A yeast living ancestor reveals the origin of genomic introgressions
A yeast living ancestor reveals the origin of genomic introgressions
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DOI：
10.1038/s41586-020-2889-1
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发表时间：
2020-11-11
期刊：
影响因子：
64.8
通讯作者：
Liti, Gianni
中科院分区：
文献类型：
--
作者：
D'Angiolo, Melania;De Chiara, Matteo;Liti, Gianni
古代杂交事件的酵母克隆后代被鉴定出来，并揭示了酿酒酵母 Alpechin 谱系的早期进化及其丰富的奇异酵母渗入。基因组渗入推动了动物 (1)、植物 (2) 和真菌 (3) 界的进化。基因渗入从古老的混合物开始，然后与一种亲本物种重复回交。然而，基因渗入如何在生殖隔离的物种（例如酵母）中发生仍不清楚。在这里，我们鉴定了祖先酵母杂交体的克隆后代，该杂交体建立了现存的酿酒酵母 Alpechin 谱系 (5)，该谱系携带丰富的奇异酵母基因渗入。我们表明，这个克隆后代（此后被定义为“活着的祖先”）保留了第一代与邻近的酿酒酵母和奇异酵母亚基因组杂交的祖先基因组结构。祖先的第一代杂种通过一百多次有丝分裂重组事件经历了灾难性的基因组不稳定，主要表现为杂合性丧失产生的纯合基因组块。这些纯合序列块通过恢复减数分裂重组来挽救杂交育性，并且是 Alpechin 谱系中存在的基因渗入的直接起源。我们提出了通过重建灭绝阶段进行基因渗入进化的合理途径，并提出基因组不稳定性允许杂种克服生殖隔离并使基因渗入出现。
A yeast clonal descendant of an ancient hybridization event is identified and sheds light on the early evolution of the Saccharomyces cerevisiae Alpechin lineage and its abundant Saccharomyces paradoxus introgressions.Genome introgressions drive evolution across the animal(1), plant(2) and fungal(3) kingdoms. Introgressions initiate from archaic admixtures followed by repeated backcrossing to one parental species. However, how introgressions arise in reproductively isolated species, such as yeast(4), has remained unclear. Here we identify a clonal descendant of the ancestral yeast hybrid that founded the extant Saccharomyces cerevisiae Alpechin lineage(5), which carries abundant Saccharomyces paradoxus introgressions. We show that this clonal descendant, hereafter defined as a 'living ancestor', retained the ancestral genome structure of the first-generation hybrid with contiguous S. cerevisiae and S. paradoxus subgenomes. The ancestral first-generation hybrid underwent catastrophic genomic instability through more than a hundred mitotic recombination events, mainly manifesting as homozygous genome blocks generated by loss of heterozygosity. These homozygous sequence blocks rescue hybrid fertility by restoring meiotic recombination and are the direct origins of the introgressions present in the Alpechin lineage. We suggest a plausible route for introgression evolution through the reconstruction of extinct stages and propose that genome instability allows hybrids to overcome reproductive isolation and enables introgressions to emerge.