Isolation of 4-aminopyridine resistant mutants affecting alkali-insoluble glucan content of cell walls in Saccharomyces cerevisiae.

ABSTRACT

Saccharomyces cerevisiae cells when grown on synthetic medium plates containing 10 mM of 4-aminopyridine (4-AP) undergo cell lysis. Using an ethylmethane sulfonate mutagenesis (EMS) screen, 4-AP resistant mutants (apr) were isolated which could grow on inhibitory concentration of 4-AP. Eighty mutants were obtained that were recessive, monogenic and formed two complementation groups. To identify genes, whose products might be interacting with the apr loci, extragenic suppressors were isolated, which reverted 4-AP resistance phenotype of apr mutants. The suppressors, when genetically characterized, were found to be recessive and represented two loci with overlapping functions. Representative alleles from apr mutants were analyzed for cell wall composition. They were found to have a higher amount of alkali-insoluble glucan signifying the role of alkali-insoluble glucan in cell wall maintenance.