The role of RIPP proteins in plant pathogenic fungi.

最近，一种名为Ustiloxin的小分泌毒素已经从曲霉菌中被鉴定出来。它是真菌中同类中第一个核糖体合成的翻译后修饰蛋白（RiPP），其中小肽序列（存在于多个序列拷贝中）从更大的肽中切除并被广泛修饰，实际上这些修饰使得不可能将这些产物与nrps衍生的天然产物区分开来。迄今为止唯一的其他真菌ripp是来自Amanita sp（蝇木耳，死亡帽等）的amatoxins，真菌以具有广泛的生物活性而闻名。小麦致病菌小麦酵母酵母（Zymoseptoria tritici）在其基因组中有一个与ustiloxin相似的基因簇，RNAseq数据显示在生物营养生长阶段大量表达，在这种小麦主要病原体向坏死性生长过渡时达到峰值。这是一种可能从效应分子中得到的表达谱，可能被用来在感染的早期阶段将宿主防御反应最小化。其他研究也表明，这一位点在不同的分离株之间是可变的，这表明，在寄主-病原体相互作用中，寄主植物正在经历频繁的遗传变化（由于植物育种者的活动），这可能是一种多样化的选择。核心蛋白的基因嵌入在一个共表达基因簇中，与各种剪裁功能的基因也存在，因此最终成熟化合物的化学结构不能轻易预测-除了其核心肽序列和可能涉及内部酪氨酸残基的环化事件。该项目旨在确定真菌产生的最终成熟代谢物，描述其在疾病期间的作用（如果有的话），然后寻求探索这类代谢物在各种宿主-病原体相互作用中的更广泛含义。该项目将涉及小麦黑麦草及相关真菌的基因组和遗传分析，利用基因破坏技术探索基因簇在这些真菌疾病中的作用。它还将涉及基因的异源表达作为一种合成生物学方法来探索该化合物的生物合成途径，并结合分析化学来确定代谢物的结构和构象。

Recently a small secreted toxin called Ustiloxin has been characterised from Aspergillus sp. It is thefirst Ribosomally synthesised Post-translationally modified Protein (RiPP) of its class in fungi, where asmall peptide sequence (present in multiple tandem copies) is excised from a larger peptide thencyclised and extensively modified, indeed the modifications make it impossible to distinguish suchproducts from NRPS-derived natural products, the only other fungal RiPPs to date are the amatoxinsfrom Amanita sp (fly agaric, deathcap & etc), fungi famous for having wide ranging biological activities.The Wheat-pathogenic fungus Zymoseptoria tritici has a similar gene cluster to ustiloxin within itsgenome, and RNAseq data shows abundant expression during the biotrophic growth stages, peakingat the transition to necrotrophic growth of this major wheat pathogen. This is the sort of expressionprofile that might be expected from an effector molecule, perhaps being used to minimise hostdefence reactions during early stages of infection. Other studies have also shown this locus to bevariable between isolates, suggesting that it is under diversifying selection as might be expected ifinvolved in host-pathogen interactions where the hostplant is undergoing frequent genetic change(due to the activity of plant breeders). The gene for the core protein is embedded in a co-expressedgene cluster with genes for various tailoring functions also present so that the chemical structure ofthe final mature compound cannot be readily predicted - other than its core peptide sequence and alikely cyclisation event involving an internal tyrosine residue.The project will aim to identify the final mature metabolite made by the fungus, to characterise itsrole (if any) during disease and to then seek to explore the wider implications of this class ofmetabolite in various host-pathogen interactions.The project will involve genomic and genetic analysis of Z. tritici and related fungi, using genedisruption techniques to explore the role of the gene cluster in disease in these fungi. It will alsoinvolve heterologous expression of the genes as a synthetic biology approach to explore thebiosynthetic pathway for this compound, coupled with analytical chemistry to determine the structureand conformation of the metabolites.