OVEREXPRESSION OF MEDAKA (ORYZIAS-LATIPES) PHOTOLYASE GENE IN MEDAKA CULTURED-CELLS AND EARLY EMBRYOS

To study the role and the regulation of the photolyase gene in the Med aka (small teleost), we constructed a eukaryotic expression plasmid of the Medaka photolyase gene and introduced it into Medaka cells in vit ro and in vivo. The expression plasmid contains a cytomegalovirus enha ncer and a thymidine kinase promoter to overexpress the photolyase gen e of the Medaka. First, we transfected this construct into cultured Me daka cells and established several lines of transfectant. Every transf ectant showed enhanced ability of pyrimidine dimer repair in the prese nce of fluorescent light. In the transfectant that showed the most enh anced ability of photorepair, the augmented transcription of photolyas e gene was observed compared with that of progenitor OL32 cells. In th is transfectant, we also observed an enhanced rate of UV survival with 20 min of fluorescent light treatment after irradiation with a 400 J/ m(2) UV sunlamp. Next, the expression construct was microinjected into the embryos of the Medaka at the one cell stage. Compared with the no ntreated counterparts, the overexpression of a photolyase gene was det ected in the microinjected embryos, but we failed to detect a signific ant increase in photoreactivability of death at the midblastula stage.