Project description:Saccharomyces pastorianus lager brewing yeasts are domesticated hybrids of Saccharomyces cerevisiae and cold-tolerant Saccharomyces eubayanus. To better understand the contribution of both parental genomes to maltose metabolism in brewing wort, this study focuses on maltose transport in the S. eubayanus type strain CBS12357T/FM1318T. To obtain complete sequences of the MAL loci of this strain, a near-complete genome assembly was generated using the Oxford Nanopore Technology MinION sequencing platform. Except for CHRXII, all sixteen chromosomes were assembled as single contigs. Four loci harboring putative maltose transporter genes (SeMALT1-4), located in subtelomeric regions of CHRII, CHRV, CHRXIII and CHRXVI, were completely resolved. The near-identical loci on CHRV and CHRXVI strongly resembled canonical S. cerevisiae MAL loci, while those on CHRII and CHRXIII showed different structures suggestive of gene loss. Functionality of the SeMALT1-4-encoded transporters was confirmed by their ability to restore growth on maltose, but not on maltotriose, of a maltose-transport-deficient S. cerevisiae strain. Simultaneous CRISPR-Cas9-assisted deletion of SeMALT2 and SeMALT4, which shared 99.7 % sequence identity, eliminated growth of S. eubayanus CBS12357T on maltose. Transcriptome analysis of S. eubayanus CBS12357T established that, in maltose-grown cultures, SeMALT2 and SeMALT4 were expressed at much higher levels than SeMALT1 and SeMALT3, thus resolving the apparent discrepancy between heterologous expression and deletion studies. These results represent a first genomic and physiological characterization of maltose transport in S. eubayanus CBS12357T and provides a valuable resource for further industrial exploitation of this yeast.
Project description:S. pastorianus strains are hybrids of S. cerevisiae and S. eubayanus that have been domesticated for several centuries in lager-beer brewing environments. As sequences and structures of S. pastorianus genomes are being resolved, molecular mechanisms and evolutionary origin of several industrially relevant phenotypes remain unknown. This study investigates how maltotriose metabolism, a key feature in brewing, may have arisen in early S. eubayanus x S. cerevisiae hybrids. To address this question, we generated a near-complete genome assembly of Himalayan S. eubayanus strains of the Holarctic subclade. This group of strains have been proposed to be the origin of the S. eubayanus subgenome of current S. pastorianus strains. The Himalayan S. eubayanus genomes harbored several copies of an SeAGT1 -oligoglucoside transporter gene with high sequence identity to genes encountered in S. pastorianus. Although Himalayan S. eubayanus strains are unable to grown on maltose and maltotriose, their maltose-hydrolase and SeMALT1 and SeAGT1 maltose-transporter genes complemented the corresponding null mutants of S. cerevisiae. Expression, in a Himalayan S. eubayanus strain, of a functional S. cerevisiae maltose-metabolism regulator gene (MALx3) enabled growth on oligoglucosides. The hypothesis that the maltotriose-positive phenotype in S. pastorianus is a result of heterosis was experimentally tested by constructing a S. cerevisiae x S. eubayanus laboratory hybrid with a complement of maltose-metabolism genes that resembles that of current S. pastorianus strains. The ability of this hybrid to consume maltotriose in brewer's wort demonstrated regulatory cross talk between sub-genomes and thereby validated this hypothesis. These results provide experimental evidence of the evolutionary origin of an essential phenotype of lager-brewing strains and valuable knowledge for industrial exploitation of laboratory-made S. pastorianus-like hybrids.
Project description:Laboratory evolution of a Saccharomyces cerevisiae x S. eubayanus hybrid under simulated lager-brewing conditions: genetic diversity and phenotypic convergence
Project description:The dynamics of the Saccharomyces carlsbergensis brewing yeast transcriptome during a production scale lager beer fermentation. The transcriptome of a lager brewing yeast (Saccharomyces carlsbergensis, syn. of S. pastorianus), was analysed at 12 different time points spanning a production-scale lager beer fermentation. Generally, the average expression rapidly increased and had a maximum value on day 2, then decreased as the sugar got consumed. Especially genes involved in protein and lipid biosynthesis or glycolysis were highly expressed during the beginning of the fermentation. Similarities as well as significant differences in expression profiles could be observed when comparing to a previous transcriptome analysis of a laboratory yeast grown in YPD. The regional distribution of various expression levels on the chromosomes appeared to be random or near-random and no reduction in expression near telomeres was observed.
Project description:The dynamics of the Saccharomyces carlsbergensis brewing yeast transcriptome during a production scale lager beer fermentation. The transcriptome of a lager brewing yeast (Saccharomyces carlsbergensis, syn. of S. pastorianus), was analysed at 12 different time points spanning a production-scale lager beer fermentation. Generally, the average expression rapidly increased and had a maximum value on day 2, then decreased as the sugar got consumed. Especially genes involved in protein and lipid biosynthesis or glycolysis were highly expressed during the beginning of the fermentation. Similarities as well as significant differences in expression profiles could be observed when comparing to a previous transcriptome analysis of a laboratory yeast grown in YPD. The regional distribution of various expression levels on the chromosomes appeared to be random or near-random and no reduction in expression near telomeres was observed. Keywords: time-course
Project description:We report the gene expression profile of two polypolid Saccharomyces pastorianus, lager yeast strains, the Group I strain CBS1538 and the Group II strain W34/70. Saccharomyces pastorianus is a hybrid of Saccharomuyces cerevisiaie and Saccharomyces eubayanus. We report that the gene expression patterns are correlated with the gene copy number of S. cerevisiae and S. eubayanus alleles.
Project description:Saccharomyces pastorianus is a natural yeast evolved from different hybridisation events between the mesophilic S. cerevisiae and the cold-tolerant S. eubayanus. This complex aneuploid hybrid carries multiple copies of the parental alleles alongside specific hybrid genes and encodes for multiple protein isoforms which impart novel phenotypes, such as the strong ability to ferment at low temperature. These characteristics lead to agonistic competition for substrates and a plethora of biochemical activities, resulting in a unique cellular metabolism. Here, we investigated the transcriptional signature of the different orthologous alleles in S. pastorianus during temperature shifts.