Radiobiological Aspects Of Plant Epigenetic Polymorphism

Abstract

The relationship of epigenetic variability with different individual radiosensitivity and adaptive capabilities was studied. Using a simple and convenient experimental model — maize seedlings with different germination terms and epigenetic patterns — the hypothesis was tested that genetically homogeneous but epigenetically different organisms have different radiosensitivity and radio adaptive capacity. Differences in the DNA methylation profiles of individual subpopulations of seedlings were used as a marker of epigenetic differences, and the yield of chromosomal aberration was used as an indicator of DNA vulnerability and its changes under different UV-C irradiation modes. In two series of experiments involving а UV-C acute single and exposure according to the scheme «adaptive - challenging», the investigation of the possible biological importance of epigenetic polymorphism has been performed. The study used a cytogenetic analysis of the yield of chromosomal aberrations and restriction analysis followed by ITS-ISSR- PCR. Significant differences have been established in chromosome aberration yield and DNA methylation profile in control and under UV-C exposure for seedlings of subpopulations differing in time of germination. The differences in the DNA methylation profiles and the yield of chromosomal aberrations in the control subpopulations of seedlings of different germination terms indicate the influence of the DNA methylation profile on DNA damage by regular metabolic factors, such as thermal vibrations or reactive oxygen species (ROS). This phenomenon can be explained by different chromatin conformation determining structural or "passive" resistance, which provides different DNA availability to damage. Methylation switching into de novo under different modes of radiation exposure could become a marker of gene expression changes due to induced repair and protection. The obtained data indicate the importance of epigenetic factors in determining the radioresistance and adaptive capacity of organisms. It points out that the epigenetic mechanisms that determine the choice of the metabolic pattern also contribute to the individual radiosensitivity and adaptive capacity of the organisms. This contribution is determined in two ways. First, the DNA methylation profile affects the initial damage processes, and second, the type of methylation switching into de novo is associated with the further development of protection and repair processes.