A resistance and susceptibility gene cluster in barley is targeted by diverse Pyrenophora teres f. teres effectors

植物免疫系统在感染过程的早期识别病原体，激活免疫反应，能够在病原体定居并对其生存构成威胁之前阻止它们。在这第一道防线上幸存下来的病原体会遇到第二道防线，这会导致更高幅度的程序性细胞死亡反应，从而有效地将一些病原体隔离在死亡细胞的病灶中。然而，对于坏死性病原体，即从死亡组织中获取养分的一类植物病原体，这种防御反应被病原体劫持并被利用来进一步疾病扩散，转化为作物歉收。该项目将填补在了解植物如何感知这类重要病原体以及免疫反应如何为植物宿主带来积极结果(抗病)方面的知识空白。因此，该项目将有助于理解植物免疫反应如何有效地阻止坏死性病原体，这一点很重要，因为它们正因其在重要作物上引起疾病的作用而广为人知，并对世界粮食安全问题做出重大贡献。所产生的信息将通过表征和定义调节寄主信号和对不同病原体的免疫的机制来传递对作物生产重要的多种病原体系统。产生的分子遗传和基因组数据以及开发的分子工具将使植物-微生物相互作用科学界广泛受益，并回答有助于在作物中部署遗传抗性的基本问题，有助于更安全的粮食供应。这项研究还将用于从寄主和病原体的角度对高中、本科生、研究生和研究生进行分子遗传学和分子植物病理学的跨学科培训。通过这笔赠款开发的合作外展计划将涉及对年轻的美洲原住民科学家的教育，以便有效地将他们招募到科学领域，有效地扩大STEM领域中最不具代表性的群体的参与。总体假设是，早期的免疫反应在阻止坏死性病原体方面是有效的，但后来引发的免疫反应导致程序性细胞死亡，有效地被尸检专家劫持以完成它们的生命周期，从而导致疾病易感性。检验这一假说的两个特定目标集中在综合评估寄主(大麦)和病原菌(大麦)在时间和空间上不同的免疫和毒力反应。这些目标将解决基本问题：1)一个多样化的受体样蛋白是否被多个坏死性营养效应器靶向，以引发坏死性营养效应器触发的敏感性(NETS)；以及2)一个高效的显性抗性基因是否激活了早期的防御反应，在坏死性营养专家定植和部署其坏死性效应器之前将其阻止？所研究的植物免疫系统的第一个组成部分是一种高度可变的受体样蛋白Spt1，它是位于整个基因组中的多种不同的坏死营养效应因子的靶标，这些效应因子进化到引发疾病。这个受体在一个与特定感病相关的局部区域包含了前所未有的变异性，这表明病原菌种群不断进化以针对这个未知的结构域，宿主在这个结构域经历了高度多样化的选择，以逃避病原菌的毒力。在受体和坏死营养效应器上收集的信息将填补关于坏死营养专家如何瞄准宿主并操纵其免疫系统中的薄弱环节以导致疾病的知识的根本空白。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The plant immune system recognizes pathogens early in the infection process, activating immune responses capable of arresting them before they colonize and establish themselves as a threat to viability. Pathogens that survive this first line of defense are met by a second line of defense that results in a higher amplitude programmed cell death response, which effectively sequesters some pathogens in foci of dead cells. However, in the case of necrotrophic pathogens, the class of plant pathogens that acquire nutrients from dead tissue, this defense response is hijacked and utilized by the pathogen to further disease proliferation, translating to crop failure. The project will fill knowledge gaps in the understanding of how plants perceive this important class of pathogens and how immunity responses result in a positive outcome for the plant host (disease resistance). Thus, the project will contribute to understanding of how plant immunity responses are effective at stopping the necrotrophic pathogens which is important as they are becoming well known for their roles in causing disease on important crops and are significantly contributing to world food security issues. The information generated will transect multiple pathosystems important to crop production through characterizing and defining the mechanism that regulates host signaling and immunity against diverse pathogens. The molecular genetic and genomic data generated and molecular tools developed, will broadly benefit the plant-microbe interactions scientific community as well as answer fundamental questions that will facilitate the deployment of genetic resistance in crops contributing to a more secure food supply. This research will also be used in cross-disciplinary training of high school, undergraduate, graduate, and post-graduate students in molecular genetics and molecular plant pathology from both the host and pathogen perspective. A collaborative outreach program developed through this grant will involve education of young Native American scientists in order to effectively recruit them into the scientific fields effectively broadening the participation of the most under represented group in the STEM fields.The overarching hypothesis is that early immunity responses are effective at stopping the necrotrophic pathogens, yet later elicited immunity responses result in programmed cell death that is effectively hijacked by the necrotophic specialists to complete their lifecycle, contributing to disease susceptibility. The two specific objectives to test this hypothesis focus on a comprehensive evaluation of the temporally and spatially distinct immunity and virulence responses from the host (barley) and pathogen (Pyrenophora teres f. teres), respectively. These aims will address fundamental questions: 1) is a diverse receptor-like protein targeted by multiple necrotrophic effectors to elicit necrotrophic effector triggered susceptibility (NETS); and 2) does a highly effective dominant resistance gene activate early defense responses, arresting the necrotrophic specialist before it colonizes and deploys its necrotrophic effector repertoire? The first component of the plant immune system investigated is a highly variable receptor-like protein, Spt1, which is targeted by multiple diverse necrotrophic effectors located throughout the genomes which evolved to incite disease. This receptor contains unprecedented variability at a localized region that correlates with specific susceptibilities, suggesting that the pathogen populations continually evolved to target this unknown domain and the host has been undergoing a high level of diversifying selection at this domain to evade pathogen virulence. The information gathered on the receptor and necrotrophic effectors will fill fundamental gaps in the knowledge of how necrotrophic specialists target the host and manipulate a weak link in its immune system to cause disease.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.