蛋白磷酸酶1（PP1）全酶由催化亚基（PP1c）和调节亚基（PP1r）组成，参与植物许多重要的生命活动过程。但是其遗传功能研究比较滞后，因此鉴定新的PP1r，研究全酶如何通过特异性调节底物来调控植物生命活动具有非常重要的意义。本项目前期工作鉴定到一个拟南芥PP1的新调节亚基PP1R3，发现其全酶的可能底物是MYBx，并鉴定到MYBx的激酶及磷酸化位点，这些组分都参与了ABA响应。在此基础上，以MYBx磷酸化修饰调控为中心，深入研究PP1R3-TOPPs全酶在ABA信号调控中的详细机理。通过质谱鉴定、生理与遗传分析、蛋白磷酸化实验、模拟磷酸化位点突变、CHIP-Seq等技术，阐明PP1R3-TOPPs通过对MYBx的磷酸化修饰如何调节ABA合成或信号转导的机理，揭示PP1调控植物响应逆境的分子机制；同时研究水稻和玉米中相关同源基因在逆境适应中的作用机理，为PP1在农作物抗逆中的应用奠定基础。

Protein phosphatase 1 (PP1) holoenzyme, consisting of a catalytic subunit (PP1c) and regulatory subunits (PP1r), is involved in many important life processes in plants. However, researches on the genetic function of PP1 are relatively retarded. Therefore, it is very important to identify new PP1r and elucidate how holoenzyme controls life processes through specifically regulating its substrates in plants. In previous work, we successfully identified a new regulatory subunit of PP1 in Arabidopsis, PP1R3, and found MYBx was a candidate substrate of PP1R3-TOPPs holoenzyme. We also identified a potential kinase of MYBx and found the phosphorylation sites of MYBx by mass spectrometry (MS). Physiological analyses showed that all those components are involved in ABA responses. Based on these preliminary results, we intend to deeply study the detailed mechanism of PP1R3-TOPPs holoenzyme in controlling ABA signaling by focusing on the regulation of phosphorylation modification of MYBx. Using strategies of MS identification, physiological and genetic analyses, protein phosphorylation experiments, site-directed mutagenesis of protein phosphorylation sites to mimic phosphorylation or dephosphorylation status, and CHIP-Seq, we plan to clarify the mechanism of how PP1R3-TOPPs control ABA biosynthesis or signal transduction via modulating the phosphorylation modification of MYBx, and reveal the molecular mechanism of PP1 in regulating stress responses in plants. Meanwhile, we propose to study the function mechanism of these related homologous genes in stress adaptation in rice and maize, which will provide strategies for PP1 utilization in improving crop adaptation to stress conditions.