Epigenetic control of virulence in the fungal plant pathogen, Zymoseptoria tritici

预计全球对小麦的需求将增加，这意味着必须保护这种食物来源的供应。感染小麦的真菌病原体是对农业和粮食安全的主要威胁。在这里，由小麦酵母菌感染引起的小麦黑斑病（STB）是欧洲最严重的小麦病害。事实上，仅在英国，STB每年就造成大约5000万英镑的损失。虽然有几种杀菌剂被用来控制小麦小扁豆的感染，但许多种群已经进化出了对杀菌剂的抗性，因此需要新的策略来控制这种病原体。近年来，一系列小麦曲霉分子工具的发展为破译其致病性调控途径和提供新的控制策略提供了机会。像许多其他植物和人类真菌病原体一样，小麦轴虫毒力的一个重要方面可能是它改变形态的能力。事实上，小麦偃麦草感染伴随着菌丝生长的转变和效应编码基因表达的诱导。最近有研究表明，在小麦感染之前，效应子编码基因位于染色质中，染色质富含异色标记，组蛋白H3赖氨酸9和27甲基化（H3K9me/H3K27me）。这表明，在感染过程中，这些抑制性异色标记的重编程是适当诱导基因表达所必需的。因此，本课题的目的是确定异染色质在控制小麦偃麦草的形态转换和毒力中的作用。染色质免疫沉淀分析将用于确定形态学转换过程中组蛋白修饰的变化。此外，通过对小麦Z. tritici基因组序列数据库的分析，发现了编码H3K9-和h3k27组蛋白甲基化酶转移酶的基因。因此，一个关键的目标将是构建在一个或两个组蛋白甲基化酶转移酶基因中携带缺失突变的菌株。利用这些敲除菌株，将有可能确定破坏异染色质对生物体适应性、形态发生转换、效应基因表达以及最终引起小麦感染的能力的影响。

The predicted increase in global demand for wheat means that it is essential that the supply of this food source is protected. Fungal pathogens that infect wheat are major threats to agriculture and food security. Here Septoria tritici blotch (STB) disease resulting from Zymoseptoria tritici infection represents the most serious wheat disease in Europe. Indeed in the UK alone, STB results in an annual loss of approximately £50 million. Although several fungicides are used to control Z. tritici infections many populations have evolved fungicide resistance so that new strategies to control this pathogen are required. Recently, the development of a range of molecular tools for Z. tritici has provided an opportunity to decipher the pathways that regulate its pathogenicity and inform new strategies for its control. . Like many other plant and human fungal pathogens, an important aspect of Z. tritici virulence is likely its ability to switch morphology. Indeed, Z. tritici infection is accompanied by a switch to hyphal growth and the induction in the expression of effector-encoding genes. Recently it has been shown that prior to wheat infection, effector-encoding genes are located in chromatin that is enriched with heterochromatic marks, histone H3 lysine 9 and 27 methylation (H3K9me/H3K27me). This suggests that reprogramming of these repressive heterochromatic marks is required for the proper induction of gene expression during the infection process. Therefore, the aim of this project is to determine the role of heterochromatin in the control of morphological switching and virulence of Z. tritici. Chromatin immunoprecipitation analysis will be employed to determine changes in histone modifications during morphological switching. Furthermore, analysis of the Z. tritici genome sequence database has revealed the genes encoding the H3K9- and the H3K27-histone methylase transferases. Therefore a key objective will be the construction of strains carrying a deletion mutation in one or both histone methylase transferase genes. Using these knockout strains it will be possible to determine the impact of disrupting heterochromatin upon organism fitness, morphogenic switching, effector gene expression and ultimately the ability to cause infection in wheat.