Departamento de Biología Molecular y Bioquímica, Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Universidad de Málaga, Málaga 12907, Spain.
Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China.
Plant Cell. 2021 Aug 13;33(7):2431-2453. doi: 10.1093/plcell/koab122.
Endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased PM integrity under multiple abiotic stresses, such as freezing, high salt, osmotic stress, and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild-type while the levels of most glycerolipid species remain unchanged. In addition, the SYT1-green fluorescent protein fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.
内质网-质膜接触位点（ER-PM CS）在所有真核细胞中都发挥着重要作用。拟南芥突变体缺乏内质网-质膜蛋白连接蛋白 synaptotagmin1（SYT1），在多种非生物胁迫下，如冷冻、高盐、渗透胁迫和机械损伤下，质膜完整性降低。在这里，我们表明，与 SYT1 一起，应激诱导的 SYT3 是一种内质网-质膜连接蛋白，也能维持质膜的完整性。SYT1 和 SYT3 的 ER-PM CS 定位依赖于质膜磷脂酰肌醇-4-磷酸，并受非生物胁迫的调节。脂质组学分析表明，与野生型相比，冷胁迫在 syt1/3 双突变体中增加了质膜中二酰基甘油的积累，而大多数甘油脂种类的水平保持不变。此外，SYT1-绿色荧光蛋白融合蛋白在体内优先与二酰基甘油结合，而与极性甘油脂的亲和力很小。我们的工作揭示了一种 SYT 依赖性的应激适应机制，该机制可以对抗非生物胁迫期间质膜中二酰基甘油的有害积累。
