UV-B对拟南芥叶片不同来源H2O2的活化和气孔关闭的诱导

在UV-B调控植物许多生理过程中过氧化氢(H2O2)作为第二信使发挥着重要作用,但H2O2来源途径并不清楚。该研究借助气孔开度分析和激光扫描共聚焦显微镜技术,探讨H2O2在介导不同剂量UV-B诱导拟南芥叶片气孔关闭过程中的酶学来源途径。结果发现:0.5W.m-2 UV-B能诱导野生型拟南芥叶片保卫细胞的H2O2产生和气孔关闭,且该效应能被NADPH氧化酶抑制剂二苯基碘(DPI)抑制,而不能被细胞壁过氧化物酶抑制剂水杨基氧肟酸(SHAM)抑制,同时该剂量UV-B也不能诱导NADPH氧化酶功能缺失单突变体AtrbohD和AtrbohF以及双突变体AtrbohD/F保卫细胞的H2O2产生和气孔关闭;相反,0.65 W.m-2 UV-B既能诱导野生型也能诱导NADPH氧化酶突变体保卫细胞的H2O2产生和气孔关闭,且该效应能被SHAM抑制,却不能被DPI抑制。结果表明,不同剂量UV-B通过活化不同生成途径的H2O2来诱导拟南芥叶片气孔关闭,即低剂量UV-B主要诱导NADPH氧化酶AtrbohD和AtrbohF途径来源的H2O2生成,而高剂量UV-B主要活化细胞壁过氧化酶途径来源的H2O2。

UV-B Activates Different Sources of H2O2 and Induces Stomatal Closure in Arabidopsis thaliana Leaves

Previous studies have shown that H₂O₂ acting as a second messenger functions in UV-B-regulated diverse processes in plants,but its origins remain elusive.The purpose of this paper is to investigate the enzymatic sources of H₂OO₂ mediating different doses of UV-B-induced stomatal closure in Arabidopsis thaliana leaves.With stomatal aperture bioassay and confocal laser-scanning microscopy,we observed that 0.5 W·m^-2 UV-B induced H₂O₂ production in guard cells and stomatal closure in wild type (WT),which were significantly inhibited by diphenylene iodonium chloride (DPI,an inhibitor of NADPH oxidase),but not by salicylhydroxamic acid (SHAM,an inhibitor of cell wall peroxidase).Meanwhile,this dose of UV-B could not induce H₂O₂ generation and stomatal closure in either single mutants AtrbohD and AtrbohF or double mutant AtrbohD/F.In contrast,0.65 W·m^-2 UV-B could induce H₂O₂ generation and stomatal closure in both WT and the three mutants,which were largely inhibited by SHAM,but not by DPI.These results demonstrate that different doses of UV-B activate distinct sources of H₂O₂ to induce stomatal closure in A.thaliana leaves.The low dose of UV-B activates NADPH oxidases AtrbohD- and AtrbohF-sources of H₂O₂ to induce stomatal closure,while the high dose of UV-B mainly activates cell wall peroxidase-sources of H₂O₂ to induce stomatal closure in A.thaliana.