Role of hydrogen peroxide in regulating glucose-6-phosphate dehydrogenase activity under salt stress

The role of hydrogen peroxide in the regulation of glucose-6-phosphate dehydrogenase (G6PDH) activity in the red kidney bean (Phaseolus vulgaris L.) roots under salt stress (100 mM NaCl) was investigated. Salt stress caused the increase of the activities of G6PDH and antioxidative enzymes including ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), as well as H2O2 production. The application of H2O2 (1 mM) also enhanced the activities of G6PDH as well as antioxidative enzymes. In the presence of exogenous CAT, H2O2 content was decreased, and the enhanced activities of G6PDH and antioxidative enzymes induced by NaCl or by exogenous H2O2 were also abolished, suggesting that the enhancement of the above enzyme activities under salt stress was a result of the increased endogenous H2O2 levels. Further results showed that the effects of NaCl and H2O2 on the activities of antioxidative enzymes were diminished by Na3PO4 (a G6PDH inhibitor), suggesting G6PDH activity is required in enhancing the activities of antioxidative enzymes. The enhanced membrane leakage, lipid peroxidation, H2O2 and O-2 - contents, G6PDH and antioxidative enzyme activities under salt stress were all recovered to control level when the red kidney bean seedlings treated with 100 mM NaCl for 6 d were transferred to the control conditions for 8 d.