title: Genome duplication and mutations in ACE2 cause multicellular, fast-sedimenting phenotypes in evolved Saccharomyces cerevisiae.
abstract: Laboratory evolution of the yeast Saccharomyces cerevisiae in bioreactor batch cultures yielded variants that grow as multicellular, fast-sedimenting clusters. Knowledge of the molecular basis of this phenomenon may contribute to the understanding of natural evolution of multicellularity and to manipulating cell sedimentation in laboratory and industrial applications of S. cerevisiae. Multicellular, fast-sedimenting lineages obtained from a haploid S. cerevisiae strain in two independent evolution experiments were analyzed by whole genome resequencing. The two evolved cell lines showed different frameshift mutations in a stretch of eight adenosines in ACE2, which encodes a transcriptional regulator involved in cell cycle control and mother-daughter cell separation. Introduction of the two ace2 mutant alleles into the haploid parental strain led to slow-sedimenting cell clusters that consisted of just a few cells, thus representing only a partial reconstruction of the evolved phenotype. In addition to single-nucleotide mutations, a whole-genome duplication event had occurred in both evolved multicellular strains. Construction of a diploid reference strain with two mutant ace2 alleles led to complete reconstruction of the multicellular-fast sedimenting phenotype. This study shows that whole-genome duplication and a frameshift mutation in ACE2 are sufficient to generate a fast-sedimenting, multicellular phenotype in S. cerevisiae. The nature of the ace2 mutations and their occurrence in two independent evolution experiments encompassing fewer than 500 generations of selective growth suggest that switching between unicellular and multicellular phenotypes may be relevant for competitiveness of S. cerevisiae in natural environments.
authors.affiliation: Department of Biotechnology, Delft University of Technology, 2628 BC, Delft, The Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: Oud
authors.forename: Victor
authors.initials: V
authors.lastname: Guadalupe-Medina
authors.forename: Jurgen F
authors.initials: JF
authors.lastname: Nijkamp
authors.forename: Dick
authors.initials: D
authors.lastname: de Ridder
authors.forename: Jack T
authors.initials: JT
authors.lastname: Pronk
authors.forename: Antonius J A
authors.initials: AJ
authors.lastname: van Maris
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Daran
mesh_terms: D001557:Benzenesulfonates; D002688:Chitinases; D004268:DNA-Binding Proteins / Q000235:genetics*; D019020:Directed Molecular Evolution; D005434:Flow Cytometry; D016368:Frameshift Mutation / Q000235:genetics; D020440:Gene Duplication / Q000235:genetics*; D005818:Genetic Engineering / Q000379:methods*; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
chemical_list: C066778:ACE2 protein, S cerevisiae; D001557:Benzenesulfonates; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C007061:C.I. Fluorescent Brightening Agent 28; D002688:Chitinases
keywords: reverse engineering; whole genome sequencing