法国蔚蓝海岸大学Gianni Liti研究小组近日取得一项新成果。他们利用酵母揭示了基因组渗入现象的起源。相关论文在线发表在2020年11月11日出版的《自然》杂志上。

在本研究中，研究人员确定了杂合酵母祖先的无性后代，后者形成了现存的酿酒酵母Alpechin亚群，该亚群携带丰富的奇异酵母渗入。研究表明，该克隆后代（以下定义为“活祖先”）保留了第一代杂合祖先的基因组结构，其包含酿酒酵母和奇异酵母的亚基因组。该杂合祖先通过一百多次有丝分裂重组产生了严重的基因组不稳定性，主要表现为由于杂合性丧失而产生的纯合基因组。

这些纯合序列通过恢复减数分裂重组而阻止了杂合物种的繁殖，并且是Alpechin谱系中基因渗入的直接起源。研究人员提出了物质在灭绝阶段通过重建进行基因组渗入进化的可行途径，并提出基因组不稳定性允许杂合物种克服生殖隔离并利于基因组渗入出现。

据悉，基因组渗入促进了动物、植物和真菌的进化。基因组渗入最先发生在古老的杂合物种中，然后反复回交到一种亲本物种。但是，目前尚不清楚在生殖隔离的物种（如酵母）中如何发生基因组渗入。

附：英文原文

Title: A yeast living ancestor reveals the origin of genomic introgressions

Author: Melania DAngiolo, Matteo De Chiara, Jia-Xing Yue, Agurtzane Irizar, Simon Stenberg, Karl Persson, Agns Llored, Benjamin Barr, Joseph Schacherer, Roberto Marangoni, Eric Gilson, Jonas Warringer, Gianni Liti

Issue&Volume: 2020-11-11

Abstract: Genome introgressions drive evolution across the animal1, plant2 and fungal3 kingdoms. Introgressions initiate from archaic admixtures followed by repeated backcrossing to one parental species. However, how introgressions arise in reproductively isolated species, such as yeast4, has remained unclear. Here we identify a clonal descendant of the ancestral yeast hybrid that founded the extant Saccharomyces cerevisiae Alpechin lineage5, 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.

DOI: 10.1038/s41586-020-2889-1

Source: https://www.nature.com/articles/s41586-020-2889-1