Poster: Global Change
Abs #
58: Repair of DNA photoproducts in antarctic mosses
In recent decades, Antarctic plants have been exposed to increased levels of UV-B radiation, as a result of springtime ozone depletion. The annual occurrence of the ozone hole also coincides with the time of emergence from winter dormancy beneath the protective snow cover, exposing plants to sudden elevations of UV-B radiation in combination with increased PAR and greater temperature fluctuations. Bryophytes, the dominant plants on continental Antarctica may be particularly susceptible to UV-B damage because of their simple structure, with most having leaves which are only one cell thick and lacking protective cuticles or epidermal layers.
UV-B radiation is able to permeate plant tissues, damaging DNA and other macromolecules. Two major photoproducts may be formed upon damage of DNA: cyclobutane-type pyrimidine dimers and pyrimidine (6,4) pyrimidones. Both forms of damage can be repaired in plants by either light-dependent (photorepair) reactions, catalysed by photolyases, or by excision repair which is light-independent. The accumulation of these photoproducts was determined in 2 Antarctic mosses, Ceratodon purpureus and Bryum pseudotriquetrum in response to high UV-B radiation. The repair of these DNA lesions was then investigated under a range of temperatures and under light and dark conditions. Monoclonal antibodies were used in an enzyme-linked immunosorbent assay to detect the formation of DNA damage products. Unlike many higher plants, significant repair of DNA photoproducts was observed in the dark, suggesting that photorepair maybe less important in these plants. These results will be discussed in relation to the capacity of Antarctic plants to withstand increased levels of UV-B radiation.
