MOLECULAR AND PHENOTYPIC ANALYSES OF SULFITE TOLERANT S. CEREVISIAE STRAINS CARRYING WILD TYPE OR ABERRANT PROMOTERS OF THE SSU1 GENE

MARÍA LAURA RAYMOND EDER; MARÍA LUZ BRAGATO; ALBERTO LUIS ROSA

Congreso; LVI Annual Meeting Argentine Society for Biochemistry and Molecular Biology (SAIB); 2020

Sulfite, a widely used preservative agent, has remarkable antimicrobial, antioxidant, and antioxydasic activities. Sulfite tolerance in the model yeast Saccharomyces cerevisiae mostly depends on cellular sulfite efflux mediated by the sulfite pump Ssu1p, encoded by the SSU1 gene. Deleterious mutations in SSU1 cause sulfite susceptibility, while some frequently recognized chromosomal rearrangements (CR) involving the SSU1 promoter region (CR-SSU1) confer higher sulfite tolerance to the corresponding mutant strains. Three CR-SSU1 have been described: the translocations XV-t-XVI and VIII-t-XVI and the inversion inv-XVI. In this work we have used microsatellite genotyping and PCR to identify and characterize CR-SSU1 in a large collection of indigenous and industrial S. cerevisiae strains. Sulfite tolerance phenotypes of strains carrying alternative alleles of the SSU1 promoter were analyzed in natural grape juice containing various sulfite concentrations. In these studies, we did not find a direct correlation between the various SSU1 promoter structures and levels of tolerance to sulfite. In this work we also developed a plating method on agar medium aimed to characterize subtle differences in sulfite tolerance among wild type strains and strains carrying single or combined CR-SSU1. This method should allow direct selection of cells carrying spontaneous and/or environmentally induced mutagenic events leading to sulfite tolerance in S. cerevisiae. Our results suggest that, in addition to structural differences among the promoter regions of the various characterized SSU1 alleles, other genetic mechanisms underlie alternative levels of sulfite tolerance in S. cerevisiae.