Characterization of radiations-induced genomic structural variations in Arabidopsis thaliana.

DNA, is assaulted by endogenous and exogenous agents that lead to the formation of damage. In order to maintain genome integrity DNA repair pathways must be efficiently activated to prevent mutations and deleterious chromosomal rearrangements. Conversely, genome rearrangement is also necessary to allow genetic diversity and evolution. The antagonist interaction between maintenance of genome integrity and rearrangements determines genome shape and organization. Therefore, it is of great interest to understand how the whole linear genome structure behaves upon formation and repair of DNA damage. For this, we used long reads sequencing technology to identify and to characterize genomic structural variations (SV) of wild-type Arabidopsis thaliana somatic cells exposed either to UV-B, to UV-C or to protons irradiations. We found that genomic regions located in heterochromatin are more prone to form SVs than those located in euchromatin, highlighting that genome stability differs along the chromosome. This holds true in Arabidopsis plants deficient for the expression of master regulators of the DNA damage response (DDR), ATM (Ataxia-telangiectasia-mutated) and ATR (Ataxia-telangiectasia-mutated and Rad3-related), suggesting that independent and alternative surveillance processes exist to maintain integrity in genic regions. Finally, the analysis of the radiations-induced deleted regions allowed determining that exposure to UV-B, UV-C and protons induced the microhomology-mediated end joining mechanism (MMEJ) and that both ATM and ATR repress this repair pathway.