Efficient use of DNA molecular markers to construct industrial yeast strains.

Saccharomyces cerevisiae yeast strains exhibit a huge genotypic and phenotypic diversity. Breeding strategies taking advantage of these characteristics would contribute greatly to improving industrial yeasts. Here we mapped and introgressed chromosomal regions controlling industrial yeast properties, such as hydrogen sulphide production, phenolic off-flavor and a kinetic trait (lag phase duration). Two parent strains derived from industrial isolates used in winemaking and which exhibited significant quantitative differences in these traits were crossed and their progeny (50-170 clones) was analyzed for the segregation of these traits. Forty-eight segregants were genotyped at 2212 marker positions using DNA microarrays and one significant locus was mapped for each trait. To exploit these loci, an introgression approach was supervised by molecular markers monitoring using PCR/RFLP. Five successive backcrosses between an elite strain and appropriate segregants were sufficient to improve three trait values. Microarray-based genotyping confirmed that over 95% of the elite strain genome was recovered by this methodology. Moreover, karyotype patterns, mtDNA and tetrad analysis showed some genomic rearrangements during the introgression procedure

Single QTL mapping and nucleotide-level resolution of a physiologic trait in wine Saccharomyces cerevisiae strains.

International audienceNatural Saccharomyces cerevisiae yeast strains exhibit very large genotypic and phenotypic diversity. However, the link between phenotype variation and genetic determinism is still difficult to identify, especially in wild populations. Using genome hybridization on DNA microarrays, it is now possible to identify single-feature polymorphisms among divergent yeast strains. This tool offers the possibility of applying quantitative genetics to wild yeast strains. In this instance, we studied the genetic basis for variations in acetic acid production using progeny derived from two strains from grape must isolates. The trait was quantified during alcoholic fermentation of the two strains and 108 segregants derived from their crossing. A genetic map of 2212 markers was generated using oligonucleotide microarrays, and a major quantitative trait locus (QTL) was mapped with high significance. Further investigations showed that this QTL was due to a nonsynonymous single-nucleotide polymorphism that targeted the catalytic core of asparaginase type I (ASP1) and abolished its activity. This QTL was only effective when asparagine was used as a major nitrogen source. Our results link nitrogen assimilation and CO(2) production rate to acetic acid production, as well as, on a broader scale, illustrating the specific problem of quantitative genetics when working with nonlaboratory microorganisms

Marker assisted selection of malic-consuming saccharomyces cerevisiae strains for winemaking. Efficiency and limits of a qtl’s driven breeding program

Natural Saccharomyces cerevisiae yeast strains exhibit very large genotypic and phenotypic diversity. Breeding programs that take advantage of this characteristic are widely used for selecting starters for wine industry, especially in the recent years when winemakers need to adapt their production to climate change. The aim of this work was to evaluate a marker assisted selection (MAS) program to improve malic acid consumption capacity of Saccharomyces cerevisiae in grape juice. Optimal individuals of two unrelated F1-hybrids were crossed to get a new genetic background carrying many « malic consumer » loci. Then, eleven quantitative trait loci (QTLs) already identified were used for implementing the MAS breeding program. By this method, extreme individuals able to consume more than 70% of malic acid in grape juice were selected. These individuals were tested in different enological matrixes and compared to their original parental strains. They greatly reduced the malic acid content at the end of alcoholic fermentation, they appeared to be robust to the environment, and they accelerated the ongoing of malolactic fermentations by Oenococcus oeni. This study illustrates how MAS can be efficiently used for selecting industrial Saccharomyces cerevisiae strains with outlier properties for winemaking.Centre français de phénomique végétalePlateforme d'Innovation " Forêt-Bois-Fibre-Biomasse du Futur

SSU1 Checkup, a Rapid Tool for Detecting Chromosomal Rearrangements Related to the SSU1 Promoter in Saccharomyces cerevisiae: An Ecological and Technological Study on Wine Yeast

Chromosomal rearrangements (CR) such as translocations, duplications and inversions play a decisive role in the adaptation of microorganisms to specific environments. In enological Saccharomyces cerevisiae strains, CR involving the promoter region of the gene SSU1 lead to a higher sulfite tolerance by enhancing the SO2 efflux. To date, three different SSU1 associated CR events have been described, including translocations XV-t-XVI and VIII-t-XVI and inversion inv-XVI. In the present study, we developed a multiplex PCR method (SSU1 checkup) that allows a rapid characterization of these three chromosomal configurations in a single experiment. Nearly 600 S. cerevisiae strains collected from fermented grape juice were genotyped by microsatellite markers. We demonstrated that alleles of the SSU1 promoter are differently distributed according to the wine environment (cellar versus vineyard) and the nature of the grape juice. Moreover, rearranged SSU1 promoters are significantly enriched among commercial starters. In addition, the analysis of nearly isogenic strains collected in wine related environments demonstrated that the inheritance of these CR shapes the genetic diversity of clonal populations. Finally, the link between the nature of SSU1 promoter and the tolerance to sulfite was statistically validated in natural grape juice containing various SO2 concentrations. The SSU1 checkup is therefore a convenient new tool for addressing population genetics questions and for selecting yeast strains by using molecular markers.Fil: Marullo, Philippe. Universite de Bordeaux; FranciaFil: Claisse, Olivier. Universite de Bordeaux; FranciaFil: Raymond Eder, María Laura. Universidad Católica de Córdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad José Sanchez Labrador S. J. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad José Sanchez Labrador S. J.; ArgentinaFil: Börlin, Marine. Universite de Bordeaux; FranciaFil: Feghali, Nadine. Lebanese University; LíbanoFil: Bernard, Margaux. Universite de Bordeaux; FranciaFil: Legras, Jean Luc. Université Montpellier II; FranciaFil: Albertin, Warren. Universite de Bordeaux; FranciaFil: Rosa, Alberto Luis. Universidad Católica de Córdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad José Sanchez Labrador S. J. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Recursos Naturales y Sustentabilidad José Sanchez Labrador S. J.; ArgentinaFil: Masneuf Pomarede, Isabelle. Universite de Bordeaux; Franci

