photosynthetic cell types. These cell types include the palisade mesophyll, which typically forms one or more cell layers on the adaxial side of the leaf. Despite their importance for photosynthesis, we know little about how palisade cells differ at the molecular level from other photosynthetic cell types. To this end, we have used a combination of cell-specific profiling using fluorescence-activated cell sorting and single-cell RNA-sequencing methods to generate a transcriptional blueprint of the palisade mesophyll in Arabidopsis thaliana leaves. We find that despite their unique morphology, palisade cells are otherwise transcriptionally similar to other photosynthetic cell types. Nevertheless, we show that some genes in the phenylpropanoid biosynthesis pathway have both palisade-enriched expression and are light-regulated. Phenylpropanoid gene activity in the palisade was required for production of the ultraviolet (UV)-B protectant sinapoylmalate, which may protect the palisade and/or other leaf cells against damaging UV light. These findings improve our understanding of how different photosynthetic cell types in the leaf can function uniquely to optimize leaf performance, despite their transcriptional similarities.
... During leaf senescence anthocyanin content is often reported to increase (Bresson et al. 2018). Enhanced transcription of flavonoid biosynthetic genes, among them DFR, has been reported in the early stage of maize leaf senescence (Zhang et al. 2014). ...
Article
Ultraviolet (UV) radiation, unless present at high doses, is recognised as a regulator of plant growth and some specific processes. The present study investigated the influence of short daily UV irradiation (15min/day, 11days) on leaf gas exchange and some biochemical and molecular markers of leaf senescence (such as stomata movements, chlorophyll breakdown, anthocyanin production, senescence-associated genes) in Micro-Tom tomato plants. The UV-induced reduction of gs (stomatal conductance) during the treatment was associated with the modified expression of some genes involved in the control of stomatal movements. We hypothesise a two-step regulation of stomatal closure involving salicylic and abscisic acid hormones. The temporal changes of gs and Anet (net photosynthetic CO2 assimilation rate) along with the pigment behaviour, suggest a possible delay of leaf senescence in treated plants, confirmed by the expression levels of genes related to senescence such as SAG113 and DFR. The UV potential to induce a persistent partial inhibition of gs without severely affecting Anet led to an increased iWUE (intrinsic water-use efficiency) during the 11-day treatment, suggesting a priming effect of short daily UV radiation towards drought conditions potentially useful in reducing the excess water use in agriculture.
... 2013; Lim and Nam 2005). These hydrolyzed molecules are transported to the developing fruits and seeds, which are very important for plant survival and sustainability in annual plants (Woo et al. 2013;Bresson et al. 2018). Leaf senescence is the last step of plant leaf growth and development, and it is affected by growth, hormones, and external environment, such as age, darkness, drought, and pathogen attacks (Lim et al. 2007). ...
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Key message Our results confirmed that SlERF.F5 can directly regulate the promoter activity of ACS6 and interact with SlMYC2 to regulate tomato leaf senescence. The process of plant senescence is complex and highly coordinated, and is regulated by many endogenous and environmental signals. Ethylene and jasmonic acid are well-known senescence inducers, but their molecular mechanisms for inducing leaf senescence have not been fully elucidated. Here, we isolated an ETHYLENE RESPONSE FACTOR F5 (SlERF.F5) from tomato. Silencing of SlERF.F5 causes accelerated senescence induced by age, darkness, ethylene, and jasmonic acid. However, overexpression of SlERF.F5 would not promote senescence. Moreover, SlERF.F5 can regulate the promoter activity of ACS6 in vitro and in vivo. Suppression of SlERF.F5 resulted in increased sensitivity to ethylene and jasmonic acid, decreased accumulation of chlorophyll content, and inhibited the expression of chlorophyll- and light response-related genes. Compared with the wild type, the qRT-PCR analysis showed the expression levels of genes related to the ethylene biosynthesis pathway and the jasmonic acid signaling pathway in SlERF.F5-RNAi lines increased. Yeast two-hybrid experiments showed that SlERF.F5 and SlMYC2 (a transcription factor downstream of the JA receptor) can interact physically, thereby mediating the role of SlERF.F5 in jasmonic acid-induced leaf senescence. Collectively, our research provides new insights into how ethylene and jasmonic acid promote leaf senescence in tomato.
... In the HOS15 loss-of-function mutant, the ORE1 transcript level was significantly downregulated compared to that in the WT in an age-dependent manner (Figure 2). RCBS1A and CAB1 play crucial roles during photosynthesis and CO 2 fixation (Izumi et al., 2012;Bresson et al., 2018). The expression levels of RCBS1A and CAB1 were significantly elevated in the HOS15 loss-of-function mutant compared to those in WT in an age-dependent manner (Figure 2). ...
