Minisymposium 3: Global Change
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M0304: Safer to be dry - desiccation protects Antarctic mosses from UV-B induced DNA damage.
Growth conditions in Antarctica are extreme, and the few plants that can grow there are exposed to a highly seasonal, rapidly variable and often extreme climate. In recent decades, these plants have also been exposed to increased levels of UV-B radiation (UV-BR), as a result of springtime ozone depletion. The annual occurrence of the ozone hole coincides with the time of emergence from winter dormancy beneath the protective snow cover, exposing plants to sudden elevations of UV-BR. 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. Some Antarctic mosses have been shown to produce screening pigments that could protect against UV-BR and they are all desiccation tolerant, in order to tolerant life in a frozen desert. We hypothesized that such mosses might be more protected in the desiccated state due to effective concentration of screening pigments. To test this 3 species of co-occurring Antarctic mosses, Bryum pseudotriquetrum, Grimmia antarctici and Ceratodon purpureus were irradiated with artificial UV-BR in either a fully hydrated or desiccated state. DNA damage in the form of cyclobutane pyrimidine dimers was significantly higher in the endemic moss, G.antarctici, than the other 2 species. In all species, desiccated moss accumulated less damage than hydrated moss. This study demonstrates that desiccation can confer protection from UV-B induced DNA damage in all 3 species but that G.antarctici is potentially more vulnerable to elevated UV-BR than the other species. Continuing ozone depletion events may thus have consequences for the endemic's future competitiveness.
