Collaborative Research: RESEARCH-PGR: Genome-wide quest for non-host resistance mechanisms in plants

在全球范围内，约15%的作物损失是由各种侵袭性病原体，特别是真菌造成的，这突出了作物保护免受病原体侵害的重要性。在自然界中，大多数植物对大多数潜在病原体具有抗性是由于一种现象，即非宿主抗性（NHR）。NHR的一个主要例子是水稻对锈病和白粉病的免疫，这些疾病对包括小麦和大麦在内的许多其他谷类作物造成严重损害。因此，NHR为所有核电站提供了一个主要的安全屏障。不幸的是，由于其遗传复杂性，NHR的分子基础在大多数情况下仍然难以捉摸，这严重限制了利用NHR潜在的免疫机制来提高作物对侵袭性病原体的抗性。这个多机构合作研究项目旨在利用创新和组合的正向和反向遗传学方法，剖析NHR在两种模式植物中对抗潜在真菌病原体的遗传和分子机制。NHR所需的植物免疫基因的鉴定和功能表征不仅将揭示NHR的分子基础（这是关于植物与微生物相互作用的十大悬而未决的问题之一），而且还将激发新的策略来设计作物对各种病原体的更广泛和更强大的抗性。该项目还将为科学界研究植物免疫机制提供宝贵的研究材料和工具。最后，这个项目将把研究与教育和外展活动结合起来。例如，项目团队将每年举办一次“CRISPR技术与应用”夏季研讨会，以加强代表性不足的少数民族本科生对植物科学的参与。非宿主抗性（NHR）是指一个植物物种的大多数测试基因型对一个病原体物种的大多数测试变异具有免疫力，这些变异可以引起其他植物物种的疾病。与宿主对适应性病原体的耐药性不同，NHR的遗传基础在很大程度上仍然未知。宿主对适应性病原体的耐药性在分子水平上得到了很好的表征。该项目的长期目标是阐明NHR的分子机制，以提高作物对侵袭性病原体的抗性。据推测，在大多数情况下，NHR是多层的，遗传上难以通过传统的手段，但通过逐步向前的遗传学和/或crispr激活的反向遗传学方法解剖。这个合作项目有四个具体目标。目的1是利用逐步向前的遗传筛选方法，确定有助于拟南芥（作为模型dicot）对抗非适应性白粉病和锈病真菌的NHR的新基因。目标2是利用多达50种不同的水稻免疫基因的多重CRISPR诱变，然后进行交叉感染筛选，鉴定水稻（作为单子叶模型）中NHR对抗白粉病和锈病真菌以及其他病原体所必需的基因。目的3是通过各种分子方法，包括比较转录组学、蛋白质组学和代谢组学，阐明控制NHR的新的免疫机制。目标4是促进社区研究和促进下一代植物科学家的教育，重点是培训代表性不足的少数民族学生。拟议研究的新知识可能有助于建立与已建立的PAMP（病原体相关分子模式）触发免疫和/或效应触发免疫相关的NHR机制框架。该奖项反映了美国国家科学基金会的法定使命，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。

Globally, ~15% of crop losses are caused by various aggressive pathogens especially fungi, highlighting the importance of crop protection against pathogens. In nature, most plants are resistant to most potential pathogens because of a phenomenon, namely nonhost resistance (NHR). A prime example of NHR is rice’s immunity to rust and powdery mildew diseases that cause serious damages to many other cereal crops including wheat and barley. Hence, NHR provides a major safety barrier for all plants. Unfortunately, due to its genetic complexity, the molecular basis of NHR in most cases remains elusive, which severely limits the exploitation of the immunity mechanisms underlying NHR for improving crop resistance against aggressive pathogens. This multi-institutional collaborative research project aims to dissect genetic and molecular mechanisms of NHR against potential fungal pathogens in two model plants using innovative and combinatorial forward and reverse genetics approaches. Identification and functional characterization of plant immunity genes required for NHR will not only reveal the molecular basis of NHR (which is among the top 10 unanswered questions concerning plant-microbe interactions) but also inspire novel strategies to engineer broader and more robust resistance in crop plants against various pathogens. This project will also generate valuable research materials and tools for the scientific community to study plant immunity mechanisms. Finally, this project will integrate research with education and outreach activities. For example, a “CRISPR Technology and Application” summer workshop in each year will be run by the project team to enhance participation of under-represented minority undergraduate students in plant science.Nonhost resistance (NHR) refers to immunity of most tested genotypes of a plant species to most tested variants of a pathogen species that can cause diseases on other plant species. Unlike host resistance, which is mounted against adapted pathogens and has been well characterized at the molecular level, the genetic basis of NHR remains largely unknown. The long-term goal of this project is to elucidate the molecular mechanisms of NHR for improving crop resistance against aggressive pathogens. It is hypothesized that NHR in most cases is multi-layered and genetically intractable by conventional means but dissectible by stepwise forward genetics and/or CRISPR-enabled reverse genetics approaches. There are four specific objectives for this collaborative project. Aim 1 is to identify novel genes contributing to NHR in Arabidopsis (as a model dicot) against non-adapted powdery mildew and rust fungi using stepwise forward genetic screens. Aim 2 is to identify genes essential for NHR against powdery mildew and rust fungi, and other pathogens in rice (as a model monocot) using multiplexed CRISPR mutagenesis of up to 50 various rice immunity genes followed by geared infection screens. Aim 3 is to elucidate novel immune mechanisms controlling NHR via various molecular methods including comparative transcriptomics, proteomics and metabolomics. Aim 4 is to facilitate community research and promote education of next-generation plant scientists with a focus on training underrepresented minority students. New knowledge from the proposed research may help establish mechanistic frameworks for NHR in connection with the well-established PAMP (pathogen-associated molecular pattern)-triggered immunity and/or effector-triggered immunity.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.