Abstract
Ultraviolet-B radiation (UVB; 280-320 nm) can damage DNA by causing formation of cyclobutane pyrimidine dimer (CPD). Photoreactivation mediated by an enzyme, photolyase, is the major pathway for repairing UVB-induced CPD in plants. Plant cell has different genome in each nuclei, chloroplast and mitochondria. It has been reported that CPD photoreactivation was involved in nuclei, but in the other two organelles in Arabidopsis. We previously reported at the meeting (the 48th Annual Meeting of The Japan Radiation Research Society, 2005) that the levels of CPD induced by UVB radiation on not only nuclei but also chloroplast and mitochondrial genome decreased dependently by exposure of blue irradiation. These results suggested that CPD photolyase, which is encoded by a single-copy gene in nuclei, could function in nuclei, chloroplast and mitochondria in rice. In this study, in order to verify this suggestion, we compared the CPD photorepair capacity in each organelle among two rice strains (Sasanishiki and Surjamkhi) and antisense CPD photolyase gene transgenic plant: Surjamkhi was more deficient in CPD photolyase activity compared with Sasanishiki, and the antisense transgenic plant has little CPD photolyase activity. As a result, we found that there was a significant difference in CPD photorepair capacity in each organelle among these plants: the CPD photorepair capacity in each organelle was faster in Sasanishiki than that in Surjamkhi, and was not detected in antisense transgenic plant. Thus, CPD photolyase functions in nuclei, chloroplast and mitochondria in rice plant.
