Autophagy is required for sulphur dioxide tolerance in S. cerevisiae

Abstract

Sulphur dioxide is used at several stages in winemaking, mainly as antioxidants and as antimicrobial, even before the onset of fermentation. Sulphites are also used as preservatives in many canned and processed foods. Its usefulness during wine fermentation depends on the relatively high tolerance to sulphites of wine strains of Saccharomyces cerevisiae. Sulphite tolerance in wine yeast strains has been related to mutations that boost transcription of SSU1, the gene coding for a plasma membrane sulphite pump required for efficient sulphite efflux. We used competition of bar-coded Yeast Knockout (YKO) collections to better understand microbial sulphite resistance, and sulphite cellular targets. Our results point to some of the cell functions that are more specifically required to survive sulphite-induced stress. For example, we found increased sulphite sensitivity for most KO strains involving genes required for autophagy, so pointing to this process as a key one in the detoxification of sulphite, probably through recycling of damaged proteins. In addition, some deletion strains, gained some competitiveness in the presence of sulphite (usually strains that were already impaired under standard growth conditions). These late functions are probably targets of sulphite (i.e. specifically sensitive to it).