title: Nitric oxide enhances salt tolerance in maize seedlings through increasing activities of proton-pump and Na+/H+ antiport in the tonoplast.
abstract: Nitric oxide (NO), an endogenous signaling molecule in animals and plants, mediates responses to abiotic and biotic stresses. Our previous work demonstrated that 100 microM sodium nitroprusside (SNP, an NO donor) treatment of maize seedlings increased K(+) accumulation in roots, leaves and sheathes, while decreasing Na(+) accumulation (Zhang et al. in J Plant Physiol Mol Biol 30:455-459, 2004b). Here we investigate how NO regulates Na(+), K(+) ion homeostasis in maize. Pre-treatment with 100 muM SNP for 2 days improved later growth of maize plants under 100 mM NaCl stress, as indicated by increased dry matter accumulation, increased chlorophyll content, and decreased membrane leakage from leaf cells. An NO scavenger, methylene blue (MB-1), blocked the effect of SNP. These results indicated that SNP-derived NO enhanced maize tolerance to salt stress. Further analysis showed that NaCl induced a transient increase in the NO level in maize leaves. Both NO and NaCl treatment stimulated vacuolar H(+)-ATPase and H(+)-PPase activities, resulting in increased H(+)-translocation and Na(+)/H(+) exchange. NaCl-induced H(+)-ATPase and H(+)-PPase activities were diminished by MB-1. 1-Butanol, an inhibitor of phosphatidic acid (PA) production by phospholipase D (PLD), reduced NaCl- and NO-induced H(+)-ATPase activation. In contrast, applied PA stimulated H(+)-ATPase activity. These results suggest that NO acts as a signal molecule in the NaCl response by increasing the activities of vacuolar H(+)-ATPase and H(+)-PPase, which provide the driving force for Na(+)/H(+) exchange. PLD and PA play an important role in this process.
authors.affiliation: College of Life Science and State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 210095 Nanjing, People's Republic of China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Liling
authors.initials: L
authors.lastname: Wang
authors.forename: Youliang
authors.initials: Y
authors.lastname: Liu
authors.forename: Qun
authors.initials: Q
authors.lastname: Zhang
authors.forename: Qiuping
authors.initials: Q
authors.lastname: Wei
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zhang
mesh_terms: D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D006706:Homeostasis; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D017494:Proton Pumps / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014867:Water / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
chemical_list: D005230:Fatty Acids, Nonesterified; D020030:Nitric Oxide Donors; D010712:Phosphatidic Acids; D017494:Proton Pumps; D017923:Sodium-Hydrogen Exchangers; D014867:Water; D009599:Nitroprusside; D009569:Nitric Oxide; D012965:Sodium Chloride; D012964:Sodium; D010739:Phospholipase D; D011188:Potassium