RLP and RLK-mediated innate immune responses in Arabidopsis and tomato triggered by PAMPS and Avrs

植物对病害的抗性或易感性主要包括三个组成部分。首先，许多微生物产生病原体相关分子模式（PAMP），如细菌鞭毛蛋白和真菌几丁质，植物已经进化出识别和响应的能力。这导致PAMP触发免疫（PTI）。其次，许多病原体产生并向植物细胞递送干扰PTI的效应蛋白，降低防御激活，导致易感性。第三，植物具有抗性（R）基因库，其编码直接或间接通过效应物作用于宿主组分识别特定病原体效应物的传感器蛋白。R基因依赖性识别导致效应子触发免疫（ETI），恢复抗性。为了了解抗性，我们需要更好地了解PTI，这不仅是因为它在作物保护中的内在利益和重要作用，而且因为参与PTI的宿主成分是病原体效应物的靶标。我们还需要知道ETI和PTI是否涉及相同的机制。通过研究对鞭毛蛋白的肽替代物flg 22的反应，在拟南芥中研究了PTI。防御激活需要结合flg 22的跨膜受体FLS 2，并且与蛋白激酶激活、活性氧产生、细胞壁强化和基因诱导相关。该提案的主要目的是1）使用正向遗传学来理解PTI，2）使用反向遗传学来理解细胞表面受体在激活植物免疫系统中的作用。遗传分析提供了一个更严格的测试是否相关的现象实际上是所研究的过程中所需要的。在正向遗传学方法中，寻找其中感兴趣的过程失活的突变体;这种突变位于该过程所需的基因中。拟南芥还对另一种称为EF-Tu的细菌PAMP蛋白及其相应的肽替代物elf 18作出反应。Elf 18通过另一种称为EFR的跨膜受体触发与flg 22非常相似的反应。然而，elf 18可以以较低的剂量使用，使得能够进行涉及数十万个诱变种子的拟南芥突变体筛选，其中每个基因都将被“击中”数十次。这使得罕见的新等位基因的基因与微妙的影响，这往往提供了最微妙的和有趣的新见解的生物学机制的恢复。在反向遗传方法中，突变体将用于研究受体蛋白在识别卵菌病原体中的作用，所述卵菌病原体包括芸苔属的霜霉病和白色锈病以及马铃薯和番茄的晚疫病病原体。我们的初步数据表明，这些细胞表面受体蛋白中的一些可能发挥作用。我们预计，这项研究计划将提供深刻的机制洞察受体蛋白如何工作。它还将识别识别后信号所需的蛋白质编码基因。这将是非常有趣的，以检查是否需要这些基因的PTI触发多个激发子或仅elf 18。可以想象，这些突变体将在对真菌和细菌引起的许多病原体的抗病性方面受到损害;这种可能性将受到测试。许多生物化学现象与PTI相关-这些将在各种突变体中进行检查，看看它们是否有差异地使一些但不是所有的elf 18反应失效。最后，将通过标准的基于图位的克隆方法分离elf 18单独或来自多种PAMP的信号传导所需的基因，然后进一步检查。

Plant resistance or susceptibility to disease primarily involves 3 components. Firstly, many microbes make Pathogen-Associated Molecular Patterns (PAMPs), such as bacterial flagellin and fungal chitin, which plants have evolved the capacity to recognize and respond to. This results in PAMP-triggered immunity (PTI). Secondly, many pathogens make and deliver to plant cells, effector proteins that interfere with PTI, lowering defence activation, resulting in susceptibility. Thirdly, plants have a repertoire of resistance (R) genes that encode sensor proteins that recognize specific pathogen effectors, either directly, or indirectly via effector action on a host component. R gene-dependent recognition results in effector-triggered immunity (ETI), restoring resistance. To understand resistance, we need to better understand PTI, not only because of its intrinsic interest and important role in crop protection, but also because host components involved in PTI are targets of pathogen effectors. We also need to know whether ETI and PTI involve the same mechanisms. PTI has been studied in Arabidopsis by investigating responses to flg22, a peptide surrogate of flagellin. Defence activation requires a transmembrane receptor FLS2 that binds flg22, and is correlated with protein kinase activation, reactive oxygen species production, cell wall fortification and gene induction. The main aim of this proposal is 1) to use forward genetics to understand PTI and 2) to use reverse genetics to understand the role of cell surface receptors in activating the immune system of plants. Genetic analysis provides a more stringent test of whether or not a correlated phenomenon is actually required for the process under study. In a forward genetic approach, mutants are sought in which the process of interest is inactivated; such mutations are in genes required for that process. Arabidopsis also responds to another bacterial PAMP protein called EF-Tu, and to its corresponding peptide surrogate elf18. Elf18 triggers, via another transmembrane receptor called EFR, a very similar response to flg22. However, elf18 can be used at lower doses, enabling an Arabidopsis mutant screen that involves 100s of thousands mutagenized seeds, in which every gene will have been 'hit' scores of times. This enables recovery of rare new alleles of genes with subtle effects, which often provide the most subtle and interesting new insights into biological mechanisms. In a reverse genetic approach, mutants will be used to investigate the role of receptor proteins in recognition of oomycete pathogens including downy mildew and white rusts of brasssicas and late blight pathogen of potato and tomato. Our initial data suggests that some of these cell surface receptor proteins may play a role. We anticipate that this research program will provide profound mechanistic insights into how the receptor proteins work. It will also identify genes encoding proteins required for signalling after recognition. It will be very interesting to examine whether these genes are required for PTI triggered by multiple elicitors or just elf18. Conceivably, such mutants will be compromised in disease resistance to many pathogens, caused by fungi as well as bacteria; this possibility will be tested. Many biochemical phenomena are correlated with PTI- these will be examined in the various mutants, to see if they differentially disable some but not all elf18 responses. Finally, genes required for signalling for either elf18 alone, or from multiple PAMPs, will be isolated by standard map-based cloning methods and then further examined.