A Novel Set of SNARE Partners Facilitating Bacterial Pathogen Defence

植物微生物病原体破坏了全世界约15%的作物生产，造成重大的农业和社会经济损失。因此，了解植物免疫是减轻未来几十年人类社会在粮食生产中面临的挑战的核心。尽管植物进化出了防御系统，但免疫是以牺牲植物生长为代价的；相比之下，为了最大化生长相关性状而培育的作物往往会在防御方面妥协。为了从战略上最大限度地提高植物的抗病性，了解植物防御机制对于最大限度地减少产量至关重要。叶片表面的气孔与环境交换气体和水分，是微生物病原体的主要入口。对细菌病原体的最初防御是气孔关闭，但病原体通常操纵这些防御并迫使气孔打开。在细胞水平上，这些操作包括控制离子转运体及其调节蛋白来防止气孔关闭。微生物病原体也劫持细胞囊泡交通，抑制分泌防御相关分子到细胞壁。植物质膜上的分泌是由所谓的SNARE蛋白介导的，这些蛋白聚集在一起，驱动膜囊泡融合的最后阶段，并将囊泡内容物运送到细胞壁和细胞外的空间。然而，在植物发病过程中，对这些过程的分子基础知之甚少，实际上对它们的协调作用一无所知。质膜SNARE SYP132与抗菌肽的分泌有关。最近，我发现它在细胞内的表达和运输与细菌感染直接相关。我观察到SYP132的表达影响气孔对细菌病原体的反应。此外，SYP132与病原体防御所必需的质膜离子转运蛋白和调节蛋白发生物理相互作用，在病原体感染期间，SNARE的运输似乎与离子转运蛋白合用。这些发现指出了这个SNARE作为气孔防御和免疫的关键调节因子的意想不到的核心作用。我的假设是SYP132的内吞作用和囊泡膜循环在细菌发病的早期阶段是至关重要的。SYP132在免疫中的运输和功能特别受其与质膜上的离子转运体和调节蛋白的相互作用调节，它们允许防御信号，抗菌分泌和气孔反应之间的协调，以抵抗疾病并调节植物与微生物的相互作用。我建议阐明SYP132的转运机制及其对转运体结合伙伴的影响，以解决对植物免疫的影响。这些研究将利用已建立的植物和病原体模型作为工作的背景。我将确定SYP132的相互作用，特别是与迄今为止鉴定的离子转运体和调节蛋白的相互作用，在细菌疾病的进展过程中是如何变化的。我将扩大SYP132相互作用组的蛋白质组学分析和测量细菌发病过程中SYP132与新伙伴和已知伙伴相互作用的定量变化的研究，以评估它们在SYP132介导的免疫中的作用。所获得的知识将为未来在可持续农业中加强防御系统的作物工程方法的努力提供信息。

Plant microbial pathogens destroy some 15% of crop production worldwide, inflicting major agricultural and socio-economic losses. Thus, understanding plant immunity is at the centre of efforts to mitigate the challenges in food production facing human society in the coming decades. Although plants have evolved defence systems, immunity comes at a cost to plant growth; crop bred to maximize growth-related traits, by contrast, often compromise on defense. To strategically maximize plant disease resistance, knowledge of the mechanisms underlying plant defences is vital to minimize reductions in yield. Stomatal pores on the leaf surface exchange gas and water with the environment and are primary entry points for microbial pathogen. The initial defence against bacterial pathogen is stomatal closure, but pathogens commonly manipulate these defences and force stomatal opening. At a cellular level, these manipulations include commandeering ion transporters and their regulatory proteins to prevent stomata closure. Microbial pathogens also hijack cellular vesicle traffic to suppress secretion of defence-related molecules to the cell wall. Secretion at the plant plasma membrane is mediated by so-called SNARE proteins that assemble to drive the final stages of membrane vesicle fusion and deliver the vesicle contents to the cell wall and space outside the cell. Yet, the knowledge of molecular basis of these processes during plant pathogenesis is sparse and virtually nothing is known of their coordination. The plasma membrane SNARE SYP132 has been associated with the secretion of antimicrobial peptides. Recently, I found that its expression and traffic within the cell are tied directly to bacterial infection. SYP132 expression, I observed, affects stomatal responses to bacterial pathogens. Furthermore, SYP132 interacts physically with the plasma membrane ion transporters and regulatory proteins that are essential for pathogen defence, and traffic of the SNARE appears to co-opt the ion transport proteins during pathogen infection. These findings point to an unexpected and central role for this SNARE as a key regulator of in stomatal defence and immunity. My hypothesis is that SYP132 endocytosis and vesicle membrane recycling are critical for early stages of bacterial pathogenesis. SYP132 traffic and functions in immunity are particularly regulated by its interactions with the ion transporters and regulatory proteins at the plasma membrane and they allow for a co-ordination between defence signalling, antimicrobial secretion and stomatal responses to fight off disease and to regulate plant-microbe interactions. I propose to elucidate the mechanisms underlying SYP132 traffic and its impact on the transporter binding partners to resolve the impact on plant immunity. These studies will make use of established plant and pathogen models as a backdrop for the work. I will determine how interactions of SYP132, particularly with the ion transporter and regulatory proteins identified to date, change during the progression of bacterial disease. I will expand the studies with proteomic analysis of the SYP132 interactome and measurement of quantitative changes in SYP132 interactions with new and known partners during bacterial pathogenesis to assess their roles in SYP132-mediated immunity. The knowledge gained will inform future efforts in approaches to engineering crops with enhanced defence systems in sustainable agriculture.