菊花系统获得抗性调节基因CmTGA1和CmTGA5提高抗病性的分子机理

Chrysanthemum × morifolium occupies an important economic position in the international flower trade. At present, a variety of diseases are the major biological stress factors in limiting its large-scale commercial production. To implore genetic resources with broad-spectrum resistance, and breed new disease-resistant germplasm of chrysanthemum are very important significance to the genetic improvement of chrysanthemum quality. TGA transcription factor, a group of basic leucine zipper, is related with biotic stress resistance of plant, and plays an important regulatory role in salicylic acid (SA)-mediated plant system acquired resistance (SAR) signal transduction pathway and makes plant get a broad spectrum resistance to pathogens. Our preliminary works showed that: the two genes of chrysanthemum, CmTGA1 and CmTGA5 are involved in SA-mediated chrysanthemum SAR and enhance chrysanthemum resistance to black spot and chrysanthemum viru B. On this basis, in this study, we intend to further analyze the spatial and temporal expression characteristics of the two genes and biochemical characteristics of their proteins; study the function of the two genes in disease resistance using overexpression and silence of single gene and double genes; research regulation of CmTGAs to their downstream genes in transcriptional level by high-throughput RNA-seq technology. Through the study, it is expected to clarify the molecular mechanism of CmTGAs in increase broad-spectrum disease resistance of chrysanthemum in theory, and to provide gene pool and theoretical basis for breeding new broad-spectrum resistance germplasm of chrysanthemum.

菊花在国际花卉贸易中占有重要的经济地位。目前，病害是限制菊花大规模商业生产的主要生物胁迫因子。发掘具有广谱抗性的基因资源，培育菊花抗病新种质，对菊花品质的遗传改良有重要意义。TGA是碱性亮氨酸拉链中的一类与植物生物胁迫抗性相关的转录因子，在水杨酸（SA）介导的植物系统获得抗性（SAR）信号转导途径中起重要调节作用，能提高植物对病原的广谱抗性。申请者前期工作表明：CmTGA1和CmTGA5基因参与了SA介导的菊花SAR，提高了菊花对黑斑病原和菊花B病毒的抗性。在此基础上，本研究拟进一步解析两个基因的时空表达特性、其蛋白产物的生化特性；通过单价基因和双价基因的过表达及沉默鉴定其抗病功能；采用高通量的RNA-seq技术研究CmTGAs对其下游基因的转录调节。通过研究有望在理论上阐明CmTGAs提高菊花广谱抗病性的分子调控机制，为培育具有广谱抗性的菊花新品种提供基因储备和理论依据。

菊花（Chrysanthemum × morifolium）在国际花卉贸易中占有重要的经济地位。目前，病害是限制菊花大规模商业生产的主要生物胁迫因子。发掘具有广谱抗性的基因资源，培育菊花抗病新种质，对菊花品质的遗传改良有重要意义。TGA是碱性亮氨酸拉链中的一类与植物生物胁迫抗性相关的转录因子，前人的研究表明：TGA在水杨酸（SA）介导的植物系统获得抗性（SAR）信号转导途径中起重要调节作用，能提高植物的广谱抗性。本研究以‘小黄菊’为试材，对CmTGA1和CmTGA5/2在菊花抗病性方面的作用和分子机理进行了解析。获得的主要结果为：二者均在在根和叶片中高量表达，且受病原菌诱导表达增强；定位在细胞核中；CmTGA1转录激活区域在其C末端，且完整蛋白发挥激活作用需要SA的诱导，而CmTGA2转录激活区域在蛋白的N末端，发挥激活作用不需要SA的诱导。二者的过量表达能使拟南芥具有对活体营养型细菌（Pst. DC3000）和死体营养型真菌（A. brassicae）的广谱抗性，但二者调控的下游关键基因存在不同：CmTGA1更多的作用于AtGLU、AtPAL和AtCHT，而CmTGA2更多的作用于AtPAL、AtPOD和AtGLU。RNA-seq分析表明在菊花中过量表达CmTGA1能显著增强海藻糖、寡糖和双糖的生物合成，促进木葡聚糖:木葡聚糖转移酶的活性，这些均与细胞壁相关物质的形成有关。因此CmTGA1基因是通过诱导与细胞壁成分形成有关的基因的表达，从而提高植株的抗性。本研究在理论上解析了CmTGAs提高拟南芥广谱抗病性的分子调控机制，为培育具有广谱抗性的菊花新品种提供了有效的基因储备和理论依据，对解决菊花大规模商业生产中的病害问题，完善菊花周年生产和建立稳定的供应技术体系具有重要的意义。. 已投稿论文题目：Overexpression of the Chrysanthemum TGA2 Gene Confers Broad Spectrum Resistance to Bacterial and Fungal Pathogens in Arabidopsis. 投稿SCI期刊Frontiers in Plant Science（IF=4.298）..