一个新的GATA转录因子调控小麦纹枯病抗性的分子机制

Sharp eyespot, caused by the soil-borne fungus Rhizoctonia cerealis, has escalated into a major threat to wheat production. Characterization of pivotal genes regulating wheat defense responses will accelerate the progress of wheat resistance breeding. Based on transcriptome analysis, a novel GATA transcriptional factor-coding gene, named TaGATA1, was isolated from resistant wheat line CI12633. Both of VIGS assay and overexpression in wheat indicated that TaGATA1 plays key role in regulating wheat resistance to sharp eyespot. However, mechanism by which TaGATA1 modulates defense responsesin wheat was unknown. The main aim of this proposal is to elucidate the functional role and molecular mechanism of TaGATA1 in wheat defense responses. We will use genetics, molecular biology, biochemical and bioinformatics to 1) mine the novel allele and develop and validate the functional molecular markers of TaGATA1 in various wheat cultivars/lines and RIL population, 2) identify the down-stream targeting genes via ChIP-seq and transactive analysis, 3) isolate and identify TaGATA1 co-regulator protein in vivo through CoIP assay, and to characterize the key residues and domains in TaGATA1. Therefore, this potential project will elucidate a novel defense signaling pathway to sharp eyespot in wheat, which benefit for the dissecting of gene network in wheat defense to sharp eyespot and for proving wheat resistance breeding.

小麦纹枯病是危害小麦生产的重要土传病害，难以防治。分离、鉴定抗性重要基因、理解其作用机制，能极大促进小麦抗病育种进程。在前期研究中，我们通过转录组学分析，从抗性小麦中分离、鉴定得到一个新型GATA转录因子基因TaGATA1。基因沉默和转基因过表达实验显示，TaGATA1是调控小麦纹枯病抗性反应的重要基因。本研究旨在解析TaGATA1调控小麦防御反应的分子机制，同时分析其对抗性反应的遗传贡献率。本申请拟在前期研究的基础上，采用多学科研究方法，鉴定TaGATA1直接调控的下游靶标基因，分离抗性反应中的调控互作蛋白，明确调控抗病反应的信号通路，解析调控下游反应的作用机制。同时，利用不同抗、感小麦材料和遗传群体，挖掘优异等位变异，分析对抗性反应的遗传贡献率。这些工作将进一步揭示小麦对纹枯病抗性反应的网络机制，为小麦抗纹枯病育种提供基因资源和理论依据。

小麦是重要的粮食作物。由禾谷丝核菌侵染引起的小麦纹枯病是一种重要的土传病害，主要在茎基部发病，严重危害小麦生产。通过该项目的实施，利用比较转录组分析，从小麦中鉴定了一个含有LLM结构域的GATA类转录因子基因TaGATA1。研究表明TaGATA1在小麦纹枯病抗性中发挥重要作用。纹枯病侵染可以诱导该基因上调表达，且在抗性小麦CI12633中有更高幅度的诱导。TaGATA1定位于3B染色体，在3A和3D染色体上有两个同源基因。亚细胞定位显示TaGATA1位于小麦原生质体的细胞核内。体外实验表明编码的蛋白可以结合GATA元件。同时，在酵母细胞中表现转录激活功能。这些实验结果表明，TaGATA1编码一个有活性的转录因子。TaGATA1转基因过表达小麦提高了对纹枯病的抗性，而通过病毒诱导的基因沉默实验表明TaGATA1的抑制表达可以显著削弱小麦的抗性。染色质免疫共沉淀结合定量PCR实验发现，TaGATA1直接结合防御基因的启动子，并激活其转录表达，进而提高纹枯病的抗性反应。不同于以前模式植物GATA类蛋白在生长和发育中的功能，本研究鉴定了GATA蛋白在植物抗病反应中的功能，并阐明了其发挥作用的分子机制，为小麦纹枯病抗性改良提供理论指导和基因资源。