Zeocin-Induced Adaptive Response in Saccharomyces cerevisiae: The Contribution of Priming Dose and Experimental...

We aimed to clarify how the priming dose and the experimental design could affect the development of an adaptive response (AR) induced by low-dose Zeocin (Zeo) in Saccharomyces cerevisiae strains with differing genetic constitution. Constant-field gel electrophoresis was used for measuring double-strand breaks (DSBs) induction and DNA rejoining; for microbiological experiments, Zimmermann's test was used for measuring survival fraction and genetic events. Favorable experimental conditions for the induction of AR in both D7ts1 and 551 strains were determined: the priming dose inducing about 20% lethality or at least a 1.5-fold increased DSB level, 45 min inter-treatment time, and recovery time of 30-45 min. Both strains developed well-expressed AR, measured by increased cell survival, but differed in their ability to develop AR, measured by reduction in DSBs. This discrepancy could be due to different DSBs rejoining rather than different DNA susceptibility, and the partial contribution of DSB repair to cell survival in the split-dose experiments. The frequency of mutagenic and recombinogenic events and DSB levels were lower in split-dose treatment. The development of AR depends on several factors: the magnitude of the priming dose, DNA susceptibility, the duration of the ITT window, the duration of recovery time, as well as genetic constitution of strains.