Abstract
To reveal the characteristics of radiation-induced mutations in higher plants, we examined intragenic mutations induced by gamma-rays and carbon ions using transgenic Arabidopsis that carries Escherichia coli rpsL gene and demonstrated that gamma-rays and carbon ions (Mean LET 112 keV/μm) induced different mutations in respect to the size of deletions. Carbon ions that have a shorter range within the diameter of Arabidopsis seeds (Mean LET 402 keV/μm) showed a higher cell killing effect than the carbon ions (LET 112), but the mutation frequency in the rpsLgene was unchanged from background mutation frequency. This suggests the possibility that large structural alterations, which can not be detected by this method, are frequently induced by the carbon ions (LET 402), because this experimental system detects intragenic mutations via plasmid rescue. The Arabidopsis mutant plants defective in the Ligase IV gene, a major determinant in the double strand break repair pathway, showed higher radiation sensitivity than the wild type. We compared the difference in Dq values between the two kinds of carbon ions (LET 112 and 402) and found that the difference in the Ligase IV mutant was much lower than that in the wild type. This suggests that the carbon ions (LET 402) induced much irreparable DNA lesions. To further examine the characteristics of mutations induced by carbon ions (LET 402), mutation detection using Arabidopsis GL1 gene and E. coli codA gene as marker genes have been carried out. We will show the characteristics of mutations detected with these marker genes.
