Sequencing of highly oxidative-stress tolerant budding yeast mutants and their progenitors

Here, we perform a screen for spontaneous mutations that improve the tolerance of haploid Saccharomyces cerevisiae to hydrogen peroxide. Chromosome IV duplication is the most frequent mutational event, as well as the only change in chromosomal copy number, seen in the screen. Genetic mapping and gene expression analysis reveal that this chromosomal duplication’s effect is mostly mediated by a single stress-responsive cytoplasmic thioredoxin peroxidase that is more quickly induced in an aneuploid mutant than its euploid progenitor. These results imply that chromosomal copy number changes can alter tolerance to specific stresses by influencing the transcriptional dynamics of individual, environmentally responsive genes.