Résumé
Saccharomyces cerevisiae strains isolated from wine, rum, bread, or oak present a wide phenotypicdivergence (1, 3). Different genome sequencing programs by our group (2,3) and others (4) have offeredclues about the different mechanisms permitting the adaptation of yeast to wine environment. Copynumber variations, translocations, and horizontal transfers have been shown to participate in theadaptation of Saccharomyces cerevisiae to the grape must (3,5). In contrast to the flood of genomic data,we have very few experimental clues on how genetic variation participated in the evolution of wine yeast,and experimental evolution is the method of choice to investigate such questions. To understand howyeast adapted to the wine environment, we built 3 x 4 recombinant populations containing either winestrains, Mediterranean oak strains (as a grape must naive population), and strains from both origins.These three populations were grown, them for 24 fermentations in a Sauvignon grape must thatcontained assimilable nitrogen and sterol at a non-limiting concentrations. In addition, the potentialeffect of the grape must microbiota was evaluated through the addition of a synthetic microflore. Afterthe evolution, evolved strains were phenotyped for their ability to grow in the grape must and fermentand compared to the ancestral population. As expected, all populations performed better at the end ofthe experiment, and populations containing wine alleles outperformed the Mediterranean oakpopulations. The effect of the presence of a synthetic microflore could only be slightly observed on themaximum fermentation speed. The comparison of the genome of adapted populations to the ancestralpool, revealed shifts in allelic frequencies in regions associated to specific molecular functions or cellularcompartment in the three adapted lineages. However, mitochondrial genes were impacted in all adaptedlineages. Interestingly, when considering the Mediterranean oak/ wine populations, the genes SSU1 andECM34 involved in sulfite resistance (5) or MDS3 and GCN1 involved in nitrogen management (6) werefound to participate in the adaptation to the grape. This highlights the complexity of the adaptation tothe grape must.