Modulation of the Effector-Triggered Immunity response by ERAD-Mediated Degradation of Activated NLRs (EMDAN)

植物抗病反应可以通过核苷酸结合富含亮氨酸的重复蛋白（称为抗性蛋白）和特异性病原体衍生的蛋白（称为效应子）的相互作用来触发。这种相互作用导致强烈的防御反应，称为效应子触发免疫（ETI），通常导致病原体感染部位的快速局部细胞死亡反应。这种反应必须受到严格的调控，以使其产生抗性，但不能过度，从而不必要地抑制植物生长。我们的初步证据表明，玉米中常见的蛋白质降解途径的一个组成部分，ZmCER 9，控制核苷酸结合富含亮氨酸的重复蛋白的降解，在它们被激活后。ZmCER 9蛋白质序列与参与称为内质网相关降解（ERAD）的过程的其他蛋白质相似，该过程降解不正确折叠的蛋白质。虽然ERAD已在酵母中表征，但在植物中知之甚少。因此，ZmCER 9的相互作用和随后的核苷酸结合富含亮氨酸的重复蛋白的降解似乎是先前未描述的机制，其介导激活后效应子触发的免疫防御应答的失活。 我们将使用一系列技术来深入了解CER 9同源物和核苷酸结合富含亮氨酸重复序列蛋白的相互作用如何控制植物中至关重要的防御反应，并确定植物中参与这一过程的其他蛋白质。这项研究将有助于更好地了解植物如何在生物胁迫下生存和茁壮成长。该项目还将为来自东北部低收入农村县的未得到充分服务的初中和高中学生提供培训机会和STEM富集，帮助培养下一代植物科学家。核苷酸结合富含亮氨酸重复序列（NLR）类型的植物抗病（R-）蛋白被激活并诱导强烈的防御反应，称为效应触发免疫或ETI，识别特异性病原体衍生的效应蛋白。ETI的有效性取决于当同源病原体不存在时的不活动，当病原体被识别时的快速诱导以及诱导后的快速抑制。泛素-蛋白酶体途径是所有真核生物中发现的主要蛋白质修饰和降解途径，由E1（泛素激活）、E2（泛素缀合）和E3（泛素连接酶）酶的顺序作用介导。 我们的初步数据表明，玉米E3-连接酶ZmCER 9介导Rp 1-D NLR R-蛋白和几种其他NLR R-蛋白的降解，特别是在活化后。基于同源性，ZmCER 9可能是内质网相关降解（ERAD）的组分，ERAD是降解不正确折叠的蛋白质的基本真核质量控制系统。ERAD在植物中的特征很差，并且没有报道CER 9复合物的底物，这意味着Rp 1-D可能是其第一个已知的底物。我们假设ERAD介导的活化NLR降解（EMDAN）是ETI在植物中失活的一般机制。我们将使用一系列分子和细胞生物学技术来确定EMDAN和相关途径在控制植物ETI中的重要性，并描述CER 9在ERAD中的作用。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。

A plant disease resistance response can be triggered by the interaction of nucleotide binding leucine-rich repeat proteins (known as resistance proteins) and specific pathogen-derived proteins known as effectors. This interaction leads to a strong defense response known as effector-triggered immunity (ETI), often resulting in a rapid localized cell death response at the site of pathogen infection. This response must be tightly regulated so it confers resistance, but not excessive so that it inhibits plant growth unnecessarily. Our preliminary evidence suggests that a component of a common protein degradation pathway in maize, ZmCER9, controls degradation of the nucleotide binding leucine-rich repeat proteins, after they are activated. ZmCER9 protein sequence is similar to other proteins involved in a process called endoplasmic reticulum associated degradation (ERAD), which degrades incorrectly-folded proteins. Although ERAD has been characterized in yeast, it is poorly understood in plants. Thus, the interaction of ZmCER9 and subsequent degradation of nucleotide binding leucine-rich repeat proteins appears to be a previously undescribed mechanism that mediates the deactivation of the effector-triggered immunity defense response after activation. We will use a range of techniques to gain insight into how the interaction of CER9 homologs and nucleotide binding leucine-rich repeat proteins control a crucial defense response in plants and identify other proteins involved in this process in plants. This study will contribute to a greater understanding of how plants survive and thrive in the face of biotic stress. This project will also provide training opportunities and STEM enrichment to underserved middle and high school students from low income, rural counties in northeastern, helping to generate the next generation of plant scientists.Plant disease resistance (R-) proteins of the nucleotide binding leucine-rich repeat (NLR) type are activated and induce a strong defense response known as effector-triggered immunity or ETI, upon recognition of specific pathogen-derived effector proteins. ETI’s effectiveness depends on inactivity when the cognate pathogen is absent, rapid induction when a pathogen is recognized and a rapid suppression after induction. The ubiquitin-proteasome pathway, mediated by the sequential actions of E1 (ubiquitin-activating), E2 (ubiquitin-conjugating) and E3 (ubiquitin ligase) enzymes is a major protein modification and degradation pathway found in all eukaryotes. Our preliminary data indicate that maize E3-ligase ZmCER9 mediates degradation of the Rp1-D NLR R-protein, and several other NLR R-proteins, specifically after activation. Based on homology, ZmCER9 is likely a component of the endoplasmic reticulum associated degradation (ERAD), a fundamental eukaryotic quality-control system that degrades incorrectly-folded proteins. ERAD in plants has been poorly characterized and there are no reported substrates of the CER9 complex, meaning that Rp1-D may represent its first known substrate. We hypothesize that ERAD-Mediated Degradation of Activated NLRs (EMDAN) is a general mechanism for the deactivation of ETI in plants. We will use a range of molecular and cell biology techniques to determine the importance of EMDAN and related pathways in controlling ETI in plants and to characterize the role of CER9 in ERAD.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.