Effects of The Rate of Environmental Change on Mutational Patterns and Evolutionary Constraints

项目总结 人们必须能够适应可能突然发生变化的环境条件 (在一代人之内)或逐渐(跨越多代人)。理论模型预测 环境变化速度的这些差异将从根本上影响 以及修复的突变的影响大小，但很少有研究对遗传学进行机械性检查 适应随着时间推移而变得更有压力的环境。此外，理论上的 模型并不总是能解释引入进化约束的众所周知的现象， 如基因与环境(GxE)的相互作用和多效性。这项研究的目标是 比较突发性事件下RNA病毒基因组进化模式和突变的影响 或逐渐的环境变化，并使用这些数据来评估 适应以不同速度变化的环境。该工程采用耐高温材料 模型噬菌体ɸ6囊状病毒的群体，以前是通过 病毒种群暴露在热休克温度下的进化实验 要么逐渐增加(逐渐增加)，要么突然增加(突然增加)。这里, 我们建议使用这些群体来检查突变固定的模式并表征 GxE相互作用和多效性在以不同速度变化的环境中的作用。 具体地说，我们将1)评估突变的数量、它们的固定时间和单倍型 突发性和渐进性种群的多样性；以及2)衡量顺序突变的影响 从选定的谱系对病毒热稳定性和生长速度的影响，并将这些影响与 世系经历的环境变化的速度。我们的研究将针对中央 进化生物学中关于选择强度和节奏的变化如何影响的问题 适应，并将阐明适应的机制基础在不同的比率 环境变化。确立在变革中发挥作用的选择压力和制约因素 环境将给我们提供预测或控制病毒进化的工具。

PROJECT SUMMARY Populations must be able to adapt in environmental conditions that may change either suddenly (within one generation) or gradually (over multiple generations). Theoretical models predict that these differences in the rate of environmental change will fundamentally influence the number and effect sizes of mutations that fix, but few studies have mechanistically examined the genetics of adaptation in environments that become more stressful over time. Moreover, the theoretical models do not always account for well-known phenomena that introduce evolutionary constraints, such as genotype by environment (GxE) interactions and pleiotropy. The goal of this research is to compare patterns of genome evolution and effects of mutations in RNA viruses under sudden or gradual environmental change, and to use these data to evaluate theoretical models of adaptation in environments that change at different rates. The project uses temperature-resistant populations of the model bacteriophage ɸ6 Cystovirus that were previously generated through an evolution experiment in which viral populations were exposed to a heat shock temperature that was increased either gradually (Gradual populations) or suddenly (Sudden populations). Here, we propose to use these populations to examine patterns of mutation fixation and to characterize the role of GxE interactions and pleiotropy in environments that change at different rates. Specifically, we will 1) evaluate the number of mutations, their times to fixation, and haplotype diversity of Sudden and Gradual populations; and 2) measure the effects of sequential mutations from select lineages on both viral thermostability and growth rate, and correlate those effects with the rate of environmental change experienced by the lineage. Our study will address the central question in evolutionary biology of how changes to the strength and tempo of selection influence adaptation, and will illuminate the mechanistic underpinnings of adaptation in different rates of environmental change. Establishing the selective pressures and constraints at play in changing environments will give us tools to predict or control viral evolution.