Glutathione, photosynthesis and the redox regulation of stress-responsive gene expression.
ABSTRACT The ubiquitous antioxidant thiol tripeptide glutathione is present in millimolar concentrations in plant tissues and is regarded as one of the major determinants of cellular redox homeostasis. Recent research has highlighted a regulatory role for glutathione in influencing the expression of many genes important in plants' responses to both abiotic and biotic stress. Therefore, it becomes important to consider how glutathione levels and its redox state are influenced by environmental factors, how glutathione is integrated into primary metabolism and precisely how it can influence the functioning of signal transduction pathways by modulating cellular redox state. This review draws on a number of recent important observations and papers to present a unified view of how the responsiveness of glutathione to changes in photosynthesis may be one means of linking changes in nuclear gene expression to changes in the plant's external environment.
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ABSTRACT: The interactive effects of some vitamins (folic acid ;vitamin B , ascorbic acid ;vitamin c, 12 and coblamin ;vitamin B) in the presence of NaCl on germination, seedling growth and some relevant metabolic changes of flax (Linum usitatissimum) seeds grown at 100, 200 and 300 mM NaCl were studied. In this investigation, flax seeds tolerated NaCl salinity up to 200 mM NaCl; the germination was completely inhibited at 300 mM NaCl. Moreover, salinity induced marked increases in soluble carbohydrates, lipid peroxidation product (MDA) as well as the reduced glutathione and proline contents which were concomitant with sharp decrease in total phenols, ascorbic acid and the total free amino acids contents. Furthermore, NaCl treatment increased the activities of some antioxidant enzymes (superoxide dismutase; SOD, ascorbate peroxidase; APX, ascorbate oxidase; ASO as well as phenol peroxidase; GPX and polyphenol oxidase; POX). On the other hand, the completely non germinated flax seeds (at 300 mM NaCl) showed an amazing capacity for recovery and germination after treatment with either folic acid, ascorbic acid or coblamin. Finally the potentiation of these vitamins was mediated by accumulation of some osmoprotectants such as polyphenols, free amino acids and proline which, associated with increasing of some water soluble antioxidants such as ascorbic acid and glutathione.
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ABSTRACT: The roles of ascorbic acid (AsA, 1 mM) under an osmotic stress [induced by 15 % (m/v) polyethylene glycol, PEG-6000] were investigated by examining morphological and physiological attributes in Brassica species. The osmotic stress reduced the fresh and dry masses, leaf relative water content (RWC), and chlorophyll (Chl) content, whereas increased the proline (Pro), malondialdehyde (MDA), and H2O2 content, and lipoxygenase (LOX) activity. The ascorbate content in B. napus, B. campestris, and B. juncea decreased, increased, and remained unaltered, respectively. The dehydroascorbate (DHA) content increased only in B. napus. The AsA/DHA ratio was reduced by the osmotic stress in all the species except B. juncea. The osmotic stress increased the glutathione (GSH) content only in B. juncea, but increased the glutathione disulfide (GSSG) content and decreased the GSH/GSSG ratio in all the species. The osmotic stress increased the activities of ascorbate peroxidase (APX) (except in B. napus), glutathione reductase (GR) (except in B. napus), glutathione S-transferase (GST) (except in B. juncea), and glutathione peroxidase (GPX), and decreased the activities of catalase (CAT) and monodehydroascorbate reductase (MDHAR) (only in B. campestris). The osmotic stress decreased the glyoxalase I (Gly I) and increased glyoxalase II (Gly II) activities. The application of AsA in combination with PEG improved the fresh mass, RWC, and Chl content, whereas decreased the Pro, MDA, and H2O2 content in comparison with PEG alone. The AsA addition improved AsA-GSH cycle components and improved the activities of all antioxidant and glyoxalase enzymes in most of the cases. So, exogenous AsA improved physiological adaptation and alleviated oxidative damage under the osmotic stress by improving the antioxidant and glyoxalase systems. According to measured parameters, B. juncea can be recognized as more drought tolerant than B. napus and B. campestris.Biologia Plantarum 12/2014; 58(4). DOI:10.1007/s10535-014-0447-0 · 1.74 Impact Factor
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ABSTRACT: The antioxidant glutathione (GSH) is an important reducing agent in cell physiology. Glutathione reductases (GR) of humans and higher organisms convert oxidized glutathione (GSSG) to two reduced GSH molecules under consumption of the co-factor NADPH. GSH acts as an antioxidant eliminating reactive oxygen species in the cell. We found a novel GR being able to accept both NADPH and much cheaper NADH for GSSG reduction. For the first time we produced it in E. coli and purified active GR from Allochromatium vinosum, determined its Km-values for NADH (0.026 mM) and NADPH (0.309 mM), as well as its temperature optimum (20 °C) and pH optimum (pH 8). Since numerous bio-diagnostic assays and enzymatic processes are dependent on GRs the possibility to use a cheaper co-substrate could help to overcome cost limitations in future.