QTL mapping of variation in H2S production

Saccharomyces cerevisiae's requirement of reduced sulfur to synthesise methionine and cysteine during alcoholic fermentation, is mainly fulfilled through the sulfur assimilation 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 on wine aroma. The amount of H2S produced is highly strain-specific and depends as well on the SO2 concentration, often added to the grape must. Applying a Bulk Segregant Analysis to a 96 strain-progeny derived from two strains with different ability to produce H2S, and comparing the allelic frequencies along the genome of pools of segregants producing opposite H2S quantities, we identified two causative regions involved in H2S production in the presence of SO2. A functional genetic analysis allowed the identification of variants in four genes: ZWF1, ZRT2, SNR2 and YLR125W, able to impact H2S formation, involved in functions and pathways until now not associated with sulfur metabolism. This data points that redox status and zinc homeostasis are linked to H2S formation in wine fermentation conditions and provides new insights into the regulation of H2S production during wine fermentation, giving a new vision of the interplay of sulfur assimilation pathway and cell metabolism.