Metabolic, organoleptic and transcriptomic impact of saccharomyces cerevisiae genes involved in the biosynthesis of linear and substituted esters

Esters constitute a broad family of volatile compounds impacting the organoleptic properties of many beverages, including wine and beer. They can be classified according to their chemical structure. Higher alcohol acetates differ from fatty acid ethyl esters, whereas a third group, substituted ethyl esters, contributes to the fruitiness of red wines. Derived from yeast metabolism, the biosynthesis of higher alcohol acetates and fatty acid ethyl esters has been widely investigated at the enzymatic and genetic levels. As previously reported, two pairs of esterases, respectively encoded by the paralogue genes ATF1 and ATF2, and EEB1 and EHT1, are mostly involved in the biosynthesis of higher alcohol acetates and fatty acid ethyl esters. These esterases have a moderate effect on the biosynthesis of substituted ethyl esters, which depend on mono-acyl lipases encoded by MGL2 and YJU3. The functional characterization of such genes helps to improve our understanding of substituted ester metabolism in the context of wine alcohol fermentation. In order to evaluate the overall sensorial impact of esters, we attempted to produce young red wines without esters by generating a multiple esterase-free strain (Δatf1, Δatf2, Δeeb1, and Δeht1). Surprisingly, it was not possible to obtain the deletion of MGL2 in the Δatf1/Δatf2/Δeeb1/Δeht1 background, highlighting unsuspected genetic incompatibilities between ATF1 and MGL2. A preliminary RNA-seq analysis depicted the overall effect of the Δatf1/Δatf2/Δeeb1/Δeht1 genotype that triggers the expression shift of 1124 genes involved in nitrogen and lipid metabolism, but also chromatin organization and histone acetylation. These findings reveal unsuspected regulatory roles of ester metabolism in genome expression for the first time

Front Microbiol

Chromosomal rearrangements (CR) such as translocations, duplications and inversions play a decisive role in the adaptation of microorganisms to specific environments. In enological strains, CR involving the promoter region of the gene lead to a higher sulfite tolerance by enhancing the SO efflux. To date, three different associated CR events have been described, including translocations XV-t-XVI and VIII-t-XVI and inversion inv-XVI. In the present study, we developed a multiplex PCR method ( checkup) that allows a rapid characterization of these three chromosomal configurations in a single experiment. Nearly 600 strains collected from fermented grape juice were genotyped by microsatellite markers. We demonstrated that alleles of the promoter are differently distributed according to the wine environment (cellar versus vineyard) and the nature of the grape juice. Moreover, rearranged promoters are significantly enriched among commercial starters. In addition, the analysis of nearly isogenic strains collected in wine related environments demonstrated that the inheritance of these CR shapes the genetic diversity of clonal populations. Finally, the link between the nature of promoter and the tolerance to sulfite was statistically validated in natural grape juice containing various SO concentrations. The checkup is therefore a convenient new tool for addressing population genetics questions and for selecting yeast strains by using molecular markers

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Genome-wide Association Study of Change in Fasting Glucose over time in 13,807 non-diabetic European Ancestry Individuals

Type 2 diabetes (T2D) affects the health of millions of people worldwide. The identification of genetic determinants associated with changes in glycemia over time might illuminate biological features that precede the development of T2D. Here we conducted a genome-wide association study of longitudinal fasting glucose changes in up to 13,807 non-diabetic individuals of European descent from nine cohorts. Fasting glucose change over time was defined as the slope of the line defined by multiple fasting glucose measurements obtained over up to 14 years of observation. We tested for associations of genetic variants with inverse-normal transformed fasting glucose change over time adjusting for age at baseline, sex, and principal components of genetic variation. We found no genome-wide significant association (P < 5 x 10(-8)) with fasting glucose change over time. Seven loci previously associated with T2D, fasting glucose or HbA1c were nominally (P < 0.05) associated with fasting glucose change over time. Limited power influences unambiguous interpretation, but these data suggest that genetic effects on fasting glucose change over time are likely to be small. A public version of the data provides a genomic resource to combine with future studies to evaluate shared genetic links with T2D and other metabolic risk traits.Peer reviewe