Résumé
During alcoholic fermentation, Saccharomyces cerevisiae requires S-containing amino acids, that it producesthrough the sulfur assimilation pathway (SAP). In this pathway, S. cerevisiae reduces sulfate into sulfur dioxide(SO₂) and sulfide (H₂S), whose overproduction is a major issue in winemaking due to its negative impact onwine aroma. The amount of H₂S produced is very strain-specific and depends as well on the SO₂ concentration, which is often added in winemaking. First, we set up a quantitative method to measure the H₂S produced during alcoholic fermentation and evaluated this production for 34 strains isolated from wine, flor or oak.Large differences between strains were detected, and strains carrying a specific allele of SKP2 (SKP2-JN10),an allelic variant related to low H₂S and SO₂ excretion (1), were identified as low producers. However, whenexposed to SO2, several strains carrying the SKP2-JN10 allele produce H₂S again. In order to decipher thegenetic bases of the H₂S production in the presence of SO₂, we used a Quantitative Trait Locus (QTL) mapping strategy using a Bulk Segregant Analysis (BSA). We crossed a moderate H₂S producer strain carrying SKP2- JN10 allele, with a strain that produced very little H₂S in the presence of SO₂. A progeny of 96 of segregants was obtained and phenotyped for sulfide production. The comparison of the genome of a pool of segregants producing high H₂S with the pool of non-producers pointed out to several genome regions possibly involved in the variations of H₂S production. We are studying the role of a number of candidate genes and we expect that this approach will provide novel targets for the breeding wine yeast starters.1 - Noble et al. 2015 Microbiol cell factory 14:68