title: Evolution of visual pigments and related molecules.
abstract: The molecular phylogenetic tree of vertebrate visual pigments, constructed on the basis of amino acid sequence identity, suggests that the visual pigments can be classified into five groups (L, ML, MS, S and Rh) and that their genes have evolved along these five gene lines. Goldfish has a UV-sensitive visual pigment (S group) localized in miniature single cone cells. Medaka has one type of rod cell containing rhodopsin (Rh group) and four types of cone cells, each of which contains a specific visual pigment with an absorption maximum that differs from those of the others. Frogs have a violet-sensitive visual pigment (S group) in small single cone cells and a blue-sensitive visual pigment (MS group) in green rod cells. Although nocturnal and diurnal geckos have rod- and cone-based retinas, respectively, they have phylogenetically closely related visual pigments. The pigments in each line may have restricted absorption maxima. We have cloned cDNAs encoding molecules involved in the phototransduction system of visual cells, such as phosphodiesterase, opsin kinase and arrestin. We then constructed phylogenetic trees of these molecules with the deduced amino acid sequences. The resulting phylogenetic trees show that these molecules are classified into two groups; one is expressed in cones and another in rods, suggesting that rods and cones contain homologous molecules with different amino acid sequences. These differences may result in the different light responses of rods and cones.
authors.affiliation: Department of Earth and Space Science, Graduate School of Science, Osaka University, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Tokunaga
authors.forename: O
authors.initials: O
authors.lastname: Hisatomi
authors.forename: T
authors.initials: T
authors.lastname: Satoh
authors.forename: Y
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: S
authors.initials: S
authors.lastname: Matsuda
authors.forename: Y
authors.initials: Y
authors.lastname: Imanishi
authors.forename: H
authors.initials: H
authors.lastname: Honkawa
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
authors.forename: Y
authors.initials: Y
authors.lastname: Tsukahara
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D006801:Humans; D010802:Phylogeny; D012168:Retinal Pigments / Q000145:classification* / Q000235:genetics*; D014785:Vision, Ocular / Q000502:physiology
chemical_list: D012168:Retinal Pigments