Loss of Heterozygosity Drives Adaptation in Hybrid Yeast.
Loss of Heterozygosity Drives Adaptation in Hybrid Yeast.
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DOI：
10.1093/molbev/msx098
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发表时间：
2017-07-01
影响因子：
10.7
通讯作者：
Dunham MJ
中科院分区：
文献类型：
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作者：
Smukowski Heil CS;DeSevo CG;Pai DA;Tucker CM;Hoang ML;Dunham MJ
杂交通常被认为是不适应的，但有时杂交可以入侵新的生态位，比它们的亲本更好地适应新的或有压力的环境。杂交后发生的基因组变化促进了基因组的分辨率和/或适应性，但目前还没有得到很好的理解。在这里，我们通过对新生种间杂交酵母酿酒酵母× uvarum及其亲本的实验进化来研究杂交基因组的进化。我们在营养有限的条件下对这些菌株进行了数百代的进化，并对所产生的培养物进行了测序，发现了许多点突变、拷贝数变化和杂合性缺失（LOH）事件，包括营养转运蛋白的种偏扩增。我们关注了一个特别有趣的例子，在这个例子中，我们在种内和种间杂交中都看到了高亲和磷酸盐转运基因PHO84上重复的LOH。利用等位基因替代方法，对不同等位基因在杂交菌株和酿酒葡萄球菌菌株背景下的适合度进行了测试，发现酿酒葡萄球菌和杂交菌株背景下的低亲和性确实是一个等位基因对另一个等位基因的选择结果。这是一个杂交基因组分辨率由对现有杂合性的正选择驱动的例子，并表明即使不频繁的异交也可能对适应产生持久的影响。
Hybridization is often considered maladaptive, but sometimes hybrids can invade new ecological niches and adapt to novel or stressful environments better than their parents. The genomic changes that occur following hybridization that facilitate genome resolution and/or adaptation are not well understood. Here, we examine hybrid genome evolution using experimental evolution of de novo interspecific hybrid yeast Saccharomyces cerevisiae × Saccharomyces uvarum and their parentals. We evolved these strains in nutrient-limited conditions for hundreds of generations and sequenced the resulting cultures identifying numerous point mutations, copy number changes, and loss of heterozygosity (LOH) events, including species-biased amplification of nutrient transporters. We focused on a particularly interesting example, in which we saw repeated LOH at the high-affinity phosphate transporter gene PHO84 in both intra- and interspecific hybrids. Using allele replacement methods, we tested the fitness of different alleles in hybrid and S. cerevisiae strain backgrounds and found that the LOH is indeed the result of selection on one allele over the other in both S. cerevisiae and the hybrids. This is an example where hybrid genome resolution is driven by positive selection on existing heterozygosity and demonstrates that even infrequent outcrossing may have lasting impacts on adaptation.