核盘菌是重要的死体营养型病原真菌，寄主范围广泛，由其引起的作物菌核病难以控制。研究表明草酸及细胞壁降解酶是核盘菌的主要致病因子，但越来越多的证据表明分泌蛋白在核盘菌致病过程中也发挥重要作用。我们报道了核盘菌分泌蛋白SSITL在侵染早期抑制寄主的抗病反应，超表达SSITL的寄主对核盘菌更加感病，SSITL发挥类似效应子（effector）的功能；后续研究中我们筛选到并证实了钙受体蛋白CAS与SSITL互作。在此基础上，本项目拟进一步定位SSITL与CAS互作的功能域或位点，并研究SSITL与CAS互作对核盘菌致病、寄主抗病反应、CAS蛋白定位及叶绿体形态等方面的影响，明确SSITL与CAS互作的生物学意义，阐明SSITL抑制寄主抗病反应的分子机理。项目的完成对深入了解核盘菌的致病机制有重要促进作用，并可为菌核病的安全防控提供新的靶标，同时将为解析死体营养型病原真菌的致病机制提供重要参考。

Sclerotinia sclerotiorum is an important plant pathogenic fungus and has a wide range of host, including oilseed rape and soybean. Sclerotinia diseases are stubborn fungal diseases. As a typical necrotrophic fungus, S. sclerotiorum has long been regarded as a destructive plant pathogen by secretion of oxalic acid and cell wall-degrading enzymes facilitating infection. But emerging evidence showed that secretory proteins also play crucial roles in the pathogenesis of S. sclerotiorum. Previously, we reported that a secretory protein SSITL (Ss-Integrin-like protein) can suppress host resistance at the early stage to facilitate the infection of S. sclerotiorum. Over expression of SSITL in host can lead them to be more susceptible to S. sclerotiorum. So SSITL is considered to be a potential effector. This result indicates that S. sclerotiorum is more complex and subtle in pathogenic tactics. In a follow-up study, the target proteins of SSITL in host were screened through an IP-Mass method. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) experiments showed that Calcium Sensing Receptor (CAS) interact with SSITL. In this project, we plan to further clarify the key domain between the interaction of SSITL and CAS. Meanwhile, we also will work out the effects of the interaction on the pathogenesis, plant resistance, CAS protein location, and the chloroplast structure. Finally, we manage to illuminate the functions and molecular mechanisms of SSITL in the host resistance suppression. The results will help us to more deeply understand the mechanism of pathogenesis in S. sclerotiorum, which gives us an important theoretical significance and application value for developing new technology to control Sclerotinia diseases. In addition, the results also will provide important information on clarifying the mechanism of pathogenesis in necrotrophic fungus.