SOME RESULTS ON THE CONTRIBUTION OF DSB DNA REJOINING FOR THE DEVELOPMENT OF ADAPTIVE RESPONSE IN Chlamydomonas reinhardtii

Dimova E., Chankova S. & Bryant P. E. (2008): Some results on the contribution of DSB DNA rejoining for the development of adaptive response in Chlamydomonas reinhardtii. Proceedings of the III Congress of Ecologists of the Republic of Macedonia with International Participation, 06-09.10.2007, Struga. Special issues of Macedonian Ecological Society, Vol. 8, Skopje. The “adaptive response” (AR) is an evolutionarily developed mechanism of living organisms for adaptation to environmental stress. Although AR has been observed in different model systems using various endpoints, its underlying molecular mechanisms are still poorly understood. This report summarizes our results which support the suggestion that a low level of initial DNA damage can trigger radiationand radiomimetic-induced AR in Chlamydomonas reinhardtii measured as acceleration of DNA double-strand break (DSB) rejoining. The level of induced DSB DNA was measured by constant field electrophoresis based on incorporation of cells into agarose blocks before cell lysis. This avoids the risk of accidental induction of DSB during manipulation. Our experiments showed that AR was induced by two DNA-damaging agents (physical and chemical). This AR could be considered as a result of up-regulated DSB DNA rejoining. Our results suggest that the radiomimetic zeocin could be used as a substitute for gamma-radiation in radio-adaptive response studies. Since unicellular green algae are a robust model for the plant cell and organism, the results obtained for C. reinhardtii could be extrapolated to higher plants. This work was supported by the Bulgarian Ministry of Education and Science (projects K-1204; B-1520; BioCORE), BAS, St Andrews University, RS, UK.