title: Parallelism of amino acid changes at the RH1 affecting spectral sensitivity among deep-water cichlids from Lakes Tanganyika and Malawi.
abstract: Many examples of the appearance of similar traits in different lineages are known during the evolution of organisms. However, the underlying genetic mechanisms have been elucidated in very few cases. Here, we provide a clear example of evolutionary parallelism, involving changes in the same genetic pathway, providing functional adaptation of RH1 pigments to deep-water habitats during the adaptive radiation of East African cichlid fishes. We determined the RH1 sequences from 233 individual cichlids. The reconstruction of cichlid RH1 pigments with 11-cis-retinal from 28 sequences showed that the absorption spectra of the pigments of nine species were shifted toward blue, tuned by two particular amino acid replacements. These blue-shifted RH1 pigments might have evolved as adaptations to the deep-water photic environment. Phylogenetic evidence indicates that one of the replacements, A292S, has evolved several times independently, inducing similar functional change. The parallel evolution of the same mutation at the same amino acid position suggests that the number of genetic changes underlying the appearance of similar traits in cichlid diversification may be fewer than previously expected.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Sugawara
authors.forename: Yohey
authors.initials: Y
authors.lastname: Terai
authors.forename: Hiroo
authors.initials: H
authors.lastname: Imai
authors.forename: George F
authors.initials: GF
authors.lastname: Turner
authors.forename: Stephan
authors.initials: S
authors.lastname: Koblmüller
authors.forename: Christian
authors.initials: C
authors.lastname: Sturmbauer
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Shichida
authors.forename: Norihiro
authors.initials: N
authors.lastname: Okada
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology; D000349:Africa; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D016384:Consensus Sequence; D029941:Fish Proteins / Q000737:chemistry* / Q000235:genetics*; D005399:Fishes / Q000235:genetics / Q000502:physiology*; D005618:Fresh Water; D008295:Malawi; D008969:Molecular Sequence Data; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics / Q000502:physiology; D010860:Pigments, Biological / Q000737:chemistry* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013057:Spectrum Analysis
chemical_list: D029941:Fish Proteins; D010860:Pigments, Biological