RT Journal Article SR Electronic T1 Divergent MLS1 promoters lie on a fitness plateau for gene expression JF bioRxiv FD Cold Spring Harbor Laboratory SP 026427 DO 10.1101/026427 A1 Andrew C. Bergen A1 Gerilyn M. Olsen A1 Justin C. Fay YR 2015 UL http://biorxiv.org/content/early/2015/09/09/026427.abstract AB Qualitative patterns of gene activation and repression are often conserved despite an abundance of quantitative variation in expression levels within and between species. A major challenge to interpreting patterns of expression divergence is knowing which changes in gene expression affect fitness. To characterize the fitness effects of gene expression divergence we placed orthologous promoters from eight yeast species upstream of malate synthase (MLS1) in Saccharomyces cerevisiae. As expected, we found these promoters varied in their expression level under activated and repressed conditions as well as in their dynamic response following loss of glucose repression. Despite these differences, only a single promoter driving near basal levels of expression caused a detectable loss of fitness. We conclude that the MLS1 promoter lies on a fitness plateau whereby even large changes in gene expression can be tolerated without a substantial loss of fitness.