title: Multiple episodic evolution events in V1R receptor genes of East-African cichlids.
abstract: Fish use olfaction to detect a variety of nonvolatile chemical signals, and thus, this sense is key to survival and communication. However, the contribution of the olfactory sense to social-especially reproductive-interactions in cichlids is still controversial. To obtain insights into this issue, we investigated the genes encoding V1Rs-possible candidates for reproductive pheromone receptors-among East-African cichlids. Interestingly, we found an excess of nonsynonymous over synonymous substitutions in four of six V1R genes in multiple cichlid lineages. First, we found that highly dimorphic V1R2 allele groups were shared among the cichlids inhabiting all East-African Great Lakes emerged through the episodic accumulation of the nonsynonymous substitutions prior to the radiation of the Lake Tanganyika species flock. We further detected such episodic events in V1R1 of the tribe Tropheini, and in V1R3 and V1R6 of the tribe Trematocarini. The excess of nonsynonymous substitutions in these examples were indicated as dN/dS > 1, which were all statistically significant by Fisher's exact test. Furthermore, we speculate that the amino acid changes in these episodic events are likely functional switch because they occurred in the putative ligand-binding pocket. Our finding of the occurrence of multiple episodic events and the unexpected gene diversity in one unique gene family is suggestive of the contribution of the V1R to the species diversification and the social interaction in cichlids.
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Nikaido
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Ota
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hirata
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Hikoyu
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Biosystems Science, School of Advanced Sciences, The Graduate University for Advanced Studies (Sokendai), Hayama, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Satta
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, JapanFoundation for Advancement of International Science, Tsukuba, Japan.
authors.forename: Mitsuto
authors.initials: M
authors.lastname: Aibara
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, JapanTanzania Fisheries Research Institute, Dar es Salaam, Tanzania.
authors.forename: Semvua I
authors.initials: SI
authors.lastname: Mzighani
authors.affiliation: Department of Zoology, Karl-Franzens-University Graz, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Sturmbauer
authors.affiliation: Department of Dementia and Higher Brain Function, Integrated Neuroscience Research Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Kimiko
authors.initials: K
authors.lastname: Hagino-Yamagishi
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, JapanFoundation for Advancement of International Science, Tsukuba, JapanDepartment of Life Sciences, National Cheng Kung University, Tainan, Taiwan nokada@fais.or.jp.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Okada
mesh_terms: D000351:Africa, Eastern; D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D005075:Biological Evolution; D023681:Cichlids / Q000235:genetics*; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics*; D005828:Genetics, Population; D060106:Lakes; D008969:Molecular Sequence Data; D010802:Phylogeny; D043563:Receptors, Pheromone / Q000235:genetics
chemical_list: D029941:Fish Proteins; D043563:Receptors, Pheromone
keywords: accelerated evolution; chemo-detection; dN/dS