How does a plant pathogen hijack its host's secretory pathway?

背景植物寄生线虫是重要的农业害虫，与寄主之间存在着复杂的相互作用。最具破坏性的物种将效应蛋白分泌到其宿主根中以诱导和维持称为摄食位点的独特结构。受影响的根细胞的一个显著特征是细胞质增殖，细胞器丰富，以中央液泡为代价形成。我们的核心假设是，线虫可以使用效应子来重新编程植物细胞的膜运输，以实现这种基本的重塑，同时还利用分泌途径发挥效应子功能。描述植物寄生线虫取食部位分泌途径细胞器的早期变化.探讨线虫效应子在影响分泌、内质网滞留和液泡转运中的作用.阐明了线虫效应物进入宿主细胞质后传递到质外体的途径。驱动线虫摄食部位发生细胞学变化的机制以及所涉及的特定效应物目前尚不清楚。这项工作还将为植物中的蛋白质运输途径提供新的见解。很准时。Denecke集团最近开发的工具促进了该项目，例如液泡和内体标记物的完整组合以及分泌物原生质体测定。实验方法。标记不同分泌途径细胞器的拟南芥双荧光报告细胞系将被线虫感染。共聚焦显微镜将被用来检查亚细胞的变化发生在早期阶段的喂养网站的形成。一系列线虫效应物将在分泌性货物原生质体测定中表达，以鉴定影响液泡和/或ER功能的那些。酵母双杂交分析将确定植物相互作用的合作伙伴的利益效应-确认共免疫沉淀。利用原生和突变体效应子进行的原生质体分泌分析将确定线虫效应子的输出途径，这些效应子在质外体中发挥作用，尽管被递送到细胞质中。该项目建立在植物寄生线虫可以重新编程宿主植物细胞的膜运输的假设上，使得维持中央液泡的正常途径被消除，从而使质膜和富含核糖体的胞质溶胶扩展。学生将测试这个假设，并确定由线虫产生的分泌蛋白效应子是否负责植物分泌途径的基本重编程。通过剖析这种寄生相互作用的机制，该项目将为植物细胞生物学的一个关键方面提供新的启示。

Background. Plant-parasitic nematodes are important agricultural pests that have complex interactions with their host. The most damaging species secrete effector proteins into their host roots to induce and maintain unique structures, termed feeding-sites. A striking feature of the affected root cells is proliferated cytoplasm enriched in organelles, formed at the expense of the central vacuole. Our core hypothesis is that nematodes can use effectors to re-programme membrane trafficking of plant cells to achieve this fundamental remodelling whilst also exploiting the secretory pathway to exert effector function.Objectives.1. Characterise the early changes to secretory pathway organelles that occur in plant parasitic nematode feeding sites.2. Investigate the role of nematode effectors in influencing secretion, ER retention and vacuolar transport.3. Elucidate the pathways by which nematode effectors introduced into the host cytoplasm are delivered to the apoplast.Novelty. The mechanism driving the cytological changes that occur in nematode feeding sites, and the specific effectors involved, are currently unknown. The work will also provide new insights into protein trafficking pathways in plants. Timeliness. The project is facilitated by tools recently developed by the Denecke Group, such as the full portfolio of vacuolar and endosomal markers and secretory cargo protoplast assays.Experimental Approach. Double-fluorescent reporter lines of Arabidopsis with different secretory pathway organelles marked will be infected with nematodes. Confocal microscopy will be used to examine subcellular changes taking place during the early stages of feeding site formation. A range of nematode effectors will be expressed in secretory cargo protoplast assays to identify those that influence vacuolar and/or ER function. Yeast-2-hybrid analysis will identify plant interacting partners for effectors of interest - confirmed by coimmunoprecipitation. Protoplast secretion assays using native and mutant effectors will define the export pathway of nematode effectors that function in the apoplast despite being delivered into the cytoplasm.The project is built on the hypothesis that plant parasitic nematodes can re-programme embrane trafficking of host plant cells so that the normal route to maintain the central vacuole is eliminated to enable expansion of the plasma membrane and the ribosome rich cytosol. The student will test this hypothesis and establish if the secreted protein effectors produced by the nematode are responsible for the fundamental reprogramming of the plant secretory pathway. By dissecting the mechanisms involved in this parasitic interaction, the project will shed new light on a key aspect of plant cell biology.