异三聚体G蛋白在UV-B诱导拟南芥气孔关闭中的作用

【目的】了解异三聚体G蛋白在紫外线B（UV-B）辐射诱导气孔关闭中的作用，为进一步阐明植物细胞转导UV-B辐射信号的机制提供依据。【方法】以拟南芥（Arabidopsis thaliana）野生型、G蛋白α亚基基因缺失突变体及其超表达株系和组成活化型株系为材料，并结合药理学试验，通过气孔开度分析确定G蛋白在0.5 W?m-2 UV-B辐射诱导拟南芥叶片气孔关闭中的作用。【结果】细菌毒素试验表明，G蛋白抑制剂百日咳毒素（PTX）能显著抑制UV-B诱导的气孔关闭，而其活化剂霍乱毒素（CTX）能模拟UV-B的作用诱导可见光下叶片气孔关闭。遗传学试验显示，UV-B不能诱导异三聚体G蛋白α亚基GPA1功能缺失突变体gpa1-1和gpa1-2的气孔关闭，却能诱导其超表达株系wGα和组成活化型株系cGα的气孔关闭，且cGα在可见光下气孔开度明显小于野生型，在UV-B辐射初期其气孔关闭速度明显快于野生型。【结论】异三聚体G蛋白α亚基参与了UV-B辐射诱导拟南芥叶片气孔关闭的信号转导过程。

Role of Heterotrimeric G Protein in UV-B-Induced Arabidopsis Stomatal Closure

【Objective】 The role of heterotrimeric G protein in UV-B-induced stomatal closure was analyzed to provide valuable evidence for further elucidating the mechanism of UV-B signaling transduction in plants.【Method】By using Arabidopsis (Arabidopsis thaliana) wild type, Gα-subunit-knockout mutants gpa1-1 and gpa1-2, wGα (a gpa1 overexpression line) and cGα (overexpression constitutively active form mutant of GPA1) combined with pharmacological analysis, the role of heterotrimeric G protein in 0.5 W?m-2 UV-B-induced stomatal closure was explored via stomatal bioassay.【Result】Pharmacological results showed that pertussis toxin (PTX), an inhibitor of G protein α subunit, inhibited UV-B-induced stomatal closure significantly. Meanwhile, cholera toxin (CTX), an activator of G protein α subunit, induced stomatal closure of leaves under light as well as UV-B radiation. Genetic data showed that UV-B-induced stomatal closure was completely impaired in the mutants gpa1-1 and gpa1-2, but not in the overexpression lines of wGα and cGα. In contrast, cGα showed not only smaller stomatal aperture than wild type under light, but also faster stomatal closure induced by UV-B than they did in the wild type.【Conclusion】 Results of this study strongly suggest the involvement of heterotrimeric G protein α subunit in the signaling transduction pathway of UV-B-induced stomatal closure in Arabidopsis.