Signaling mechanisms in plant innate immunity

描述（由申请人提供）：先天免疫是植物、动物和人类中最古老、进化上最保守的中枢防御系统，用于区分宿主与非自身微生物病原体。它提供了对传染病的诱导防御的第一道防线，是防止不断和无处不在的微生物入侵的基础。先天免疫的一个关键功能是通过模式识别受体检测微生物相关分子模式（MAMPs，如细菌鞭毛蛋白），并启动适当的防御反应。最近的发现表明，在植物、动物和人类中，富含亮氨酸重复序列的受体对多种mapps的识别和多种MAPK级联反应的激活具有显著的趋同进化。尽管在植物、蠕虫、苍蝇、哺乳动物和人类中，MAPK级联在介导MAMP信号传导中具有普遍和必要的作用，但由于功能冗余、突变致病性和不同信号通路中共享成分的复杂性，交织在一起的信号网络的分子机制仍然难以捉摸。本研究项目旨在以拟南芥为模型系统，建立MAMP信号趋同的调控框架。本实验旨在整合分子、生化、细胞、遗传学和基因组学方法，剖析多功能BAK1-MAPKKK复合物和MAPKK-MAPK级联，并分析下游WRKY转录因子在植物防御反应中控制多种靶基因的作用。具体而言，该项目将重点研究15个拟南芥基因在鞭毛蛋白信号传导中的功能，并利用基于细胞的检测、转基因植物和具有鞭毛蛋白受体FLS2、受体信号伙伴BAK1、MAPKKK-MAPKK-MAPK级联和WRKY转录因子特异性缺陷的功能缺失突变体。通过蛋白质相互作用、磷酸化和泛素化分析、定量RT- PCR、全基因组微阵列和染色质免疫沉淀等方法，阐明植物先天免疫的关键和保守的信号机制。三个具体目标是：分析BAK1-MAPKKK信号复合物Aim 2的相互作用和调控。解析MAPKK-MAPK级联在收敛MAMP信号中的作用。明确WRKY转录因子的功能和调控。公共卫生相关性：强大的先天免疫系统是预防持续和无所不在的微生物入侵的基础，并为植物、动物和人类提供了第一道诱导防御传染病的防线。先天免疫的一个关键功能是检测微生物相关分子模式（MAMPs）并启动适当的防御反应。最近的发现揭示了丰富亮氨酸重复模式识别受体在MAMP感知中的显著趋同进化和多个MAPK级联的激活。从受体激酶信号复合物到相互交织的MAPK级联和WRKY转录控制的研究将发现先天免疫信号传导的新颖和基本的分子机制，并为未来改善农业、环境和可再生能源生产以及治疗感染性、炎症性和自身免疫性疾病的人类健康提供创新工具。

DESCRIPTION (provided by applicant): Innate Immunity is the most ancient and evolutionarily conserved central defense system that distinguishes host-self from non-self microbial pathogens in plants, animals and humans. It provides the first line of inducible defense against infectious diseases and underlies the prevention of constant and omnipresent microbial invasion. A key function of innate immunity is the detection of microbe-associated molecular patterns (MAMPs, such bacterial flagellin) by pattern recognition receptors and the launch of appropriate defense responses. Recent discoveries have revealed remarkable convergent evolution in the recognition of diverse MAMPs by leucine-rich-repeat receptors and the activation of multiple MAPK cascades in plants, animals and humans. Despite the universal and essential involvement of MAPK cascades in mediating MAMP signaling in plants, worms, flies, mammals and humans, the molecular mechanisms underlying the intertwined signaling webs remain mostly elusive due to the complexity of functional redundancy, mutant lethality and shared components in distinct signaling pathways. The goal of this research project is to establish a regulatory framework for the convergent MAMP signaling using Arabidopsis thaliana as a model system. The proposed experiments aim to integrate molecular, biochemical, cellular, genetic, and genomic approaches to dissect the multifunctional BAK1-MAPKKK complexes and MAPKK-MAPK cascades, and to analyze the downstream WRKY transcription factors in controlling diverse target genes in plant defense responses. Specifically, the project will focus on characterizing and integrating the functions of 15 Arabidopsis genes in flagellin signaling using cell- based assays, transgenic plants and loss-of-function mutants with specific defects in the flagellin receptor FLS2, receptor signaling partner BAK1, MAPKKK-MAPKK-MAPK cascades and WRKY transcription factors. Protein interaction, phosphorylation and ubiquitination assays, quantitative RT- PCR, whole-genome microarray and chromatin-immunoprecipitation will be carried out to elucidate the key and conserved signaling mechanisms in plant innate immunity. Three Specific Aims are: Aim 1. Analyze interactions and regulations of BAK1-MAPKKK signaling complexes Aim 2. Dissect the MAPKK-MAPK cascade functions in convergent MAMP signaling Aim 3. Define functions and regulations of WRKY transcription factors. PUBLIC HEALTH RELEVANCE: The powerful innate immune system underlies the prevention of constant and omnipresent microbial invasion, and provides the first line of inducible defense against infectious diseases in plants, animals and humans. A key function of innate immunity is the detection of microbe- associated molecular patterns (MAMPs) and the launch of appropriate defense responses. Recent discoveries have revealed remarkable convergent evolution in MAMP perception by leucine-rich- repeat pattern recognition receptors and the activation of multiple MAPK cascades. The proposed research from receptor kinase signaling complexes to intertwined MAPK cascades and WRKY transcriptional controls will discover novel and fundamental molecular mechanisms in innate immune signaling, and provide innovative tools for future improvement of agriculture, environment and renewable energy production, as well as human health in treating infectious, inflammatory and autoimmune diseases.