Hydrogen peroxide is involved in methyl jasmonate-induced senescence of rice leaves
2006
Hung, Kuo Tung | Hsu, Yi-Ting | Kao, Ching Huei
The role of H₂O₂ in the senescence of detached rice leaves induced by methyl jasmonate (MJ) was investigated. MJ treatment resulted in H₂O₂ production in detached rice leaves, which was prior to the occurrence of leaf senescence. Dimethylthiourea, a chemical trap of H₂O₂, was observed to be effective in inhibiting MJ-induced senescence and MJ-increased malondialdehyde (MDA) content in detached rice leaves. Diphenyleneiodonium chloride (DPI) and imidazole (IMD), inhibitors of NADPH oxidase, prevented MJ-induced H₂O₂ production, suggesting that NADPH oxidase is a H₂O₂-generating enzyme in MJ-treated detached rice leaves. DPI and IMD also inhibited MJ-promoted senescence and MJ-increased MDA content in detached rice leaves. Phosphatidylinositol 3-kinase inhibitors wortmannin (WM) or LY 294002 (LY) inhibited MJ-induced H₂O₂ production and senescence of detached rice leaves. Exogenous H₂O₂ reversed the inhibitory effect of WM or LY. In terms of leaf senescence, it was observed that rice seedlings of cultivar Taichung Native 1 (TN1) are jasmonic acid (JA)-sensitive and those of cultivar Tainung 67 (TNG67) are JA-insensitive. On treatment with JA, H₂O₂ accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Evidence was also provided to show that MJ-induced H₂O₂ production in detached rice leaves is abscisic acid (ABA)-independent. Ethylene action inhibitor, silver thiosulfate, was observed to inhibit MJ- and ABA-induced H₂O₂ production and senescence of detached rice leaves, suggesting that the action of MJ and ABA is ethylene-dependent.
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