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Multiple endogenous and environmental signals regulate the intricate and highly complex processes driving leaf senescence in plants. A number of genes have been identified in a variety of plant species, including Arabidopsis, which influence leaf senescence. Previously, we have shown that HOS15 is a multifunctional protein that regulates several physiological processes, including plant growth and development under adverse environmental conditions. HOS15 has also been reported to form a chromatin remodeling complex with PWR and HDA9 and to regulate the chromatin structure of numerous genes. However, unlike PWR and HDA9, the involvement of HOS15 in leaf senescence is yet to be identified. Here, we report that HOS15, together with PWR and HDA9, promotes leaf senescence via transcriptional regulation of SAG12/29, senescence marker genes, and CAB1/RCBS1A, photosynthesis-related genes. The expression of ORE1, SAG12 , and SAG29 was downregulated in hos15-2 plants, whereas the expression of photosynthesis-related genes, CAB1 and RCBS1A , was upregulated. HOS15 also promoted senescence through dark stress, as its mutation led to a much greener phenotype than that of the WT. Phenotypes of double and triple mutants of HOS15 with PWR and HDA9 produced phenotypes similar to those of a single hos15-2 . In line with this observation, the expression levels of NPX1 , APG9 , and WRKY57 were significantly elevated in hos15-2 and hos15/pwr, hos15/hda9, and hos15/pwr/hda9 mutants compared to those in the WT. Surprisingly, the total H3 acetylation level decreased in age-dependent manner and under dark stress in WT; however, it remained the same in hos15-2 plants regardless of dark stress, suggesting that dark-induced deacetylation requires functional HOS15. More interestingly, the promoters of APG9 , NPX1 , and WRKY57 were hyperacetylated in hos15-2 plants compared to those in WT plants. Our data reveal that HOS15 acts as a positive regulator and works in the same repressor complex with PWR and HDA9 to promote leaf senescence through aging and dark stress by repressing NPX1, APG9, and WRKY57 acetylation.
... Individual leaves likewise go through developmental stages of which the final stage, leaf senescence, causes the death of this particular plant organ (Keskitalo et al. 2005). Leaf senescence is a highly complex genetically programmed process, which is accompanied by comprehensive morphological, physiological and molecular changes (Woo et al. 2019(Woo et al. , 2013Kim et al. 2018;Wu et al. 2012;Shirzadian Khorramabad 2013), and includes the ordered degradation of macromolecules and remobilization of reclaimed nutrients to benefit the next generation or remainder of the plant (Maillard et al. 2015;Distelfeld et al. 2014;Gregersen et al. 2008;Kim et al. 2017;Bresson et al. 2018). ...
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Key message Our manuscript is the first to find a link between activity of SAL1/OLD101 against IP3 and plant leaf senescence regulation and ROS levels assigning a potential biological role for IP3. Abstract Leaf senescence is a genetically programmed process that limits the longevity of a leaf. We identified and analyzed the recessive Arabidopsis stay-green mutation onset of leaf death 101 (old101). Developmental leaf longevity is extended in old101 plants, which coincided with higher peroxidase activity and decreased H2O2 levels in young 10-day-old, but not 25-day-old plants. The old101 phenotype is caused by a point mutation in SAL1, which encodes a bifunctional enzyme with inositol polyphosphate-1-phosphatase and 3′ (2′), 5′-bisphosphate nucleotidase activity. SAL1 activity is highly specific for its substrates 3-polyadenosine 5-phosphate (PAP) and inositol 1, 4, 5-trisphosphate (IP3), where it removes the 1-phosphate group from the IP3 second messenger. The in vitro activity of recombinant old101 protein against its substrate IP3 was 2.5-fold lower than that of wild type SAL1 protein. However, the in vitro activity of recombinant old101 mutant protein against PAP remained the same as that of the wild type SAL1 protein. The results open the possibility that the activity of SAL1 against IP3 may affect the redox balance of young seedlings and that this delays the onset of leaf senescence.
... Leaf color was evaluated by harvesting 6 leaf tips (10-12 cm in length), wiped with 70% ethanol, and arranged on a white background. Leaves were photographed by using Nikon D5100 (Nikon Corp, Tokyo, Japan), processed by Image J software [57], and analyzed by automated colorimetric assay [58]. The pixels were grouped into four categories, namely green, green-yellow, yellow, and brown. ...
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Drought is one of the significant threats to the agricultural sector. However, there is limited knowledge on plant response to drought stress and post-drought recovery. Pandanus amaryllifolius, a moderate drought-tolerant plant, is well-known for its ability to survive in low-level soil moisture conditions. Understanding the molecular regulation of drought stress signaling in this plant could help guide the rational design of crop plants to counter this environmental challenge. This study aimed to determine the morpho-physiological, biochemical, and protein changes of P. amaryllifolius in response to drought stress and during recovery. Drought significantly reduced the leaf relative water content and chlorophyll content of P. amaryllifolius. In contrast, relative electrolyte leakage, proline and malondialdehyde contents, and the activities of antioxidant enzymes in the drought-treated and recovered samples were relatively higher than the well-watered sample. The protein changes between drought-stressed, well-watered, and recovered plants were evaluated using tandem mass tags (TMT)-based quantitative proteomics. Of the 1415 differentially abundant proteins, 74 were significantly altered. The majority of proteins differing between them were related to carbon metabolism, photosynthesis, stress response, and antioxidant activity. This is the first study that reports the protein changes in response to drought stress in Pandanus. The data generated provide an insight into the drought-responsive mechanisms in P. amaryllifolius.
