CAREER: Unraveling the metabolic interface between pathogenic Pseudomonas syringae bacteria and host plants

该项目的总体目标是开发一个研究和教育的综合计划，以提高细菌病原体如何感染植物的知识，并向本科生和服务不足的高中生介绍STEM发现的兴奋。植物的细菌性病害导致美国许多重要作物的总产量和销售能力的重大损失。虽然植物有一个免疫系统，可以提供有效的抵抗感染，细菌已经进化出复杂的对抗措施，可以有效地抑制这些宿主的防御。因此，感染结果的一个重要决定因素是细菌和宿主植物能够多快地部署各自的毒力和防御策略。该项目将研究植物和细菌之间发生的化学信号事件，重点是病原菌如何感知植物衍生的代谢产物以开始感染，以及植物如何干扰这种感知过程。作物中的细菌性疾病通常通过非特异性抗菌剂如铜喷雾剂来控制。从该项目中获得的知识可能导致开发新的细菌疾病化学抑制剂，以及更抗病的工程作物。该项目的研究目标将被纳入三个主要的教育活动：1）为来自俄勒冈州和华盛顿服务不足的农村和城市高中的学生举办校园STEM夏令营，2）对学生进行功能基因组学课程的培训，3）为高中生提供夏季实验室研究实习。植物病原菌假单胞菌（Pseudomonaserichingae）必须在感染的早期阶段迅速部署其III型分泌系统（T3 SS）才能致病。特定的植物来源的有机酸和氨基酸，以及简单的糖，诱导T3 SS编码基因在P. pastingae，但这些信号是如何感知的知之甚少。在以前的工作中，研究者确定了一个转录因子SetA，它是糖诱导的T3 SS基因在P. eriningae中最大表达所必需的。该项目的第一个目标是确定SetA如何调节T3 SS主调节因子hrpL的表达，并确定可能调节SetA活性的细胞内代谢物信号。研究人员还确定了一个双组分系统，AauS-AauR，它直接将宿主衍生的氨基酸信号的检测与T3 SS编码基因的调节联系起来。第二个目标是确定宿主信号如何激活AauS以及下游反应调节因子AauR如何调节T3 SS编码基因。提出的方法包括生物化学方法来评估调节SetA和AauS-AauR功能的蛋白质-代谢物、蛋白质-DNA和蛋白质-蛋白质相互作用。利用代谢组学，研究人员还发现，在宿主防御反应期间，特定的T3 SS诱导代谢物在叶片中的丰度减少。该项目的第三个目标是确定调节这些代谢物丰度的分子机制，以及丁香假单胞菌如何通过AauS/AauR和SetA独立机制感知这些宿主信号。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The overall goal of this project is to develop an integrated program of research and education that advances knowledge of how bacterial pathogens infect plants, and introduces undergraduates and under-served high school students to the excitement of discovery in STEM. Bacterial diseases of plants cause significant losses in overall yield and marketability of many important US crops. Although plants have an immune system that can provide effective resistance against infection, bacteria have evolved sophisticated counter-measures that can effectively suppress these host defenses. As a result, an important determinant of infection outcomes is how rapidly both bacteria and host plant can deploy their respective virulence and defense strategies. This project will investigate chemical signaling events that occur between plants and bacteria, with a focus on how pathogenic bacteria perceive plant-derived metabolites to start an infection, as well as how plants may interfere with this perception process. Bacterial diseases in crops are frequently controlled by non-specific antimicrobials such as copper sprays. Knowledge gained from this project could lead to the development of novel chemical inhibitors of bacterial diseases, as well as engineered crops that are more disease resistant. Research objectives of this project will be integrated into three main educational activities: 1) on-campus summer STEM camps for students from under-served rural and urban high schools in Oregon and Washington, 2) training of students in a functional genomics course and 3) summer-long laboratory research internships for high school students. The plant pathogen Pseudomonas syringae must rapidly deploy its type III secretion system (T3SS) at early stages of infection to be virulent. Specific plant-derived organic acids and amino acids, together with simple sugars, induce T3SS-encoding genes in P. syringae, yet how these signals are perceived is poorly understood. In previous work the investigator identified a transcription factor SetA that is required for maximal sugar-induced expression of T3SS genes in P. syringae. The project’s first objective is to determine how SetA regulates expression of T3SS master regulator hrpL and to identify the intracellular metabolite signal(s) that may regulate SetA activity. The investigator also identified a two-component system, AauS-AauR, that directly links detection of host-derived amino acid signals to regulation of T3SS-encoding genes. A second objective is to determine how host signals activate AauS and how the downstream response regulator AauR regulates T3SS-encoding genes. Proposed methods include biochemical approaches to assess protein-metabolite, protein-DNA and protein-protein interactions that regulate the functions of SetA and AauS-AauR. Using metabolomics, the investigator also discovered that specific T3SS-inducing metabolites decrease in abundance in leaves during a host defense response. The project’s third objective is to determine the molecular mechanism(s) that regulate the abundance of these metabolites, and how these host signals are perceived by P. syringae through AauS/AauR- and SetA-independent mechanisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.