Histone Modifications and Mediator Complex in Plant Innate Immunity to Necrotrophic Fungi

植物真菌病原菌对作物生产造成巨大影响。尤其是坏死性真菌是农艺作物和园艺作物普遍存在的病原菌。尽管对植物-病原菌的相互作用进行了广泛的研究，但对这些病原菌的抗性关键成分，包括信号识别、信号转导和防御激活机制，还知之甚少。一对拟南芥E3环连接酶，组蛋白单体1/2(HUB1和HUB2)是抵御坏死性真菌的关键成分。Hub1和hub2突变株对番茄灰霉病菌和油菜链格孢菌表现出极强的敏感性。这一观察为剖析染色质修饰和相关调节因子在植物防御中的作用开辟了一条途径。本项目的总体目标是剖析组蛋白修饰在植物免疫中的作用，特别强调对坏死性真菌的修饰。了解病原体侵染过程中染色质修饰的状态以及这种修饰是如何完成的，对于揭示植物如何实现对病原体和多变的环境条件的灵活性是至关重要的。如何对特定的DNA序列进行染色质修饰以响应特定的感染，以及调节它的因素将是重要的，需要确定。这位研究人员试图从拟南芥免疫反应的基因定义的调节点入手，建立组蛋白H2B修饰、转录激活子和共激活子与植物防御反应之间的联系机制。其具体目的是(1)明确HUB1/HUB2在防御中的作用机制；(2)确定HUB1相互作用蛋白的防御和分子功能。这两个具体目标将确定新的遗传成分和调控针对坏死性真菌的免疫反应的调节机制。该项目将为从本科生到博士后水平的学生提供遗传学、分子生物学和生物化学领域的培训。通过研究植物对真菌反应的基本方面，该项目将为产生对世界上一些最广泛和最具破坏性的病原体的遗传抗性铺平道路。这些知识还将有助于理解环境信号是如何整合并传递到植物细胞机械以实现适应性反应的。对重要植物病原体防御机制的详细了解可以形成可持续的、环境友好的作物保护措施，并提高公共安全。

Fungal pathogens of plants cause tremendous impacts on crop production. Particularly, necrotrophic fungi are widespread pathogens of agronomic and horticultural crops. Despite extensive studies on plant-pathogen interactions, critical components of resistance against these groups of pathogens, including mechanisms of signal recognition, transduction and activation of defenses are poorly understood. A pair of Arabidopsis RING E3 ligases, HISTONE MONOUBIQUITINATION 1/2 (HUB1 and HUB2) are key components of defense against necrotrophic fungi. The hub1 and hub2 mutants show extreme susceptibility to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola. This observation has opened an avenue for dissecting the role of chromatin modification and associated regulators in plant defense. The overall goal of this project is to dissect the role of histone modification in plant immunity with a particular emphasis on necrotrophic fungi. Knowledge of the state of chromatin modifications during pathogen infection and how this modification is accomplished is central to unraveling how plants achieve flexibility in responding to pathogens and changeable environmental conditions. How chromatin modifications are conferred on specific DNA sequences in response to particular infection and the factors that regulate it will be important to determine. The investigator seeks to establish the mechanisms that link histone H2B modification, transcriptional activators and co-activators to plant defense responses by starting from a genetically defined regulatory point of Arabidopsis immune response. The specific aims are to (1) Define the mechanisms of HUB1/HUB2 function in defense and (2) Characterize the defense and molecular functions of HUB1 interacting proteins. These two specific aims will define novel genetic components and regulatory mechanisms that govern immune responses against necrotrophic fungi.This project will provide training for students from undergraduate to post-doctoral levels in the areas of genetics, molecular biology and biochemistry. By investigating fundamental aspects of plant responses to fungi, this project will pave the way for generating genetic resistance against some of the world's most widespread and devastating pathogens. Such knowledge will also help understand how environmental signal are integrated and transmitted to the plant cellular machinery to achieve adaptive responses. A detailed knowledge of defense mechanisms against important plant pathogens can shape crop protection measures that are sustainable, environmentally friendly as well as enhancing public safety.