Abscisic acid-induced hydrogen peroxide is required for anthocyanin accumulation in leaves of rice seedlings

The role of hydrogen peroxide (H2O2) in abscisic acid (ABA)-induced anthocyanin accumulation in detached and intact leaves of rice seedlings was investigated. Treatment with ABA resulted in an accumulation of anthocyanins in detached rice leaves. Dimethylthiourea, a chemical trap for H2O2, was observed to be effective in inhibiting ABA-induced accumulation of anthocyanins. Inhibitors of NADPH oxidase (diphenyleneiodonium chloride and imidazole), phosphatidylinositol 3-kinase (wortmannin and LY 294002), and a donor of nitric oxide (N-tert-butyl-α-phenylnitrone), which have previously been shown to prevent ABA-induced H2O2 accumulation in detached rice leaves, inhibited ABA-induced anthocyanin increase. Exogenous application of H2O2, however, was found to increase the anthocyanin content of detached rice leaves. In terms of H2O2 accumulation, intact (attached) leaves of rice seedlings of cultivar Taichung Native 1 (TN1) are ABA sensitive and those of cultivar Tainung 67 (TNG67) are ABA insensitive. Upon treatment with ABA, H2O2 and anthocyanins accumulated in leaves of TN1 seedlings but not in leaves of TNG67. Our results, obtained from detached and intact leaves of rice seedlings, suggest that H2O2 is involved in ABA-induced anthocyanin accumulation in this species.