Hydrogen Peroxide is Involved in the Regulation of Ascorbate and Glutathione Metabolism in Wheat Leaves under Water Stress

This study investigated the regulation of ascorbic acid and glutathione metabolism by hydrogen peroxide in wheat leaves under water stress. The results showed that H2O2 level, the activities of ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase, L-galactono-1,4-lactone dehydrogenase and gamma-glutamylcysteine synthetase, and the contents of reduced ascorbate, reduced glutathione, total ascorbate and total glutathione were increased by water stress. And above increases were suppressed by pre-treatment with NADPH oxidase inhibitor diphenyleneiodonium chloride. Application of DPI also reduced H2O2 level, the activities of gamma-ECS, GalLDH, APX, GR, DHAR and MDHAR, and the contents of AsA, GSH, total ascorbate and total glutathione, compared with control. Application of H2O2 to DPI-inhibited wheat seedlings prevented the reduction in the activities of APX, GR, MDHAR, DHAR, GalLDH and gamma-ECS, and the contents of AsA, GSH, total ascorbate and total glutathione induced by DPI under water stress. Meanwhile, pre-treatment with DPI increased the malondialdehyde content and electrolyte leakage. Application of H2O2 to DPI-inhibited wheat seedlings prevented the increases in MDA content and EL. Our results suggested that water stress-induced H2O2 is a signal that leads to the up-regulation of ascorbate and glutathione metabolism and has an important role for acquisition of water-stress tolerance in wheat.