Ionising radiation exposure: how it affects gene expression and pine tree morphology

Ionising radiation continues to pose an environmental threat to human and non-human biota, for example at sites of nuclear disasters like the Chornobyl and Fukushima exclusion zones. Pine trees are especially sensitive to radiation, and
therefore of high interest for research on radioactive contamination of the environment. To better understand the radiation response of the highly
sensitive pine tree – commonly found at the Chornobyl and Fukushima exclusion zones, we investigated whether gene expression is altered by radiation (dose rate: 682 μGy/h) in a 10-week laboratory exposure experiment of young Pinus
sylvestris seedlings.
RT-qPCR revealed a lower expression of METHYLTRANSFERASE 1 (MET1) in roots at week 10 of the cultivation. Phenotypically, the roots of irradiated seedlings weighed less at week 10 compared to control roots. Moreover, at weeks 4 and
6, the total length of plants was significantly lower for the irradiated group. Furthermore, exposure to ionising radiation seemed to alter the morphology of
the shoot apex, although no changes in gene expression were observed in the shoot tissue.
Aside from the molecular and phenotypical analyses of irradiated samples, attempts were made to develop a protocol for flow cytometry imaging of stained pine nuclei to investigate differences in chromatin condensation in irradiated samples. Using fluorescence microscopy we confirmed nuclei were
successfully extracted and stained. However, we were not able to visualise the nuclei using a flow cytometric approach.
In conclusion, results here may indicate changes in methylation in irradiated seedlings, and its potential role in morphological changes will be discussed here.