Distinct pathways mediate UV-induced apoptosis in Drosophila embryos.

Cell death in Drosophila is regulated by many of the same signals that control apoptosis in mammalian systems. For all the three major cell death pathways that have been described in humans, homologous components have been identified in Drosophila. Here we report that distinct pathways mediate UV-induced apoptosis at different developmental stages in the Drosophila embryo. In midstage embryos, UVC irradiation induces reaper expression and cell death through a mei-41(dATM)-dependent pathway; UVB does not have the same effect. In contrast, in pregastrulation embryos, both UVB and UVC promote apoptosis via transcriptional induction of the Drosophila Apaf-1/ced-4 homolog. This early UV response requires E2F but not mei-41 function and appears to be independent of DNA damage.