title: NO accumulation alleviates H2O2-dependent oxidative damage induced by Ca(NO3)2stress in the leaves of pumpkin-grafted cucumber seedlings.
abstract: Nitric oxide (NO) and hydrogen peroxide (H2O2), two important signaling molecules, are stimulated in plants by abiotic stresses. In this study, we investigated the role of NO and its interplay with H2O2in the response of self-grafted (S-G) and salt-tolerant pumpkin-grafted (Cucurbita maxima × C. moschata) cucumber seedlings to 80 mM Ca(NO3)2stress. Endogenous NO and H2O2production in S-G seedlings increased in a time-dependent manner, reaching maximum levels after 24 h of Ca(NO3)2stress. In contrast, a transient increase in NO production, accompanied by H2O2accumulation, was observed at 2 h in rootstock-grafted plants. Nw-Nitro-l-Arg methyl ester hydrochloride (l-NAME), an inhibitor of nitric oxide synthase (NOS), tungstate, an inhibitor of nitrate reductase (NR), and 2-(4-carboxyphenyl)-4,4,5,5-tetramethy-limidazoline-1-oxyl-3-oxide (cPTIO), a scavenger of NO, were found to significantly inhibit NO accumulation induced by salt stress in rootstock-grafted seedlings. H2O2production was unaffected by these stress conditions. Ca(NO3)2stress-induced NO accumulation was blocked by pretreatment with an H2O2scavenger (dimethylthiourea, DMTU) and an inhibitor of NADPH oxidase (diphenyleneiodonium, DPI). In addition, maximum quantum yield of PSII (Fv/Fm), as well as the activities and transcript levels of antioxidant enzymes, were significantly decreased by salt stress in rootstock grafted seedlings after pretreatment with these above inhibitors; antioxidant enzyme transcript levels and activities were higher in rootstock-grafted seedlings compared with S-G seedlings. These results suggest that rootstock grafting could alleviate the oxidative damage induced by Ca(NO3)2stress in cucumber seedlings, an effect that may be attributable to the involvement of NO in H2O2-dependent antioxidative metabolism.
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Shu
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Xu
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Ya-Hong
authors.initials: YH
authors.lastname: An
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.|Nanjing Agricultural University (Suqian) Academy of Protected Horticulture, Suqian 223800, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Sun
authors.affiliation: College of Horticulture, Key Laboratory of Southern Vegetables Genetic Improvement of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.|Nanjing Agricultural University (Suqian) Academy of Protected Horticulture, Suqian 223800, China.
authors.forename: Shi-Rong
authors.initials: SR
authors.lastname: Guo
mesh_terms: D017610:Calcium Compounds / Q000633:toxicity*; D018553:Cucumis sativus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D028464:Cucurbita / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism
chemical_list: D017610:Calcium Compounds; D009569:Nitric Oxide; D006861:Hydrogen Peroxide