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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Fusion of two divergent fungal individuals led to the recent emergence of a unique widespread pathogen species
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Fusion of two divergent fungal individuals led to the recent emergence of a unique widespread pathogen species

机译：两个不同真菌个体的融合导致了最近出现的一种独特的广泛病原体物种

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摘要

In a genome alignment of five individuals of the ascomycete fungus Zymoseptoria pseudotritici, a close relative of the wheat pathogen Z. tritici (synonym Mycosphaerella graminicola), we observed peculiar diversity patterns. Long regions up to 100 kb without variation alternate with similarly long regions of high variability. The variable segments in the genome alignment are organized into two main haplotype groups that have diverged ~3% from each other. The genome patterns in Z. pseudotritici are consistent with a hybrid speciation event resulting from a cross between two divergent hap-loid individuals. The resulting hybrids formed the new species without backcrossing to the parents. We observe no variation in 54% of the genome in the five individuals and estimate a complete loss of variation for at least 30% of the genome in the entire species. A strong population bottleneck following the hybridization event caused this loss of variation. Variable segments in the Z. pseudotritici genome exhibit the two haplotypes contributed by the parental individuals. From our previously estimated recombination map of Z. tritici and the size distribution of variable chromosome blocks untouched by recombination we estimate that the hybridization occurred ~380 sexual generations ago. We show that the amount of lost variation is explained by genetic drift during the bottleneck and by natural selection, as evidenced by the correlation of presence/ absence of variation with gene density and recombination rate. The successful spread of this unique reproductively isolated pathogen highlights the strong potential of hybridization in the emergence of pathogen species with sexual reproduction.
机译：在子囊菌真菌Zymoseptoria pseudotritici的五个个体（小麦病原体Z. tritici（同义词Mycosphaerella graminicola）的近亲）的基因组比对中，我们观察到了独特的多样性模式。高达100 kb的无变化长区域与类似的具有高可变性的长区域交替出现。基因组比对中的可变节段被组织为两个主要的单倍型组，彼此相差约3％。 Z. pseudotritici中的基因组模式与两个不同单倍体个体之间杂交产生的杂种形成事件一致。由此产生的杂种形成了新物种，而没有与亲本回交。我们没有观察到五个个体中54％的基因组发生变异，并估计整个物种中至少30％的基因组变异完全消失。杂交事件后强烈的种群瓶颈导致这种变异的丧失。伪小麦Z.基因组中的可变区段显示出由亲本个体贡献的两种单倍型。根据我们先前估计的Z. tritici重组图和重组未触及的可变染色体块的大小分布，我们估计杂交发生在约380个有性世代之前。我们表明，丢失的变异量是由瓶颈期间的遗传漂移和自然选择来解释的，正如变异存在/不存在与基因密度和重组率的相关性所证明的那样。这种独特的生殖分离病原体的成功传播突出了具有性繁殖的病原体物种出现杂交的强大潜力。

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