Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada.
Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Canada.
Nat Commun. 2024 Nov 28;15(1):10319. doi: 10.1038/s41467-024-54105-4.
Hybrids between species exhibit plastic genomic architectures that could foster or slow down their adaptation. When challenged to evolve in an environment containing a UV mimetic drug, yeast hybrids have reduced adaptation rates compared to parents. We find that hybrids and their parents converge onto similar molecular mechanisms of adaptation by mutations in pleiotropic transcription factors, but at a different pace. After 100 generations, mutations in these genes tend to be homozygous in the parents but heterozygous in the hybrids. We hypothesize that a lower rate of loss of heterozygosity (LOH) in hybrids could limit fitness gain. Using genome editing, we first demonstrate that mutations display incomplete dominance, requiring homozygosity to show full impact and to entirely circumvent Haldane's sieve, which favors the fixation of dominant mutations. Second, tracking mutations in earlier generations confirmed a different rate of LOH in hybrids. Together, these findings show that Haldane's sieve slows down adaptation in hybrids, revealing an intrinsic constraint of hybrid genomic architecture that can limit the role of hybridization in adaptive evolution.
物种间的杂种表现出可塑的基因组结构，这可能促进或减缓它们的适应。当受到在含有紫外线模拟药物的环境中进化的挑战时，与亲本相比，酵母杂种的适应速度降低。我们发现杂种及其亲本通过多效转录因子的突变趋同于类似的适应分子机制，但速度不同。在 100 代后，这些基因中的突变在亲本中往往是纯合的，但在杂种中是杂合的。我们假设杂种中杂合性丢失率 (LOH) 较低可能会限制适应性增益。使用基因组编辑，我们首先证明突变表现出不完全显性，需要纯合性才能显示出完全的影响，并完全绕过有利于显性突变固定的哈代筛。其次，在早期世代追踪突变证实了杂种中存在不同的 LOH 率。总之，这些发现表明哈代筛在杂种中减缓了适应速度，揭示了杂种基因组结构的内在限制，这可能限制了杂交在适应性进化中的作用。
