EFFECT OF NITROGEN STARVATION ON DNA REPAIR IN SACCHAROMYCES CEREVISIAE

The gamma radiation response of diploid yeast Saccharomyces cerevisiae was studied under the condition of nitrogen starvation. An increase in radioresistance was observed when the cells were grown either on solid or in liquid media containing low nitrogen supply. Most of the induced resistance was obtained in the first 1h of incubation in the stress medium. Cells incubated in synthetic liquid medium with limited nitrogen source showed an increase in radioresistance with time as the nitrogen supply in the medium became depleted. Diploid strains carrying a mutation at the RAD52 locus did not show increased radioresistance in synthetic low nitrogen medium. The frequencies of gene conversion at a tryptophan locus and reverse mutation at an isoleucine locus were studied for the strain D7 under nitrogen stress. Our results suggest that nitrogen starvation induces DNA repair which is essentially error free and is mediated through activated recombination pathways.