Meeting Abstract

P2.14  Saturday, Jan. 5  Mechanisms underlying photorepair and photoprotection of Ultraviolet-C irradiated Austrofundulus limnaeus embryos and implications for a novel developmental stage WAGNER, J.T.*; PODRABSKY, J.E.; Portland State University; Portland State University josw@pdx.edu

Populations of the annual killifish Austrofundulus limnaeus are able to persist in ephemeral pond habitats through production of drought and anoxia tolerant embryos that enter diapause while buried in desiccated mud. Annual killifish, including A. limnaeus, are unique among teleosts because their normal embryonic development involves a process of complete blastomere dispersion across the yolk surface by 4 days post-fertilization (dpf). The embryonic blastomeres subsequently reaggregate at a random site on the yolk surface to form the embryonic axis by 10 dpf, developing into the embryo proper. Previous investigators have suggested that the dispersed cell phase might buffer embryos against environmental stresses by allowing surrounding undamaged blastomeres to divide mitotically and replace damaged or dying cells. We explored the validity of this hypothesis by exposing embryos of A. limnaeus to massive doses of Ultraviolet-C (UV-C) radiation. Our results indicated a high tolerance of UV-C when embryos are allowed to recover in photoreactivating light. Without photoreactivating light, significantly higher proportions of embryos develop abnormally if UV-C irradiation occurs during embryonic axis formation when compared to dispersed blastomere stages or diapausing embryos. We also profiled the expression of stem cell-specific transcription factors and axis-formation factors during the dispersion and reaggregation phases of A. limnaeus development using real-time qPCR. The mechanisms that support tolerance of UV-C irradiation of A. limnaeus embryos and the evolutionary implications of the apparent “developmental buffering” observed in the dispersed cell phase are explored.