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Ascorbate-Glutathione Pathway and Stress Tolerance in Plants
Plants are sessile organisms that live under a constant barrage of biotic and abiotic insults. Both biotic and abiotic stress factors have been shown to a ect various aspects of plant system including the acceleration in the formation of reactive oxygen species (ROS). e ascorbate (AsA)-glutathione (GSH) pathway is a key part of the network of reactions involving enzymes and metabolites with redox properties for the detoxi cation of ROS, and thus to avert the ROS-accrued oxidative damage in<span class="external-identifiers"> <a target="_blank" rel="external noopener noreferrer" href="https://doi.org/10.1007/978-90-481-9404-9_5">doi:10.1007/978-90-481-9404-9_5</a> <a target="_blank" rel="external noopener" href="https://fatcat.wiki/release/edka4xboivbfbbhdppzhk4pr5e">fatcat:edka4xboivbfbbhdppzhk4pr5e</a> </span>
more »... s. e present book mainly deals with the information gained through the cross-talks and inter-relationship studies on the physiological, biochemical and molecular aspects of the cumulative response of various components of AsA-GSH pathway to stress factors and their signi cance in plant stress tolerance. Advanced students, junior researchers and faculty in Plant Stress Physiology/Plant Biochemistry and concerned elds can be bene ted with the present edited volume. Abstract Acclimation of plants to drought is often associated with increased levels of reactive oxygen species (ROS), such as superoxide anion (O 2 · − ), hydrogen peroxide (H 2 O 2 ), hydroxyl radical (HO·) and singlet oxygen ( 1 O 2 ), which are toxic for the cells. ROS are by-products of aerobic metabolism, and their production is enhanced during drought conditions through the disruption of electron transport system and oxidizing metabolic activities occurring in chloroplasts, mitochondria and microbodies. Under non-stressful conditions, ROS are efficiently eliminated by non-enzymatic and enzymatic antioxidants, whereas during drought conditions the production of ROS exceeds the capacity of the antioxidative systems to remove them, causing oxidative stress. The non-enzymatic antioxidant system includes ascorbate and glutathione, located both within the cell and in the apoplast. They are two constituents of the antioxidative ascorbate-glutathione cycle which detoxify H 2 O 2 in the chloroplasts. Ascorbate (AsA) is a major primary antioxidant compound synthesized on the inner membrane of the mitochondria which reacts chemically with 1 O 2 , O 2 · − , HO· and thiyl radical, and acts as the natural substrate of many plant peroxidases. Moreover, AsA is involved in other functions such as plant growth, gene regulation, modulation of some enzymes, and redox regulation of membrane-bound antioxidant compounds. Glutathione (GSH) is a tripeptide synthesized in the cytosol and chloroplasts which scavenges 1 O 2 and H 2 O 2 , and it is oxidized to glutathione disulfide (GSSG) when acts as an antioxidant and redox regulator. GSH is the substrate of glutathione S-transferases, which have a protective role in the detoxification of xenobiotics, and dehydroascorbate reductase (DHAR). Finally, GSH is a precursor of phytochelatins, which regulate cellular heavy metals levels, and is involved in gene expression. This review, based on the most significant studies published in A. Sofo ( ) and A. Scopa A. Sofo et al. the last decade, focuses on the changes of antioxidant enzyme activities (ascorbate peroxidase, APX; monodehydroascorbate reductase, MDHAR; dehydroascorbate reductase, DHAR; glutathione reductase, GR), and of the levels of some compounds involved in the ascorbate-glutathione cycle (ascorbate and glutathione pools , H 2 O 2 and a -tocopherol) in plants grown under water shortage.
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