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 investig ated in the sublittoral red alga Rhodymenia pseudopalmata at different temp eratures, using immunofluorescent detection of thymine dimers. Photoreactiv ation of thymine dimers was completed within about 3 h at 6, 12 and 18 degr ees C in the presence of ultraviolet-ii radiation (UVAR) and photosynthetic ally active radiation (PAR) but no repair was found in dark-incubated fragm ents after 16-17 h. In plants previously exposed to a low UVBR dose (biolog ically 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 hi gh 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 differe nce was found at 18 degrees C. It is concluded that R, pseudopalmata is abl e to repair DNA damage induced by high UVBR doses efficiently.