Mechanism of resistance to sulphite in Saccharomyces cerevisiae

Growth inhibition and cell killing caused by sulphite were reduced in seven Saccharomyces cerevisiae sulphite-resistant independent mutants, compared to their parental strains. Genetic analysis showed that in the seven mutants resistance was inherited as a single-gene dominant mutation and that all the analyzed mutations were allelic, thus identifying a major gene responsible for sulphite resistance in S. cerevisiae. Two of the mutants, MBS20-9 and MBS30, were further characterized. 35S-sulphite uptake experiments showed that the ability to accumulate sulphite was markedly reduced in the two resistant strains. No difference between resistant and sensitive strains with respect to glyceraldehyde-3-phosphate dehydrogenase sensitivity to sulphite, or to intracellular glutathione content, were revealed. In contrast, the extracellular acetaldehyde concentration was higher in the resistant mutants, both in the presence and in the absence of sulphite.