Grant: Discovery Grants Program - Individual

Wine strains of S. cerevisiae have developed complex regulatory mechanisms to cope with high initial sugar concentrations, depleting nutrients, and gradually increasing ethanol concentrations in fermenting grape juice. The molecular and cellular adaptations of industrial wine yeasts to these long-term environmental stresses during grape must fermentation have not been well studied. To investigate how yeast adapts to the harsh conditions during the fermentation of grape must, genome-wide transcription was assayed at five time points during alcoholic fermentation. For each gene, the temporal trend throughout the fermentation process was summarized with two parameter values that describe the overall change and shape of the expression profile. A seeded clustering algorithm was applied in order to group the genes around the expression patterns exhibited by 20 genes whose temporal trends span the range of patterns observed across the entire transcriptome. Analyses of the yeast transcriptome throughout wine fermentations revealed that 40% of the yeast genome significantly changed expression levels to mediate long-term adaptation to fermentation stress; 223 genes were dramatically induced at various points during fermentation and were designated as Fermentation Stress Response (FSR) genes. The FSR is novel and 62% of the genes involved have not been implicated in global stress responses; 28% of the FSR genes have no functional annotation. Functional analyses of these 62 non-annotated FSR genes are in currently in progress. In addition, we found 20 non-annotated genes that were significantly down-regulated and 31 non-annotated genes that were significantly up-regulated during wine fermentations. In this grant application we will construct null mutants of all 51 non-annotated genes and use a systems biology approach, transcriptomics, proteomics and metabolomics, to establish functions of these non-annotated genes that are regulated during wine fermentations.