Isolation and characterization of maltose non utilizing (mnu) mutants mapping outside the MAL1 locus in Saccharomyces cerevisiae*

Summary

The MAL1 locus of Saccharomyces cerevisiae comprises three genes necessary for maltose utilization. They include regulatory, maltose transport and maltase genes designated MAL1R, MAL1T and MAL1S respectively. Using a MAL1 strain transformed with an episomal, multicopy plasmid carrying the MAL2 locus, five recessive and one dominant mutant unable to grow on maltose, but still retaining a functional MAL1 locus were isolated. All the mutants could use glycerol, ethanol, raffinose and sucrose as a sole carbon source; expression of the maltase and maltose permease genes was severely and coordinately reduced. Only the dominant mutant failed to accumulate the MAL1R mRNA.

Maltase, Mutant isolation, MAL Genes, Yeast, Sugar

*

A preliminary account of this work has been presented at the meeting: Gene Expression and Regulation: the Legacy of Luigi Gorini, held in Milan, Italy on 12–14 October 1987.