Cloning and molecular analysis of two different ILV5 genes from a brewing strain of Saccharomyces cerevisiae

Identification of genes and proteins induced during the lag and early exponential phase of lager brewing yeasts

AIMS

The aim of the present study is to identify genes and proteins whose expression is induced in lager brewing yeast during the lag phase and early exponential growth.

METHODS AND RESULTS

Two-dimensional gel electrophoresis was used to identify proteins induced during the lag and early exponential phase of lager brewing yeast in minimal medium. The identified, early-induced proteins were Ade17p, Eno2p, Ilv5gp, Sam1p, Rps21p and Ssa2p. For most of these proteins, the patterns of induction differed from those of the corresponding genes. However, the genes had similar early expression patterns in minimal medium as observed during lager brewing conditions. The expression of previously identified early-induced genes in Saccharomyces cerevisiae grown in minimal medium, ADO1, ALD6, ASC1, ERG4, GPP1, RPL25, SSB1 and YKL056C, was also early induced in lager yeast under brewing conditions.

CONCLUSIONS

The results indicate that the above-mentioned genes in general are induced during the lag phase and early exponential growth in Saccharomyces yeasts. The processes in which these genes take part are likely to play an important role during growth initiation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Increased knowledge regarding the early growth phase of lager brewing yeast was obtained. Further, the universality of the identified expression patterns suggests new methodologies for optimization and control of growth initiation during brewing fermentations.

Molecular cloning of a novel allele of SMR1 which determines sulfometuron methyl resistance in Saccharomyces cerevisiae

A different mutation (SMR1B) to SMR1-410 (ilv2), which determines resistance to sulfometuron methyl in Saccharomyces cerevisiae, was cloned by PCR. Sequence analysis indicated a C to T change at position 575 of the ILV2 coding sequence, which results in a proline transition to leucine at position 192. Similarly to SMR1-410, the SMR1B gene was confirmed as a convenient dominant selective marker for yeast transformation including industrial strains.