异三聚体G蛋白在UV-B诱导拟南芥气孔关闭中的作用

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

【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-2UV-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。

【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.