Chronic exposure to ionising radiation (IR) in the Chernobyl Exclusion Zone has created a natural experiment for plant evolution. We collected Arabidopsis thaliana seeds from a reference plot (Babchin) and two radioactively contaminated plots (Vygrebnaya Sloboda and Masany), established their respective seed lines in vitro and studied their physiology and genomes. Seeds were challenged with acute γ-irradiation (150 Gy), heat (50 °C) and oxidative stress (0.01 µM methyl viologen). The radiation legacy manifested as contrasting stress response profiles and suppressed germination in chronically irradiated lines, which was rescued by exogenous ROS. Genome resequencing of plants from the heavily contaminated plot, Masany, revealed decreased nucleotide diversity and signs of a selective sweep, accompanied by increased fixation rates for single-nucleotide polymorphisms (SNPs) in exons. Compared to the non-irradiated reference population, genes accumulating unique SNPs in Masany were related to DNA repair, cell cycle and mitosis, phragmoplast assembly, response to oxidative stress, Ca 2+/ROS signalling, and epigenetic processes. Together, the data show that decades of low-dose irradiation drive rapid microevolution in A. thaliana, favouring mutations that bolster genome stability and stress-signalling networks while probably compromising seed performance. These findings provide the first field-scale genomic evidence of the targeted accumulation of mutations in specific genomic regions of chronically irradiated plants, suggesting that long-term exposure to chronic ionising radiation may alter population genetic structure.
Blinova et al. (Fri,) studied this question.
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