渗透胁迫应答反应分子作用机理的阐释是理解植物自身抗逆性建立的重要过程。尽管前期研究发现拟南芥SnRK2型蛋白激酶参与渗透胁迫应答反应调节，但相关的分子基础尚未知晓。本组近期研究表明同源进化树上不同分支的两个拟南芥SnRK2型蛋白激酶通过调节质膜H+-ATPase活性功能冗余地参与抵御渗透胁迫，并且这一过程很可能受到SnRK3型蛋白激酶的调控。本项目拟在此基础上，通过根际质子外流、质膜H+-ATPase活性、蛋白质-蛋白质相互作用、质膜H+-ATPase活性异源重建、蛋白激酶活性、植物渗透势等分析与测定，揭示SnRK2在SnRK3调控下通过调节质膜H+-ATPase活性参与植物抵御渗透胁迫的分子机理。这不仅有助于理解渗透胁迫激活SnRK2的作用机制，而且有助于理解质膜H+-ATPase形成的跨膜电势与渗透胁迫下植物水分调节（增加根部水分吸收和减少叶片水分散失）相互关联的作用机制。

Determining the molecular basis of osmotic stress responses in plants is one of the most important progresses to understand stress tolerance of plants. Previous study revealed that SnRK2-type protein kinases are involved in the modulation of plant osmotic stress responses. However, the underlying mechanism remains enigmatic. Our recent data indicate that two SnRK2-type protein kinases function redundantly in plant osmoregulation. These two members have been divided into different subclasses in the plant SnRK2-type protein kinase family. Furthermore, the kinase activity of SnRK2-type protein kinases in response to osmotic stress may be modulated by SnRK3-type protein kinases. Based on above progresses, this project is attempted to demonstrate the underlying molecular basis of the impact of SnRK3-type protein kinases upon SnRK2-type protein kinases mediated plasma membrane H+-ATPase in plant osmoregulation. To accomplish it, we will adopt many techniques, i.e. determining the efflux of proton in roots, measuring the activity of plasma membrane H+-ATPase, protein-protein interaction assay, reconstitution of the proton transport mediated by plasma membrane H+-ATPase in a heterogeneous system, kinase assay, and osmotic potential measurement. When completed, it is hopeful to provide novel insight into understanding the activating mechanism of SnRK2-type protein kinases by osmotic stress. Moreover, it is also hopeful to understand the coordination between the established electrical potential across plasma membrane by H+-ATPase and plant water modulation in response to osmotic stress, which is attempted to increase water uptake in roots and decrease water loss in leaves under osmotic stress condition.