... During the loss of green color, chlorophyll undergoes complex changes from its colored derivatives to colorless products (Archetti et al., 2009). Together with the strong positive correlation between the degradation of chlorophyll and photosynthesis decrease, the chlorophyll content is the most popular trait for quantifying leaf senescence (Jiang et al., 2004;Ougham et al., 2008;Bresson et al., 2017;Zhao et al., 2019). ...
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Senescence in plants is a complex trait, which is controlled by both genetic and environmental factors and can affect the yield and quality of cotton. However, the genetic basis of cotton senescence remains relatively unknown. In this study, we reported genome-wide association studies (GWAS) based on 185 accessions of upland cotton and 26,999 high-quality single-nucleotide polymorphisms (SNPs) to reveal the genetic basis of cotton senescence. To determine cotton senescence, we evaluated eight traits/indices. Our results revealed a high positive correlation ( r >0.5) among SPAD value 20 days after topping (SPAD20d), relative difference of SPAD (RSPAD), nodes above white flower on topping day (NAWF0d), nodes above white flower 7 days after topping (NAWF7d), and number of open bolls on the upper four branches (NB), and genetic analysis revealed that all traits had medium or high heritability ranging from 0.53 to 0.86. Based on a multi-locus method (FASTmrMLM), a total of 63 stable and significant quantitative trait nucleotides (QTNs) were detected, which represented 50 genomic regions (GWAS risk loci) associated with cotton senescence. We observed three reliable loci located on chromosomes A02 (A02_105891088_107196428), D03 (D03_37952328_38393621) and D13 (D13_59408561_60730103) because of their high repeatability. One candidate gene (Ghir_D03G011060) was found in the locus D03_37952328_38393621, and its Arabidopsis thaliana homologous gene (AT5G23040) encodes a cell growth defect factor-like protein (CDF1), which might be involved in chlorophyll synthesis and cell death. Moreover, qRT-PCR showed that the transcript level of Ghir_D03G011060 was down-regulated in old cotton leaves, and virus-induced gene silencing (VIGS) indicated that silencing of Ghir_D03G011060 resulted in leaf chlorosis and promoted leaf senescence. In addition, two candidate genes (Ghir_A02G017660 and Ghir_D13G021720) were identified in loci A02_105891088_107196428 and D13_59408561_60730103, respectively. These results provide new insights into the genetic basis of cotton senescence and will serve as an important reference for the development and implementation of strategies to prevent premature senescence in cotton breeding programs.
... As in the adult plants, the fresh weight of pldα1-1 rosettes was significantly lower (36%) compared with the WT and complemented lines (Figures 2E,F). Expressions of Senescence-Associated Genes 13 (SAG13, At2g29350) and the transcription factor ANAC092/ NAC2/ORE1 (At5g39610) are commonly used as markers of senescence (Balazadeh et al., 2010;Bresson et al., 2018). Expressions of these genes were higher in all Mg 2+ -treated WT, pldα1-1 and complemented plants in comparison with untreated controls. ...
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Magnesium (Mg ²⁺ ) is a macronutrient involved in essential cellular processes. Its deficiency or excess is a stress factor for plants, seriously affecting their growth and development and therefore, its accurate regulation is essential. Recently, we discovered that phospholipase Dα1 (PLDα1) activity is vital in the stress response to high-magnesium conditions in Arabidopsis roots. This study shows that PLDα1 acts as a negative regulator of high-Mg ²⁺ -induced leaf senescence in Arabidopsis. The level of phosphatidic acid produced by PLDα1 and the amount of PLDα1 in the leaves increase in plants treated with high Mg ²⁺ . A knockout mutant of PLDα1 ( pldα1-1 ), exhibits premature leaf senescence under high-Mg ²⁺ conditions. In pldα1-1 plants, higher accumulation of abscisic and jasmonic acid (JA) and impaired magnesium, potassium and phosphate homeostasis were observed under high-Mg ²⁺ conditions. High Mg ²⁺ also led to an increase of starch and proline content in Arabidopsis plants. While the starch content was higher in pldα1-1 plants, proline content was significantly lower in pldα1-1 compared with wild type plants. Our results show that PLDα1 is essential for Arabidopsis plants to cope with the pleiotropic effects of high-Mg ²⁺ stress and delay the leaf senescence.
