Sed1 gene length and sequence polymorphisms in ferals strains of Saccharomyces cerevisiae

The SED1 gene (YDR077W), coding for the major cell wall glycoprotein of Saccharomyces cerevisiae stationary-
phase cells, contains two blocks of tandem repeat units located within two distinct regions of the nucleotide
sequence. A PCR survey of the SED1 open reading frames (ORFs) of 186 previously uncharacterized grape
must isolates of S. cerevisiae yielded 13 PCR profiles arising from different combinations of seven SED1 length
variants in individuals homozygous or heterozygous for the gene. Comparison of the nucleotide sequences of
a group of representatives of each of the seven length variants with those of S288C and the type strain,
CBS1171, unequivocally identified them as SED1 alleles and provided evidence for the presence of two
minisatellite-like sequences, variable in length, within the ORF of an S. cerevisiae gene. The segregation
analyses of the SED1 length variants and other genetic markers in 13 isolates representative of each PCR
profile suggested that molecular mechanisms involved in minisatellite expansion and contraction may be
responsible for SED1 heterozygosities within a population of homothallic must isolates of S. cerevisiae.