Differential regulation by glucose and fructose of a gene encoding a specific fructose/H+ symporter in Saccharomyces sensu stricto yeasts.
Saccharomyces cerevisiae transports fructose through a facilitated diffusion system common to other hexoses and mediated by the Hxt proteins. The related species S. pastorianus (carlsbergensis) and S. bayanus produce, in addition, a specific fructose/H(+) symporter. We have previously cloned a gene (FSY1) encoding the active fructose symporter from S. pastorianus PYCC 4457. Expression of Fsy1p in a S. cerevisiae mutant (hxt-null) devoid of the facilitated diffusion system allows growth on fructose but not on glucose. Here we present results concerning the regulation of Fsy1p expression, both in S. pastorianus and S. bayanus, where it occurs naturally, and in suitably engineered S. cerevisiae transformants. To that purpose, we made use of both Northern blot analysis and a Fsy1p-GFP fusion protein. The expression of Fsy1p is strongly regulated by both the carbon source and its concentration in the growth medium. In S. pastorianus, as well as in S. bayanus, very low concentrations of either fructose or glucose induced expression but higher sugar concentrations prevented transcription of the gene. Glucose was considerably more effective than fructose in repressing FSY1 expression. Proper regulation of the gene in S. cerevisiae seems to be exquisitely dependent on sugar transport. Analysis of Fsy1 expression in S. cerevisiae mutants shows that repression is mainly dependent on Mig1p, the final effector of the main glucose repression pathway. Interestingly, Mig1p also seems to mediate repression of FSY1 expression by high maltose concentrations.
Rodrigues de Sousa
Helena
H
Centro de Recursos Microbiológicos (CREM), Biotechnology Unit, Faculty of Sciences and Technology, New University of Lisbon, 2829-516 Caparica, Portugal.
Spencer-Martins
Isabel
I
Gonçalves
Paula
P
D001692:Biological Transport / Q000502:physiology; D015152:Blotting, Northern; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D005632:Fructose / Q000378:metabolism*; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000737:chemistry / Q000235:genetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D016254:Mutagenesis, Insertional; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D012440:Saccharomyces / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013050:Spectrometry, Fluorescence
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C414489:FSY1 protein, Saccharomyces pastorianus; D005656:Fungal Proteins; D008164:Luminescent Proteins; C085976:MIG1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D005632:Fructose; D005947:Glucose