A sulphite-inducible form of the sulphite efflux gene SSU1 in a Saccharomyces cerevisiae wine yeast

Abstract

Sulphite is widely used as a preservative in foods and beverages for its antimicrobial and antioxidant activities, particularly in winemaking where SO2is frequently added. Thus, sulphite resistance mechanisms have been extensively studied in the fermenting yeastSaccharomyces cerevisiae.Sulphite detoxification, involving a plasma membrane protein encoded by theSSU1gene, is the most efficient resistance mechanism inS. cerevisiae.In this study, we characterized the unusual expression pattern ofSSU1in the wine strain 71B. We provide, for the first time, evidence ofSSU1induction by sulphite. The study ofSSU1expression during fermentation and in different growth conditions showed that sulphite is the main regulator ofSSU1expression, explaining its specific pattern. Combining analyses of gene expression and growth behaviour in response to sulphite, we found that 71B displayed unique behavioural patterns in response to sulphite pre-adaptation that may be explained by changes inSSU1expression. Examination of the genomic organization of theSSU1locus and sequencing of the region revealed three different alleles in 71B, two of which corresponded to translocated VIII–XVI forms. The lack of differences between promoter regions suggests that this inducibleSSU1expression pattern is due to modification of regulatory/signalling pathways.