禾谷镰刀菌TRI6相关调控因子影响DON产生的分子机制

Wheat scab or head blight caused by Fusarium graminearum is one of the most important diseases of wheat and barley worldwide. It not only causes significant yield losses but also results in the contamination of infected kernels with mycotoxins, such as deoxynivalenol (DON) that are harmful to human and animals. DON is also an important virulence factor in F. graminearum. Although the trichothecene biosynthetic gene clusters have been studied extensively, the global regulation of DON synthesis in F. graminearum are not well characterized. Various environmental factors are known to influence DON accumulation in infected wheat tissues, but the underlying mechanisms are not clear. In this study, we aim to determine regulatory mechanisms that control DON production and accumulation in F. graminearum. Genes that are directly interacting with TRI6, the key transcription factor regulating TRI gene expression, will be identified and characterized. Transcription factors regulating TRI6 expression and promoter elements of TRI6 also will be characterized. We also propose to determine the role of nitrogen and carbon metabolisms and pH signal in DON synthesis by functional characterization of the ARE1, CRE1 and PAC1 genes, the three key regulators of N and C metabolisms and pH signal, respectively. In addition, the interactions among these regulatory genes functionally related to TRI6 also will be identified. Results from proposed experiments will significantly improve our understanding of global regulatory mechanisms involved in mycotoxin production in F. graminearum. In the long run, this study will be beneficial to develop novel strategies to reduce DON contamination and control wheat scab disease.

小麦赤霉病是世界性真菌病害，不仅造成小麦严重减产、品质降低，更为重要的是受害小麦粒含真菌毒素DON，可引起人畜中毒。虽然禾谷镰刀菌中参与DON合成的TRI基因已较清楚，但对赤霉病菌毒素产生的总体调控机制缺乏了解，多种环境因子都可影响DON在小麦中的积累，但相关的调控基因及作用机制尚不清楚。TRI6是调控TRI基因的重要转录因子，项目拟全面分离鉴定与TRI6直接互作的基因并进行功能分析；同时对TRI6启动子的特征进行系统分析并分离鉴定与TRI6启动子结合的调控因子；对可能调控TRI6表达并参与碳氮代谢和pH信号的关键调控因子CRE1、ARE1和PAC1进行分析，以明确其与TRI6的作用关系以及碳氮代谢与pH信号在DON产生中的调控作用；并明确这些毒素合成调控因子之间的相互作用关系，从而进一步了解禾谷镰刀菌中DON产生和积累的调控机制，为小麦赤霉病的防治与减轻毒素污染新策略的建立提供科学依据。

小麦赤霉病是我国小麦生产上的一种重要病害，该病害不仅严重影响小麦品质和质量，更为重要的是受害小麦粒含真菌毒素DON，可引起人畜中毒。目前已对禾谷镰刀菌DON生物合成途径有了较为深入的认识，但对该途径和对次生代谢的总体性调控尚缺乏了解。因此，开展对赤霉病菌毒素产生调控机制的研究，对于小麦赤霉病毒素污染的可持续控制具有重要的理论和实际意义。本项目通过功能分析禾谷镰刀菌中氮代谢调控因子AreA、pH信号调控因子PacC、活性氧相关转录因子FgAP1，FgSKN7和FgATF1，以及cAMP信号、环腺苷酸磷酸二酯酶基因FgPDE1和FgPDE2 在DON 产生中的作用，进一步明确了这些TRI6相关转录因子在毒素合成调控网络中的作用，阐明了AreA可能位于cAMP-PKA信号通路的下游，它可通过铵通透酶实现对MAPK和PKA通路的影响；活性氧相关转录因子FgSKN7是接受上游ROS信号并直接参与调控DON合成的核心调控因子；外源施加cAMP可诱导禾谷镰刀菌DON毒素的合成，并且FgPDE2 对DON合成和PKA活性具有负调控作用；TRI6和TRI10基因在cAMP-PKA信号途径调控DON合成过程中存在作用差异。研究结果可进一步了解禾谷镰刀菌中DON产生和积累的调控机制，对建立新的减轻小麦赤霉病毒素污染防控策略的制定提供有效的科学理论依据。