RPG: Molecular Evolution of Gene Transcription in Evolved Strains of Yeast

生物自然群体中基因调控的差异可能是自然选择过程中遗传变异的最重要来源。本研究的目的是研究基因调控的一个分子方面，即基因转录，以响应正选择、中性突变和纯化选择。在葡萄糖有限的环境中，参与葡萄糖代谢的基因受到强烈的选择，而参与半乳糖代谢的基因则不被使用。增强葡萄糖利用的正选择可能导致参与半乳糖代谢的基因活性增加，从而导致这些基因的半乳糖诱导性丧失。在这种环境下，唯一的氮源是硫酸铵，酵母必须代谢所有的氨基酸。氨基酸代谢基因对细胞生长至关重要，其调控受到纯化选择的影响。提出的工作的第一个目标是评估积极选择对其产物参与葡萄糖代谢的基因的转录调控的影响；中性突变对半乳糖代谢相关基因诱导性的影响，以及纯化选择对氨基酸合成相关基因转录调控的影响。第二个目标是确定基因启动子区域的核苷酸序列差异是否可以解释转录差异。

9408317 Brown Differences in gene regulation in natural populations of organisms may serve as the most important source of genetic variation for the process of natural selection. The purpose of the proposed research is to investigate one of the molecular aspects of gene regulation, namely gene transcription, in response to positive selection, neutral mutation, and purifying selection. In a glucose-limited environment, genes engaged in glucose metabolism are under strong selection, and the genes for galactose metabolism are not used. Positive selection for enhanced glucose utilization may lead to increased activity of genes involved in galactose metabolism leading to the loss of galactose inducibility in these genes. In this environment, the sole nitrogen source is ammonium sulfate, and yeast must metabolize all amino acids. Genes for amino acid metabolism are critically important for cell growth, and their regulation is subject to purifying selection. The first objective of the proposed work is to assess the effect of positive selection on transcriptional regulation of genes whose products are involved in glucose metabolism; the effect of neutral mutations on the inducibility of genes whose products are involved in galactose metabolism, and the effect of purifying selection on the transcriptional regulation of genes involved in amino acid synthesis. The second objective is to determine whether nucleotide sequence differences in the promoter regions of genes may account for the transcriptional differences.