Systematic changes in gene expression patterns following adaptive evolution in yeast

Culturing a population of Saccharomyces cerevisiae for many generations und er conditions to which it is not optimally adapted selects for fitter genet ic variants, This simple experimental design provides a tractable model of adaptive evolution under natural selection. Beginning,vith a clonal, foundi ng population, independently evolved strains were obtained from three indep endent cultures after continuous aerobic growth in glucose-limited chemosta ts for more than 250 generations. DNA microarrays were used to compare geno me-wide patterns of gene expression in the evolved strains and the parental strain. Several hundred genes were found to have significantly altered exp ression in the evolved strains, Many of these genes showed similar alterati ons in their expression in all three evolved strains, Genes with altered ex pression in the three evolved strains included genes involved in glycolysis , the tricarboxylic acid cycle, oxidative phosphorylation, and metabolite t ransport. These results are consistent with physiological observations and indicate that increased fitness is acquired by altering regulation of centr al metabolism such that less glucose is fermented and more glucose is compl etely oxidized.