... During vegetative growth, the leaves at 590 positions 5 to 9 within the rosette were labelled from bottom to top for the following analyses: leaf 5 -591 chlorophyll extraction; leaf 6 -sugar content; leaf 7 -whole genome bisulfite sequencing (WGBS); 592 leaf 8 -hormone analyses; leaf 9 -H 2 O 2 content. Four developmental stages were chosen roughly 593 corresponding to the following stages from the "Timetable of Arabidopsis Growth Stages" as described byBresson et al. (2018). Principle component analysis (PCA) was 601 performed with R by using pixel counts from the ACA analysis for green, green-yellow, yellow, brown 602 and total leaf pixels and by using leaf fresh weights with the function prcomp.Linear regression 603 analysis with k-mer validation for the correlation of ACA with chlorophyll concentrations was 604 performed with the 'ceret' package of R. Data indexing was performed using the createMultiFolds 605 function with k = 5 and times = 10. ...
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The lifespan of plants and tissues is restricted by environmental and genetic components. Following the transition to reproductive growth, leaf senescence ceases cellular life in monocarpic plants to remobilize nutrients to storage organs. We observed altered leaf to seed ratios, faster senescence progression and enhanced nitrogen remobilization from the leaves in two methylation mutants (ros1 and the triple dmr1/2 cmt3 knockout). DNA methylation in wild type Col-0 leaves initially moderately declined with progressing leaf senescence, predominantly in the CG context, while the ultimate phase of leaf discoloration was associated with moderate de novo methylation of cytosines, primarily in the CHH context. Relatively few differentially methylated regions, including one in the ROS1 promoter linked to the down-regulation of ROS1, were present, but these were unrelated to known senescence-associated genes. Differential methylation patterns were identified in transcription factor binding sites, such as the W-boxes that are targeted by WRKYs, which impaired transcription factor binding when methylated in vitro. Mutants that are defective in DNA methylation showed distinct nitrogen remobilization, which was associated with altered patterns of leaf senescence progression. But moderate methylome changes during leaf senescence were not specifically associated with up-regulated genes during senescence.
... Two parameters were calculated: Fv/Fm-the maximum quantum efficiency of PSII and Fv/F0-the maximum primary yield of the photochemistry of PSII. For a healthy sample, the Fv/Fm ratio is around 0.83 and lowers as plant stress increases, reaching 0.3 at the end of senescence [54]. ...
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Caraway (Carum carvi L.) essential oil is a candidate for botanical herbicides. A hypothesis was formulated that the sand-applied maltodextrin-coated caraway oil (MCEO) does not affect the growth of maize (Zea mays L.). In the pot experiment, pre-emergence application of five doses of MCEO was tested on four maize cultivars up to the three-leaf growth stage. The morphological analyses were supported by the measurements of relative chlorophyll content (SPAD), two parameters of chlorophyll a fluorescence, e.g., Fv/Fm and Fv/F0, and fluorescence emission spectra. The analyzed MCEO contained 6.5% caraway EO with carvone and limonene as the main compounds, constituting 95% of the oil. The MCEO caused 7-day delays in maize emergence from the dose of 0.9 g per pot (equal to 96 g m−2). Maize development at the three-leaf growth stage, i.e., length of roots, length of leaves, and biomass of shoots and leaves, was significantly impaired already at the lowest dose of MCEO: 0.4 g per pot, equal to 44 g m−2. A significant drop of both chlorophyll a fluorescence parameters was noted, on average, from the dose of 0.7 g per pot, equal to 69 g m−2. Among the tested cultivars, cv. Rywal and Pomerania were less susceptible to the MCEO compared to the cv. Kurant and Podole. In summary, maize is susceptible to the pre-emergence, sand-applied MCEO from the dose of 44 g m−2.
... Intrinsically, initiation of senescence is the consequence of integrated signals, including endogenous and environmental signals (Bresson et al., 2018). Developmental senescence, which is a coordinated physiological process, could be induced by the endogenous factors (Zentgraf et al., 2004). ...
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Cation gradients in plant cellular compartments are maintained by the synergistic actions of various ion exchangers, pumps, and channels. Cation/Ca2+ exchanger (CCX) is one of the clades of the Ca2+/cation antiporter super family. Here, five SlCCX genes were identified in tomato. Sequence analysis indicated that SlCCXs have the conserved motifs as the CCX domain. Analysis of the expression level of each member of tomato CCX gene family under cation (Mg2+, Mn2+, Na+, and Ca2+) treatment was determined by qRT-PCR. Tomato CCX demonstrated different degrees of responding to cation treatment. Changes in SlCCX1-LIKE expression was induced by Mg2+ and Mn2+ treatment. Analysis of the expression of SlCCX genes in different tissues demonstrated that constitutive high expression of a few genes, including SlCCX1-LIKE and SlCCX5, indicated their role in tomato organ growth and development. Overexpression of SlCCX1-LIKE dramatically induced leaf senescence. Transcriptome analysis showed that genes related to ROS and several IAA signaling pathways were significantly downregulated, whereas ETH and ABA signaling pathway-related genes were upregulated in overexpression of SlCCX1-LIKE (OE-SlCCX1-LIKE) plants, compared with the wild type (WT). Moreover, overexpression of SlCCX1-LIKE plants accumulated more ROS content but less Mg2+ content. Collectively, the findings of this study provide insights into the base mechanism through which CCXs regulate leaf senescence in tomato.
