DNA Double-Strand Breaks in Tobacco BY-2 Cells and CHO-K1 Cells Irradiated with Gamma Rays

Abstract

In tobacco protoplasts from BY-2 cell line and CHO-K1 cells irradiated with ⁶⁰Co gamma rays, DNA double-strand breaks (DSB) were measured by pulsed-field gel electrophoresis. Linear relationship between dose and number of DSB was found, and number of DSB per Gy were 27.8 +/- 1.4 in tobacco cells and 39.6 +/- 1.2 in CHO-K1 cells. On the other hand, mean lethal doses (D₀) of gamma rays based on the colony formation assay were 10.7 Gy in tobacco cells and 1.4 Gy in CHO-K1 cells. Consequently, the average numbers of DSB needed to induce cell killing were calculated to be 297.5 +/- 14.9 in tobacco cells and 55.4 +/- 1.7 in CHO-K1 cells. From these, it is suggested that the efficiencies of induction and repair of DSB are different between tobacco cells and CHO-K1 cells. [J Radiat Res 44:435 (2003)]