REPAIR OF DNA-DAMAGE INDUCED BY ULTRAVIOLET-RADIATION

Studies documenting the depletion of the ozone layer and the resulting increases in UV-B radiation (280-320 nm) at the Earth's surface have served to focus attention on the biological effects of UV light. One o bvious target for UV-B-induced damage is DNA. Although all biological tissues are rich in UV-absorbing agents (largely nucleic acids and pro teins) and plants produce additional UV-absorbing pigments, no DNA in superficial tissue can completely avoid UV exposure. Plants, like all living organisms, must have some capacity for the repair of UV-induced DNA damage. Because plants are unique in the obligatory nature of the ir exposure to UV, it is also conceivable that they may have evolved p articularly efficient mechanisms for the elimination of UV-induced DNA damage. This review will summarize what we know about DNA repair mech anisms in higher plants. Readers interested in broader aspects of W-in duced damage and UV filters are directed to recent reviews (Middleton and Teramura, 1994; Strid et al., 1994; Fiscus and Booker, 1995). Our knowledge of DNA repair mechanisms in plants lags far behind our under standing of these pathways in animals, and a significant number of que stions concerning the basic phenomenology of DNA repair in plants rema in to be addressed.