... Thus, the degradation of chlorophyll was also a main marker of senescence of plant leaves. In Zea mays 11 , Sorghum bicolor 12 , and Arabidopsis thaliana 13 , chlorophyll contents were closely related to leaf senescence. Besides, during leaf senescence, some genes involved in photosynthesis would be down regulated expressed, resulting in the decrease of the photosynthetic ability of leaves 14,15 . ...
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To study the physiological and molecular regulating mechanism of ancient Camellia oleifera which kept a exuberant vitality for more than one hundred years, leaves of 30a year old and > 100 year old Camellia oleifera were selected as targets. On the basis of the study of the generation and the clearance of reactive oxygen species, sequencing analysis of the transcriptome and expression profiling by high throughput sequencing analysis technique was conducted to study differentially expressed functional genes related to the tree age. It showed that the chlorophyll content and enzyme activities increased in ancient Camellia oleifera leaves. Expression of chlorophyll a/b binding protein gene, auxin related gene, the signal transduction factor and the transcription factor gene in ancient trees were all higher than mature tree. The down regulated gene expression of inductive genes related to protein degradation in ancient tree. Under the comprehensive function of those factors, ancient Camellia oleifera leaves still kept an exuberant vitality which was very useful for studies of stress resistance molecular biology and genetic improvement of Camellia oleifera.
... The potential phytotoxic effect of EOs on the photosynthetic efficiency of plants was evaluated by estimating the maximum quantum efficiency of photosystem II (Fv/Fm) with a fluorimeter (Handy PEA+, Hansatech Instruments Ltd., Norfolk, United Kingdom). For a healthy sample, this ratio is around 0.83 and lowers as plant stress increases, reaching 0.3 at the end of senescence (Bresson et al., 2018). Moreover, the maximum quantum yield of photosystem II has been used to evaluate foliar response after EO application (Synowiec et al., 2015(Synowiec et al., , 2019. ...
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The use of conventional pesticides is debated because of their multiple potential adverse effects on non-target organisms, human health, pest resistance development and environmental contaminations. In this setting, this study focused on developing alternatives, such as trunk-injected essential oil (EO)-based biopesticides. We analysed the ecophysiology of apple trees (Malus domestica) following the injection of Cinnamomum cassia and Mentha spicata nanoemulsions in the tree's vascular system. Targeted and untargeted volatile organic compounds (VOCs) analyses were performed on leaf-contained and leaf-emitted VOCs and analysed through dynamic headspace-gas chromatography-mass spectrometry (DHS-GC-MS) and thermal desorption unit (TDU)-GC-MS. Our results showed that carvone, as a major constituent of the M. spicata EO, was contained in the leaves (mean concentrations ranging from 3.39 to 19.7 ng g DW −1) and emitted at a constant rate of approximately 0.2 ng g DW −1 h −1. Trans-cinnamaldehyde, C. cassia's major component, accumulated in the leaves (mean concentrations of 83.46 and 350.54 ng g DW −1) without being emitted. Furthermore, our results highlighted the increase in various VOCs following EO injection, both in terms of leaf-contained VOCs, such as methyl salicylate, and in terms of leaf-emitted VOCs, such as caryophyllene. Principal component analysis (PCA) highlighted differences in terms of VOC profiles. In addition, an analysis of similarity (ANOSIM) and permutational multivariate analysis of variance (PERMANOVA) revealed that the VOC profiles were significantly impacted by the treatment. Maximum yields of photosystem II (Fv/Fm) were within the range of 0.80-0.85, indicating that the trees remained healthy throughout the experiment. Our targeted analysis demonstrated the systemic translocation of EOs through the plant's vascular system. The untargeted analysis, on the other hand, highlighted the potential systemic acquired resistance (SAR) induction by these EOs. Lastly, C. cassia and M. spicata EOs did not appear phytotoxic to the treated trees, as demonstrated through chlorophyll fluorescence measurements. Hence, this work can Frontiers in Plant Science | www.frontiersin.org 1 April 2021 | Volume 12 | Article 650132 Werrie et al. Biopesticide Trunk-Injection be seen as a proof of concept for the use of trunk-injected EOs given the systemic translocation, increased production and release of biogenic VOCs (BVOCs) and absence of phytotoxicity. Further works should focus on the ecological impact of such treatments in orchards, as well as apple quality and production yields.
