Dissecting the Arms Race between Pathogenic Bacteria and the Plant Immune System

剖析病原菌与植物免疫系统之间的军备竞赛

• 批准号: RGPIN-2014-06347
• 负责人: Guttman, David
• 金额: $ 4.44万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=628905
• 关键词: Dissecting; Arms; Race; between; Pathogenic

Pathogens and their hosts engage in a co-evolutionary arms race for survival, which is mediated by pathogen virulence factors and the host immune system. The first level of cellular interaction is the recognition of conserved microbe-associated molecular patterns (MAMPs) by host pattern recognition receptors (PRRs). Some pathogens are able to suppress this immune response via type III secreted effectors (T3SEs). Some plant hosts can in turn respond to T3SEs via nucleotide binding leucine rich repeat resistance proteins (NLRs), which trigger a second layer of immunity upon recognition of T3SE activity.This proposal has two major goals:Goal 1. Dissect the arms race between the HopZ family of T3SEs and their host targets. HopZ alleles are carried by the agronomically-important phytopathogenic bacterium Pseudomonas syringae. This diverse family of T3SEs has four major allele sub-families that can act as either virulence factors or immune elicitors depending on the presence of the ZAR1 NLR in Arabidopsis. We have recently shown that one HopZ allele acetylates a variety of host proteins including the pseudokinase ZED1 and a family of kinases closely related to ZED1 called ZRKs. ZED1 is monitored / guarded by ZAR1. - Our hypotheses are: HopZ T3SEs target ATP-binding domain proteins; different HopZ alleles target different members of the ZED1/ZRK family; HopZ acetylation of ZRKs interferes with their kinase activity; and inhibition of ZRK activity suppresses immune signaling. - Our specific aims for this goal are to: 1a) Determine which HopZ alleles are acetyltransferases. 1b) Assess physical and biochemical interactions between the HopZ and ZED1/ZRK families. 1c) Identify residues putatively important for interaction and post-translational modification in the HopZ and ZRK families. 1d) Determine if specific ZRK family members are important for bacterial virulence or host immunity. And 1e) Determine if post-translation modification of HopZ or ZRK proteins modulates virulence or immune activation.Goal 2. Dissect the arms race between bacterial MAMPs and plant PRRs. We have developed novel screens to identify new MAMPs and their cognate PRRs, and want to determine what role these interactions play during the very early stages of host adaptation. - Our hypotheses are: there are many more MAMPs in any given pathosystem than have been previously characterized; MAMP-PRR interactions are highly specific, but most interactions signal through a fairly small number of regulatory PRRs; MAMP variation can result in modulation of host specificity; and the first step in a host switch involves evolution of MAMPs away from PRR recognition. - Our specific aims for this goal are to: 2a) Identify the PRRs that recognize newly identified MAMPs. 2b) Validate the direct interaction of PRRs and MAMPs. 2c) Identify the first changes associated with host range expansion via experimental evolution. And 2d) Determine how MAMPs evolve over recent evolutionary time and the consequence of this for immune elicitation.These studies continue our comparative and functional dissection of one of the best established pathosystems for host-specificity research. Through these aims we will decode the range of functional interactions between a diverse family of bacterial T3SEs and the even more diverse family of host proteins with which they interact. We will then mechanistically characterize the interactions that modulate bacterial virulence and host immunity. We will also examine the diversity of MAMPs and their cognate PRRs. We will determine how this variation influences host specificity, and produce fundamental research that will be the foundation for future applied work focusing on the use of MAMPs as alternative antimicrobials.

病原体及其宿主参与共同进化的生存军备竞赛，这是由病原体毒力因子和宿主免疫系统介导的。细胞相互作用的第一个水平是宿主模式识别受体（PRR）对保守的微生物相关分子模式（MAMP）的识别。一些病原体能够通过III型分泌效应物（T3 SE）抑制这种免疫应答。一些植物宿主又可以通过核苷酸结合富含亮氨酸的重复抗性蛋白（NLR）来响应T3 SE，所述NLR在识别T3 SE活性时触发第二层免疫。剖析T3 SE的HopZ家族与其宿主目标之间的军备竞赛。HopZ等位基因由农学上重要的植物病原性细菌假单胞菌携带。这个不同的T3 SE家族有四个主要的等位基因亚家族，它们可以作为毒力因子或免疫激发子，这取决于拟南芥中ZAR 1 NLR的存在。我们最近发现，一个HopZ等位基因乙酰化多种宿主蛋白质，包括假激酶ZED 1和一个与ZED 1密切相关的激酶家族，称为ZRKs。ZED 1由ZAR 1监控/保护。- 我们的假设是：HopZ T3 SE靶向ATP结合结构域蛋白;不同的HopZ等位基因靶向ZED 1/ZRK家族的不同成员; ZRK的HopZ乙酰化干扰其激酶活性; ZRK活性的抑制抑制免疫信号传导。- 我们的具体目标是：1a）确定哪些HopZ等位基因是乙酰转移酶。1b）评估HopZ和ZED 1/ZRK家族之间的物理和生物化学相互作用。1c）鉴定对于HopZ和ZRK家族中的相互作用和翻译后修饰至关重要的残基。1d）确定特定的ZRK家族成员对于细菌毒力或宿主免疫是否重要。和1 e）确定HopZ或ZRK蛋白的翻译后修饰是否调节毒力或免疫激活。剖析细菌MAMP和植物PRR之间的军备竞赛。我们已经开发了新的屏幕来识别新的MAMPs和它们的同源PRR，并希望确定这些相互作用在宿主适应的早期阶段发挥什么作用。- 我们的假设是：在任何给定的病理系统中，MAMPs的数量比以前鉴定的要多得多; MAMP-PRR相互作用是高度特异性的，但大多数相互作用通过相当少量的调节PRR发出信号; MAMP变异可导致宿主特异性的调节;宿主转换的第一步涉及MAMPs从PRR识别中进化出来。- 我们的具体目标是：2a）识别识别新识别的MAMP的PRR。2b）验证PRR和MAMP的直接相互作用。2c）通过实验进化识别与宿主范围扩展相关的第一批变化。和2d）确定MAMPs在最近的进化时间中如何进化以及其对免疫激发的影响。这些研究继续了我们对宿主特异性研究中最好的病理系统之一的比较和功能解剖。通过这些目标，我们将解码细菌T3 SE的不同家族和与它们相互作用的宿主蛋白质的更多样化家族之间的功能相互作用的范围。然后，我们将机械特性的相互作用，调节细菌的毒力和宿主免疫力。我们还将研究MAMP及其同源PRR的多样性。我们将确定这种变化如何影响宿主特异性，并进行基础研究，这将是未来应用工作的基础，重点是使用MAMPs作为替代抗菌剂。