EVOLUTIONARY GENETICS OF VERTEBRATE VISION

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Vision has profound effects on evolution of organisms by affecting survivorship through such basic behaviors as mate choice and foraging strategies. The long-term goal of the proposed research is to elucidate evolutionary changes of the structure-function relationships of the most basic molecules in vision, visual pigments. This proposal focuses on the molecular bases of adaptive evolution considering l) red and green (red/green) color vision, 2) ultraviolet (UV) vision, and 3) rod- and cone- specificities of visual pigments. Color vision and the photoreceptor cell specificity are characterized by using wavelength of maximal absorptions (lambda max) and rates of regeneration and decomposition of visual pigments, respectively. The genetics and molecular bases of adaptive evolution of red/green color vision will be studied using the red and green opsins of goldfish (C. auratus), goat (C. hircus), white-tailed deer (O. virginianus), European rabbit (O. cuniculus), rat (R. norvegicus), gray squirrel (S. carolinensis), guinea pig (C. porcellus), and primates that represent the entire red/green spectra at approximately 510-560 nm. The genetics and adaptive evolution of UV vision will be studied by using UV opsins of goldfish, American chameleon (A. carolinensis), Puerto Rican lizards (A. cristatellus and A. gundlachi), Tokay gecko (G. gekko), pigeon (C. livia), chicken (G. gallus), rat, and mouse (M. musculus), whose lambda max values range from 360 to 420 nm. For both analyses, we will first predict potentially important amino acid changes that may cause lambda max-shifts of the visual pigments. Wild type and mutant opsins, derived by site-directed mutagenesis or in chimeric forms, will be expressed in cultured COS1 cells, and reconstituted with 11-cis retinal. Evaluating lambda max values of the resulting pigments, we will study the effects of amino acid changes on the lambda max-shifts. Studying rates of regeneration and hydroxylamine sensitivities of visual pigments of American chameleon and Tokay gecko, we will also study the molecular mechanisms responsible not only for photoreceptor specificities of visual pigments but also for adaptive processes of visual pigments to the pure-rod and pure cone environments.