Low-level Radiocaesium Exposure Alters Gene Expression in Roots of Arabidopsis

Radiocaesium is one of the main anthropogenic sources of internal and external exposure to beta- and gamma-radiation (e.g. from global fallout of atmospheric atomic bomb testing and from the Chernobyl reactor accident). Here we investigated gene expression by suppression subtractive hybridization (SSH) and reverse transcription-polymerase chain reaction (RT-PCR) in Arabidopsis thaliana, which was induced by the root uptake of 134Cs. SSH analysis resulted in the isolation of 46 clones that were differentially expressed at 30 Bq cm(-3) 134Cs. Most of the expressed sequence tags identified belonged to genes encoding proteins that were involved in cell growth, cell division and the development of plants, and in proteins controlling translation, general metabolism and stress defence, including a DNA excision repair protein. The accumulation of caesium in plant material was measured in plants grown for 5 wk on agar contaminated by up to 60 Bq cm(-3) 134Cs. 134Cs was found to accumulate, in particular, in leaf rosettes and was dependent on the activity concentration in the growth media. The data indicate that low-level ionizing radiation influences important cellular responses, resulting in a changed gene-expression profile.