Electrophoretic variants of phosphoglucomutase in Saccharomyces species

Strains of Saccharomyces cerevisiae and species with which S. cerevisiae is interfertile display a characteristic pattern of electrophoretic variants of phosphoglucomutase (PGM) consisting of a major component and one or two minor components, all of which migrate toward the cathode. The patterns are consistent with an earlier finding that two unlinked genes, one of which has two known alleles, determine the synthesis of PGM in S. cerevisiae. The PGM patterns of strains of S. fragilis, S. lactis, and S. marxianus, species thought to be closely related to each other and only distantly related to S. cerevisiae, also displayed a characteristic pattern of PGM variants, but it was quite different from that of S. cerevisiae. In these species five or six electrophoretic variants could be detected, all of which migrated toward the anode. We interpret the differences in the PGM variants of the two groups of species as a reflection of differences in genetic composition which have arisen in two phylogenetically distinct groups that have become sexually isolated from each other.