... The parameters of traditional RGB model are mainly the mean values of each color channel and their combined values, which can approximately describe the color depth of the leaves and estimate the chlorophyll content of the leaves (Dey et al., 2016Yadav et al., 2010Adamsen et al., 1999;Hu et al., 2010;Ali et al., 2012;Han et al., 2014). Moreover, the RGB model re ects the soil moisture and nutrient level (Barbedo et al., 2019Humplík et al., 2015aBresson et al., 2018. However, the mean values of image parameters is not comprehensive enough in the description of color distribution (Li et al., 2014), as a result, RGB model is generally used in the studies of water, fertility and disease which may drastically change the leaf color (Neilson et al., 2015;Bai et al., 2018;Gracia-Romero et al., 2017;Sancho-Adamson et al., 2019). ...
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Background: The high quality and efficient production of greenhouse vegetation depend on the micrometeorology environmental adjusting such as the system warming, illumination supplement. In order to improve the quantity, quality and efficiency of greenhouse vegetation, it is necessary to figure out the relationship between the crop growth conditions and environmental meteorological factors, which could give constructive suggestions for precise control of greenhouse environment and reducing the running cost. The parameters from the color information of plant canopy reflect the internal physiological conditions, thus, RGB model has been widely used in the color analysis of digital pictures of leaves. Results: The color scale for single leaf, single plant, and the populate canopy of Begonia Fimbristipula Hance (BFH) photographs are all have a skewed cumulative distribution histograms. The color gradation skewness-distribution (CGSD) parameters of the RGB model were increased from 4 to 20 after the skewness analysis, which greatly expanded the canopy leaf color information and could simultaneously describe the depth and distribution characteristics of canopy color. The 20 CGSD parameters were sensitive to the micrometeorology factors, especially to the radiation and temperature accumulation. The multiple regression models of mean, median, mode and kurtosis parameters to microclimate factors were established, and the spatial models of skewness parameters were optimized. Conclusions: The models constructed based on the color gradation skewness-distribution (CGSD) parameters of the RGB model, can well explain the response of canopy color to microclimate factors and can be used to monitor the variation of plant canopy color under different micrometeorology.
... During the onset and progression of senescence, several thousand genes are differentially expressed [7,132]. Senescence-associated gene-regulatory networks in Arabidopsis, rice, and wheat have uncovered the significant role of genes in the transcription factors family NAC and WRKY [8,28,214,215]. In Arabidopsis thaliana, approximately 2500 genes transcribed during leaf senescence have been identified (~130 are transcription factors) [131]. In Wheat approximately 52,905 high confidence genes are expressed (~2210 are TFs) during senescence, of them 9533 are identified as differentially expressed gene (DEGs) (~341 are TFs) [8]. ...
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Wheat leaf senescence is a developmental process that involves expressional changes in thousands of genes that ultimately impact grain protein content (GPC), grain yield (GY), and nitrogen use efficiency. The onset and rate of senescence are strongly influenced by plant hormones and environmental factors e.g. nitrogen availability. At maturity, decrease in nitrogen uptake could enhance N remobilization from leaves and stem to grain, eventually leading to leaf senescence. Early senescence is related to high GPC and somewhat low yield whereas late senescence is often related to high yield and somewhat low GPC. Early or late senescence is principally regulated by up and down-regulation of senescence associated genes. Integration of external and internal factors together with genotypic variation influence senescence associated genes in a developmental age dependent manner. Although regulation of genes involved in senescence has been studied in rice, Arabidopsis, maize, and currently in wheat, there are genotype-specific variations yet to explore. A major effort is needed to understand the interaction of positive and negative senescence regulators in determining the onset of senescence. In wheat, increasing attention has been paid to understand the role of positive senescence regulator, e.g. GPC-1, regulated gene network during early senescence time course. Recently, gene regulatory network involved early to late senescence time course revealed important senescence regulators. However, the known negative senescence regulator TaNAC-S gene has not been extensively studied in wheat and little is known about its value in breeding. Existing data on senescence-related transcriptome studies and gene regulatory network could effectively be used for functional study in developing nitrogen efficient wheat varieties.
... For the improved hybrid lines, the reduction of the percentage of green leaves = [(PGL WW -PGL DS )/ PGL WW ] × 100%, WW represents well-watered condition, and DS represents drought stress condition. The optimal photochemical efficiency of PSII (Fv/Fm; Maxwell and Johnson, 2000;Bresson et al., 2018) was measured after 2 h of dark adaption using a closed FluorCam instrument (Photon Systems Instruments, Czech Republic). After harvesting, ear weight of maize inbred lines was measured with at least three plants per line, and those of the improved hybrids and Jidan27 were measured with at least eight plants from each kind. ...
