Abstract
Ultraviolet-B (UVB) radiation induces photodamage in DNA, including the formation of cyclobutane pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photodimers [(6-4) photoproducts]. Two major repair mechanisms for such DNA damage are excision repair and photoreactivation. In photoreactivation, the enzyme photolyase mediates the repair of damaged DNA by binding to CPDs or (6-4) photoproducts in a lesion-specific manner. In plants, the CPD photolyase is a crucial factor for determining UVB sensitivity. In rice, however, the relative contribution of (6-4) photolyase to UVB resistance is unclear. We measured the activity of (6-4) photolyase and the UVB sensitivity of three rice cultivars. There was no correlation between (6-4) photolyase activity and UVB sensitivity. Furthermore, we investigated the UVB sensitivity of (6-4) photolyase-deficient mutant rice. No difference was found between wild-type rice and the mutant. It was reported that the Arabidopsis mutant defective in (6-4) photolyase was more sensitive to UVB than the wild-type. On the other hand, our results suggested that the activity of (6-4) photolyase was not significantly affected the UVB sensitivity of rice.
