Efficient photoreactivation of UVBR-induced DNA damage in the sublittoral macroalga Rhodymenia pseudopalmata (Rhodophyta)

Repair of DNA damage induced by ultraviolet-B radiation (UVBR) was investigated in the sublittoral red alga Rhodymenia pseudopalmata at different temperatures, using immunofluorescent detection of thymine dimers. Photoreactivation of thymine dimers was completed within about 3 h at 6, 12 and 18 degrees C in the presence of ultraviolet-ii radiation (UVAR) and photosynthetically active radiation (PAR) but no repair was found in dark-incubated fragments after 16-17 h. In plants previously exposed to a low UVBR dose (biologically effective dose: BEDDNA300 = 1.6 kJ m(-2); unweighted irradiance = 0.72 W m(-2) for 4 h), photoreactivation started within the first hour under UVAR + PAR at 18 degrees C but repair only started after 1-2 h at 12 and 6 degrees C. At 6 degrees C, repair was more efficient after exposure to a high UVBR dose (BEDDNA300 = 3.9 kJ m(-2); unweighted irradiance = 0.78 W m(-2) for 5 h) than to a lower dose (BEDDNA300 = 1.6 kJ m(-2)); no such difference was found at 18 degrees C. It is concluded that R, pseudopalmata is able to repair DNA damage induced by high UVBR doses efficiently.