Isolation and characterization of sulfite mutants of Saccharomyces cerevisiae

Abstract

Sulfite-resistant and sulfite-sensitive mutants of Saccharomyces cerevisiae were isolated and characterized. Genetic analysis indicated that one and four genes were responsible for the resistant and sensitive responses, respectively, and suggested that defects in methionine and cysteine metabolism were not involved. Some resistant alleles, all of which were dominant, conferred greater resistance than others. Mutations conferring sensitivity were recessive and one co-segregated with impaired respiration. Two of the sensitive mutants exhibited cross-sensitivity to other metabolic inhibitors: sulfometuron methyl, cycloheximide, oligomycin, and antimycin A. A 50% glutathione deficiency in one sensitive mutant was not sufficient in itself to account for its sensitivity. Screening of other relevant mutants revealed that relative to wild-type, met8 and a thioredoxin null mutant are sensitive, and met3 and met14 mutants are not. Reduced production of extracellular acetaldehyde, a compound that detoxifies sulfite, was observed in three of the four sensitive mutants. However, acetaldehyde was also underproduced in the resistant mutant. Because sulfite is a reducing agent, cells were tested for coincident sensitivity or resistance to ascorbate, selenite, dithiothreitol, nitrite, thiosulfate, reduced glutathione, and cysteine. No consistent pattern of responses to these agents emerged, suggesting that the response to sulfite is not a simple function of redox potential.

Glucose Signaling in Saccharomyces cerevisiae

“…4) (117, 179, 247). Mutations in GRR1 were shown long ago to impair the regulatory response to glucose (11) and have since been associated with a broad array of phenotypes, including cell elongation, decreased divalent cation transport, defects in sporulation, and slow growth or lethality in combination with defective amino acid biosynthetic pathways (21,114,158,215,427,431).…”

Factors Supporting Cysteine Tolerance and Sulfite Production in Candida albicans

“…Due to its antimicrobial and antioxidative properties, sulfite is also well known for its common use as a preservative in food industries, in particular during the production of wine (1). The molecular basis of sulfite tolerance has therefore been intensively studied in fermenting yeasts and led to the identification of the sulfite efflux pump Ssu1 in Saccharomyces cerevisiae (2,3). Overexpression of SSU1 in S. cerevisiae resulted in enhanced sulfite resistance, and the gene was shown to be positively controlled by the transcription factor Fzf1 (4)(5)(6).…”

Regulation and Recognition of SCFGrr1 Targets in the Glucose and Amino Acid Signaling Pathways

“…This broad array of roles is apparent in the phenotype of cells lacking Grr1, which exhibit multiple abnormalities including cell elongation, slow growth on glucose, increased sensitivity to osmotic stress and nitrogen starvation, decreased divalent cation transport, enhanced filamentous growth, defects in sporulation, and slow growth or inviability when combined with amino acid biosynthetic mu-tants (5,9,33,43,57,58). Although the requirement for Grr1 in those processes has been well documented, its targets in most of those pathways are poorly characterized.…”