Abstract
Ionizing radiation is known to induce mutations by forming oxidative damage on DNA. Previously, we investigated γ-ray-induced mutations in dry seeds of the model plant Arabidopsis. The result suggested that mutational effect of oxidative guanine, which is one of the major oxidative DNA damage, was low in Arabidopsis dry seeds. In this study, we analyzed γ-ray-induced mutation spectrum in Arabidopsis seedling, which has high water content and cell proliferation activity, in order to investigate the effect of oxygen radicals by water radiolysis and misincorporation of oxidized dNTPs during DNA replication on mutagenesis. Moreover, to evaluate the effect of nucleotide pool sanitization system on γ-ray-induced mutations, we analyzed a mutant deficient in the Arabidopsis NUDT1 gene that is a homologue of Escherichia coli mutT and human MTH. For mutation spectrum analysis, we utilized the rpsL-transgenic Arabidopsis to detect the mutations in γ-irradiated plants by plasmid rescue technique.
Background mutant frequency of the nudt1 mutant was comparable to that of wild type plant, suggesting that the deficiency of nucleotide pool sanitization enzyme hardly affects on mutagenesis under normal condition in Arabidopsis. The γ-ray sensitivity of the nudt1 mutant was slightly higher, but not statistically significant, than that of wild type plant. No difference in the extent of mutant frequency induced by γ-rays was found between the wild type and nudt1 plants. However, the mutation spectra induced by γ-rays were different between the wild type and nudt1 plants. From these results, it was suggested that the NUDT1 deficiency obviously affects on the mutagenesis but not the plant growth following γ-irradiation.
