Silencing of CPD Photolyase Makes Arabidopsis Hypersensitive and Hypermutable in Response to UV-B Radiation

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Plants are exposed to solar ultraviolet radiation (UV), which has deleterious effects on plant growth, development and physiology. Cyclobutane pyrimidine dimers (CPDs) are a major form of UV-induced DNA damage. It is conceivable that the reversal of CPDs is important for the reduction of lethal and mutagenic effects. Photoreactivation catalyzed by CPD photolyase is an efficient CPD repair system with a mechanism dependent on UV-A/visible light, which is contained in solar radiation. Photoreactivation presumably functions to protect plants from solar UV. We generated a CPD photolyase knock-down in Arabidopsis thaliana by RNA interference (RNAi) to investigate the role of CPD photorepair for protection of plants from solar UV. These knock-down lines exhibited hypersensitivity to UV-B and an increased occurrence of mutation induced by UV-B radiation compared with Arabidopsis proficient in CPD photolyase. Mutations induced by UV-B were determined by an rpsL mutation assay system. G:C to A:T transitions were frequently observed in CPD photolyase knock-down lines at the site of dipyrimidine sequences. A high incidence of frameshifts was observed in irradiated knock-down lines. These results indicate that CPD photoreactivation plays an important role for UV resistance of Arabidopsis and suppression of UV-induced mutagenesis.
2008-05-20