The involvement of hydrogen peroxide in abscisic acid-induced activities of ascorbate peroxidase and glutathione reductase in rice roots

Abstract

We have monitored the changes in antioxidant enzyme activities and H2O2 concentrations in roots of rice (Oryza sativa L., cv. Taichung Native 1) seedlings treated with exogenous abscisic acid(ABA). Decrease in superoxide dismutase (SOD) and catalase (CAT) activities was observed in rice roots in the presence of ABA. However, ascorbate peroxide (APX) and glutathione reductase (GR) activities were increased after the ABA treatment. ABA treatment resulted in an increase in H2O2 concentrations in rice roots. Pre-treatment with dimethylthiourea, a chemical trap for H2O2, and diphenyleneiodonium chloride (DPI), a well known inhibitor of NADPH oxidase, inhibited ABA-induced accumulation of H2O2 and ABA-induced activities of APX and GR. ABA-induced accumulation of H2O2 was found to be prior to ABA-induced activities of APX and GR. Our results suggest that H2O2 is involved in ABA-induced APX and GR activities in rice roots.