Plant response to DNA damage: the role of the ATM gene
The gene ATM codes for a protein kinase activated in response to DNA damage, in particular double strand breaks. In mammals, the targets of this protein participate in DNA repair, cell cycle control, and apoptosis or programmed cell death. In humans, the modification of the ATM gene is responsible for ataxia-telangiectasia, a disease characterised, for example, by chromosomal disorders, a greater predisposition to cancer, and marked sensitivity to ionising radiation. A homologous gene was identified in the plant Arabidopsis thaliana, and the effects of its modification could thus be characterised. Deactivation in Arabidopsis thaliana of this homologue, AtATM, induced hypersensitivity to gamma-rays and methylmethane sulphonate, a compound that, indirectly, also causes double strand breaks in DNA. Sensitivity to UV-B radiation, which causes other types of damage to DNA, remained unchanged, however. This genotoxic sensitivity profile of atm mutants of Arabidopsis suggests a specific defect in the repair of double strand breaks in DNA. This sensitivity to double strand breaks is correlated with an inability of the mutants to express genes involved in the detection and/or repair of DNA breaks after exposure to radiation.
©CEA/A. Tissier
In addition, the mutants display partial sterility due to a high rate of chromosomal fragmentation during meiosis. However, the meiotic recombination genes (SPO11 and DMC1) are expressed normally in the mutant, leaving unanswered a certain number of questions about the role of the ATM gene in Arabidopsis during meiosis.
These results show that, from plants to mammals, this gene plays a central role in the response to DNA damage during both stress and growth. The findings were published in the journal Plant Cell, and were the subject of special editorial comment.