title: Color vision of ancestral organisms of higher primates.
abstract: The color vision of mammals is controlled by photosensitive proteins called opsins. Most mammals have dichromatic color vision, but hominoids and Old World (OW) monkeys enjoy trichromatic vision, having the blue-, green-, and red-sensitive opsin genes. Most New World (NW) monkeys are either dichromatic or trichromatic, depending on the sex and genotype. Trichromacy in higher primates is believed to have evolved to facilitate the detection of yellow and red fruits against dappled foliage, but the process of evolutionary change from dichromacy to trichromacy is not well understood. Using the parsimony and the newly developed Bayesian methods, we inferred the amino acid sequences of opsins of ancestral organisms of higher primates. The results suggest that the ancestors of OW and NW monkeys lacked the green gene and that the green gene later evolved from the red gene. The fact that the red/green opsin gene has survived the long nocturnal stage of mammalian evolution and that it is under strong purifying selection in organisms that live in dark environments suggests that this gene has another important function in addition to color vision, probably the control of circadian rhythms.
authors.affiliation: Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park 16802, USA. nxm2@psu.edu
authors.forename: M
authors.initials: M
authors.lastname: Nei
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics; D003118:Color Perception / Q000502:physiology*; D005399:Fishes / Q000502:physiology; D000882:Haplorhini / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D011323:Primates / Q000235:genetics* / Q000502:physiology; D017299:Rod Opsins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D017386:Sequence Homology, Amino Acid
chemical_list: D017299:Rod Opsins; C095855:long-wavelength opsin; C095854:middle-wavelength opsin