The aim of this study was to assay the capability of Chlamydomonas reinhardtii strains with different level of radio-resistance to develop "adaptive response" (AR) to the herbicide paraquat (PQ). AR was evaluated using two endpoints: micro-colony assay and DNA double-strand breaks (DSB) rejoining. The level of induced DSB was measured by constant field gel electrophoresis based on incorporation of cells into agarose blocks before cell lysis. It was obtained that the strains with WT radio-resistance developed a strong PQ-induced AR evaluated on the basis of micro-colony assay. No AR was registered in radio-resistant strains. It was also obtained that a certain low level of primary induced DSB is necessary to trigger PQ-induced AR in the studied Chlamydomonas reinhardtii strains. A good correspondence was observed between the magnitude of AR measured as microcolony cell survival and DNA damage remaining, suggesting that non-repaired DSB could be responsible for cell death. In WT strains accelerated DSB rejoining in PQ-induced AR was observed.
Key words: adaptive response, paraquat, micro-colony assay, DSB-DNA rejoining, Chlamydomonas
Topic: BIOLOGY