title: NO and H2O2contribute to SO2toxicity via Ca2+signaling in Vicia faba guard cells.
abstract: NO and H2O2have been implicated as important signals in biotic and abiotic stress responses of plants to the environment. Previously, we have shown that SO2exposure increased the levels of NO and H2O2in plant cells. We hypothesize that, as signaling molecules, NO and H2O2mediate SO2-caused toxicity. In this paper, we show that SO2hydrates caused guard cell death in a concentration-dependent manner in the concentration range of 0.25 to 6 mmol L-1, which was associated with elevation of intracellular NO, H2O2, and Ca2+levels in Vicia faba guard cells. NO donor SNP enhanced SO2toxicity, while NO scavenger c-PTIO and NO synthesis inhibitors L-NAME and tungstate significantly prevented SO2toxicity. ROS scavenger ascorbic acid (AsA) and catalase (CAT), Ca2+chelating agent EGTA, and Ca2+channel inhibitor LaCl3also markedly blocked SO2toxicity. In addition, both c-PTIO and AsA could completely block SO2-induced elevation of intracellular Ca2+level. Moreover, c-PTIO efficiently blocked SO2-induced H2O2elevation, and AsA significantly blocked SO2-induced NO elevation. These results indicate that extra NO and H2O2are produced and accumulated in SO2-treated guard cells, which further activate Ca2+signaling to mediate SO2toxicity. Our findings suggest that both NO and H2O2contribute to SO2toxicity via Ca2+signaling.
authors.affiliation: School of Life Science, Shanxi University, 92 Wucheng Road, Taiyuan, 030006, China.|Department of Statistics, University of Missouri-Columbia, Columbia, MO, 65211, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Yi
authors.affiliation: School of Life Science, Shanxi University, 92 Wucheng Road, Taiyuan, 030006, China.
authors.forename: Heli
authors.initials: H
authors.lastname: Bai
authors.affiliation: School of Life Science, Shanxi University, 92 Wucheng Road, Taiyuan, 030006, China.
authors.forename: Meizhao
authors.initials: M
authors.lastname: Xue
authors.affiliation: School of Life Science, Shanxi University, 92 Wucheng Road, Taiyuan, 030006, China. yihl@sxu.edu.cn.
authors.forename: Huilan
authors.initials: H
authors.lastname: Yi
mesh_terms: D002374:Catalase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester; D015398:Signal Transduction / Q000187:drug effects; D031307:Vicia faba / Q000378:metabolism*
chemical_list: D006861:Hydrogen Peroxide; D002374:Catalase; D019331:NG-Nitroarginine Methyl Ester
keywords: Ca2+; Cytotoxicity; H2O2; Nitric oxide; SO2; Vicia faba guard cell