Signaling mechanisms in plant innate immunity

描述(申请人提供)：先天免疫是最古老和进化上保守的中央防御系统，区分植物、动物和人类中的宿主自身和非自身微生物病原体。它提供了对传染病的第一道诱导防御，并奠定了防止持续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。最近的发现揭示了在植物、动物和人类中，富含亮氨酸的重复受体识别不同的MAMP和激活多个MAPK级联的显著收敛进化。尽管MAPK级联在植物、蠕虫、苍蝇、哺乳动物和人类中广泛而重要地参与了MAMP信号转导，但由于不同信号通路中复杂的功能冗余、突变致命性和共享成分，这些相互交织的信号网络背后的分子机制仍然很难理解。本研究的目的是以拟南芥为模型系统，建立MAMP融合信号的调控框架。这些实验旨在结合分子、生化、细胞、遗传和基因组学方法，剖析多功能的BAK1-MAPKKK复合体和MAPKK-MAPK级联，并分析WRKY下游转录因子在植物防御反应中控制不同靶基因的作用。具体地说，该项目将专注于利用基于细胞的分析、转基因植物和在鞭毛蛋白受体FLS2、受体信号伙伴BAK1、MAPKKK-MAPKK-MAPK级联和WRKY转录因子中存在特定缺陷的功能丧失突变体来表征和整合15个拟南芥基因在鞭毛蛋白信号转导中的功能。将通过蛋白质相互作用、磷酸化和泛素化分析、定量RT-PCR、全基因组芯片和染色质免疫沉淀来阐明植物天然免疫中的关键和保守的信号机制。目的：1.分析BAK1-MAPKKK信号复合体的相互作用和调控；2.剖析MAPKK-MAPK级联功能在收敛的MAMP信号中的作用；3.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为防止持续和无处不在的微生物入侵奠定了基础，并提供了抵御植物、动物和人类感染疾病的第一道防线。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。最近的发现揭示了富含亮氨酸的重复模式识别受体在MAMP感知上的显着收敛进化和多个MAPK级联的激活。从受体激酶信号复合体到相互交织的MAPK级联和WRKY转录调控的研究将发现天然免疫信号中新的和基本的分子机制，并为未来改善农业、环境和可再生能源生产，以及在治疗传染病、炎症性疾病和自身免疫性疾病方面改善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.