Müller Lena, Grath Sonja, von Heckel Korbinian, Parsch John
Department of Biology II, University of Munich (LMU), 82152 Planegg-Martinsried, Germany.
Int J Evol Biol. 2012;2012:963976. doi: 10.1155/2012/963976. Epub 2012 Jan 12.
Genes with sexually dimorphic expression (sex-biased genes) often evolve rapidly and are thought to make an important contribution to reproductive isolation between species. We examined the molecular evolution of sex-biased genes in Drosophila melanogaster and D. ananassae, which represent two independent lineages within the melanogaster group. We find that strong purifying selection limits protein sequence variation within species, but that a considerable fraction of divergence between species can be attributed to positive selection. In D. melanogaster, the proportion of adaptive substitutions between species is greatest for male-biased genes and is especially high for those on the X chromosome. In contrast, male-biased genes do not show unusually high variation within or between populations. A similar pattern is seen at the level of gene expression, where sex-biased genes show high expression divergence between species, but low divergence between populations. In D. ananassae, there is no increased rate of adaptation of male-biased genes, suggesting that the type or strength of selection acting on sex-biased genes differs between lineages.
具有性别二态性表达的基因（性别偏向基因）通常进化迅速，被认为对物种间的生殖隔离有重要贡献。我们研究了黑腹果蝇和拟果蝇中性别偏向基因的分子进化，它们代表了黑腹果蝇组内的两个独立谱系。我们发现，强烈的纯化选择限制了物种内的蛋白质序列变异，但物种间相当一部分的差异可归因于正选择。在黑腹果蝇中，物种间适应性替换的比例在雄性偏向基因中最大，在X染色体上的那些基因中尤其高。相比之下，雄性偏向基因在种群内或种群间并未表现出异常高的变异。在基因表达水平上也观察到类似模式，即性别偏向基因在物种间表现出高表达差异，但在种群间差异较低。在拟果蝇中，雄性偏向基因的适应率没有增加，这表明作用于性别偏向基因的选择类型或强度在不同谱系间有所不同。