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Leaf senescence is important for crop yield. In this study, population genetics and transcriptomic profiling were combined to dissect its genetic basis in maize. For this, the progenies of an elite maize hybrid Jidan27 and its parental lines Si-287 (early senescence) and Si-144 (stay-green), as well as 173 maize inbred lines were used, and two novel loci and their candidate genes, Stg3 (ZmATG18b) and Stg7 (ZmGH3.8) were identified, which are predicted to be the members of autophagy and auxin pathways, respectively. Genomic variations in the promoter regions of these two genes were detected, and four allelic combinations existed in the examined maize inbred lines. The Stg3 Si-144/Stg7 Si-144 allelic combination with a lower ZmATG18b expression level and higher ZmGH3.8 expression level could distinctively delay leaf senescence, increase ear weight and significantly reduce ear weight loss under drought stress, while opposite effects were observed in the Stg3 Si-287/Stg7 Si-287 combination with a higher ZmATG18b expression level and lower ZmGH3.8 expression level. Thus, we identify a potential interaction between autophagy and auxin which could modulate the timing of maize leaf senescence.
... Precocious or early senescence caused by harsh growth conditions, on the other hand, compromises crop yield in an agricultural setting (Wu et al., 2012;Bengoa Luoni et al., 2019). Initiation and progression of leaf senescence can be affected by a large number of endogenous and environmental factors including developmental stage, age, phytohormones, environmental cues such as temperature, darkness, and pathogens (Bresson et al., 2018). All these factors and related signaling pathways form a complex network in fine-tuning the initiation and progression of leaf senescence. ...
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... The chlorophyll contents were estimated once a week by measuring the middle parts of the flag or second upper leaves using a CCM-300 chlorophyll meter (Opti-Sciences, Hudson, NH). To quantify the progressive leaf and panicle color modification from green to green-yellow, to yellow, and to brown, the Automated Colourimetric Assay (ACA) described in the previous report was used 35 . After scanning of detached leaves or panicles, background removed images of single leaf or panicle was prepared by using ImageJ. ...
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At present, chlorophyll meters are widely used for a quick and nondestructive estimate of the chlorophyll (Chl) content in plant leaves. Chlorophyll meters allows to estimate the Chl content in relative units—the chlorophyll index (CI). However, using such meters, one can face a problem of converting the CI into the absolute values of the pigment content and comparing the data acquired with different devices and for different plant species. Many Chl meters (SPAD-502, CL-01, CCM-200) demonstrated a high degree of correlation between the CI and the absolute pigment content, and a number of formulas have been deduced for different plant species to convert the CI into the absolute value of the photosynthetic pigment content. However, such data have not yet been acquired for the atLEAF+ chlorophyll meter. The purpose of the present research was to assess the applicability of the atLEAF+ Chl meter for estimating Chl content. A significant speciesspecific exponential relationships between the atLEAF value (corresponding to CI) and extractable Chl a, Chl b, Chl (a+b) for Calamus dioicus and Cleistanthus sp. were shown. The correlations between the atLEAF values and the content of Chl a, Chl b, and Chl (a+b) per unit of leaf area was stronger than per unit of dry leaf mass. The atLEAF value—Chl b correlation was weaker than that of atLEAF value—Chl a and atLEAF value—Chl (a+b) correlations. The influence of light conditions (Chl a/b ratio) on the atLEAF value has also been shown. The obtained results indicate that on condition of the right calibration the atLEAF+ Chl meter is a cheap and convenient tool for a quick nondestructive estimate of Chl content and can be used for this purpose along with other Chl meters.
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Effects of abiotic and biotic stresses on plant photosynthetic performance lead to fitness and yield decrease. The maximum quantum efficiency of photosystem II (F v/F m) is a parameter of chlorophyll fluorescence (ChlF) classically used to track changes in photosynthetic performance. Despite recent technical and methodological advances in ChlF imaging, the spatio-temporal heterogeneity of F v/F m still awaits for standardized and accurate quantification. We developed a method to quantify the dynamics of spatial heterogeneity of photosynthetic efficiency through the distribution-based analysis of F v/F m values. The method was applied to Arabidopsis thaliana grown under well-watered and severe water deficit (survival rate of 40%). First, whole-plant F v/F m shifted from unimodal to bimodal distributions during plant development despite a constant mean F v/F m under well-watered conditions. The establishment of a bimodal distribution of F v/F m reflects the occurrence of two types of leaf regions with contrasted photosynthetic efficiency. The distance between the two modes (called S) quantified the whole-plant photosynthetic heterogeneity. The weighted contribution of the most efficient/healthiest leaf regions to whole-plant performance (called W max) quantified the spatial efficiency of a photosynthetically heterogeneous plant. Plant survival to water deficit was associated to high S values, as well as with strong and fast recovery of W max following soil rewatering. Hence, during stress surviving plants had higher, but more efficient photosynthetic heterogeneity compared to perishing plants. Importantly, S allowed the discrimination between surviving and perishing plants four days earlier than the mean F v/F m. A sensitivity analysis from simulated dynamics of F v/F m showed that parameters indicative of plant tolerance and/or stress intensity caused identifiable changes in S and W max. Finally, an independent comparison of six Arabidopsis accessions grown under well-watered conditions indicated that S and W max are related to the genetic variability of growth. The distribution-based analysis of ChlF provides an efficient tool for quantifying photosynthetic heterogeneity and performance. S and W max are good indicators to estimate plant survival under water stress. Our results suggest that the dynamics of photosynthetic heterogeneity are key components of plant growth and tolerance to stress.
