Mutation spectrum analysis in higher plants

Yoshihara, Ryohei; Hase, Yoshihiro; Nozawa, Shigeki; Narumi, Issei; Takimoto, Koichi*; Sakamoto, Ayako

Ionizing radiation has been applied to various plants for decades to generate many useful agricultural resources. Nevertheless, it is still unclear how the radiation effectively induces mutations in higher plants. To clarify the molecular mechanisms for radiation-induced mutagenesis in higher plants, we have been developing novel systems to detect various types of mutations occurring . The gene encodes the S12 subunit of the 30S ribosomal protein, to which streptomycin binds. We subcloned the gene together with an vector ori between LB and RB sites of a binary vector, which was then introduced into the genome. From the transgenic plants grown under the presence or absence of mutagens, we retrieved the coding region using a plasmid rescue approach. When the transgenic plants were grown for two weeks under normal conditions, mutations of the gene occurred with a frequency of 3.310. Moreover, the rescue analysis revealed that the -ray exposure elevated the mutant frequency by about three times. However, G:C to T:A transversions resulting from the mispairing of 8-oxo-G with adenine did not increase significantly with rays. This result suggests that plants may have a system that differs from other organisms to tolerate oxidative damage to DNA.