玉米多抗基因ZmCCoAOMT2的分子机理研究

Multiple disease resistance (MDR) has been defined as host plant resistance to two or more diseases. Selection and deployment of crops with MDR encoded at a single locus is a major breeding objective. ZmCCoAOMT2 is the first cloned MDR gene associated with quantitative disease resistance to southern leaf blight and gray leaf spot in maize. Previous study suggested that resistance might be caused by allelic variation of ZmCCoAOMT2 expression causing differences in levels of metabolites of the phenylpropanoid pathway. The most significant variant associated with resistance was located in the 3’-UTR region of ZmCCoAOMT2. However, molecular mechanisms underlying ZmCCoAOMT2 remain not clear. Here, using degradome sequencing and bioinformatic analysis, miRNA targets in the 3’-UTR region as well as genome-wide disease resistance responsive miRNA targets will be identified and further verified. On the other hand, transcriptome profiling will be investigated after pathogen infection in both resistant and susceptible lines. Combined with metabolites data, best candidates will be picked up for functional study. Dissection of functional loci and molecular mechanism underlying ZmCCoAOMT2 will provide theoretical guidance and functional marker for breeding for durable and multiple disease resistance variety in maize.

多抗是指寄主植物可同时抗两种或两种以上的病害，培育多抗品种是作物育种的一个重要目标。ZmCCoAOMT2是在玉米中克隆的第一个同时抗小斑病和灰斑病的数量抗性基因，前期的研究表明，抗、感材料中基因的诱导表达水平变异导致苯丙素代谢途径发生改变，从而引起抗病性差异，位于基因的3’-UTR的变异与抗病性的相关性最高，但其参与该基因的表达调控机理还未阐明。本研究在此基础上，将对该基因3’-UTR的功能展开深入研究，拟通过降解组测序、结合生物信息学分析，筛选出与该基因3’-UTR区靶位点作用的候选miRNA以及抗病反应相关的其他miRNA和靶位点，并进行验证。同时，通过转录组分析、结合之前的脂氧合酶途径和苯丙氨酸代谢途径产物分析，寻找参与抗病反应的关键候选基因，开展后续的功能研究。本研究对基因功能位点的精确解析和分子机理研究，将为培育持久、多抗的玉米材料提供丰富的理论基础和可靠的功能标记。

多抗是指寄主植物可同时抗两种或两种以上的病害，培育多抗品种是作物育种的一个重要目标。ZmCCoAOMT2是在玉米中克隆的第一个同时抗小斑病和灰斑病的数量抗性基因。本研究在此基础上，明确了位于ZmCCoAOMT2启动子区的转座子插入缺失变异是影响抗病性的主要原因，开发了基因的功能分子标记。通过转录组、小RNA和代谢组分析，筛选到一批参与抗病反应的关键候选基因及候选小RNA，利用候选基因的突变体，初步验证了三个基因可能参与玉米多抗反应。针对ChSK1基因开展深入研究，玉米突变体、CRISPR/Cas9基因编辑材料分析表明，ChSK1突变或敲除可以显著增强玉米对小斑病的抗性。活性氧检测及转录组分析发现，ChSK1可能通过抑制基础免疫反应增加植物感病性，该基因为培育玉米小斑病持久抗病性品种提供了新的思路和靶点基因。本研究挖掘到的抗病相关候选基因，为解析玉米和病原菌的互作机理奠定了基础，为深入探究玉米多抗数量性状的形成提供了支撑，也为玉米的抗病分子育种提供了理论依据和基因资源。