Fitness trade-offs lead to suppressor tolerance in yeast

To dissect the genetic basis of such trade-offs, we crossed strains with contrasting tolerance levels on rich media, and analyzed the fitness distribution patterns in the offspring. Combining bulk segregant analysis and quantitative tetrad analysis, we identified two genes, namely MKT1 and RGA1, to be involved in suppressor tolerance. We showed that alleles from the tolerant parent for both genes conferred to significant gain of fitness, which increased the suppressor tolerance. Our results offered a detailed dissection of suppressor tolerance in a natural yeast isolate and provide insights into the molecular basis of trade-offs between fitness and evolutionary potential.