Abstract
Nitrogen composition of the grape must has an impact on yeast growth and fermentation kinetics as well as on the organoleptic properties of the final product. In some technological processes, such as white wine/rosé winemaking, the yeast-assimilable nitrogen content is sometimes insufficient to cover yeast requirements, which can lead to slow or sluggish fermentations. Growth is nevertheless quickly restored upon relief from nutrient starvation, e.g.through the addition of ammonium nitrogen, allowing fermentation completion. The aim of this study was to determine how nitrogen repletion affected the genomic cell response of a Saccharomyces cerevisiae wine yeast strain, in particular within the first hour after nitrogen addition. We found almost 4000 genes induced or repressed, sometimes within minutes after nutrient changes. Some of the transcriptional responses to nitrogen depended on the TOR pathway, which controls positively ribosomal protein genes, amino acid and purine biosynthesis or amino acid permease genes and negatively stress-response genes, RTG specific TCA cycle genes and NCR sensitive genes. Some unexpected transcriptional responses concerned all the glycolytic genes, the starch and glucose metabolism and citrate cycle-related genes that were down-regulated, as well as genes from the lipid metabolism.
