DNA DAMAGE AND REPAIR: INDUCTION AND REMOVAL OF THYMINE DIMERS IN ULTRAVIOLET LIGHT IRRADIATED INTACT WATER PLANTS

Abstract— The production of UV-induced thymine dimers and their fate upon post-irradiation incubation in the dark was studied in DNA of the intact water plants Wolffia microscopica and Spirodela polyrhiza. The results demonstrate production of thymine dimers, and the ability of the plant cells to remove the dimers from their DNA. The rate of removal is rapid during the first few h of post-irradiation incubation in the dark. It continues at a slower rate for the next 24–48 h, at which time it is essentially complete. The disappearance of thymine dimers in light or in the dark is analogous to the well-known processes in other biological systems, namely, photoreactivation and dark excision.