Genes required for transcription of STA1 encoding an extracellular glucoamylase in the yeast Saccharomyces.

Mutants of Saccharomyces diastaticus with defects in starch fermentation were isolated.In addition to the mutations in the STA1structural gene for glucoamylase (stal) and in the transcription factor (garni), we recovered two new complementation groups, designated gam2 and gam3.These starch-nonfermenting mutants secreted little or no glucoamylase.The garni and gam2mutants were pleiotropically defective in use of nonfermentable carbon sources, and consequently did not undergo meiosis and sporulation.No pleiotrophy was detected in the garni mutant.RNAblot analysis revealed that GAM2 and GAMS are also required for transcription of STAL S. diastaticus is able to use starch as a carbon source by secreting glucoamylase which cleaves starch to yield glucose.1}This organism is closely related to Saccharomyces cerevisiae, a starch-nonfermenting species, since haploid cells of these species are able to mate, and they are genetically similar to each other.2)However, tetrad analysis of crosses between these species revealed that S. cere-