DNA sequence polymorphisms in the genus Saccharomyces. II. Analysis of the genesRDN1, HIS4, LEU2 andTy transposable elements in Carlsberg, Tuborg and 22 bavarian brewing strains

Abstract

The genotypes of the Carlsberg and Tuborg bottom fermenting (lager) Saccharomyces strains as well as those of 13 other bottom fermenting yeasts and 9 top fermenting yeasts from the collection of the Wissenschaftliche Station fur Brauerei in Munich were analysed fro restriction fragment length differences in theRDN1 ribosomal RNA gene cluster on chromosome XII as well as in the chromosome III regions containing theHIS4 (histidine 4) andLEU2 (leucine 2) genes. All brewing strains had the same form IIRDN1 gene cluster. The top fermenting strains yielded identical Sall restriction endonuclease fragment patterns (I) when probed with theHIS4 gene probe of plasmid pC503. The pattern corresponds to that found in genetic standard strain S288C. The bottom fermenting strains were all heterozygous for theHIS4 patterns I and II known to originate from homeologous regions of two chromosomes.Molecular hybridisation of aLEU2 gene probe to Sall restricted DNA of the bottom fermenting yeast strains gave identical fragment patterns (III+IV), while a pattern designated II+III was most common in top fermenting strains. Two additional patterns were found among the latter.The transposable elementTy1 from a genetic standard strain distinguishes the genotypes of various lager strains as well as those of top fermenting yeasts. Hybridisation ofTy1 to EcoRI restricted DNA of Carlsberg lager strain BK 2246 yields four diagnostic fragments, while the DNA of Tuborg lager strain BK 2224 is characterized by an additional 5.5 kb fragment. Conversely Sall restricted DNA of the Carlsberg strain contains a 10 kb fragment absent from the genome of the Tuborg strain. Three different restriction fragment patterns are found after probing with theTy1 element among the Bavarian bottom fermenting yeasts. More complex patterns with at least 10 restriction fragments hybridising to theTy1 element are found among the top fermenting strains from the Munich collection. Five different genotypes have been identified among 9 strains tested.Ty1 transposing elements will be helpful markers in the characterisation of improved brewing strains.