Data from: Extensive recombination of a yeast diploid hybrid through meiotic reversion

In somatic cells, recombination between the homologous chromosomes followed by equational segregation leads to loss of heterozygosity events (LOH), allowing the expression of recessive alleles and the production of novel allele combinations that are potentially beneficial upon Darwinian selection. However, inter-homolog recombination in somatic cells is rare, thus reducing potential genetic variation. Here, we explored the property of S. cerevisiae to enter the meiotic developmental program, induce meiotic Spo11-dependent double-strand breaks genome-wide and return to mitotic growth, a process known as Return To Growth (RTG). Whole genome sequencing of 36 RTG strains derived from the hybrid S288c/SK1 diploid strain demonstrates that the RTGs are bona fide diploids with mosaic recombined genome, derived from either parental origin. Individual RTG genome-wide genotypes are comprised of 5 to 87 homozygous regions due to the loss of heterozygous (LOH) events of various lengths, varying between a few nucleotides up to several hundred kilobases. Furthermore, we show that reiteration of the RTG process shows incremental increases of homozygosity. Phenotype/genotype analysis of the RTG strains for the auxotrophic and arsenate resistance traits validates the potential of this procedure of genome diversification to rapidly map complex traits loci (QTLs) in diploid strains without undergoing sexual reproduction.

在体细胞中，同源染色体之间发生重组后伴随均等分离，会引发杂合性缺失（Loss of Heterozygosity, LOH）事件，使得隐性等位基因得以表达，并产生新的等位基因组合，这类组合在达尔文选择下可能具有适应性优势。然而，体细胞内的同源间重组十分罕见，因此限制了潜在的遗传变异产生。本研究探索了酿酒酵母（S. cerevisiae）进入减数分裂发育程序、在全基因组范围内诱导Spo11依赖型减数分裂双链断裂，随后重返有丝分裂生长的特性，这一过程被称为生长回归（Return To Growth, RTG）。我们对源自杂交二倍体菌株S288c/SK1的36株RTG菌株进行全基因组测序，结果显示RTG菌株均为真正的二倍体，其基因组呈嵌合重组状态，遗传物质来自两个亲本之一。单株RTG菌株的全基因组基因型包含5至87个因杂合性缺失（LOH）事件形成的纯合区域，这些区域长度各异，从数个核苷酸到数百千碱基对不等。此外，我们发现重复执行RTG过程会使基因组的纯合度呈渐进式提升。对RTG菌株的营养缺陷型与抗砷性性状进行表型-基因型分析，证实了该基因组多样化方法无需进行有性生殖，即可快速定位二倍体菌株中的复杂性状位点（Quantitative Trait Loci, QTLs）。