Résumé
Background: In conditions of nitrogen limitation, Saccharomyces cerevisiae strains differ in their fermentationcapacities, due to differences in their nitrogen requirements. The mechanisms ensuring the maintenance ofglycolytic flux in these conditions are unknown. We investigated the genetic basis of these differences, bystudying quantitative trait loci (QTL) in a population of 133 individuals from the F2 segregant populationgenerated from a cross between two strains with different nitrogen requirements for efficient fermentation.Results: By comparing two bulks of segregants with low and high nitrogen requirements, we detected fourregions making a quantitative contribution to these traits. We identified four polymorphic genes, in three of thesefour regions, for which involvement in the phenotype was validated by hemizygote comparison. The functions ofthe four validated genes, GCN1, MDS3, ARG81 and BIO3, relate to key roles in nitrogen metabolism and signaling,helping to maintain fermentation performance.Conclusions: This study reveals that differences in nitrogen requirement between yeast strains results from acomplex allelic combination. The identification of three genes involved in sensing and signaling nitrogen andspecially one from the TOR pathway as affecting nitrogen requirements suggests a role for this pathway inregulating the fermentation rate in starvation through unknown mechanisms linking nitrogen signaling toglycolytic flux.