Díaz Fernando, Wolf Jason, de Brito Reinaldo A
Department of Biology, Colgate University, Hamilton, NY, US.
Milner Centre for Evolution and Department of Life Sciences, University of Bath, Bath, UK.
Genome Biol Evol. 2023 May 8;15(5). doi: 10.1093/gbe/evad071.
The extent to which hybridization disrupts a gene's pattern of expression likely governs its propensity for introgression, while its extent of molecular divergence can itself underlie such disruption. Together, these phenomena shape the landscape of sequence and transcriptional divergence across the genome as species diverge. To understand this process, we characterize gene expression inheritance, regulatory divergence, and molecular divergence in the reproductive transcriptomes of species linked by gene flow: the fruit flies Anastrepha fraterculus and A. obliqua, which show evidence of gene flow despite clear evolutionary divergence. We find that their transcriptional patterns are a mosaic between those typically observed within and between allopatric species. Transcripts showing transgressive expression in hybrids or cis-regulatory divergence between species are associated with greater sequence divergence. This may reflect pleiotropic constraints that make them resistant to gene flow or they may be more likely to experience divergent selection. While these more divergent gene classes are likely to be important contributors to species differences, they are relatively rare. Instead, most differentially regulated transcripts, including those linked to reproduction, show high degrees of dominance in hybrids and trans-regulated divergence between species, suggesting widespread genetic compatibility that potentially allowed for introgression. These findings provide insights into how postzygotic isolating mechanisms might evolve in the presence of gene flow: regions showing cis-regulatory divergence or transgressive expression contribute to reproductive isolation, while regions with dominant expression and trans-regulatory divergence allow for introgression. These patterns create a genomic mosaic of transcriptional regulation that is tied to sequence divergence.
杂交对基因表达模式的破坏程度可能决定了其基因渗入的倾向，而其分子差异程度本身可能是这种破坏的基础。随着物种分化，这些现象共同塑造了整个基因组中序列和转录差异的格局。为了理解这一过程，我们对通过基因流联系起来的物种的生殖转录组中的基因表达遗传、调控差异和分子差异进行了表征：果蝇Anastrepha fraterculus和A. obliqua，尽管它们在进化上有明显差异，但仍有基因流的证据。我们发现它们的转录模式是在异域物种内部和之间通常观察到的模式的混合体。在杂种中表现出超亲表达或物种间顺式调控差异的转录本与更大的序列差异相关。这可能反映了使其对基因流具有抗性的多效性限制，或者它们可能更有可能经历分歧选择。虽然这些差异更大的基因类别可能是物种差异的重要贡献者，但它们相对较少。相反，大多数差异调控的转录本，包括那些与生殖相关的转录本，在杂种中表现出高度的显性以及物种间的反式调控差异，这表明广泛的遗传相容性可能允许基因渗入。这些发现为合子后隔离机制在基因流存在的情况下可能如何进化提供了见解：表现出顺式调控差异或超亲表达的区域有助于生殖隔离，而具有显性表达和反式调控差异的区域则允许基因渗入。这些模式创造了一个与序列差异相关的转录调控的基因组镶嵌体。
