NaHCO3等碱性盐危害比中性盐更严重，但对抗碱性盐的分子机制知之甚少；根系泌酸是抗碱胁迫的基本途径，但在果树上未引起足够重视。前期研究发现激酶VvSERK1和质子泵VvPHA3分别在蛋白和磷酸化水平上响应NaHCO3胁迫，并且二者互作。本研究拟从表达/泌酸时空特性上阐明VvSERK1与VvPHA3、泌酸具有相关性，并鉴定VvSERK1、VvPHA3通过调控根系泌酸提高碱性盐抗性的功能；揭示磷酸化是VvPHA3活性调节的主要方式，鉴定VvPHA3的磷酸化位点，并阐明VvSERK1能结合并磷酸化VvPHA3，进而调节其活性，促进泌酸、提高碱性盐抗性；并评价VvPHA3在VvSERK1介导的抗碱性盐途径中的贡献。最终揭示一条“VvSERK1−VvPHA3−泌酸”的抗碱性盐途径。预期结果将首次阐明VvSERK1介导的抗碱性盐途径，揭示泌酸调控机理，也有助于泌酸在调节果树碱性盐抗性方面的应用。

Alkaline salts such as NaHCO3 are more harmful than neutral salt, however the mechanism underlying the tolerance to alkaline salts remains largely unknown. Secretion of organic acids is a fundamental way to resist alkaline stress in plants, however it has not received enough attentions in fruit trees. Our previous studies indicated that the kinase VvSERK1 and proton pump PHA3 responded to NaHCO3 at the levels of protein and phosphorylation, respectively, and additionally the two proteins interacted with each other. In this project, the correlation of VvSERK1 with VvPHA3 and organic acid secretion will be analyzed through determining the time-space characteristics of protein expression/secretion. Additionally, the functions of VvSERK1 and VvPHA3 in regulating secretion of organic acid and alkaline salt tolerance will be identified. The phosphorylation of VvPHA3 as the primary way of its activity regulation will be disclosed and additionally, the key phosphorylation site of VvVHA3 will be identified. Moreover, it will be elucidated that VvSERK1 phosphorylates VvPHA3 and thereby promotes its activity and enhances the levels of organic acid secretion and alkaline salt tolerance. Meanwhile, the contribution of VvVHA3 in the VvSERK1-mediated pathway will be evaluated. Collectively, the molecular pathway of “VvSERK1−VvPHA3-organic acid secretion” will be unraveled in this project. The expected results will disclose the VvSERK1-mediated pathway related to alkaline salt tolerance for the first time, unravel the molecular mechanism of organic acid secretion, and favor the application of organic acid secretion in enhancing the alkaline salt tolerance of fruit trees.