Evolution of Avian Photopigments: From Sequences to Color Vision

描述（由申请人提供）：尽管是视觉科学的基础，但光色素光谱调谐的分子基础仍然知之甚少。由任何视蛋白残基取代引起的光谱位移取决于遗传背景，这意味着设计一个实验来阐明每个位置的视蛋白残基取代的功能后果是不可能的。另一方面，进化已经在视觉系统上进行了数百万年的实验，并提供了一个独特的机会来了解光谱变化是如何发生的。动物生活在非常多样化的光环境中，有些动物表现出惊人的色彩多样性。研究动物的视觉系统如何适应这种多变的条件，使得阐明包括人类在内的脊椎动物的视觉色素光谱调节成为可能（Yokoyama 1997; 2008）。与大多数哺乳动物不同，鸟类具有出色的色彩视觉，为揭示陆生脊椎动物视觉系统的多样性提供了最好的模型系统。然而，鸟类的视力仍未得到充分研究。该研究旨在评估近亲鸟类的视觉系统如何适应不同的条件和视觉刺激。15只新大陆鸣鸟视锥蛋白基因的完整编码序列表明，鸣鸟视蛋白存在着氨基酸差异。观察到的近80%的取代在结合袋内或邻近，因此有可能改变视蛋白的光谱灵敏度。这些位点突变的功能后果将通过在体外再生、表达和测量所有观察到的光色素变异的光谱灵敏度来评估。在研究了光谱调谐的分子机制之后，我们计划评估影响鸟类光色素进化的选择力。四面体色彩空间将用于评估观察到的莺的光色素差异如何转化为颜色感知和辨别的差异，以及它们与羽毛和栖息地特性的关系。这一分析还将检验每种物种的颜色视觉与进化后的羽毛特征之间可能存在的进化关系。该研究将填补我们对光色素光谱调谐的理解的重大空白，从而有助于我们目前对色觉的理解，包括人类色觉缺陷的分子基础。

DESCRIPTION (provided by applicant): Despite being fundamental to vision science, the molecular basis of photopigments' spectral tuning remains poorly understood. Spectral shifts caused by substitutions at any opsin residue depend on genetic background, which means that designing an experiment to elucidate the functional consequences of opsin residue substitutions at each position is impossible. Evolution, on the other hand, has been experimenting on visual systems for millions of years and offers a unique opportunity to understand how spectral shifts occur. Animals live in very diverse light environments and some exhibit a spectacular diversity of colors. Studying how animal visual systems adapt to such variable conditions makes it possible to elucidate visual pigments spectral tuning in vertebrates, including humans (Yokoyama 1997; 2008). Unlike most mammals, birds have excellent color vision, and provide the best model system for uncovering diversity in the visual system of terrestrial vertebrates. However, vision in birds remains understudied. The proposed research aims to evaluate how the visual systems of closely related species of birds have adapted to different conditions and visual stimuli. Complete coding sequences for all cone opsin genes in 15 New World warblers indicate there is substantial amino acid variation in warbler opsins. Nearly 80% of the observed substitutions are in, or adjacent to the binding pocket, and therefore, have the potential to alter the opsins' spectral sensitivity. The functional consequences of mutations at each of these sites will be assessed by regenerating, expressing and measuring the spectral sensitivity of all the observed photopigment variants in vitro. After studying the molecular mechanisms of spectral tuning, we plan to evaluate selective forces that have shaped the evolution of photopigments in birds. Tetrahedral color spaces will be used to evaluate how the observed differences in the photopigments of warblers translate into differences in color perception and discrimination, and how they relate to plumage and habitat properties. This analysis will also test for a possible evolutionary relationship between each species' color vision and the evolved plumage characteristics. The proposed research will fill a significant gap in our understanding of photopigment spectral tuning, thereby contributing to our current understanding of color vision, including the molecular basis of human color vision deficiencies. PUBLIC HEALTH RELEVANCE: Studying how vision evolves in organisms such as birds, is an important route towards improved understanding of human vision and vision deficiencies. Here, "natural experiments" provided by evolution, give us the opportunity to study the mechanisms of spectral tuning in visual pigments.