玉米9-oxylipins途径介导禾谷镰孢菌茎腐病抗性的机制及调控网络解析

Fusarium graminearum is one of the most devasting fungal pathogens of cereal crops, such as wheat and corn, which can cause fusarium ear rot and Gibberella stalk rot, resulting in significant yield loss in maize production . However, it remains largely unknown about the molecular mechanisms underlying the resistance of maize to F. graminearum. Exploring the resistance mechanisms and the regulation of signal transduction network will be very helpful to identify the resistance genes and to efficiently control the stalk rot caused by F. graminearum in maize. We have previously reported that F. verticilliodes could hijack maize 9-Lipoxynase ZmLOX3 and its catalyzed lipid metabolites 9-oxylipins to facilitate its pathogenicity, implying that 9-LOXs and 9-oxylipin pathways may play important roles in modulating the maize resistance to F. graminearum. To understand whether specific 9-LOXs and 9-oxylipins contribute differentially to either the resistance or susceptibility of maize, and to explore the signal transduction pathways mediated by 9-LOXs and 9-oxylipins, we propose to carry out the screening and identification of maize transposon-insertional mutants to obtain near isogenic lines either resistant or susceptible to F. graminearum, in different genetic background. These mutants along with wild type lines will be used to investigate the disease phenotypes, while the spatial and temporal changes of endogenous phytohormones and oxylipin contents will be measured in the mutants vs wild types upon infection with F. graminearum. High through-put sequencing and qRT-PCR will be employed to investigate the genes possibly involved in the resistance to F. graminearum stalk rot. The findings obtained from this proposal will not only help us to understand the function of 9-oxylipin pathways in maize resistance to F. graminearum stalk rot, but also provide insights into the regulation of signaling network, eventually be helpful to maize breeding for disease resistance.

禾谷镰孢菌是小麦、玉米等禾谷类作物重要的真菌病害，引起的穗腐和茎腐病会导致玉米严重减产，但有关玉米抵抗禾谷镰孢菌的分子机制尚不清楚。研究玉米禾谷镰孢菌茎腐病的抗性机制和信号调控网络对筛选和鉴定抗性基因资源、有效控制玉米茎腐病具重要意义。项目前期研究发现，轮枝镰孢菌可"劫持"玉米9-脂氧合酶基因ZmLOX3和9-oxylipins以提高致病性，提示9-oxylipin途径可能参与调控禾谷镰孢菌抗性或致病性。项目将筛选抗、感不同的9-LOX近等基因系突变体，考查9-LOX基因突变对禾谷镰孢菌抗性的影响，研究病原菌侵染后突变体和野生型中内源激素以及9-oxylipins的时空变化，利用高通量测序结合功能验证的方法鉴定抗性途径相关的新型功能基因。研究将不仅能明确9-oxylipin途径在抵抗禾谷镰孢菌茎腐病中的功能，且有助于阐明有关信号网络的调控机制，从而为玉米抗病分子育种提供理论依据。

禾谷镰孢菌是引起玉米茎腐病和穗粒腐病的重要病害之一，但有关玉米抵抗禾谷镰孢菌的分子机制尚不清楚。我们的前期研究提示轮枝镰孢菌可“劫持”玉米9-LOX基因ZmLOX3 和9-oxylipins用 以提高致病性，提示9-oxylipin 途径可能参与调控禾谷镰孢菌抗性或致病性。项目通过筛选和鉴定抗、感差异明显的自交系和9-LOX 近等基因系突变体材料，通过多种方法考查了9-LOX 基因突变对禾谷镰孢菌抗性的影响，研究了接种禾谷镰孢菌后突变体和野生型中内源激素以及茉莉酸类oxylipins 的时空变化，并利用2对抗感差异明显的材料（包括1对自交系和1对lox5-3突变体和野生型B73）进行了RNA-seq高通量测序，解析了禾谷镰孢菌茎腐病抗性差异的分子和遗传基础，解析了玉米中JA信号模块在禾谷镰孢菌抗性中的作用和可能机制，明确了茉莉酸信号途径在9-LOX 基因突变后导致的茎腐病抗性增强中发挥重要作用。因此，项目明确了9-oxylipin 途径在抵抗禾谷镰孢菌茎腐病中的功能，阐明了9-LOX途径通过反馈调节JA信号途径来控制禾谷镰孢菌茎腐病抗性的信号网络，为玉米茎腐病抗性分子育种提供理论参考。