Genome Evolution in Polar Fishes

生活在南极和北极严酷、低于冰点的水域中的鱼类提供了适应极端环境的有趣例子。两极的物种都独立进化出了应对持续寒冷温度的方法，包括抗冻蛋白的进化。在冷冻条件下，这些化合物会附着在冰晶上并阻止其生长。这会降低组织冰点并减少动物受伤或死亡的机会。虽然极地水域生存所需的独特适应能力似乎会减少这些栖息地的物种多样性，但最近的证据表明，与温暖水域中的鱼类相比，极地环境中的鱼类的物种形成率更高。尽管事实上寒冷的温度会减缓细胞过程，人们预计这会降低这些物种的分子进化速率。为了确定海洋鱼类中物种形成速率和分子进化之间的关系，该项目将比较多种极地和非极地鱼类的基因组。通过这样做，它将（1）阐明极地环境中进化速率如何变化，（2）确定塑造极地鱼类适应轨迹的总体趋势，以及（3）确定功能差异如何塑造新型化合物的进化，例如一些极地鱼类赖以生存的抗冻蛋白。除了培训新一代科学家外，该项目还将开发小学和本科科学课程的课程和外展活动。材料将在美国西部各地的教室中提供，重点是农村学校，作为促进农村社区进化教育网络的一部分。为了更好地了解极地鱼类的生物学和抗冻蛋白（AFP）的进化，本研究将从基因型和表型背景上比较适应寒冷的生物体与相关非极地物种的进化史。在此过程中，这项研究将测试极地环境中的进化速度是否会减慢，这可能是由于细胞过程的限制。它还将评估积极选择和放松选择对基因和途径的影响，这两者似乎都是适应极地环​​境的关键适应性策略。为了解决极端适应发生的具体机制，研究人员将确定温度和溶解氧的全局梯度如何塑造基因组变异并影响多种鳗鱼（鳝科）的适应轨迹。然后将使用体外实验方法来测试有关拷贝数变异在 AFP 进化中的作用的功能假设，以及多种抗冻蛋白亚型的进化方式和原因。 通过比较多种极地和非极地鱼类的基因组，该项目将阐明极地环境中进化速率的变化，确定塑造冷适应海洋鱼类适应轨迹的总体趋势，并确定功能差异如何塑造新型蛋白质的进化。该项目的战略规划目标是更好地了解生物体适应当前环境的遗传基础，以及极地鱼类在不同进化时间尺度上对变化条件做出反应的方式。该项目由地球科学局极地项目办公室的南极生物和生态系统项目以及生物科学局分子和细胞生物科学部的分子生物物理学项目共同资助。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，认为值得支持。

Fish that reside in the harsh, subfreezing waters of the Antarctic and Arctic provide fascinating examples of adaptation to extreme environments. Species at both poles have independently evolved ways to deal with constant cold temperature, including the evolution of antifreeze proteins. Under freezing conditions, these compounds attach to ice crystals and prevent their growth. This lowers the tissue freezing point and reduces the chance the animal will be injured or killed. While it might seem that the need for unique adaptations to survive in polar waters would reduce species diversity in these habitats, recent evidence showed higher speciation rates in fishes from polar environments as compared to those found in warmer waters. This is despite the fact cold temperatures slow cellular processes, which had been expected to lower rates of molecular evolution in these species. To determine how rates of speciation and molecular evolution are linked in marine fishes, this project will compare the genomes of multiple polar and non-polar fishes. By doing so, it will (1) clarify how rates of evolution vary in polar environments, (2) identify general trends that shape the adaptive trajectories of polar fishes, and (3) determine how functional differences shape the evolution of novel compounds such as the antifreeze proteins some polar fishes rely upon to survive. In addition to training a new generation of scientists, the project will develop curriculum and outreach activities for elementary and undergraduate science courses. Materials will be delivered in classrooms across the western United States, with a focus on rural schools as part of a network for promoting evolutionary education in rural communities.To better understand the biology of polar fishes and the evolution of antifreeze proteins (AFPs), this research will compare the evolutionary histories of cold-adapted organisms to those of related non-polar species from both a genotypic and phenotypic context. In doing so, this research will test whether evolutionary rates are slowed in polar environments, perhaps due to constraints on cellular processes. It will also evaluate the effects of positive selection and the relaxation of selection on genes and pathways, both of which appear to be key adaptive strategies involved in the adaptation to polar environments. To address specific mechanisms by which extreme adaptation occurs, researchers will determine how global gradients of temperature and dissolved oxygen shape genome variation and influence adaptive trajectories among multiple species of eelpouts (family Zoarcidae). An in-vitro experimental approach will then be used to test functional hypotheses about the role of copy number variation in AFP evolution, and how and why multiple antifreeze protein isoforms have evolved. By comparing the genomes of multiple polar and non-polar fishes, the project will clarify how rates of evolution vary in polar environments, identify general trends that shape the adaptive trajectories of cold-adapted marine fishes, and determine how functional differences shape the evolution of novel proteins. This project addresses the strategic programmatic aim to provide a better understanding of the genetic underpinnings of organismal adaptations to their current environment and ways in which polar fishes may respond to changing conditions over different evolutionary time scales. The project is jointly funded by the Antarctic Organisms and Ecosystems Program in the Office of Polar Programs of the Geosciences Directorate, and the Molecular Biophysics Program of the Division of Molecular and Cellular Biosciences in the Biological Sciences Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.