State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
New Phytol. 2018 Jul;219(2):654-671. doi: 10.1111/nph.15178. Epub 2018 Apr 20.
Endosomal sorting machineries regulate the transport of their cargoes among intracellular compartments. However, the molecular nature of such intracellular trafficking processes in pathogenic fungal development and pathogenicity remains unclear. Here, we dissect the roles and molecular mechanisms of two sorting nexin proteins and their cargoes in endosomal recycling in Fusarium graminearum using high-resolution microscopy and high-throughput co-immunoprecipitation strategies. We show that the sorting nexins, FgSnx41 and FgSnx4, interact with each other and assemble into a functionally interdependent heterodimer through their respective BAR domains. Further analyses demonstrate that the dimer localizes to the early endosomal membrane and coordinates endosomal sorting. The small GTPase FgRab5 regulates the correct localization of FgSnx41-FgSnx4 and is consequently required for its trafficking function. The protein FgSnc1 is a cargo of FgSnx41-FgSnx4 and regulates the fusion of secreted vesicles with the fungal growing apex and plasma membrane. In the absence of FgSnx41 or FgSnx4, FgSnc1 is mis-sorted and degraded in the vacuole, and null deletion of either component causes defects in the fungal polarized growth and virulence. Overall, for the first time, our results reveal the mechanism of FgSnc1 endosomal recycling by FgSnx41-FgSnx4 heterodimer which is essential for polarized growth and pathogenicity in F. graminearum.
内体分拣机制调节细胞内隔室之间货物的运输。然而，致病真菌发育和致病性中这种细胞内运输过程的分子性质仍不清楚。在这里，我们使用高分辨率显微镜和高通量共免疫沉淀策略，剖析了两个分选连接蛋白及其货物在镰刀菌属内体再循环中的作用和分子机制。我们表明，分选连接蛋白 FgSnx41 和 FgSnx4 通过它们各自的 BAR 结构域相互作用并组装成功能上相互依赖的异二聚体。进一步的分析表明，二聚体定位于早期内体膜并协调内体分拣。小分子 GTPase FgRab5 调节 FgSnx41-FgSnx4 的正确定位，因此是其运输功能所必需的。蛋白质 FgSnc1 是 FgSnx41-FgSnx4 的货物，调节分泌囊泡与真菌生长顶端和质膜的融合。在缺乏 FgSnx41 或 FgSnx4 的情况下，FgSnc1 被错误分拣并在液泡中降解，而缺失任一成分都会导致真菌极性生长和毒力缺陷。总的来说，我们的结果首次揭示了 FgSnc1 由 FgSnx41-FgSnx4 异二聚体进行内体再循环的机制，该机制对于 F. graminearum 的极性生长和致病性是必不可少的。
