TITLE	Nitric oxide counteracts the senescence of rice leaves induced by hydrogen peroxide
AUTHOR	Kuo Tung HUNG Department of Agronomy, National Taiwan University, Taipei, Taiwan, Republic of China Ching Huei KAO* Department of Agronomy, National Taiwan University, Taipei, Taiwan, Republic of China
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ABSTRACT	In the present study, we evaluate the protective effect of nitric oxide (NO) against the senescence of rice leaves promoted by hydrogen peroxide (H2O2). Senescence of rice leaves was determined by decreases in protein content. H2O2 treatment resulted in (1) increases in leaf H2O2 content, (2) induction of leaf senescence, (3) increases in lipid peroxidation, (4) decreases in ascorbic acid (AsA) and reduced form glutathione (GSH) contents, and (5) increases in antioxidative enzyme activities (ascorbate peroxidase, glutathione reductase, and peroxidase). NO donors [N-tert-butyl-a-phenylnitrone (PBN), sodium nitroprusside, 3-morpholinosydonimine, and AsA + NaNO2] were effective in reducing H2O2-induced leaf senescence. PBN prevented H2O2-increased H2O2 content, H2O2-induced lipid peroxidation, H2O2-decreased AsA and GSH contents, and H2O2-increased antioxidative enzyme activities. The protective effect of PBN on H2O2-promoted senescence, H2O2-increased H2O2 content and lipid peroxidation, H2O2-decreased AsA and GSH contents, and H2O2-increased antioxidative enzyme activities was reversed by 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a NO-specific scavenger, suggesting that the protective effect of PBN is attributable to the NO released. Reduction of H2O2-induced senescence by NO in rice leaves is most likely mediated through its ability to scavenge H2O2.
KEYWORD	Hydrogen peroxide; Lipid peroxidation; Nitric oxide; Oryza sativa;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 46 Number 1 January 2005, page 21-28, 8 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China