In order to study the molecular evolution of the yeasts grouped in the
Saccharomyces sensu stricto species complex by analysis of the
MEL gene family, we have cloned and sequenced two new species-specific
MEL genes from
Saccharomyces yeasts:
S. paradoxus (
MELp) and a Japanese
Saccharomyces sp. (
MELj). The clones were identified by sequence homology to the
S. cerevisiae MEL1 gene. Both clones revealed an ORF of 1413 bp coding for a protein of 471 amino acids. The deduced molecular weights of the
α-galactosidase enzymes were 52 767 for
MELp and 52 378 for
MELj. The nucleotide sequences of the
MELp (EMBL accession no. X95505) and the
MELj (EMBL accession no. X95506) genes showed 74.7% identity. The degree of identity of
MELp to the
MEL1 gene was 76.8% and to the
S. pastorianus MELx gene, 75.7%. The
MELj coding sequence was 75.1% identical to the
MEL1 gene and 80.7% to the
MELx gene. The data suggest that
MEL1,
MELj, MELp, and
MELx genes are species-specific
MEL genes. The strains studied each have only one
MEL locus. The
MELp gene is located on the
S. paradoxus equivalent of
S. cerevisiae chromosome X; the
MELj gene was on the chromosome that comigrates with the
S. cerevisiae chromosome VII/XV doublet and hybridizes to the
S. cerevisiae chromosome XV marker
HIS3.
Key words MEL gene - α-galactosidase - Saccharomyces cerevisiae - Saccharomyces paradoxus
Received: 20 February 1996/Accepted: 1 July 1996