Duquesne University, Pittsburgh, PA, USA.
J Mol Evol. 2014 Jan;78(1):87-99. doi: 10.1007/s00239-013-9602-z. Epub 2013 Nov 27.
In species where females mate with multiple males during a single ovulatory cycle, sperm competition is hypothesized to increase the rate of adaptive evolution of proteins expressed in male reproductive tissues through recurrent selective sweeps (positive selection). The hominoids, comprising apes and humans, are a group of closely related primates with extensive variation in mating behaviors and predicted levels of sperm competition. Since previous studies of individual male reproductive genes have shown evidence of positive selection, we estimated rates of evolution of a comprehensive set of proteins expressed in ejaculated semen. Our results show that these proteins in hominoids do not have elevated rates of nonsynonymous substitutions (Ka) compared with a control dataset of nonreproductive genes. Species with greater sperm competition do not have faster rates of seminal protein evolution. Although at these broad levels our hypotheses were not confirmed, further analyses indicate specific patterns of molecular evolution. Namely, the Ka of seminal genes is more strongly correlated with measures of tissue specificity than nonreproductive genes, suggesting that the former may more readily adapt to tissue-specific functions. Proteins expressed from the seminal vesicles evolve more rapidly than those from other male reproductive tissues. Also, several gene ontology categories show elevated rates of protein evolution, not seen in the control data set. While the generalization that male reproductive genes evolve rapidly in hominoids is an oversimplification, a subset of proteins can be identified that are likely targets for adaptive evolution driven by sexual selection.
在雌性个体在一个单一的排卵周期内与多个雄性个体交配的物种中,通过反复的选择清除(正选择),精子竞争被假设会增加雄性生殖组织中表达的蛋白质的适应性进化速度。人科动物包括猿类和人类,是一组密切相关的灵长类动物,在交配行为和预测的精子竞争水平上存在广泛的变异。由于先前对个体雄性生殖基因的研究表明存在正选择的证据,我们估计了一套广泛表达于射出精液中的蛋白质的进化速度。我们的研究结果表明,这些人科动物的蛋白质与非生殖基因的控制数据集相比,没有更高的非同义替换率(Ka)。具有更高精子竞争的物种并没有更快的精液蛋白进化速度。虽然在这些广泛的层面上,我们的假设没有得到证实,但进一步的分析表明了特定的分子进化模式。即,精液基因的 Ka 与组织特异性的衡量指标比非生殖基因更为密切相关,这表明前者可能更容易适应组织特异性功能。来自精囊的蛋白质比来自其他雄性生殖组织的蛋白质进化得更快。此外,几个基因本体类别显示出比对照数据集更高的蛋白质进化率,这在对照数据集中没有出现。虽然雄性生殖基因在人科动物中快速进化的概括是一种过于简单的说法,但可以确定一组蛋白质可能是由性选择驱动的适应性进化的目标。