摘 要 ：拟南芥AtJ3(Arabidopsis thaliana DnaJ homolog 3)为一蛋白分子伴侣,在植物体内可通过与PKS5(SOS2-like protein kinase 5)蛋白激酶形成复合物来抑制PKS5的活性;同时AtJ3-PKS5复合物可对质膜上H+-ATPase质子转运活性进行正向调节,并参与对外源ABA的响应。为揭示AtJ3-PKS5复合物参与质膜H+-ATPase活性调节及对外源ABA响应中的作用,本研究以拟南芥AtJ3、PKS5不同突变体为材料,在盐及ABA共同处理下对AtJ3-PKS5复合物的功能及作用机制进行了探讨。结果显示,在2种因素共同处理下,AtJ3-PKS5复合物可同时对处理因素进行响应。即AtJ3-PKS5复合物可对质膜上H+-ATPase质子转运活性进行调节,并使细胞内pH值发生变化,同时还可诱导ABI5下游ABA响应基因的表达;外源ABA可引起AtJ3从细胞核向细胞质的转运,从而增强了AtJ3对H+-ATPase活性的调节。说明AtJ3-PKS5复合物在对H+-ATPase活性调节及对外源ABA响应的交互代谢途径中起着关键调节子的作用。
Abstract:Arabidopsis thaliana DnaJ homolog 3 (AtJ3), an Arabidopsis chaperone, interacts with SOS2-like protein kinase 5 (PKS5) to form the AtJ3-PKS5 complex and achieves its function through repressing activity of PKS5 in vivo. Moreover, the AtJ3-PKS5 complex positively regulates plasma membrane H+-ATPase activity and is involved in exogenous ABA response in Arabidopsis. In this study, salt- and ABA-treated Arabidopsis AtJ3 and PKS5 mutants were explored to elucidate the function and mechanism of the AtJ3-PKS5 complex in the simultaneous regulation of membrane H+-ATPase activity and ABA response. Results showed that the AtJ3-PKS5 complex not only led to changes in the cytosolic pH value via regulation of plasma membrane H+-ATPase activity, but also activated expression of the ABA-related responsive genes under the two treatments. Additionally, exogenous application of ABA induced trafficking of AtJ3 from the nucleus to the cytoplasm to enhance H+-ATPase activity, indicating that the AtJ3-PKS5 complex functions in ABA-meditated pH homeostasis. Taken together, our results suggest that the AtJ3-PKS5 complex might serve as a key regulator in a crosstalk metabolic pathway of H+-ATPase activity regulation and exogenous ABA response.