Zhang Liang, Li Xiaoyi, Li Dekuan, Sun Yuna, Li Ying, Luo Qin, Liu Zhibin, Wang Jianmei, Li Xufeng, Zhang Hong, Lou Zhiyong, Yang Yi
1Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, State Key Laboratory of Hydraulics and Mountain River Engineering, College of Life Sciences, Sichuan University, Chengdu, 610065 China.
2National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing, 100101 China.
Cell Discov. 2018 Jun 19;4:30. doi: 10.1038/s41421-018-0029-y. eCollection 2018.
The function of abscisic acid (ABA) is mediated by its receptors termed RCARs/PYR1/PYLs. Modulation of ABA signaling is vital for plant growth and development. The RCAR-PP2C-SnRK2 regulatory modules have been defined as the core components in ABA signaling. However, it is still not clear whether and how the ABA receptors could be modified at the initial post-translational stage to fine-tune ABA transduction pathway. Here we identify and characterize the putative receptor-like cytoplasmic kinase (RLCK) in Arabidopsis named CARK1, which interacts with RCAR3 (PYL8) and RCAR11 (PYR1) in the manner of phosphorylation. Structural studies of CARK1 revealed the critical active site, N204, which accounts for the kinase activity and the direct interaction with RCAR3/RCAR11. CARK1 phosphorylates RCAR3/RCAR11 at one conserved threonine site, T77/T78. Our genetic analyses further demonstrated that positively regulates ABA-mediated physiological responses and overexpression of in Arabidopsis distinctly promotes the drought resistance. Moreover, the phosphor-mimic form of RCAR11 in the mutant is able to functionally complement the ABA sensitivity. CARK1 positively regulates ABA-responsive gene expression and enhances RCAR3/RCAR11's inhibition to Clade A PP2C. Taken together, our studies strongly support the functional significance of CARK1 in positively regulating ABA signaling via phosphorylation on RCAR3/RCAR11 in Arabidopsis.
脱落酸（ABA）的功能由其受体RCARs/PYR1/PYLs介导。ABA信号传导的调节对植物生长发育至关重要。RCAR-PP2C-SnRK2调节模块已被定义为ABA信号传导的核心组件。然而，ABA受体在翻译后初始阶段是否以及如何被修饰以微调ABA转导途径仍不清楚。在这里，我们鉴定并表征了拟南芥中一种假定的类受体胞质激酶（RLCK），名为CARK1，它以磷酸化的方式与RCAR3（PYL8）和RCAR11（PYR1）相互作用。CARK1的结构研究揭示了关键的活性位点N204，它决定了激酶活性以及与RCAR3/RCAR11的直接相互作用。CARK1在一个保守的苏氨酸位点T77/T78处磷酸化RCAR3/RCAR11。我们的遗传分析进一步表明， 正向调节ABA介导的生理反应，在拟南芥中过表达 明显促进抗旱性。此外， 突变体中RCAR11的磷酸模拟形式能够在功能上补充ABA敏感性。CARK1正向调节ABA响应基因的表达，并增强RCAR3/RCAR11对A类PP2C的抑制作用。综上所述，我们的研究有力地支持了CARK1通过对拟南芥中RCAR3/RCAR11进行磷酸化来正向调节ABA信号传导的功能意义。
