San-Jose Luis M, Ducrest Anne-Lyse, Ducret Valérie, Béziers Paul, Simon Céline, Wakamatsu Kazumasa, Roulin Alexandre
Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland.
Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, 470-1192, Japan.
Mol Ecol. 2015 Jun;24(11):2794-808. doi: 10.1111/mec.13193. Epub 2015 May 14.
Variants of the melanocortin-1 receptor (MC1R) gene result in abrupt, naturally selected colour morphs. These genetic variants may differentially affect sexual dimorphism if one morph is naturally selected in the two sexes but another morph is naturally or sexually selected only in one of the two sexes (e.g. to confer camouflage in reproductive females or confer mating advantage in males). Therefore, the balance between natural and sexual selections can differ between MC1R variants, as suggest studies showing interspecific correlations between sexual dimorphism and the rate of nonsynonymous vs. synonymous amino acid substitutions at the MC1R. Surprisingly, how MC1R is related to within-species sexual dimorphism, and thereby to sex-specific selection, has not yet been investigated. We tackled this issue in the barn owl (Tyto alba), a species showing pronounced variation in the degree of reddish pheomelanin-based coloration and in the number and size of black feather spots. We found that a valine (V)-to-isoleucine (I) substitution at position 126 explains up to 30% of the variation in the three melanin-based colour traits and in feather melanin content. Interestingly, MC1R genotypes also differed in the degree of sexual colour dimorphism, with individuals homozygous for the II MC1R variant being 2 times redder and 2.5 times less sexually dimorphic than homozygous individuals for the VV MC1R variant. These findings support that MC1R interacts with the expression of sexual dimorphism and suggest that a gene with major phenotypic effects and weakly influenced by variation in body condition can participate in sex-specific selection processes.
黑皮质素-1受体（MC1R）基因的变异会导致突然的、自然选择的毛色形态。如果一种形态在两性中是自然选择的，而另一种形态仅在两性中的一性中是自然选择或性选择的（例如为生殖期雌性提供伪装或为雄性提供交配优势），那么这些基因变异可能会对两性异形产生不同影响。因此，自然选择和性选择之间的平衡在MC1R变异之间可能会有所不同, 正如研究表明两性异形与MC1R处非同义与同义氨基酸替换率之间存在种间相关性所暗示的那样。令人惊讶的是，MC1R如何与种内两性异形相关，从而与性别特异性选择相关, 尚未得到研究。我们在仓鸮（Tyto alba）中解决了这个问题，仓鸮在基于红色褐黑素的着色程度以及黑色羽毛斑点的数量和大小方面表现出明显的变化。我们发现，第126位的缬氨酸（V）到异亮氨酸（I）取代解释了三种基于黑色素的颜色特征和羽毛黑色素含量中高达30%的变异。有趣的是，MC1R基因型在性颜色二态性程度上也有所不同，II MC1R变异纯合个体的红色程度是VV MC1R变异纯合个体的2倍，两性异形程度则低2.5倍。这些发现支持MC1R与两性异形的表达相互作用，并表明一个具有主要表型效应且受身体状况变化影响较小的基因可以参与性别特异性选择过程。
