Genome-Wide Study of the Adaptation of Saccharomyces cerevisiae to the Early Stages of Wine Fermentation

Abstract

This work was designed to identify yeast cellular functions specifically affected by the stress factors predominating during the early stages of wine fermentation, and genes required for optimal growth under these conditions. The main experimental method was quantitative fitness analysis by means of competition experiments in continuous culture of whole genome barcoded yeast knockout collections. This methodology allowed the identification of haploinsufficient genes, and homozygous deletions resulting in growth impairment in synthetic must. However, genes identified as haploproficient, or homozygous deletions resulting in fitness advantage, were of little predictive power concerning optimal growth in this medium. The relevance of these functions for enological performance of yeast was assessed in batch cultures with single strains. Previous studies addressing yeast adaptation to winemaking conditions by quantitative fitness analysis were not specifically focused on the proliferative stages. In some instances our results highlight the importance of genes not previously linked to winemaking. In other cases they are complementary to those reported in previous studies concerning, for example, the relevance of some genes involved in vacuolar, peroxisomal, or ribosomal functions. Our results indicate that adaptation to the quickly changing growth conditions during grape must fermentation require the function of different gene sets in different moments of the process. Transport processes and glucose signaling seem to be negatively affected by the stress factors encountered by yeast in synthetic must. Vacuolar activity is important for continued growth during the transition to stationary phase. Finally, reduced biogenesis of peroxisomes also seems to be advantageous. However, in contrast to what was described for later stages, reduced protein synthesis is not advantageous for the early (proliferative) stages of the fermentation process. Finally, we found adenine and lysine to be in short supply for yeast growth in some natural grape musts.

Genomic expression program of Saccharomyces cerevisiae along a mixed-culture wine fermentation with Hanseniaspora guilliermondii

“…In the mixed-culture fermentation, the over-representation of these “stress-responsive” regulons was considerably less prominent, suggesting that the environment of the mixed fermentation could be less stressful for S. cerevisiae cells than the environment of the single-culture fermentation, as discussed above. Significantly, Sko1, Hot1 and Skn7, three of the stress-responsive factors that emerged from our analysis, are all known to be become activated upon phosphorylation by the Hog1 kinase [ 36 ], which was found to play an essential role in S. cerevisiae ability to ferment grape-juice medium [ 37 ]. Several positive regulators of pseudohyphal growth were also found to be over-represented in the dataset of genes up-regulated throughout the single and mixed-culture fermentations, albeit in this last dataset the enrichment is less pronounced (Fig.…”

Population Structure and Comparative Genome Hybridization of European Flor Yeast Reveal a Unique Group of Saccharomyces cerevisiae Strains with Few Gene Duplications in Their Genome

“…MCH2 is a putative monocarboxylic acid transporter with homology with mammalian transporters, although its involvement in monocarboxylic acid transport has not been shown experimentally [62] . Nonetheless, a recent study showed that this gene is important for yeast survival during the second phase of alcoholic fermentation (during alcohol accumulation) [63] . In addition, Zara et al found that succinic, lactic and acetic acids could not provide consistent growth as a sole carbon source under aging conditions [64] .…”

Evolution unscathed:Darwin Devolvesargues on weak reasoning that unguided evolution is a destructive force, incapable of innovation

“…; Novo et al. ). It is important to point out that these mutations are often pleiotropic (Qian et al.…”