title: Molecular basis of fructose utilization by the wine yeast Saccharomyces cerevisiae: a mutated HXT3 allele enhances fructose fermentation.
abstract: Fructose utilization by wine yeasts is critically important for the maintenance of a high fermentation rate at the end of alcoholic fermentation. A Saccharomyces cerevisiae wine yeast able to ferment grape must sugars to dryness was found to have a high fructose utilization capacity. We investigated the molecular basis of this enhanced fructose utilization capacity by studying the properties of several hexose transporter (HXT) genes. We found that this wine yeast harbored a mutated HXT3 allele. A functional analysis of this mutated allele was performed by examining expression in an hxt1-7Delta strain. Expression of the mutated allele alone was found to be sufficient for producing an increase in fructose utilization during fermentation similar to that observed in the commercial wine yeast. This work provides the first demonstration that the pattern of fructose utilization during wine fermentation can be altered by expression of a mutated hexose transporter in a wine yeast. We also found that the glycolytic flux could be increased by overexpression of the mutant transporter gene, with no effect on fructose utilization. Our data demonstrate that the Hxt3 hexose transporter plays a key role in determining the glucose/fructose utilization ratio during fermentation.
authors.affiliation: Equipe de Microbiologie, UMR Sciences pour l'Oenologie, INRA-ENSAM-UMI, 2 place Viala, F-34060 Montpellier cedex 1, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Guillaume
authors.forename: Pierre
authors.initials: P
authors.lastname: Delobel
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Sablayrolles
authors.forename: Bruno
authors.initials: B
authors.lastname: Blondin
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D003001:Cloning, Molecular; D005632:Fructose / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D051246:Glucose Transport Proteins, Facilitative; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D051246:Glucose Transport Proteins, Facilitative; C090595:HXT3 protein, S cerevisiae; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D002245:Carbon Dioxide; D005632:Fructose