Distinct evolutionary patterns between chemoreceptors of 2 vertebrate olfactory systems and the differential tuning hypothesis
Distinct evolutionary patterns between chemoreceptors of 2 vertebrate olfactory systems and the differential tuning hypothesis
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DOI：
10.1093/molbev/msn107
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发表时间：
2008-08-01
影响因子：
10.7
通讯作者：
Zhang, Jianzhi
中科院分区：
文献类型：
--
作者：
Grus, Wendy E.;Zhang, Jianzhi
大多数四足动物有两个嗅觉系统，主要嗅觉系统（MOS）和犁鼻系统（VNS）。根据双嗅觉假说，MOS检测环境气味，而VNS识别种内信息素线索。然而，这种严格的功能区别已经被最近的报道所模糊，这两种系统都可以感知两种类型的信号。对有限数量的受体的研究表明，MOS受体是广泛调谐的通才，而VNS受体是狭窄调谐的专家。然而，这种区别是否适用于所有MOS和VNS受体仍然未知。差分调谐假说预测，多面手MOS受体检测一组重叠的配体，因此更有可能是保守的进化时间比专业VNS受体，这将在一个更谱系特异性的方式演变。在这里，我们测试这一预测所有嗅觉化学感受器的进化模式的MOS表达的气味受体（OR）和微量胺相关受体（TAAR）和VNS表达犁鼻1型受体（V1 Rs）和犁鼻2型受体（V2 Rs）在7个四足动物（小鼠，大鼠，狗，负鼠，鸭嘴兽，鸡，青蛙）。V1 Rs和V2 Rs的同源性显示出丰富的谱系特异性基因获得/丢失，并且在物种之间几乎没有一对一的直系同源物。相反的模式被发现为OR和TAAR。功能数据和OR的配体结合位点的分析证实，旁系同源化学感受器比直系同源物更可能具有不同的配体，并且旁系同源化学感受器之间的功能分歧在基因复制后相对较快地建立。总之，这些结果强烈表明，VNS化学感受器库的功能配置文件比MOS化学感受器库的发展快得多，并且差分调谐假设适用于大多数，如果不是全部的MOS和VNS受体。
Most tetrapod vertebrates have 2 olfactory systems, the main olfactory system (MOS) and the vomeronasal system (VNS). According to the dual olfactory hypothesis, the MOS detects environmental odorants, whereas the VNS recognizes intraspecific pheromonal cues. However, this strict functional distinction has been blurred by recent reports that both systems can perceive both types of signals. Studies of a limited number of receptors suggest that MOS receptors are broadly tuned generalists, whereas VNS receptors are narrowly tuned specialists. However, whether this distinction applies to all MOS and VNS receptors remains unknown. The differential tuning hypothesis predicts that generalist MOS receptors detect an overlapping set of ligands and thus are more likely to be conserved over evolutionary time than specialist VNS receptors, which would evolve in a more lineage-specific manner. Here we test this prediction for all olfactory chemoreceptors by examining the evolutionary patterns of MOS-expressed odorant receptors (ORs) and trace amine-associated receptors (TAARs) and VNS-expressed vomeronasal type 1 receptors (V1Rs) and vomeronasal type 2 receptors (V2Rs) in 7 tetrapods (mouse, rat, dog, opossum, platypus, chicken, and frog). The phylogenies of V1Rs and V2Rs show abundant lineage-specific gene gains/losses and virtually no one-to-one orthologs between species. Opposite patterns are found for ORs and TAARs. Analysis of functional data and ligand-binding sites of ORs confirms that paralogous chemoreceptors are more likely than orthologs to have different ligands and that functional divergence between paralogous chemoreceptors is established relatively quickly following gene duplication. Together, these results strongly suggest that the functional profile of the VNS chemoreceptor repertoire evolves much faster than that of the MOS chemoreceptor repertoire and that the differential tuning hypothesis applies to the majority, if not all, of MOS and VNS receptors.