[34] Chlorophylls and carotenoids: Pigments of photosynthetic biomembranes.

Methods in enzymology (Impact Factor: 1.9). 01/1987; 148C:350-382. DOI: 10.1016/0076-6879(87)48036-1
Source: PubMed
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ascorbate (vitamin C) plays an important role in detoxification of reactive oxygen species (ROS) in most living organisms. Monodehydroascorbate reductase (MDHAR; EC is crucial to regeneration of the oxidized form of ascorbate (monodehydroascorbate) so that it can be recycled to maintain ROS scavenging ability. The MDHAR gene from Brassica rapa L was cloned and introduced into Arabidopsis thaliana (L.) Heynh. to test the hypothesis that enhanced ROS scavenging activity of BrMDHAR alleviates freezing stress. BrMDHAR was expressed under the control of either the CaMV 355 promoter or stress inducible SWPA2 promoter. Ectopic expression of BrMDHAR led to the up-regulation of many antioxidant genes, including APX, DHAR, GR, SOD, GPX, and PRX Q, which are involved in ascorbate-glutathione cycle. And, transgenic plants showed improved stress tolerance against freezing with exhibiting higher levels of chlorophyll content and antioxidant molecules such as ascorbate and glutathione as well as alleviated redox status and malondialdehyde contents. These results suggested that ectopic expression of BrMDHAR conferred improved tolerance to freezing stress not only by simply recycling ascorbate, but also by inducing co-regulation of the ascorbate-glutathione cycle, which in turn enhances the antioxidant capacity of the host plants.
    South African Journal of Botany 09/2013; 88:388-400. DOI:10.1016/j.sajb.2013.08.015 · 1.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Symbioses with arbuscular mycorrhizal fungi (AMF) may increase plant tolerance to heavy metals, in addition to the improvement in phosphorus (P) uptake by plants. This study evaluated the effects of the interaction between an increase in the soil phosphorus level and the colonization by Rhizophagus clarus on several biochemical and physiological parameters of Crotalaria juncea plants cultivated in a soil with a high copper (Cu) level. Plant growth and photosynthetic pigment fluorescence parameters, as well as the superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) enzyme activities in C. juncea plants, were analyzed. The experiment was conducted in a greenhouse, and a 3 × 2 factorial design was employed, including the natural P level, 40, and 100 mg P kg−1, with and without R. clarus inoculation, with three replicates in a soil with a high Cu level (65 mg kg−1). The results demonstrate that the combination of the addition of P together with AMF inoculation improved the plant nutritional status, with consequent increases in the levels of P, K, Mg, Fe, Zn, and chlorophyll a fluorescence parameters. Furthermore, mycorrhization and phosphorus addition increased the activities of the SOD and CAT enzymes, which are responsible for the removal of reactive oxygen species when plants are exposed to high Cu levels. This synergistic effect between P application and inoculation with R. clarus could be of technological interest for achieving increased growth of C. juncea cultivated in soils with high Cu levels via the promotion of effective mechanisms for reducing Cu phytotoxicity.
    Applied Soil Ecology 07/2015; 91. DOI:10.1016/j.apsoil.2015.02.008 · 2.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The influence of phytochrome B overproduction in 50- to 60-day-old transgenic potato plants (Solanum tuberosum L., lines Dara 5 and Dara 12 with moderate and intense expression of PHYB, respectively) on the resistance of photosynthetic apparatus to UV-B irradiation was investigated. In plants unexposed to UV-B, there was no significant difference in photosynthetic rates (P n) and fluorescence parameters (F v/F m, qN, qP) between the nontransformed (NT) line and Dara-5 and Dara-12 lines, whereas the content of photosynthetic pigments per 1 cm2 leaf area was higher in the transgenic plants. Irradiation with UV-B resulted in the decrease in photosynthetic rate in NT plants by 35-45%, whereas in Dara-12 line this rate was lowered by only 20-25%. Exposure to UV-B reduced the amplitudes of both fast and slow components of delayed fluorescence (DF), which indicated the diminished efficiency of photosystem II (PSII). The decrease in the maximum amplitude of the slow DF component was markedly lower in Dara-12 (19%) than in NT line (33%). The maximal photochemical quantum yield of PSII (F v/F m ratio) in plants exposed to UV-B was also suppressed stronger in NT line than in Dara-12. The line Dara-5 had intermediate position among other lines in terms of UV-B resistance of photosynthesis and PSII activity, but it was closer to NT than to Dara-12. Thus, the potato plants actively expressing the gene of Arabidopsis phytochrome B apoprotein (PHYB) demonstrated a higher resistance of photosynthetic apparatus to UV-B radiation compared to nontransformed plants. The elevated UV-B tolerance is most likely related to the increased leaf content of chlorophyll, carotenoids, and flavonoids.
    Russian Journal of Plant Physiology 03/2015; 62(2):204-209. DOI:10.1134/S1021443715020119 · 0.76 Impact Factor