水稻广谱抗病负调控因子OsBONs的免疫信号研究

Rice blast and rice sheath blight, the most devastating rice diseases are leading to significant yield losses and threatening food security. One of the most efficient strategies is to discover new resistance sources, breeding of broad-spectrum and durable disease resistant varieties to prevent and control diseases. We previously have shown that OsBON1 and OsBON3 function as suppressors of broad-spectrum disease resistance, and knockout of OsBONs enhanced resistance to rice bacterial and fungal pathogens with either hemibiotrophic or necrotrophic life styles. OsBONs regulated the tradeoff between immunity and growth in rice as well. Through genetic screening, molecular and biochemistry assays, we isolated a novel protein OsBIP1 (OsBON-Interacting Protein 1) that acts as a negative regulator of rice innate immunity. This proposal will further explore the mechanism and signaling pathways in rice broad-spectrum disease resistance mediated by OsBONs-OsBIP1 module. This project aims to establish an innovation research system which fine-tune immune activation and growth fitness in rice based on OsBONs, and to provide a new research concept for broad-spectrum disease resistance. This project will also shed new lights on the balance between immunity and agronomic traits in rice, and provide concrete foundation and novel genetic sources for broad-spectrum disease resistance breeding.

稻瘟病、纹枯病等水稻毁灭性病害严重影响水稻产量和品质。发掘新的水稻抗源，选育广谱和持久抗病品种是预防和控制水稻病害的有效策略之一。申请人在前期研究中发现，OsBON1和OsBON3是水稻广谱抗病负调控蛋白，OsBONs基因敲除植株对半活体营养型和坏死营养型病原菌都具有抗性。同时OsBONs也是调控水稻免疫与生长发育平衡的重要节点。本项目在已有研究基础上，通过遗传筛选、分子和生化分析鉴定出一个新的免疫负调控蛋白OsBIP1与OsBONs互作。本项目将进一步探究OsBONs-OsBIP1模块在水稻广谱抗病中发挥功能的机制和信号通路。初步建立一个以OsBONs为关键节点的水稻广谱抗病与产量性状协调的创新研究体系，为水稻广谱抗病提供新的研究思路。本项目也希望通过对广谱抗病和生长发育平衡新机制的深入研究，为今后的遗传育种和生产转化提供扎实的理论依据和材料基础。

植物在感知病原菌时会激活免疫反应，但当免疫反应组成型激活时，往往会影响植物的生长和产量。本项目发现了禾本科植物中一个保守的免疫抑制网络，协调了免疫平衡。这一网络以OsBONs的一个互作蛋白，钙感应子RESISTANCE OF RICE TO DISEASES1 (ROD1) 为核心。ROD1通过激活过氧化氢酶的活性来促进活性氧（ROS）的清除，泛素化则调节了其蛋白的稳定性。ROD1功能丧失后会对多种病原菌产生抗性。通过对大约3000份水稻种质资源的分析，在籼稻中普遍存在具有农业生态学特异分布的天然ROD1等位基因，能增强抗性而不影响产量。稻瘟病菌效应蛋白AvrPiz-t在结构上模拟ROD1，并激活相同的ROS清除途径以抑制宿主免疫力并促进毒力。本研究揭示了一个由宿主和病原菌共同采用的分子框架，该框架整合了钙感应和ROS平衡以抑制植物免疫。.本项目获得的重要结果和关键数据如下：.1. 水稻ROD1通过促进过氧化氢酶活性清除活性氧抑制免疫反应；.2. ROD1是一个钙感应子，并通过泛素化介导的蛋白质降解精细调控其含量；.3. ROD1的自然变异对籼稻和粳稻的免疫产生影响；.4. 稻瘟病菌的效应蛋白AvrPiz-t利用ROD1的免疫抑制途径促进其毒力。.本项目的研究不仅拓宽了人们对于作物抗病性基础理论的认知，也为设计新的抗病基因、开发新的高产抗病作物品种提供了新的研发思路。