Pleiotropic glucose repression-resistant mutation in Saccharomyces carlesbergensis.

We describe the characterization of a mutation of the locus GLR1. This mutation allowed for (i) the glucose repression-insensitive synthesis ot the enzymes maltase, galactokinase, alpha-galactosidase, reduced nicotinamide adenine dinucleotide-cytochrome c reductase, and cytochrome c oxidase and (ii) growth on maltose in the presence of the gratuitous glucose repressor D-glucosamine. The glucosamine resistance cosegregated with the glucose-insensitive synthesis of the enzymes listed above. In addition, crosses between the glucosamine-resistant mutant and isogenic sensitive strains gave only tetrads containing two resistant and two sensitive spores. Thus, a single pleiotropic mutation is responsible for both phenotypes. We call the locus GLR1, for glucose regulation, and the glucose repression-insensitive mutation glr1-1.