EVOLUTIONARY GENETICS OF VERTEBRATE VISION

视觉通过配偶选择和觅食策略等基本行为影响生物的生存，对生物的进化有着深远的影响。本研究的长期目标是阐明视觉中最基本分子视觉色素的结构-功能关系的进化变化。这篇论文的重点是考虑到1)红色和绿色（红/绿）色觉，2)紫外线（UV）视觉，以及3)视色素的棒状和锥状特异性的适应进化的分子基础。色觉和光感受器细胞特异性分别用最大吸收波长（λ max）和视觉色素的再生和分解速率来表征。利用金鱼（C. auratus）、山羊（C. hircus）、白尾鹿（O. virginianus）、欧洲兔（O. cuniculus）、大鼠（R. norvegicus）、灰松鼠（S. carolinensis）、豚鼠（C. porcellus）和灵长类动物的红/绿光谱，研究红/绿视觉适应进化的遗传学和分子基础。利用金鱼、美洲变色龙（A. carolinensis）、波多黎各蜥蜴（A. cristatellus和A. gundlachi）、Tokay壁虎（G. gekko）、鸽子（C. livia）、鸡（G. gallus）、大鼠和小鼠（M. musculus）的UV视蛋白，研究其λ max值在360 ~ 420 nm之间的遗传和适应进化。对于这两种分析，我们将首先预测可能导致视觉色素λ最大位移的潜在重要氨基酸变化。野生型和突变型视蛋白，通过定点突变或嵌合形式获得，将在培养的COS1细胞中表达，并与11-顺式视网膜重组。评估所得色素的λ max值，我们将研究氨基酸变化对λ max移位的影响。通过对美洲变色龙和Tokay壁虎视觉色素再生速率和羟胺敏感性的研究，我们还将研究视觉色素光感受器特异性的分子机制以及视觉色素对纯杆和纯锥环境的适应过程。

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.