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Figure 2
JNK-mediated hid induction induces apoptosis in the retina in response to UV irradiation. (A, B) hid is induced by UV irradiation in the Drosophila retina in a JNK-dependent manner. (A) hid expression 2 h after UV irradiation was detected by monitoring lacZ expression from a hid reporter line (Russell et al, 1998; Cox et al, 2000; Cullen and McCall, 2004; Sen et al, 2004). The irradiated eye is shown on the right (UV) and the shielded eye on the left (Ctrl). (B) Similarly, hid induction in wild-type animals (w1118, left panel) could be observed using RT–PCR on retina dissected from pupae 2.5 h after irradiation (rp49 transcript levels serve as internal controls). Induction of hid was not observed in hep1 hemizygous males (right panel), indicating a requirement for JNK signaling in the transcriptional response to UV. (C, D) Overexpression of constitutively active Hep (Hepact) in developing photoreceptors and cone cells causes apoptosis. Increased TUNEL-positive cells were observed in larval eye imaginal discs expressing Hepact under the control of Sep-Gal4 (D), compared to wild-type discs (C). Sep-Gal4 is active in the developing photoreceptors and cone cells posterior to the morphogenetic furrow (arrowhead; Jasper et al, 2002). (E, F) JNK activation is sufficient to induce hid expression in the developing retina. In situ hybridization demonstrating hid induction in response to overexpression of Hepact under the control of Sep-Gal4 (F). (G–J) The resulting adult eye phenotype (G; sep-Gal4, UAS-Hepact is abbreviated as SH) is reduced in hid mutant backgrounds (in heterozygous conditions for hid (alleles W05014 and W1) as well as all three RGH genes (Df(H99)).
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