Role of the Bti9 LysM-receptor-like kinase in PAMP-triggered immunity

植物依靠双层免疫系统来防御病原体。第一个系统依赖于识别病原体相关分子模式(PAMP)的细胞外受体，从而激活PAMP触发的免疫(PTI)。在第二个系统中，植物通常使用细胞内的受体来识别病原体毒力蛋白(效应器)，这些蛋白被传递到植物细胞中，并已进化为抑制PTI。第二道防线被称为效应器触发免疫(ETI)。在本项目中，我们将利用番茄与细菌病原菌紫花假单胞菌PV之间的相互作用来研究PTI的分子基础。番茄(PST)。PST将效应物AvrPtoB传递到植物细胞中，在那里它抑制PTI并促进细菌毒力。在前期工作中，我们确定了AvrPtoB的一个可能的寄主毒力靶点，命名为AvrPtoB-番茄相互作用蛋白9(Bti9)。Bti9具有PAMP受体的特征，其胞外区由三个LysM结构域和胞内丝氨酸/苏氨酸蛋白激酶组成。该项目将检验Bti9是一种PAMP受体的假设，该受体识别细菌细胞壁成分多肽聚糖，并随后通过其激动域触发细胞内信号事件。此外，该项目试图确定效应器AvrPtoB是否干扰Bti9激酶的活性，Bti9与其他宿主蛋白的联系，或者可能干扰Bti9在植物细胞中的定位。本项目研究了Bti9的功能，Bti9-AvrPtoB相互作用的结构方面，以及AvrPtoB可能干扰Bti9的机制。最近发现的PTI对植物抗病的重要性，为培育对病原菌具有广泛持久抗性的作物开辟了新的可能性。这项研究的重点是PTI的一个关键方面--一种潜在的新型细菌导向的PAMP受体，以及病原体效应因子进化到抑制其功能的机制。这项研究将在四个领域产生广泛影响：1)PI和他的实验室成员将继续改进最近开发的基于网络的模块，向高中教师介绍植物免疫以及植物病害的社会和经济后果；2)来自全国各地的学生将接受培训，作为博伊斯·汤普森研究所主办的NSF支持的植物基因组学夏季研究计划的一部分；3)国际和平协会将继续积极开展几项外展工作(过去的活动包括领导一年一度的“实地日”活动，向暑期实习生介绍纽约农业中的疾病问题)；以及4)国际和平协会为康奈尔大学新生开发了一门新课程，题为：植物、苍蝇和人类的先天免疫(BIOG 1250)，这项研究的成果将纳入本课程。

Plants rely on a two-layered immune system to defend themselves against pathogens. The first system relies on extracellular receptors that recognize pathogen-associated molecular patterns (PAMPs) and thereby activates PAMP-triggered immunity (PTI). In the second system, plants use typically intracellular receptors to recognize pathogen virulence proteins (effectors) that are delivered into the plant cell and which have evolved to suppress PTI. This second line of defense is termed effector-triggered immunity (ETI). In this project, the molecular basis of PTI will be investigated using the interaction between tomato and the bacterial pathogen, Pseudomonas syringae pv. tomato (Pst). Pst delivers an effector, AvrPtoB, into the plant cell where it suppresses PTI and promotes bacterial virulence. In preliminary work, a possible host virulence target of AvrPtoB was identified and termed AvrPtoB-tomato-interacting protein 9 (Bti9). Bti9 has characteristics of a PAMP receptor with a putative extracellular region consisting of three LysM domains and an intracellular serine/threonine protein kinase. This project will test the hypothesis that Bti9 is a PAMP receptor that recognizes a bacterial cell wall component, peptidoglycan, and subsequently triggers intracellular signaling events via its kinase domain. Furthermore, the project seeks to determine whether the effector AvrPtoB interferes either with Bti9 kinase activity, the association of Bti9 with other host proteins, or possibly with Bti9 localization in the plant cell. This project investigates the function of Bti9, the structural aspects of the Bti9-AvrPtoB interaction, and the mechanism by which AvrPtoB may interfere with Bti9. The recent discovery of the importance of PTI to plant disease resistance has opened up new possibilities for the development of crop plants with broad, durable resistance to pathogens. This research focuses on a key aspect of PTI - a potentially novel bacterial-directed PAMP receptor and the mechanisms by which a pathogen effector has evolved to suppress its function.There are four areas where this research will have broad impact: 1) the PI and members of his lab will continue to improve a recently developed web-based module for High School teachers to introduce their students to plant immunity and to the social and economic consequences of plant diseases; 2) students from across the country will be trained as part of the NSF-supported Plant Genomics Summer Research Program hosted by the Boyce Thompson Institute; 3) the PI will continue to be active in several outreach efforts (past activities include leadership of an annual 'Field Day' that introduces summer interns to disease problems in New York agriculture); and 4) the PI has developed a new course for Cornell freshmen entitled: Innate Immunity in Plants, Flies, and Humans (BioG 1250) and results from this research will be incorporated into this course.