Rejoining of DNA double-strand breaks and clastogenic effects in higher-plant tobacco cells irradiated with rays

Yokota, Yuichiro; Wada, Seiichi*; Tanaka, Atsushi; Narumi, Issei

There is an interesting but still-unsolved issue in radiation biology: a part of higher plants show high radiation tolerance. In this study, we investigated the rejoining ability of DNA double-strand breaks (DSBs) in tobacco cells by pulsed-field gel electrophoresis (PFGE) assay and clastogenic effects by micronucleus (MN) assay. In the PFGE assay, an equal level of DSB rejoining ability was observed between tobacco cells and Chinese hamster cells. We monitored MN formation in tobacco cells and found that the rate (cells having at least one MN per observed cells) reached the maximum at 2 day-post-irradiation (DPI). The MN formation rate at 2 DPI increased with ray dose and was 40 % at LD (27.4 Gy). In mammalian cells irradiated with LD of rays, MN formation rates are generally 30 % or less. In summary, tobacco cells are permissive to clastogenic effects of ionizing radiation, and this appears to contribute the radiation tolerance.