Molecular Aspects of Plant Adaptation to Life in the Chernobyl Zone

Abstract

With each passing year since the Chernobyl accident of 1986, more questions arise about the potential for organisms to adapt to radiation exposure. Often this is thought to be attributed to somatic and germline mutation rates in various organisms. We analyzed the adaptability of native Arabidopsis plants collected from areas with different levels of contamination around the Chernobyl nuclear power plant from 1986 to 1992. Notably, progeny of Chernobyl plants resisted higher concentrations of the mutagens Rose Bengal and methyl methane sulfonate. We analyzed the possible molecular mechanisms of their resistance to mutagens and found a more than 10-fold lower frequency of extrachromosomal homologous recombination, significant differences in the expression of radical scavenging (CAT1 and FSD3) and DNA-repair (RAD1 and RAD51-like) genes upon exposure to mutagens (Rose Bengal and x-rays), and a higher level of global genome methylation. This data suggests that adaptation to ionizing radiation is a complex process involving epigenetic regulation of gene expression and genome stabilization that improves plants' resistance to environmental mutagens.

Transcriptional Upregulation of DNA Damage Response Genes in Bank Voles (Myodes glareolus) Inhabiting the Chernobyl Exclusion Zone

“…A lack of change in expression of Brca1 in bank voles from the CEZ indicates that the homologous recombination repair pathway is not a key component of the response to environmental radionuclides, consistent with a recent study of expression of DBS repair pathways during exposure to IR (Liu et al, 2016). Arabidopsis from the CEZ show reduced recombination, which might prevent gross chromosomal rearrangements (Kovalchuk et al, 2014).…”

“…Moreover, a change in fur color of bank voles within the CEZ was attributed to downregulation of pheomelanin to reallocate antioxidants to ROS defense (Boratynski et al, 2014). Indeed, upregulation of oxidative stress response genes Cat and Fsd3 in Arabidopsis (Kovalchuk et al, 2014) indicate that increased ROS defense could be a key coping strategy against exposure to environmental radionuclides.…”

“…After exposure to high doses (750 Gy) of IR, DNA repair activity in pollen and seed from two species of plant depended upon the composition of radionuclides in the soil in which the parental plants had grown (Boubriak et al, 2008). Progeny of Arabidopsis inhabiting areas around Chernobyl exhibited low recombination rates, despite X-ray induced upregulation of homologous recombination repairrelated Rad54-like in samples from a contaminated area (Kovalchuk et al, 2014). Unfortunately these studies within the CEZ did not use replicate samples from contaminated and uncontaminated sites, making it challenging to determine whether radiation or a third variable accounts for these effects.…”

Impact assessment of long-term chronic radiation exposure on plant populations

“…Laboratory studies of repair inhibitions, dose-effect relationships for low-and high-LET radiations, measurements of unscheduled DNA synthesis and an efficacy of the single strand breaks recovery [15] suggest that the divergence of populations in terms of resistance is connected with a selection for changes in the effectiveness of repair systems. Another study on the possible mechanisms of adaptations to radioactive contamination [16] showed extremely low (more than 10-fold) recombination levels, and a higher level of global genome methylation in chronically irradiated plants that may have prevented extensive genome rearrangements. Although our understanding of mechanisms of adaptation is far from complete, these studies give good evidence that the response of biological systems to stress have been produced by normal evolutionary processes in relation to the environments in which the populations occur.…”

Indicators of climate change adaptation from molecules to ecosystems

“…Due to the hierarchy of different biological processes operative from molecules to biomes, the rate of biological adaptation is difficult to predict. While molecular and physiological processes can occur within minutes to days and months, biome-level processes typically take tens of years to even millions of years (Kowalchuk et al 2004;Gienapp et al 2008;Carroll et al 2016). The crucial question is whether biological adaptation is fast enough to cope with global climate change (Stocker et al 2013).…”