拟南芥AtJ3与PKS5相互作用参与植物ABA响应

AtJ3 is Involved in ABA Response through Interaction with the PKS5 Kinase in Arabidopsis

脱落酸(abscisic acid,ABA)在植物生长、发育及环境胁迫响应中有着广泛的作用。前期研究已鉴定了诸多参与植物ABA信号转导的元件。本研究以拟南芥(Arabidopsis thaliana)蛋白激酶PKS5(SOS2-like protein kinase 5)为诱饵蛋白,使用酵母双杂交筛选到与PKS5相互作用的蛋白分子伴侣At J3(Arabidopsis thaliana Dna J homolog 3)。At J3 T-DNA突变体atj3-1与atj3-2表现出萌发期ABA表型。在外源ABA处理下,atj3-1与atj3-2种子发芽率降彽、幼苗黄化、生长矮小。atj3-1与PKS5双突变体atj3-1pks5-1、atj3-1pks5-3和atj3-1pks5-4表现出与At J3或PKS5突变体相同的ABA表型。亚细胞定位与转基因研究显示At J3与PKS5有相同的表达模式。免疫共沉淀与体外磷酸化测试确认At J3与PKS5存在相互作用并抑制PKS5激酶活性。研究结果表明:At J3与PKS5相互作用,通过抑制PKS5激酶活性共同参与植物ABA信号响应过程。

The phytohormone abscisic acid （ABA） has a wide range of important roles in plant growth and development as well as abiotic stress response. Previous studies identified the enormous components involved in ABA responses in plants. We identified a chaperon AtJ3 （Arabidopsis thaliana DnaJ homolog 3; heat shock protein 40-like） using yeast two-hybrid assays in which PKS5 was used as bait. The At J3 T-DNA mutants atj3-1 and aq3-2 displayed ABA phenotypes. Seed germinations them showed stunted growth and leaf chlorotic symptoms of atj3-1 and atj3-2 decreased, and the seedlings of under ABA. Double mutants of atj3-1pksS-1, atj3- lpks5-3 and atj3-1pksS-4 had similar ABA phenotypes as mutants of At J3 or PKSS. Moreover, the assays of subcellular location and transgenic plants showed that AtJ3 has overlapping expression pattern with PKS5. By co-immunoprecipitation and in vitro phosphorylation, AtJ3 physically interacts with PKS5 and represses the PKS5 kinase activity. Therefore, At J3 interacts with PKS5 in response to ABA by repressing the PKS5 kinase activity.