Genome Sequence of the Lager Brewing Yeast, an Interspecies Hybrid

Abstract

This work presents the genome sequencing of the lager brewing yeast (Saccharomyces pastorianus) Weihenstephan 34/70, a strain widely used in lager beer brewing. The 25 Mb genome comprises two nuclear sub-genomes originating from Saccharomyces cerevisiae and Saccharomyces bayanus and one circular mitochondrial genome originating from S. bayanus. Thirty-six different types of chromosomes were found including eight chromosomes with translocations between the two sub-genomes, whose breakpoints are within the orthologous open reading frames. Several gene loci responsible for typical lager brewing yeast characteristics such as maltotriose uptake and sulfite production have been increased in number by chromosomal rearrangements. Despite an overall high degree of conservation of the synteny with S. cerevisiae and S. bayanus, the syntenies were not well conserved in the sub-telomeric regions that contain lager brewing yeast characteristic and specific genes. Deletion of larger chromosomal regions, a massive unilateral decrease of the ribosomal DNA cluster and bilateral truncations of over 60 genes reflect a post-hybridization evolution process. Truncations and deletions of less efficient maltose and maltotriose uptake genes may indicate the result of adaptation to brewing. The genome sequence of this interspecies hybrid yeast provides a new tool for better understanding of lager brewing yeast behavior in industrial beer production.

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

“…Lager strains are allopolyploid hybrids of Saccharomyces cerevisiae and a Saccharomyces bayanus-like yeast 15,53 that was recently identified as Saccharomyces eubayanus sp. nov. 44 .…”

Isolation of Meiotic Segregants from a Bottom Fermenting Yeast

“…The array-CGH experiments revealed that the SB-type Chromosome XI left arm was missing, and relative hybridization ratios of the SC-type Chromosome X right arm of Weihenstephan34/70-1A was decreased. Nakao et al 9 reported that some bottom fermenting yeast strains possessed a chimera-type Chromosome XI (SC left arm -SB right arm). The reason why signals of the SBtype Chromosome XI left arm of Weihenstephan34/70-1A were missing, seemed to be that SB-type Chromosome XI was missed from the Weihenstephan34/70-1A genome, while chimera-type Chromosome XI (SC left arm -SB right arm) remained.…”

“…The reason why signals of the SBtype Chromosome XI left arm of Weihenstephan34/70-1A were missing, seemed to be that SB-type Chromosome XI was missed from the Weihenstephan34/70-1A genome, while chimera-type Chromosome XI (SC left arm -SB right arm) remained. It has been reported that some bottom fermenting yeast strains possess a chimera-type Chromosome Xs (SC left arm -SB right arm, SB left arm -SC right arm) 9,12 . Thus, the reason why the signal of the SC-type Chromosome X right arm of Weihenstephan 34/70-1A was decreased appears to be similar in the case of Chromosome XIs.…”

“…These probes were designed from our in-house draft genome sequence of our original bottom fermenting yeast strain BF1, which is almost identical to the project sequence 9 (project accession no. ABPO00000000), and positioned at intervals of 600 nucleotides on average.…”

“…The effect of the overexpression of IME1 on the spore frequency of bottom fermenting yeast S. pastorianus (a natural hybrid of S. cerevisiae and S. bayanus 9,[17][18][19] ) was analyzed by introducing the SC (S. cerevisiae) type or SB (S. bayanus) type of IME1 gene contained within plasmids pIB574 or pIB565, respectively. There was a greater increase in sporulation frequency upon introduction of the SB-IME1 gene over the SC-IME1 gene, using either of the two bottom fermenting yeast strains (Table I).…”