Résumé
Background: The volatile metabolites produced by Saccharomyces cerevisiae
during alcoholic fermentation, which are mainly esters, higher alcohols
and organic acids, play a vital role in the quality and perception of
fermented beverages, such as wine. Although the metabolic pathways and
genes behind yeast fermentative aroma formation are well described, little
is known about the genetic mechanisms underlying variations between
strains in the production of these aroma compounds. To increase our
knowledge about the links between genetic variation and volatile
production, we performed quantitative trait locus (QTL) mapping using 130
F2-meiotic segregants from two S. cerevisiae wine strains. The segregants
were individually genotyped by next-generation sequencing and separately
phenotyped during wine fermentation. Results: Using different QTL mapping
strategies, we were able to identify 65 QTLs in the genome, including 55
that influence the formation of 30 volatile secondary metabolites, 14 with
an effect on sugar consumption and central carbon metabolite production,
and 7 influencing fermentation parameters. For ethyl lactate, ethyl
octanoate and propanol formation, we discovered 2 interacting QTLs each.
Within 9 of the detected regions, we validated the contribution of 13
genes in the observed phenotypic variation by reciprocal hemizygosity
analysis. These genes are involved in nitrogen uptake and metabolism
(AGP1, ALP1, ILV6, LEU9), central carbon metabolism (HXT3, MAE1), fatty
acid synthesis (FAS1) and regulation (AGP2, IXR1, NRG1, RGS2, RGT1, SIR2)
and explain variations in the production of characteristic sensorial
esters (e.g., 2-phenylethyl acetate, 2-metyhlpropyl acetate and ethyl
hexanoate), higher alcohols and fatty acids. Conclusions: The detection of
QTLs and their 51 interactions emphasizes the complexity of yeast
fermentative aroma formation. The validation of underlying allelic
variants increases knowledge about genetic variation impacting metabolic
pathways that lead to the synthesis of sensorial important compounds. As a
result, this work lays the foundation for tailoring S. cerevisiae strains
with optimized volatile metabolite production for fermented beverages and
other biotechnological applications.