Hartmann Fanny E, Sánchez-Vallet Andrea, McDonald Bruce A, Croll Daniel
Plant Pathology, Institute of Integrative Biology, Zurich, Switzerland.
ISME J. 2017 May;11(5):1189-1204. doi: 10.1038/ismej.2016.196. Epub 2017 Jan 24.
Fungal pathogens can rapidly evolve virulence towards resistant crops in agricultural ecosystems. Gains in virulence are often mediated by the mutation or deletion of a gene encoding a protein recognized by the plant immune system. However, the loci and the mechanisms of genome evolution enabling rapid virulence evolution are poorly understood. We performed genome-wide association mapping on a global collection of 106 strains of Zymoseptoria tritici, the most damaging pathogen of wheat in Europe, to identify polymorphisms linked to virulence on two wheat varieties. We found 25 distinct genomic loci associated with reproductive success of the pathogen. However, no locus was shared between the host genotypes, suggesting host specialization. The main locus associated with virulence encoded a highly expressed, small secreted protein. Population genomic analyses showed that the gain in virulence was explained by a segregating gene deletion polymorphism. The deletion was likely adaptive by preventing detection of the encoded protein. Comparative genomics of closely related species showed that the locus emerged de novo since speciation. A large cluster of transposable elements in direct proximity to the locus generated extensive rearrangements leading to multiple independent gene losses. Our study demonstrates that rapid turnover in the chromosomal structure of a pathogen can drive host specialization.
在农业生态系统中，真菌病原体可迅速向抗性作物进化出毒力。毒力的增加通常由编码植物免疫系统识别的蛋白质的基因发生突变或缺失介导。然而，人们对促成毒力快速进化的基因组进化位点和机制知之甚少。我们对欧洲最具破坏性的小麦病原体——小麦黄斑叶枯病菌（Zymoseptoria tritici）的106个菌株的全球收集品系进行了全基因组关联图谱分析，以确定与两种小麦品种毒力相关的多态性。我们发现了25个与病原体繁殖成功相关的不同基因组位点。然而，宿主基因型之间没有共享位点，这表明宿主特异性。与毒力相关的主要位点编码一种高表达的小分泌蛋白。群体基因组分析表明，毒力的增加是由一个分离的基因缺失多态性所解释的。该缺失可能通过阻止对编码蛋白的检测而具有适应性。近缘物种的比较基因组学表明，该位点自物种形成以来从头出现。紧邻该位点的一大簇转座元件产生了广泛的重排，导致多个独立的基因丢失。我们的研究表明，病原体染色体结构的快速变化可驱动宿主特异性。
