Abstract
Cyclobutane pyrimidine dimer (CPD) photolyase monomerizes UV-induced CPD in DNA by using light energy of UVA and visible light. CPD photolyase is a simple and effecient repair system, and widely distributed among species from bacteria to higher plants. In plants, CPD photolyase is a crucial factor for determining UVB sensitivity. We previously reported that the native rice CPD photolyase was phosphorylated. There is no report that CPD photolyase is phosphorylated in organism other than rice plant.
We analyzed the phosphorylation status of CPD photlyase in several plant species. It was found that the phosphorylation of CPD photolyase was not a common event among plant species. Next, we tried to determine the phosphorylation site of rice CPD photolyase. We constructed plasmids carrying the genes encoding rice CPD photolyase which replaced the putative phosphorylation site with alanine residue by site-directed mutagenesis method. It was found that the peptide sequence including phosphorylation site was distinctive in some plant species.
Furthermore, we found that CPD photolyase localized to chloroplasts, mitochondria and nuclei and efficiently repairs UVB induced CPDs in all DNA-containing organelles in rice plants. We prepared organelle-enriched fractions from rice plants, and detected CPD photolyase phosphorylated status. Mitochondria demonstrated a high proportion of non-phosphorylated CPD photolyase, whereas nuclei and chloroplasts had a relatively high proportion of the phosphorylated form. In this workshop, we discuss about the significance of phosphorylation on CPD photolyase in plants.
