the evolution of gene expression qtl in saccharomyces cerevisiae在酿酒酵母基因表达qtl的进化.pdf

The Evolution of Gene Expression QTL in Saccharomyces cerevisiae James Ronald, Joshua M. Akey* Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America Understanding the evolutionary forces that influence patterns of gene expression variation will provide insights into the mechanisms of evolutionary change and the molecular basis of phenotypic diversity. To date, studies of gene expression evolution have primarily been made by analyzing how gene expression levels vary within and between species. However, the fundamental unit of heritable variation in transcript abundance is the underlying regulatory allele, and as a result it is necessary to understand gene expression evolution at the level of DNA sequence variation. Here we describe the evolutionary forces shaping patterns of genetic variation for 1206 cis-regulatory QTL identified in a cross between two divergent strains of Saccharomyces cerevisiae. We demonstrate that purifying selection against mildly deleterious alleles is the dominant force governing cis-regulatory evolution in S. cerevisiae and estimate the strength of selection. We also find that essential genes and genes with larger codon bias are subject to slightly stronger cis-regulatory constraint and that positive selection has played a role in the evolution of major trans-acting QTL. Citation: Ronald J, Akey JM (2007) The Evolution of Gene Expression QTL in Saccharomyces cerevisiae. PLoS ONE 2(8): e678. doi:10.1371/ journal.pone.0000678 INTRODUCTION RESULTS Gene expression is the primary intermediate between information Genomic distribution of regulatory QTL encoded by the genome and higher order phenotypes, and as In segregants derived from a cross betwee