Arabidopsis thaliana seedlings show an age-dependent response on growth and DNA repair after exposure to chronic γ-radiation

• We exposed Arabidopsis thaliana seedlings of different ages to chronic γ-radiation.
• Growth response differs between ages upon exposure.
• Patterns of DNA repair and cell cycle transcription upon exposure are age-dependent.

The biosphere is constantly exposed to ionising radiation, due to cosmic radiation and the presence of natural and anthropogenic radionuclides in the environment. The biological effects of the resulting radiation exposure are currently poorly understood in plants, due to a large influence of parameters such as species, cultivar, experimental setup and plant age on the response. In this study, 7-, 10- and 14-day-old Arabidopsis thaliana seedlings were exposed to 96 h and 168 h of 100 mGy h−1 chronic γ-radiation in a hydroponic setup. The response of growth, photosynthesis and the transcription of genes involved in DNA repair, cell cycle and signalling were measured. The results show that there is a difference in growth response between plants of different ages and decreasing radiosensitivity with increasing seedling age. This is linked to differences in regulation of DNA repair and cell cycle control at the transcriptional level.