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Abstract：
The interorganelle communication mediated by membrane contact sites (MCSs) is an evolutionary hallmark of eukaryotic cells. MCS connections enable the nonvesicular exchange of information between organelles and allow them to coordinate responses to changing cellular environments. In plants, the importance of MCS components in the responses to environmental stress has been widely established, but the molecular mechanisms regulating interorganelle connectivity during stress still remain opaque. In this report, we use the model plant Arabidopsis thaliana to show that ionic stress increases endoplasmic reticulum (ER)-plasma membrane (PM) connectivity by promoting the cortical expansion of synaptotagmin 1 (SYT1)-enriched ER-PM contact sites (S-EPCSs). We define differential roles for the cortical cytoskeleton in the regulation of S-EPCS dynamics and ER-PM connectivity, and we identify the accumulation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] at the PM as a molecular signal associated with the ER-PM connectivity changes. Our study highlights the functional conservation of EPCS components and PM phosphoinositides as modulators of ER-PM connectivity in eukaryotes, and uncovers unique aspects of the spatiotemporal regulation of ER-PM connectivity in plants.
摘要：
由膜接触位点（MCSs）介导的细胞器间通讯是真核细胞的进化标志。MCS连接使细胞器之间的信息非囊泡交换，并使它们能够协调对不断变化的细胞环境的反应。在植物中,MCS组件在应对环境压力中的重要性已得到广泛确立，但是在应激过程中调节细胞器间连接的分子机制仍然不清楚。在这份报告中,我们使用模型植物拟南芥表明，离子应激通过促进突触结合蛋白1（SYT1）富集的ER-PM接触位点（S-EPCSs）的皮质扩张来增加内质网（ER）-质膜（PM）的连通性。我们定义了皮质细胞骨架在S-EPCS动力学和ER-PM连接调节中的不同作用，我们确定了磷脂酰肌醇4,5-二磷酸[PI（4,5）P2]在PM处的积累，作为与ER-PM连通性变化相关的分子信号。我们的研究强调了EPCS组件和PM磷酸肌醇作为真核生物中ER-PM连接调节剂的功能保守性，并揭示植物中ER-PM连通性的时空调节的独特方面。
