Collaborative Research: Causes of Parallel Molecular Evolution

分子进化始于DNA的随机变化，但随后自然选择消除了一些变化，保留了其他变化。一个重要的问题是，不同物种如何适应类似的环境挑战;它们是通过对DNA进行相似还是不同的改变来适应？该项目将探讨进化的原因，并通过研究生活在安第斯山脉高海拔地区的鸟类及其生活在低海拔地区的近亲来预测进化变化的可能性。该项目将探索血红蛋白（血液中携带氧气的蛋白质）发生变化的方式，以使氧气在不同的大气条件下（高海拔和低海拔）吸收和释放。该项目将为博士后和研究生提供跨学科培训，并包括一个公共宣传部分，重点是“适应极端环境”，向小学生教授自然选择如何进化。所有数据和样本将链接到西南生物博物馆（美国）的标本券。新墨西哥州），并将通过一个开放获取的数据储存库访问。该项目旨在评估平行分子进化的普遍性，并通过检查独立定居在高海拔环境中的多个物种的血红蛋白（Hb）适应机制来测试关于其原因的假设。Hb功能的实验分析将用于识别和表征在安第斯山脉具有对比海拔范围限制的多种鸟类中Hb-O2亲和力进化变化的分子基础。比较将涉及多个同源复制的“分类对”（成对的同种种群或原产于高海拔或低海拔的密切相关的物种）。在高海拔和低海拔类群的功能不同的血红蛋白的情况下，通过多个氨基酸取代区分，定点诱变和祖先蛋白复活的组合将被用来检查在所有可能的途径，连接祖先（低亲和力）血红蛋白和衍生（高亲和力）血红蛋白的顺序突变步骤的功能效果。除了测量每种工程化Hb突变体的氧合性质之外，还将测量可以潜在地与Hb-O2亲和力折衷的另外的功能和结构性质。通过将定点诱变实验的结果与Hb功能的遗传复制变化相关联，这种蛋白质工程分析将阐明多效性限制在促进平行分子进化中的作用。

Molecular evolution starts from random changes in DNA, but then natural selection eliminates some of the changes and retains the others. An important question concerns the adaptation of different species to a similar environmental challenge; would they do it through similar or different changes to the DNA? This project will address the causes of evolution, and the possibility to predict evolutionary change by studying birds living at high altitude in the Andes, and their close relatives living at low altitudes. The project will explore the ways in which the hemoglobins (the oxygen carrying proteins of the blood) have changed to enable the uptake and release of oxygen under different atmospheric conditions (high and low altitude). This project will provide interdisciplinary training for postdoctoral and graduate students and includes a public outreach component that will focus on 'adaptation to extreme environments' to teach elementary school students how evolution by natural selection works. All data and samples will be linked to specimen-vouchers at the Museum of Southwestern Biology (U. New Mexico) and will be accessible through an open-access data repository. This project is designed to assess the pervasiveness of parallel molecular evolution and to test hypotheses about its causes by examining mechanisms of hemoglobin (Hb) adaptation in multiple species that have independently colonized high-altitude environments. Experimental analyses of Hb function will be used to identify and characterize the molecular basis of evolved changes in Hb-O2 affinity in multiple bird species that have contrasting altitudinal range limits in the Andes. The comparisons will involve multiple phylogenetically replicated 'taxon pairs' (pairs of conspecific populations or closely related species that are native to high- or low-altitude). In cases where functionally distinct Hbs of high- and low-altitude taxa are distinguished by multiple amino acid substitutions, a combination of site-directed mutagenesis and ancestral protein resurrection will be used to examine the functional effects of sequential mutational steps in all possible pathways that connect the ancestral (low-affinity) Hb and the derived (high-affinity) Hb. In addition to measuring oxygenation properties of each engineered Hb mutant, additional functional and structural properties that can potentially trade-off with Hb-O2 affinity will also be measured. By relating the results of the site-directed mutagenesis experiments to phylogenetically replicated changes in Hb function, this protein-engineering analysis will illuminate the role of pleiotropic constraints in promoting parallel molecular evolution.