Adaptive Evolution of Color Vision

描述（由申请人提供）：动物已经多样化并适应了地球上众多的栖息地和环境。我们研究的长期目标是阐明在分子和功能水平上驱动这些适应性变化的机制。我们计划使用视觉作为模型系统来完成这个目标。为了确定改变视觉色素最大吸收波长的关键氨基酸（AA）变化，视觉科学家分析了“当代”色素。实验进化生物学家也操纵“当代”色素，推断过去。然而，忽视视觉色素的进化过程，既不能阐明视觉色素光谱调谐的分子基础，也不能阐明视觉色素的进化机制。幸运的是，光转导和进化生物学中悬而未决的核心问题可以通过基因工程和操纵适当的“祖先色素”来同时解决。在此，我们建议阐明驱动脊椎动物RH2、SWS1和SWS2色素适应性进化的分子机制，这些色素具有；最大波长分别为~450 ~ 530 nm、~355 ~ 440 nm和~400 ~ 460 nm。我们不仅通过确定视色素光谱调谐的分子基础，而且通过建立具有不同视色素组的生物体与其生态环境之间的关系来解决这个问题。对于每个色素类群，我们计划：1)推断出~15种祖先色素的AA序列，并对其进行工程改造，确定它们的归属；最大值，2)推断出AA的变化使；max, 3)通过突变祖先色素确定关键的AA变化；4)利用量子力学/分子力学（QM/MM）方法建立视觉色素光谱调谐的普遍化学原理，这些方法已被证明是非常有效的。我们还将测试这些视觉色素的适应性进化的可能性，通过检查方向是否；不同物种视色素的最大位移与生物生态环境的变化相匹配。为此，三种色素基团各带可变；多个物种中的max将根据它们所处的环境被划分为不同的类别，并测试适应性进化的可能性。由于迄今为止检测到的几乎所有鱼类SWS1色素都对紫外线敏感，我们还计划通过调查生活在0-200米深处的鱼类，寻找对紫外线敏感的SWS1色素，这些鱼类以小鱼为食，不需要紫外线视觉进行狩猎。考虑到SWS1色素中发生的强AA相互作用，我们还计划阐明在其进化过程中如何积累各种关键的AA变化，并了解紫外线色素对紫外线敏感所需的化学结构前提条件，反之亦然。

DESCRIPTION (provided by applicant): Animals have diversified and adapted to fill the numerous habitats and environments on this earth. The long-term goal of our studies is to elucidate mechanisms that drive these adaptive changes at the molecular and functional levels. We plan to accomplish this goal using vision as a model system. To identify critical amino acid (AA) changes that modify the wavelengths of maximal absorption (;maxs) of visual pigments, vision scientists analyze "contemporary" pigments. Experimental evolutionary biologists also manipulate "contemporary" pigments and infer the past. However, by ignoring the evolutionary processes of visual pigments, neither the molecular basis of spectral tuning in visual pigments nor the evolutionary mechanisms of visual pigments can be elucidated. Fortunately, the central unanswered questions in phototransduction and evolutionary biology can be solved simultaneously by genetically engineering and manipulating proper "ancestral pigments." Here, we propose to elucidate the molecular mechanisms that drive adaptive evolution of RH2, SWS1, and SWS2 pigments in vertebrates, which have ;maxs of ~450-530, ~355-440, and ~400-460 nm, respectively. We approach the problem not only by determining the molecular basis of spectral tuning in visual pigments but also by establishing the relationships between organisms with different sets of visual pigments and their ecological environments. For each pigment group, we plan to 1) infer the AA sequences of ~15 ancestral pigments and engineer them and determine their ;maxs, 2) infer AA changes that shift the ;max, 3) identify the critical AA changes by mutating ancestral pigments, and 4) establish the universal chemical principle of the spectral tuning in visual pigments by using the quantum mechanical/molecular mechanical (QM/MM) methods, which have been proven to be highly effective. We shall also test the possibility of adaptive evolution of these visual pigments by examining whether the directions of the ;max-shifts of visual pigments in various species match with the changes in the organisms' ecological environments. For this purpose, each of the three pigment groups with variable ;maxs in multiple species will be classified into distinct classes according to their environments and tested for the possibility of adaptive evolution. Since virtually all fish SWS1 pigments examined to date are UV-sensitive, we also plan to search for violet-sensitive SWS1 pigments in different fishes, by surveying fishes that live at depths of 0-200 m and prey on small fishes and do not require UV vision for hunting. Considering the strong AA interactions that occur in SWS1 pigments, we also plan to elucidate how various critical AA changes could have accumulated during its evolution and learn the chemical structural preconditions required for UV pigments to become violet-sensitive and vice versa.