植物固有免疫系统是其识别外源病原菌，快速启动防御性反应的过程。其中病原相关分子模式激发的免疫反应（PTI）主要通过细胞表面的模式识别受体（PRRs）识别微生物相关分子模式（MAMP/PAMP）进而引发基础免疫。植物通过细胞表面LRR-RLP型受体RBPG1识别灰霉菌分泌的内切聚半乳糖醛酸酶（BcPG3），在共受体SOBIR1的辅助下，激活下游信号通路。但对于RBPG1与配体BcPG3的相互作用机制，以及受体复合物的活化机制还不清楚。本项目拟通过结构生物学与生物化学相结合的方法，按照从胞外到胞内的顺序，对RBPG1与BcPG3的识别、配体诱导受体复合体发生构象变化、SOBIR胞内端激酶结构域激活机制等进行深入研究，系统阐明BcPG3诱导RBPG1-SOBIR1复合体活化的分子机制。该工作将首次揭示LRR-RLP型受体的激活机制，并为抗性植株的选育、特异性杀菌剂的设计提供理论基础。

Plants depend on innate immunity to cope with exogenous pathogens. Pathogen-associated molecular pattern-triggered immunity (PTI) is initiated when PAMPs (pathogen-associated molecular pattern) or MAMPs (microbe associated molecular pattern) is recognized by the PRRs (pattern recognition receptors) on the plant cell surface and then triggers the basal immune response. Botritis cinerea endopolygalacturonases 3(BcPG3) can be recognized by the cell surface receptor named Responsiveness to Botrytis Polygalacturonase 1 (RBPG1), which belongs to the Leucine-rich repeat receptor-like proteins (LRR-RLPs). SOBIR1 (Suppresror of BIR1), a co-receptor of RBPG1 is also involved in the activation of the downstream signaling pathway. However, the way how RBPG1 and BcPG3 are interacting, and activation mechanism of the receptor complex are still unknow. This project aims at illuminating the molecular mechanisms of BcPG3-induced activation of RBPG1-SOBIR1 complex by using structural and biochemical anaylsis. Our proposed research project will be performed based on the immunal signaling cascade from extracellular to intracellular: the binding affinity between RBPG1 and BcPG3, BcPG3-induced conformational change of the receptor complex and the activation mechanism of SOBIR1’s cytoplasmic kinase domain. For the first time, our work will reveal the LRR-RLPs activation mechanism, and provide a basis for fungal resistant plant breeding and specific fungicide designing.