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 H 2 O 2 production. The application of H 2 O 2 (1 mM) also enhanced the activities of G6PDH as well as antioxidative enzymes. In the presence of exogenous CAT, H 2 O 2 content was decreased, and the enhanced activities of G6PDH and antioxidative enzymes induced by NaCl or by exogenous H 2 O 2 were also abolished, suggesting that the enhancement of the above enzyme activities under salt stress was a result of the increased endogenous H 2 O 2 levels. Further results showed that the effects of NaCl and H 2 O 2 on the activities of antioxidative enzymes were diminished by Na 3 PO 4 (a G6PDH inhibitor), suggesting G6PDH activity is required in enhancing the activities of antioxidative enzymes. The enhanced membrane leakage, lipid peroxidation, H 2 O 2 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.