Connections among Genotype, Phenotype and Fitness in Escherichia coli High Temperature Lines

要更好地理解进化遗传适应过程，必须在一定程度上依赖于更好地理解遗传变化如何与生物体结构和功能特征(表型)的变化相联系，从而提高繁殖成功率(即适应性)。然而，基因和表型之间的关系还不是很清楚，限制了对进化过程的理解。这项由该奖项资助的工作将以前所未有的规模调查大肠杆菌中的基因和表型之间的关系。通过人工选择实验，该细菌已在100多个重复种群中适应了一年的热应激(42.2℃)。每个种群的一个克隆已经通过基因组测序完成了基因分型。这笔赠款将表征这些复制群体的表型，然后将这些表型与已知的基因类型明确地联系起来。将被测量的表型包括基因表达模式和细胞代谢特征。特别令人感兴趣的是通过转录终止基因Rho或RNA聚合酶亚单位基因rpoB突变而适应的克隆之间的对比。这项工作将确定这些不同的遗传解决方案是否会导致表型上类似的功能变化，以及这两条适应途径是否相互排斥。为了解决后一个问题，Rho和rpoB的突变将被引入到单一的遗传背景中，而双突变体的进化适合度将在高温下确定。通过表征与适应相关的表型变化和遗传相互作用，这项工作将影响进化理论的核心，包括关于适应过程的经典观点。此外，该项目将继续一个成功的外展项目，将K-12教师引入实验室模块，以促进基于大肠杆菌模型的课堂上的“动手”进化论教学。

An improved understanding of the process of evolutionary genetic adaptation must rely in part on a better understanding of how genetic changes are linked to changes in structural and functional characteristics of organisms (phenotypes) that result in improved reproductive success (i.e., fitness). However, the relationship between genotype and phenotype is not well understood, limiting an understanding of the evolutionary process. The work funded by this award will investigate the relationship between genotype and phenotype on an unprecedented scale in the bacterium Escherichia coli. The bacterium has been adapted through artificial selection experiments to thermal stress (42.2 C) for one year in over 100 replicate populations. A clone from each population has been genotyped completely by genomic sequencing. This grant will characterize the phenotypes of these replicate populations and then relate these phenotypes explicitly to the known genotypes. The phenotypes that will be measured include patterns of gene expression and features of cell metabolism. Of particular interest will be a contrast between clones that adapted by mutations in either the transcriptional termination gene rho or the RNA polymerase subunit gene rpoB. The work will determine whether these different genetic solutions lead to similar functional changes in phenotypes and whether the two adaptive pathways are mutually exclusive. To address the latter issue, mutations of both rho and rpoB will be introduced into a single genetic background, and the evolutionary fitness of double mutants will be determined at high temperature. By characterizing both phenotypic changes and genetic interactions associated with adaptation, this work will impact the heart of evolutionary theory, including classical views on the adaptive process. In addition, this project will continue a successful outreach project that introduced K-12 teachers to lab modules that facilitate "hands on" teaching of evolution in the classroom, based on the E. coli model.