RESUMO
Saccharomyces cerevisiae is the main microorganism responsible for wine alcoholic fermentation. The oenological phenotypes resulting from fermentation, such as the production of acetic acid, glycerol, and residual sugar concentration are regulated by multiple genes and vary quantitatively between different strain backgrounds. With the aim of identifying the quantitative trait loci (QTLs) that regulate oenological phenotypes, we performed linkage analysis using three crosses between highly diverged S. cerevisiae strains. Segregants from each cross were used as starter cultures for 20-day fermentations, in synthetic wine must, to simulate actual winemaking conditions. Linkage analysis on phenotypes of primary industrial importance resulted in the mapping of 18 QTLs. We tested 18 candidate genes, by reciprocal hemizygosity, for their contribution to the observed phenotypic variation, and validated five genes and the chromosome II right subtelomeric region. We observed that genes involved in mitochondrial metabolism, sugar transport, nitrogen metabolism, and the uncharacterized ORF YJR030W explained most of the phenotypic variation in oenological traits. Furthermore, we experimentally validated an exceptionally strong epistatic interaction resulting in high level of succinic acid between the Sake FLX1 allele and the Wine/European MDH2 allele. Overall, our work demonstrates the complex genetic basis underlying wine traits, including natural allelic variation, antagonistic linked QTLs and complex epistatic interactions between alleles from strains with different evolutionary histories.
Assuntos
Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/fisiologia , Vinho , Ácido Acético/metabolismo , Bebidas Alcoólicas , Alelos , Epistasia Genética , Evolução Molecular , Fermentação , Microbiologia de Alimentos , Genes Fúngicos , Ligação Genética , Variação Genética , Glicerol/metabolismo , Modelos Genéticos , Fases de Leitura Aberta , Fenótipo , Locos de Características QuantitativasRESUMO
AIMS: To study genomic and phenotypic changes in wine yeasts produced in short time periods analysing yeast strains possibly derived from commercial strains recently dispersed. METHODS AND RESULTS: We conducted a genomic and phenotypic comparison between the commercial yeast strain EC1118 and two novel strains (LV CB and L-957) isolated from different wine areas industrially intervened <20 years ago. Molecular analysis by amplified fragment length polymorphism (AFLP) and RAPD-PCR was not able to distinguish between these strains. However, comparative genomic hybridization (aCGH) showed discrete DNA gains and losses that allowed unequivocal identification of the strains. Furthermore, analysis of aCGH data supports the hypothesis that strains LV CB and L-957 are derivatives from strain EC1118. Finally, scarce phenotypic differences in physiological and metabolic parameters were found among the strains. CONCLUSION: The wine yeasts have a very dynamic genome that accumulates changes in short time periods. These changes permit the unique genomic identification of the strains. SIGNIFICANCE AND IMPACT OF THE STUDY: This study permits the evaluation of microevolutive events in wine yeasts and its relationship with the phenotype in this species.