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As sessile organisms, plants have to continuously adjust growth and development to ever-changing environmental conditions. At the end of the growing season, annual plants induce leaf senescence to reallocate nutrients and energy-rich substances from the leaves to the maturing seeds. Thus, leaf senescence is a means with which to increase reproductive success and is therefore tightly coupled to the developmental age of the plant. However, senescence can also be induced in response to sub-optimal growth conditions as an exit strategy, which is accompanied by severely reduced yield. Here, we show that class III homeodomain leucine zipper (HD-ZIPIII) transcription factors, which are known to be involved in basic pattern formation, have an additional role in controlling the onset of leaf senescence in Arabidopsis. Several potential direct downstream genes of the HD-ZIPIII protein REVOLUTA (REV) have known roles in environment-controlled physiological processes. We report that REV acts as a redox-sensitive transcription factor, and directly and positively regulates the expression of WRKY53, a master regulator of age-induced leaf senescence. HD-ZIPIII proteins are required for the full induction of WRKY53 in response to oxidative stress, and mutations in HD-ZIPIII genes strongly delay the onset of senescence. Thus, a crosstalk between early and late stages of leaf development appears to contribute to reproductive success.
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Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970-1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010-2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.
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Plant autophagy, one of the essential proteolysis systems, balances proteome and nutrient levels in cells of the whole plant. Autophagy has been studied by analysing Arabidopsis thaliana autophagy-defective atg mutants, but the relationship between autophagy and chlorophyll (Chl) breakdown during stress-induced leaf yellowing remains unclear. During natural senescence or under abiotic-stress conditions, extensive cell death and early yellowing occurs in the leaves of atg mutants. A new finding is revealed that atg5 and atg7 mutants exhibit a functional stay-green phenotype under mild abiotic-stress conditions, but leaf yellowing proceeds normally in wild-type leaves under these conditions. Under mild salt stress, atg5 leaves retained high levels of Chls and all photosystem proteins and maintained a normal chloroplast structure. Furthermore, a double mutant of atg5 and non-functional stay-green nonyellowing1-1 (atg5 nye1-1) showed a much stronger stay-green phenotype than either single mutant. Taking these results together, it is proposed that autophagy functions in the non-selective catabolism of Chls and photosynthetic proteins during stress-induced leaf yellowing, in addition to the selective degradation of Chl–apoprotein complexes in the chloroplasts through the senescence-induced STAY-GREEN1/NYE1 and Chl catabolic enzymes.
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Breakdown of leaf proteins, particularly chloroplast proteins, is a massive process in senescing leaves. In spite of its importance in internal N recycling, the mechanism(s) and the enzymes involved are largely unknown. Senescenceassociated vacuoles (SAVs) are small, acidic vacuoles with high cysteine peptidase activity. Chloroplast-targeted proteins re-localize to SAVs during senescence, suggesting that SAVs might be involved in chloroplast protein degradation. SAVs were undetectable in mature, non-senescent tobacco leaves. Their abundance, visualized either with the acidotropic marker Lysotracker Red or by green fluorescent protein (GFP) fluorescence in a line expressing the senescence-associated cysteine protease SAG12 fused to GFP, increased during senescence induction in darkness, and peaked after 2-4 d, when chloroplast dismantling was most intense. Increased abundance of SAVs correlated with higher levels of SAG12 mRNA. Activity labelling with a biotinylated derivative of the cysteine protease inhibitor E-64 was used to detect active cysteine proteases. The two apparently most abundant cysteine proteases of senescing leaves, of 40 kDa and 33 kDa were detected in isolated SAVs. Rubisco degradation in isolated SAVs was completely blocked by E-64. Treatment of leaf disks with E-64 in vivo substantially reduced degradation of Rubisco and leaf proteins. Overall, these results indicate that SAVs contain most of the cysteine protease activity of senescing cells, and that SAV cysteine proteases are at least partly responsible for the degradation of stromal proteins of the chloroplast. © The Author 2013. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: [email protected] /* */
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The light-harvesting chlorophyll a/b-binding (LHCB) proteins are the apoproteins of the light-harvesting complex of photosystem II. In the present study, we observed that downregulation of any of the six LHCB genes resulted in abscisic acid (ABA)-insensitive phenotypes in seed germination and post-germination growth, demonstrating that LHCB proteins are positively involved in these developmental processes in response to ABA. ABA was required for full expression of different LHCB members and physiologically high levels of ABA enhanced LHCB expression. The LHCB members were shown to be targets of an ABA-responsive WRKY-domain transcription factor, WRKY40, which represses LHCB expression to balance the positive function of the LHCBs in ABA signalling. These findings revealed that ABA is an inducer that fine-tunes LHCB expression at least partly through repressing the WRKY40 transcription repressor in stressful conditions in co-operation with light, which allows plants to adapt to environmental challenges.
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