糖基转移酶新基因TaUGT6在小麦抗赤霉病菌DON毒素积累中的作用机制研究

Fusarium head blight (FHB), a devastating disease in wheat worldwide, results in yield loses and mycotoxin accumulation such as deoxynivalenol (DON) which poses a serious threat to food safety. UDP-glycosyltransferase enzymes (UGTs) are known to contribute detoxification and enhance FHB resistance by glycosylating DON into DON-3-Glucoside (D3G) in plant. However, a comprehensive investigation of wheat (Triticum aestivum) UGT genes is still lacking. Before this project, we carried out genome-wide analysis of family-1 UDP glycosyltransferases (UGT) and identification of one novel UGT genes TaUGT6, which was highly induced under Fusarium graminearum inoculation in resistance variety Sumai 3 but not in susceptible variety Annong 8455. This project will determine the function of TaUGT6 in resistance to DON accumulation and FHB in wheat, and also give a preliminary study about the mechanism. We will firstly do the enzyme activity assay to determine its ability to transfer DON into D3G, and transform TaUGT6 into Arabidopsis and wheat to determine its function in resistance to FHB and DON accumulation at the same time. Then we will identify differences in the gene by sequencing between resistance and susceptible varieties. We will also examine the expression pattern of TaUGT6 in different wheat varieties under biotic and abiotic conditions, and also test the subcellular localization and do the phylogenetic analysis. To clarify the mechanism of the TaUGT6, we will do the promoter deletion assay and yeast library screening assay. Our work will establish a foundation for further understanding of the mechanism of resistance to FHB in wheat, and will be helpful for molecular breeding for FHB resistance.

小麦赤霉病是全球普遍发生的重要病害，不仅降低产量，其产生的脱氧雪腐镰刀菌烯醇（DON）等毒素还威胁着人畜健康。植物UDP-葡萄糖基转移酶（UGT）可以降低DON的毒性而提高赤霉病抗性，但目前对小麦中UGT的研究还不充分。我们通过全基因组分析及验证，发现一个新基因TaUGT6只在抗病品种苏麦3号中受赤霉病菌诱导高表达而在感病品种安农8455中不受诱导表达。本课题拟进一步明确该基因在抗DON毒素积累及抗赤霉病中的作用。首先通过酶活测定确定TaUGT6使DON转化D3G的能力，其次转化拟南芥和小麦确定其功能。同时通过序列分析确定TaUGT6在不同抗性品种间的序列差异，利用赤霉病菌、DON及植物激素SA和JA诱导确定该基因在不同抗性品种间的表达差异，随后进行亚细胞定位和进化树分析。最后通过启动子缺失实验确定响应DON处理的关键作用区段及酵母文库筛选获得与其相互作用的蛋白，初步揭示其作用机制。

小麦赤霉病是全球普遍发生的重要病害，不仅降低产量，其产生的脱氧雪腐镰刀菌烯醇（DON）等毒素还威胁着人畜健康及促进赤霉病扩展。植物UDP-葡萄糖基转移酶（UGT）可以降低DON的毒性而提高赤霉病抗性。我们前期通过全基因组分析及验证，发现了新基因TaUGT6在抗病品种苏麦3号中受赤霉病菌和DON诱导高表达。通过RT-qPCR分析，发现TaUGT6只在抗病品种苏麦3号中受赤霉病菌诱导高表达而在感病品种安农8455中不受诱导表达；进化树分析发现TaUGT6与小麦中已报道的5个赤霉病抗性相关UGT同源性较高；通过酶活测定发现TaUGT6可以糖基化DON为D3G；拟南芥中过量表达可以显著提高对DON的耐受性；小麦中过量表达可以在一定程度上抑制赤霉病扩展；TaUGT6转录起始位点上游的−436和−1200 bp之间存在两个响应DON的区段；通过酵母双杂交筛选和验证，鉴定到22个与TaUGT6相互作用的蛋白。本研究新发现TaUGT6基因可以通过降低DON毒性而提高对赤霉病的抗性，为赤霉病抗性机制的理解及抗赤霉病育种材料创制奠定了一定的基础。