Host: The Japan Radiation Research Society
The radiation effects on mutation at tandem repeat loci in plant genome were investigated. A tandem repeat locus similar to mammalian unstable loci, such as ESTR in mouse, was identified by BLAST searches of the arabidopsis genome database. The locus consists of an array of 6 bp repeat units, ATGGGG. The length of the array varied greatly between ecotypes of arabidopsis, which indicates high frequency of mutation resulting from gain or loss of the repeat units in the locus. The change in the length of the locus was analyzed in the descendants of the plants irradiated with 137Cs gamma rays at 50 mGy/h (50-59 Gy in total) during their growth. Among 328 descendants of the irradiated plants, four plants showed changes in the length of the locus, whereas no changes were observed in 516 descendants of non-irradiated plants. Among the four mutated plants, two plants showed large loss of the repeats (nine and ten repeats, respectively) in the locus. The occurrence of the large deletions implies that a simple model of replication slippage cannot account for mutation events at this locus. These results suggest that the mutation in the tandem repeat locus is unique not only in the high mutation frequency but also in the mode of mutation.
