Yokota, Y., Shikazono, N., Tanaka, A., Hase, Y., Funayama, T., Wada, S. and Inoue, M. Comparative Radiation Tolerance Based on the Induction of DNA Double-Strand Breaks in Tobacco BY-2 Cells and CHO-K1 Cells Irradiated with Gamma Rays. Radiat. Res. 163, 520–525 (2005).
Higher plants are generally more tolerant to ionizing radiation than mammals. To explore the radiation tolerance of higher plants, the induction of DNA double-strand breaks (DSBs) by γ rays was investigated in tobacco BY-2 cells and compared with that in Chinese hamster ovary (CHO)-K1 cells as a reference. This is the first examination of radiation-induced DSBs in a higher plant cell. The resulting DNA fragments were separated by pulsed-field gel electrophoresis and stained with SYBR Green I. The initial yield of DSBs was then quantified from the fraction of DNA fragments shorter than 1.6 Mbp based on the assumption of random distribution of DSBs. The DSB yield in tobacco BY-2 cells (2.0 ± 0.1 DSBs Gbp−1 Gy−1) was only one-third of that in CHO-K1 cells. Furthermore, the calculated number of DSBs per diploid cell irradiated with γ rays at the mean lethal dose was five times greater in BY-2 cells (263 ± 13) than in CHO-K1 cells. These results suggest that the radiation tolerance of BY-2 cells appears to be due not only to a lower induction of DNA damage but also to a more efficient repair of the induced DNA damage.