Analysis of DNA damages induced by ion beam, ray and UVB radiation in Arabidopsis

Teranishi, Mika*; Yamaguchi, Hiroko*; Sakamoto, Ayako; Hidema, Jun*

Radiation induce DNA damages, such as strand breaks, oxidative damage, and cyclobutane pyrimidine dimer (CPD) possibly resulting in an increased mutation frequency. Although it is important to know which DNA damage converted into a mutation, little is known about the types and extent of DNA damage induced by radiation in plant cells. We measured the number of DNA damages induced by ionizing radiation (carbon and helium ion beams, rays) and non-ionizing radiation (UVB) in Arabidopsis seedlings. The irradiated seedlings were harvested immediately and used for preparing an agarose plug, which were subjected to denature and non-denature agarose gel electrophoresis using static field electrophoresis and biased sinusoidal field gel electrophoresis. The number of DNA strand breaks were calculated using the molecular length standard curve and the quantity of DNA at each migration position as shown by the quantitative image data. As a result, irradiation of seedlings with 960 Gy of carbon ions resulted in up to 1.9 DNA double-strand breaks per megabase (Mb). Given that the total size of the Arabidopsis genome is 135 Mb, 960 Gy of carbon ions induce 257 DNA double-strand breaks per genome. Our results indicated that double-strand breaks were most inducible DNA damage by irradiation of carbon ions while single-strand breaks were most inducible by irradiation of helium ions and rays.