内质网—质膜接触点(EPCS)是普遍存在于真核生物细胞中的亚细胞结构，植物细胞中EPCS 的分子基础，动态调控机制及生物学功能仍不清楚。项目前期研究发现Synaptotagmin1 (Syt1)介导的EPCS (S-EPCS)是调节植物抗病的重要亚细胞结构。本项目拟在拟南芥—丁香假单胞菌的互作体系下，通过运用新发展的EPCS光遗传学标记工具和原位邻近蛋白标记技术对EPCS动态分析和相应分子机器原位鉴定，分离EPCS调控蛋白并明确其功能，深入揭示内质网和质膜互作介导的植物防御反应抵抗细菌侵染和二者的互作机制。本项目首次系统性针对植物EPCS的原位蛋白质组展开鉴定，研究结果将极大的丰富领域对植物EPCS维持机制的认识，有利于后续生物学功能研究的进一步开展。此外，通过分析EPCS调控植物抗病的生理机制，挖掘EPCS的新功能，鉴定植物抗病的新组分， 为植物细菌病害防治提供新思路和新靶标。

Endoplasmic reticulum (ER)-plasma membrane (PM) contact sites (EPCS) represent a general feature of all eukaryotic cells. Due to lack of knowing the molecular composition in this specialized sub-compartment, the biological significances of EPCS remain unclear in plant cells. Using forward genetic approaches, we identified a mutant of Arabidopsis synaptotagmin1 (Syt1), a key EPCS tether protein, is significantly susceptible to bacterial phytopathogens. Furthermore, several critical innate immune responses are impaired in syt1 mutant, including suppressed burst of reactive oxygen species and calcium signaling, as well as decreased immune receptor abundance at PM. However, the MAP kinase cascade and callose deposition are not affected by loss of Syt1. These data suggested that Syt1 is a novel component required for plant defense against bacteria pathogens. Additionally, we identified a bacterial effector that specifically targets EPCS to suppress plant immune system, suggesting that EPCS regulates plant defense at multiple levels. Based on these preliminary results, we aim to uncover the function of ER-PM contact site during plant immunity. To complete this aim, we developed new optogenetic tool that reversibly labeling EPCS in plant cells to monitor the dynamics of EPCS upon bacteria infection at high spatial-temporal resolution. Moreover, we will systematically dissect the molecular machinery of EPCS by TurboID-based proximity labeling, and screen Syt1-interacting partners involved in plant defense and target proteins of the bacterial effector. Further characterization of the candidate interactors will not only helps us to understand the importance of EPCS during plant-microbe interaction, but also sets the stage to uncover more uncharted functions of hitherto underexplored ER–PM contact sites.