UCD School of Biology and Environmental Science and UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland.
Genome Res. 2010 Jan;20(1):1-9. doi: 10.1101/gr.099416.109. Epub 2009 Dec 1.
The ability to smell is governed by the largest gene family in mammalian genomes, the olfactory receptor (OR) genes. Although these genes are well annotated in the finished human and mouse genomes, we still do not understand which receptors bind specific odorants or how they fully function. Previous comparative studies have been taxonomically limited and mostly focused on the percentage of OR pseudogenes within species. No study has investigated the adaptive changes of functional OR gene families across phylogenetically and ecologically diverse mammals. To determine the extent to which OR gene repertoires have been influenced by habitat, sensory specialization, and other ecological traits, to better understand the functional importance of specific OR gene families and thus the odorants they bind, we compared the functional OR gene repertoires from 50 mammalian genomes. We amplified more than 2000 OR genes in aquatic, semi-aquatic, and flying mammals and coupled these data with 48,000 OR genes from mostly terrestrial mammals, extracted from genomic projects. Phylogenomic, Bayesian assignment, and principle component analyses partitioned species by ecotype (aquatic, semi-aquatic, terrestrial, flying) rather than phylogenetic relatedness, and identified OR families important for each habitat. Functional OR gene repertoires were reduced independently in the multiple origins of aquatic mammals and were significantly divergent in bats. We reject recent neutralist views of olfactory subgenome evolution and correlate specific OR gene families with physiological requirements, a preliminary step toward unraveling the relationship between specific odors and respective OR gene families.
嗅觉能力受哺乳动物基因组中最大的基因家族——嗅觉受体 (OR) 基因调控。尽管这些基因在人类和小鼠的完成基因组中得到了很好的注释，但我们仍然不知道哪些受体结合特定的气味，或者它们如何完全发挥作用。以前的比较研究在分类学上受到限制，主要集中在物种内 OR 假基因的百分比上。没有研究调查过功能 OR 基因家族在系统发育和生态上多样化的哺乳动物中的适应性变化。为了确定 OR 基因库在多大程度上受到栖息地、感觉特化和其他生态特征的影响，从而更好地理解特定 OR 基因家族的功能重要性，以及它们结合的气味，我们比较了 50 种哺乳动物的功能性 OR 基因库。我们在水生、半水生和飞行哺乳动物中扩增了 2000 多个 OR 基因，并将这些数据与来自大多数陆生哺乳动物的 48000 个 OR 基因结合，这些基因是从基因组项目中提取的。系统基因组学、贝叶斯分配和主成分分析将物种按生态型（水生、半水生、陆生、飞行）进行分区，而不是按系统发育关系进行分区，并确定了对每种栖息地重要的 OR 家族。水生哺乳动物的多个起源独立地减少了功能性 OR 基因库，而蝙蝠的 OR 基因库则有显著的差异。我们拒绝了嗅觉亚基因组进化的近期中立主义观点，并将特定的 OR 基因家族与生理需求相关联，这是揭示特定气味与相应 OR 基因家族之间关系的初步步骤。
