Sulphite tolerance requires proper autophagic function in Saccharomyces cerevisiae

Abstract

Sulphur dioxide (often dosed as bisulphite salts) has had widespread use in winemaking for centuries. It is used at several stages of the process, and for several purposes, mainly as antioxidants and as antimicrobials, 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 industrial wine strains of the yeast Saccharomyces cerevisiae. Sulphite tolerance of these yeast strains is related to mutations that promote high level transcription of SSU1, the gene coding for a plasma membrane sulphite pump required for efficient sulphite efflux.

This work was designed, in order to better understand sulphite cellular targets in yeast, as well as microbial sulphite resistance.

By competition of bar-coded Yeast Knockout (YKO) collections we have identified some of the cell functions that are more specifically required in order to survive sulphite insult.

Our results show 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. Conversely, some deletion yeast strains, that were impaired under no-stressed conditions, recovered some competitiveness in the presence of sulphite. These functions are probably specifically sensitive to sulphite, so that already defective strains do not suffer from an additional impairment in the presence of sulphite.