Directed evolution for cell separation in budding yeast

Abstract

AbstractHaploid and diploid natural isolates of the yeastSaccharomyces cerevisiaewere evolved under a daily transfer protocol that selected against clumpy growth and for cell separation. For the haploid populations, whole genome sequencing revealed strong selection to deactivateAMN1, a known regulator of cell separation, recapitulating evolution that likely occurred during the domestication of common lab strains. We also observed multiple mutational hits to the Rim101 pathway, which was not expected. Mutations to bothAMN1and the Rim101 pathway were strongly associated with cell separation. In the diploid populations, we observed the parallel emergence of a large partial deletion of chrIII, the so-called Hawthorn’s deletion. We show that this deletion is associated with reduced clumpy growth. The mechanism by which Hawthorne’s deletion affects cell separation is unknown but may be related to an effect on budding pattern.