Abstract
Rice plants overexpressing OsHCTR increased the amount of NAD(P)(H) by the activation of NAD synthetase and NAD kinase. Moreover, transgenic rice had high tolerance against several stresses such as H2O2, UV, submergence, NaCl, and rice blast. Since reduced form of NAD(P) is a great source of redox in vivo, we were prompted to investigate NAD(P)H-producing pathway. Generally, NADH is produced in TCA cycle and glycolysis, whereas NADPH is produced pentose-phosphate pathway and malic enzyme. The activity of NADH-producing enzymes in TCA cycle decreased and malic enzyme was strongly activated in transgenic line, indicating that NADPH-producing route was accelerated. Analysis of numerous metabolites revealed upregulating glutathione (GSH) level in transgenic line. We also confirmed the activation of GSH reductase and GSH peroxidase. Thus, acceleration of GSH cycle using increased NADPH level may contribute to the ROS tolerance.
