摘要
In gnathostomes, chemosensory receptors (CR) expressed in olfactory epithelia are encoded by evolutionarily dynamic gene families encoding odorant receptors (OR), trace amine-associated receptors (TAAR), V1Rs and V2Rs. A limited number of OR-like sequences have been found in invertebrate chordate genomes. Whether these gene families arose in basal or advanced vertebrates has not been resolved because these families have not been examined systematically in agnathan genomes. Petromyzon is the only extant jawless vertebrate whose genome has been sequenced. Known to be exquisitely sensitive to several classes of odorants, lampreys detect fewer amino acids and steroids than teleosts. This reduced number of detectable odorants is indicative of reduced numbers of CR gene families or a reduced number of genes within CR families, or both, in the sea lamprey. In the lamprey genome we identified a repertoire of 59 intact single-exon CR genes, including 27 OR, 28 TAAR, and four V1R-like genes. These three CR families were expressed in the olfactory organ of both parasitic and adult life stages. An extensive search in the lamprey genome failed to identify potential orthologs or pseudogenes of the multi-exon V2R family that is greatly expanded in teleost genomes, but did find intact calcium-sensing receptors (CASR) and intact metabotropic glutamate receptors (MGR). We conclude that OR and V1R arose in chordates after the cephalochordate-urochordate split, but before the diversification of jawed and jawless vertebrates. The advent and diversification of V2R genes from glutamate receptor-family G protein-coupled receptors, most likely the CASR, occurred after the agnathan-gnathostome divergence.
摘要译文
在肠球菌中，通过编码气味受体（或），痕量胺相关受体（Taar），V1R和V2RS的进化动态基因家族，在嗅觉上皮细胞中表达的化学感应受体（Cr）编码。在无脊椎动物曲线基因组中发现了有限数量的或类似序列。这些基因家族是否在基础或晚期脊椎动物中出现并未解决，因为这些家庭尚未在酰野几何因中系统地检查。 Petromyzon是唯一只有其基因组的脊椎动物已经测序的唯一的脊椎动物。已知对几类气味剂敏感，Lampreys检测较少的氨基酸和类固醇。这种缩小的可检测的气味剂数表明在海参中减少了Cr基因家族的数量或Cr家族内的基因减少的基因数量。在Lamprepy Genom组中，我们鉴定了59个完整的单外显子Cr基因的再胃，包括27或，28幅和四个V1R样基因。这三个Cr家族在寄生和成年生命阶段的嗅觉器官中表达。在Lamprey基因组中进行了广泛的搜索，未能识别多外显然的V2R系列的潜在直脑或伪原，这些v2R系列在Textost基因组中大大扩展，但确实发现完整的钙传感受体（CasR）和完整的代谢谷氨酸受体（MGR）。我们得出结论，或者和V1R在Cephalochordate-Urochordate分裂后的脊索动物中出现，而是在多变和Jawless脊椎动物的多样化之前。从谷氨酸受体 - 家庭G蛋白偶联受体中的V2R基因的出现和多样化，最有可能是Casr，发生在酰脱肠道 - 肠道内的发散后发生。
Scot Libants; Kevin Carr; Hong Wu; John H Teeter; Yu-Wen Chung-Davidson; Ziping Zhang; Curt Wilkerson;Weiming Li. The sea lamprey Petromyzon marinusgenome reveals the early origin of several chemosensory receptor families in the vertebrate lineage[J]. BMC Ecology and Evolution, 2009,9