Abstract
Ultraviolet-B radiation (UV-B, 280~320nm) 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. Sensitivity to UVB varies widely among rice cultivars. We previously indicated that a difference in UVB sensitivity among rice cultivars is tightly linked with an alteration of function of photolyase resulting from spontaneously occurring mutations in the CPD photolyase gene. Here, in order to demonstrate directly that CPD photolyase activity is a crucial factor for determining UVB sensitivity in rice, we constructed transgenic rice plants with five to thirty-fold higher CPD photolyase activity or very low activity in comparison with UV-resistant rice cultivar Sasanishiki (wild type). Rice plants with higher CPD photolyase activity, by overexpressing CPD photolyase, showed strong resistance to UVB-caused growth inhibition, whereas rice plants with very low activity, by insertion ob antisense CPD photolyase gene, was severely damaged. These results emphasize that CPD photolyase activity plays an important role in preventing UVB-caused growth inhibition, and the increases in CPD photolyase activity can lead to increasing resistance to UVB radiation.
