Patterns of variation during adaptation in functionally linked loci

An understanding of the distribution of natural patterns of genetic variation is relevant to such fundamental biological fields as evolution and development. One recent approach to understanding such patterns has been to focus on the constraints which may arise as a function of the network or pathway context in which genes are embedded. Despite theoretical expectations of higher evolutionary constraint for genes encoding upstream versus downstream enzymes in metabolic pathways, empirical results have varied. Here we combine two complementary models from population genetics and enzyme kinetics to explore genetic variation as a function of pathway position when selection acts on whole-pathway flux. We are able to qualitatively reproduce empirically observed patterns of polymorphism and divergence and suggest that expectations should vary depending on the evolutionary trajectory of a population. Upstream genes are initially more polymorphic and diverge faster after an environmental change,...

对遗传变异自然模式分布的认知，与进化、发育等核心生物学分支紧密相关。当前理解此类模式的一种新近研究路径，聚焦于基因所处的网络或通路背景所催生的约束效应。尽管理论层面曾预测，代谢通路中编码上游酶的基因，其进化约束程度应高于下游酶编码基因，但相关实证研究结果却并不统一。本文结合种群遗传学（population genetics）与酶动力学（enzyme kinetics）中的两种互补模型，探讨了当选择作用于整条通路的代谢通量时，遗传变异随通路位置的变化规律。我们得以定性复现实证观测到的多态性（polymorphism）与分化（divergence）模式，并提出相关预期应随种群的进化轨迹而异：环境改变发生后，上游基因最初的多态性更高，且分化速率也更快……