CAREER: The Role of the HrpR/S Proteins in the Regulation of Virulence in the Plant Pathogenic Bacterium Pseudomonas syringae.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。知识价值：丁香假单胞菌是许多农作物的重要经济病原菌。该病的特点是在受感染植物的叶子和果实上出现坏死病变。丁香假单胞菌表达毒力基因，包括编码多组分III型分泌系统（T3SS）的基因，该系统是植物寄主定殖所必需的。T3SS将细菌效应蛋白直接输送到宿主细胞中。效应物破坏植物信号通路，破坏植物防御反应。其他丁香假单胞菌毒力基因参与植物毒素的合成，植物毒素是一种低分子量化合物，可损害植物细胞或影响疾病发展。在大多数细菌中，包括丁香假单胞菌，毒力基因的表达受到宿主环境信号的严格调控。本项目重点研究了丁香假单胞菌毒力基因表达的两个调控因子HrpR和HrpS，这两个调控因子在一个复杂的调控回路中起作用。在这个回路中，HrpR和HrpS激活hrpL基因的表达，该基因编码T3SS、效应基因和植物毒素生物合成基因的直接调节因子。HrpRS调控级联的几个方面还没有很好地描述。特别是，本项目将研究在通常感染丁香假单胞菌的植物中Hrp的调控表达模式。本研究的具体目的是：(1)确定hrpL基因上游HrpR和HrpS的DNA结合位点；(2)鉴定丁香属中hrpL以外直接受HrpR和HrpS调控的基因；(3)研究环境信号对HrpR的调控。这一目标还将包括植物内部和植物表面的表达研究。了解HrpR和HrpS如何控制毒力基因表达，将有助于更好地了解丁香假单胞菌如何引发植物感染和操纵植物生理。综合研究/教学计划：该项目还包括由首席研究员制定综合教学/研究/推广计划的努力。将与青年探索科学（YES）项目建立伙伴关系，该项目教育来自弱势少数民族的弱势高中生。作为这一教育推广计划的一部分，密苏里大学圣路易斯市分校将开设一门课程。在该项目中，本科生创造了与植物与微生物相互作用有关的互动学习活动。然后，这些大学生将在圣路易斯科学中心与YES高中学生一起促进这些活动，项目由七个部分组成。这些高中生还将在夏季受雇于圣路易斯科学中心，对一些植物与微生物相互作用的活动进行改编，以便向公众展示。更广泛的影响：HrpR和HrpS是开发新的控制措施的合适目标，这些措施也可能对其他重要的植物病原体有效。该项目还将支持培养植物病理学和分子生物学研究方面的研究生和本科生。这些学生将获得各种分子、遗传、生化和生物信息学技术方面的专业知识，这将增加他们未来在生物科学领域的职业机会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Intellectual Merit: Pseudomonas syringae is an economically significant bacterial pathogen of many crop plants. The disease is characterized by the appearance of necrotic lesions on the leaves and fruits of infected plants. P. syringae expresses virulence genes, including those encoding a multi-component Type III secretion system (T3SS) which is necessary to colonize the plant host. The T3SS delivers bacterial effector proteins directly into host cells. Effectors disrupt plant signaling pathways and undermine plant defense responses. Other P. syringae virulence genes are involved in the synthesis of phytotoxins, which are low molecular weight compounds that damage plant cells or influence disease development. In most bacteria, including P. syringae, virulence gene expression is tightly regulated in response to environmental signals that exist in the host. This project focuses on HrpR and HrpS, two regulators of P. syringae virulence gene expression that function in a complex regulatory circuit. In this circuit, HrpR and HrpS activate expression of the hrpL gene, which encodes a direct regulator of T3SS, effector, and phytotoxin biosynthesis genes. Several aspects of the HrpRS regulatory cascade are not well characterized. In particular, this project will address the Hrp regulatory expression pattern in plants that are normally infected by P. syringae. The specific objectives of the research are to: (i) determine the DNA binding sites for HrpR and HrpS upstream of the hrpL gene, (ii) identify genes in P. syringae other than hrpL that are directly regulated by HrpR and HrpS, and (iii) examine the regulation of hrpRS by environmental signals. This objective will also include expression studies in and on the plant. Learning more about how HrpR and HrpS control virulence gene expression will contribute to a better understanding of how P. syringae initiates plant infection and manipulates plant physiology. Integrated Research/Teaching program: The project also includes efforts by the principal investigator to develop an integrated teaching/research/outreach program. A partnership will be developed with the Youth Exploring Science (YES) program, which educates disadvantaged high school students from underrepresented minorities. As part of this educational outreach program, a course will be developed at the University of Missouri-St. Louis in which undergraduates create interactive learning activities related to plant-microbe interactions. The university students will then facilitate these activities with the YES high school students in a seven part program at the St. Louis Science Center. The high school students also will be employed by the St. Louis Science Center during the summer to adapt some of the plant-microbe interactions activities for presentation to the general public.Broader impacts: HrpR and HrpS are appropriate targets for the development of new control measures, which may also be effective against other important plant pathogens. The project will support also the training of graduate and undergraduate students in plant pathology and molecular biology research. These students will gain expertise in a variety of molecular, genetic, biochemical, and bioinformatic techniques that will enhance their future career opportunities in the biological sciences.