Adaptive evolution by mutations in theFLO11gene

• DOI: 10.1073/pnas.0601713103
• Publication Date: 2006-07-15T01:55:46Z
• Authors: Manuel Fidalgo; Ramon R. Barrales; Jose I. Ibeas; Juan Jimenez
• Keywords: 0301 basic medicine; Membrane Glycoproteins; Saccharomyces cerevisiae Proteins; Base Sequence; Models, Genetic; Cell Membrane; Molecular Sequence Data; Genetic Variation; Membrane Proteins; Evolution, Molecular; Saccharomyces; 03 medical and health sciences; Adaptive mechanisms; Buoyant biofilm; Yeast hydrophobicity; Biofilms; Mutation; Promoter Regions, Genetic; Alleles

In nature,Saccharomycesyeasts manifest a number of adaptive responses to overcome adverse environments such as filamentation, invasive growth, flocculation and adherence to solid surfaces. CertainSaccharomyceswild yeasts, namely “flor yeasts,” have also acquired the ability to form a buoyant biofilm at the broth surface. Here we report that mutations in a single gene, identified asFLO11, separate these “floating” yeasts from their nonfloating relatives. We have determined that the capability to form a self-supporting biofilm at the liquid surface is largely dependent on two changes in theFLO11gene. First, we identified a 111-nt deletion within a repression region of theFLO11promoter that significantly increasesFLO11gene expression. Secondly, we found rearrangements within the central tandem repeat domain of the coding region that yield a more hydrophobic Flo11p variant. Together, these mutations result in dramatic increase in cell surface hydrophobicity, which in turn confers these yeasts the ability to float by surface tension, an adaptive mechanism to gain direct access to oxygen within oxygen-poor liquid environments.