Adaptive evolution by mutations in the FLO11 gene
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas, Carretera de Utrera Km1, 41013 Sevilla, Spain
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Edited by Gregory A. Petsko, Brandeis University, Waltham, MA, and approved June 6, 2006 (received for review March 1, 2006)
Abstract
In nature, Saccharomyces yeasts manifest a number of adaptive responses to overcome adverse environments such as filamentation, invasive growth, flocculation and adherence to solid surfaces. Certain Saccharomyces wild 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 as FLO11, 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 the FLO11 gene. First, we identified a 111-nt deletion within a repression region of the FLO11 promoter that significantly increases FLO11 gene 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.
Footnotes
- †To whom correspondence should be addressed. E-mail: jjimmar{at}upo.es
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↵*Deceased, July 16, 2004.
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Author contributions: J.J. designed research; M.F., R.R.B., J.I.I., and J.J. performed research; M.F. and J.J. analyzed data; and J.J. wrote the paper.
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Conflict of interest statement: No conflicts declared.
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This paper was submitted directly (Track II) to the PNAS office.
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Data deposition: The sequence reported in this paper has been deposited in the EMBL database (accession no. AM262523).
- Abbreviations:
- YPD,
- yeast extract/peptone/dextrose.
Abbreviation:
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Freely available online through the PNAS open access option.
- © 2006 by The National Academy of Sciences of the USA
