DNA damage, repair monitoring and epigenetic DNA methylation changes in seedlings of Chernobyl soybeans

- External chronic radiation and internally incorporated radionuclides after Chernobyl accident induce genome instability in the plant genome.
- Induced DNA strand breaks were efficiently repaired at the soybean cotyledon stage.
- Development of a new experimental design of the Methylation-sensitive comet assay adapted for a plant model system.
- A slight fluctuation in the CCGG methylation pattern was connected with adaptation capacity in Chernobyl plants.

This pilot study was carried out to assess the effect of radio-contaminated Chernobyl environment on plant genome integrity 27 years after the accident. For this purpose, nuclei were isolated from root tips of the soybean seedlings harvested from plants grown in the Chernobyl area for seven generations. Neutral, neutral-alkaline, and methylation-sensitive comet assays were performed to evaluate the induction and repair of primary DNA damage and the epigenetic contribution to stress adaptation mechanisms. An increased level of single and double strand breaks in the radio-contaminated Chernobyl seedlings at the stage of primary root development was detected in comparison to the controls. However, the kinetics of the recovery of DNA breaks of radio-contaminated Chernobyl samples revealed that lesions were efficiently repaired at the stage of cotyledon. Methylation-sensitive comet assay revealed comparable levels in the CCGG methylation pattern between control and radio-contaminated samples with a slight increase of approximately 10% in the latter ones. The obtained preliminary data allow us to speculate about the onset of mechanisms providing an adaptation potential to the accumulated internal irradiation after the Chernobyl accident.Despite the limitations of this study, we showed that comet assay is a sensitive and flexible technique which can be efficiently used for genotoxic screening of plant specimens in natural and human-made radio-contaminated areas, as well as for safety monitoring of agricultural products.