Saccharomyces cerevisiae strain:ICV GRE Genome sequencing. Saccharomyces cerevisiae strain:ICV GRE

The wine industry needs better-adapted yeasts to grow at low temperature because it is interested in fermenting at low temperature to improve wine aroma. Elucidating the response to cold in Saccharomyces cerevisiae is of paramount importance for the selection or genetic improvement of wine strains. We followed a global approach by comparing transcriptomic, proteomic and genomic changes in two commercial wine strains, which showed clear differences in their growth and fermentation capacity at low temperature. These strains were selected according to the maximum growth rate in a synthetic grape must during miniaturized batch cultures at different temperatures. The fitness differences of the selected strains were corroborated by directly competing during fermentations at optimum and low temperatures. The up-regulation of the genes of the sulfur assimilation pathway and glutathione biosynthesis evidenced a crucial role in better performance at low temperature. The presence of some metabolites of these pathways, such as S-Adenosilmethionine (SAM) and glutathione, counteracted the differences in growth rate at low temperature in both strains. Generally, the proteomic and genomic changes observed in both strains also supported the importance of these metabolic pathways in adaptation at low temperature. This work reveals a novel role of the sulfur assimilation pathway in adaptation at low temperature. We propose that a greater activation of this metabolic route enhances the synthesis of key metabolites, such as glutathione, whose protective effects can contribute to improve the fermentation process.

葡萄酒工业亟需适配低温生长的酵母菌株，因行业期望通过低温发酵提升葡萄酒香气品质。解析酿酒酵母（Saccharomyces cerevisiae）的低温应答机制，对于葡萄酒酵母菌株的筛选与遗传改良至关重要。本研究采用全局分析策略，对比了两株商业葡萄酒酵母在不同温度下的转录组、蛋白质组与基因组变化——这两株菌株在低温环境下的生长与发酵能力存在显著差异。上述菌株是根据不同温度下微型分批培养体系中合成葡萄汁内的最大生长速率筛选得到的。通过在最适温度与低温发酵条件下开展竞争性培养实验，验证了所选菌株的适应性差异。硫同化途径（sulfur assimilation pathway）与谷胱甘肽生物合成（glutathione biosynthesis）相关基因的上调表达，证明了这两条途径在菌株低温下的优良发酵表现中发挥关键作用。添加该途径的部分代谢物（如S-腺苷甲硫氨酸（S-Adenosilmethionine，SAM）与谷胱甘肽），可抵消两株菌株在低温下的生长速率差异。总体而言，两株菌株的蛋白质组与基因组变化也进一步佐证了上述代谢途径在低温适应中的重要性。本研究揭示了硫同化途径在低温适应中的全新功能，我们提出，该代谢通路的更强激活可促进谷胱甘肽等关键代谢物的合成，其保护性作用有助于优化发酵过程。