Abstract
To develop the factors related to UVB tolerance of rice, UVB-resistant rice cultivar "Sasanishiki" seeds were irradiated with carbon ion beam (320 MeV; 12C6+, 80 Gy), and two UVB tolerant and three UVB sensitive mutants were isolated. We focused on a UVB tolerant mutant UVTSa-319, because the UVTSa-319 has no mutation in the levels of UV-absorbing compounds, or CPD photorepair activity, which has been thought as factors related UVB tolerance. We found that about 40 kbp on chromosome 7 containing 2 genes which has unknown function was deleted in UVTSa-319. In general, UVB radiation causes DNA damages such as CPD,(6-4) photoproducts, or oxidative DNA damage, and these DNA damages can be mutagenic or lethal by impeding replication and transcription. To confirm whether the UVTSa-319 mutant has mutation in replication processes, UVTSa-319 and wild-type were treated with Hydroxy Urea (Replication block agent) and Mitomycin C (DNA damaging agent) and the sensitivity to these agents of the mutant was investigated. As a result, we found that UVTSa-319 was more tolerant to these agents than wild-type.
