Departamento de Ecología, Genética y Evolución; Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires; Argentina.
Evol Bioinform Online. 2012;8:89-104. doi: 10.4137/EBO.S8484. Epub 2012 Jan 9.
Previous comparative genomic studies of genes involved in olfactory behavior in Drosophila focused only on particular gene families such as odorant receptor and/or odorant binding proteins. However, olfactory behavior has a complex genetic architecture that is orchestrated by many interacting genes. In this paper, we present a comparative genomic study of olfactory behavior in Drosophila including an extended set of genes known to affect olfactory behavior. We took advantage of the recent burst of whole genome sequences and the development of powerful statistical tools to analyze genomic data and test evolutionary and functional hypotheses of olfactory genes in the six species of the Drosophila melanogaster species group for which whole genome sequences are available. Our study reveals widespread purifying selection and limited incidence of positive selection on olfactory genes. We show that the pace of evolution of olfactory genes is mostly independent of the life cycle stage, and of the number of life cycle stages, in which they participate in olfaction. However, we detected a relationship between evolutionary rates and the position that the gene products occupy in the olfactory system, genes occupying central positions tend to be more constrained than peripheral genes. Finally, we demonstrate that specialization to one host does not seem to be associated with bursts of adaptive evolution in olfactory genes in D. sechellia and D. erecta, the two specialists species analyzed, but rather different lineages have idiosyncratic evolutionary histories in which both historical and ecological factors have been involved.
先前关于果蝇嗅觉行为相关基因的比较基因组学研究仅集中于特定的基因家族，如气味受体和/或气味结合蛋白。然而，嗅觉行为具有复杂的遗传结构，由许多相互作用的基因来调控。在本文中，我们对果蝇的嗅觉行为进行了比较基因组学研究，包括了一套扩展的已知影响嗅觉行为的基因。我们利用最近爆发的全基因组序列和强大的统计工具来分析基因组数据，并测试了在具有全基因组序列的黑腹果蝇种系的六个物种中，嗅觉基因的进化和功能假说。我们的研究揭示了嗅觉基因广泛存在纯化选择，而正选择的发生率有限。我们表明，嗅觉基因的进化速度主要与生命周期阶段和它们参与嗅觉的生命周期阶段数量无关。然而，我们检测到基因产物在嗅觉系统中的位置与进化速度之间存在关系，占据中心位置的基因比外围基因受到更多的约束。最后，我们证明，专一性地适应一个宿主似乎与 D. sechellia 和 D. erecta 这两个专化种的嗅觉基因的适应性进化爆发无关，而是不同的进化枝具有独特的进化历史，其中涉及到历史和生态因素。
