Transcriptome analysis of wine yeast strains under sulphite-induced stress conditions

Sulphite is widely used in winemaking for its antimicrobial and antioxidant properties, although its toxic effect on human health is proven. For this reason strategies for reducing chemical preservatives in winemaking is strongly demanded. Wine yeasts can cope with SO2 by different systems, such as acetaldehyde production, sulphite uptake and reduction or SO2 export. The aim of this work was to study the genes involved in sulphites response in S. cerevisiae and see how different strains respond to SO2 addition in the early stage of fermentation. In this study 10 strains has been chosen among those whose genome has been sequenced: 6 commercial yeasts, EC1118, AWRI796, AWRI1631, VIN13, QA23, VL3, and 4 isolated directly from vineyard, R008, R103, P301, P283. The strain S288C was added to the analysis, as reference. Fermentation trials in synthetic must were conducted at laboratory scale to assess the main technological and quality traits and to investigate strain behaviours towards sulphite. The 4 strains showing the strongest differences in terms of response to SO2 were selected. To clarify the genetic basis of this complex enological trait we performed transcription profiling using SOLID technology. The analysis was conducted during fermentation process mimicking winemaking condition, in synthetic must supplemented with 25 mg/l of SO2 in 1l-capacity bioreactors. For all strains, fermentation rate was determined overall the process, together with sulphite and acetaldehyde production. RNA seq was performed at early exponential phase (6 g/l of CO2 produced) to investigate yeast adaptation under sulphite conditions. Gene expression analysis suggested that both specific gene activities and more general genetic pathways are involved in sulphite response.