Natural History Museum, University of Oslo, Oslo, Norway.
Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway.
Mol Biol Evol. 2020 Feb 1;37(2):488-506. doi: 10.1093/molbev/msz235.
Seminal fluid proteins (SFPs) mediate an array of postmating reproductive processes that influence fertilization and fertility. As such, it is widely held that SFPs may contribute to postmating, prezygotic reproductive barriers between closely related taxa. We investigated seminal fluid (SF) diversification in a recently diverged passerine species pair (Passer domesticus and Passer hispaniolensis) using a combination of proteomic and comparative evolutionary genomic approaches. First, we characterized and compared the SF proteome of the two species, revealing consistencies with known aspects of SFP biology and function in other taxa, including the presence and diversification of proteins involved in immunity and sperm maturation. Second, using whole-genome resequencing data, we assessed patterns of genomic differentiation between house and Spanish sparrows. These analyses detected divergent selection on immunity-related SF genes and positive selective sweeps in regions containing a number of SF genes that also exhibited protein abundance diversification between species. Finally, we analyzed the molecular evolution of SFPs across 11 passerine species and found a significantly higher rate of positive selection in SFPs compared with the rest of the genome, as well as significant enrichments for functional pathways related to immunity in the set of positively selected SF genes. Our results suggest that selection on immunity pathways is an important determinant of passerine SF composition and evolution. Assessing the role of immunity genes in speciation in other recently diverged taxa should be prioritized given the potential role for immunity-related proteins in reproductive incompatibilities in Passer sparrows.
精液蛋白 (SFPs) 介导一系列交配后生殖过程，影响受精和生育能力。因此，人们普遍认为 SFP 可能有助于密切相关分类群之间交配后、合子前生殖障碍。我们使用蛋白质组学和比较进化基因组学方法的组合，研究了最近分化的雀形目物种对（Passer domesticus 和 Passer hispaniolensis）中的精液（SF）多样化。首先，我们对这两个物种的 SF 蛋白质组进行了特征描述和比较，揭示了与其他分类群中 SFP 生物学和功能的已知方面的一致性，包括参与免疫和精子成熟的蛋白质的存在和多样化。其次，使用全基因组重测序数据，我们评估了家雀和西班牙麻雀之间的基因组分化模式。这些分析检测到免疫相关 SF 基因的分歧选择和包含许多 SF 基因的区域的正选择扫荡，这些基因在物种之间也表现出蛋白质丰度多样化。最后，我们分析了 11 种雀形目物种的 SFPs 分子进化，发现 SFPs 中的正选择率明显高于基因组的其余部分，并且在正选择的 SF 基因集中与免疫相关的功能途径显著富集。我们的研究结果表明，免疫途径的选择是雀形目 SF 组成和进化的重要决定因素。鉴于免疫相关蛋白在 Passer 麻雀生殖不相容中的潜在作用，评估其他最近分化的分类群中免疫基因在物种形成中的作用应该是优先事项。
