Piezophilic adaptation in deep sea amphipods

深海（2000米以下）是地球上最后的生态边界。它占海洋生物圈的近86%，但我们对在那里生活和繁衍的生物知之甚少。工程技术的最新发展使我们能够在马里亚纳海沟底部近11000米深的地方开始探索和采样海洋。这让我们对在海洋最深处发现的生物有了更深入的了解，但这些生物是如何在巨大的压力下生存下来的仍然是一个很大的未知数，否则这些压力会损害或阻止许多基本的细胞过程。显然，深海生物一定积累了大量的进化适应能力，这意味着它们的生物化学不会像陆地或浅水物种那样受到压力的影响。这个项目的根本目的是确定这些适应是什么。高压对生化过程的攻击的“前线”是RNA分子，它携带着生物体一生必须制造的所有蛋白质的“蓝图”，也直接参与蛋白质的构建。我们认为深海生物已经适应了高压，因为它们拥有一套结构更稳定的RNA分子，同样，当它们形成时，它们编码的蛋白质也具有更高的稳定性。我们可以通过比较占据整个海洋深度范围的生物体中许多不同基因的核苷酸序列来验证这些想法。我们将集中在一组世界性的片脚甲壳类动物，它们出现在所有的海洋和所有的深度。我们项目的独特之处在于，我们已经收集了进行这种分析所需的样本，这是一项重要的任务，否则将非常昂贵和耗时。我们预测，我们将看到许多基因上的选择特征，这些基因有助于在更深处发生的片足类物种的生化反应，并表明压力将限制通过突变改变序列的能力。此外，我们期望看到更深层次物种的RNA序列通常具有更高的稳定性，因为它们具有更高比例的更稳定的构建块。我们也将超越仅仅看RNA序列，还将研究这些分子的3D结构。我们再次预测，在更深层次的物种中，RNA分子会倾向于形成某些构象（称为发夹），并且RNA分子中会有一些构建块，它们就像桥梁一样，在我们所研究的不同的片脚类物种中，维持结构的保守性。总的来说，这个项目可以提供一些进化过程的第一个见解，这些进化过程定义了哪些物种存在于深海中，反过来解释了为什么有些物种不存在。这可以告诉我们很多关于控制生物在地球上和不同栖息地的空间分布的规则，并提供一些关于不同地区的群落如何受到不断变化的环境影响的信息。

The deep ocean (below 2000m) represents the last ecological frontier on the planet. It accounts for >86% of the ocean biosphere, yet we know remarkably little about the organisms that live and thrive there. Recent developments in engineering technology has allowed us to begin to explore and sample the oceans right down to full ocean depth at close to 11000 metres at the bottom of the Mariana Trench. This has given us a lot of insight into what organisms are found at the deepest depths of our oceans, but what is still a big unknown is how these organisms can survive the crushing pressures that should otherwise compromise, or indeed prevent, many basic cellular processes. Clearly, deep ocean organisms must have accumulated a number of evolutionary adaptations that means their biochemistry is not affected in the same way by pressure as terrestrial or shallow water species. It is the underlying aim of this project to identify what these adaptations are. The "front line" of attack by high pressure on biochemical processes is on the RNA molecules that carry the "blueprint" for all of the proteins that an organism must make throughout life, and are also directly involved in protein construction. We think that deep ocean organisms have adapted to high pressures by having a suite of RNA molecules that are structurally more stable, and likewise code for proteins with a higher stability when they form. We can test these ideas by comparing the nucleotide sequences of lots of different genes in organisms that occupy the full range of ocean depths. We will focus on a group of cosmopolitan amphipod crustaceans that occur in all the oceans and at all depths. What is unique about our project is we have already collected the samples we need to undertake this type of analysis, which is a non-trivial task and would otherwise be preclusively expensive and time-consuming.We predict we will see the signatures of selection operating on lots of genes that help chaperone biochemical reactions in those amphipod species occurring at deeper depth, and suggest that pressure will constrain the ability to change sequence through mutation. Moreover we expect to see that the RNA sequences in deeper species generally have a higher stability by having a higher ratio of the more stable building blocks. We will also move beyond just looking at RNA sequence and also examine the 3D structures these molecules make. Again we predict there are certain conformations that the RNA molecules will tend to form (termed hairpins) in the deeper species, and there will some building blocks in the RNA molecules that act like bridge keystones for maintaining structure that will be conserved across the different amphipod species we are examining.Overall, this project can provide the first insights into some of the evolutionary processes that define which species are present in the deep sea, and conversely explain why some species are absent. This can tell us a lot about the rules that govern the spatial distribution of organisms across the planet and in different habitats, and provide some information about how communities in different areas will be affected by a changing environment.