Ectopic expression of human p53 inhibits entry into S phase and induces apoptosis in the Drosophila eye imaginal disc

Transgenic flies in which ectopic expression of human p53 was targeted to t he Drosophila eye imaginal disc were established. On sectioning of adult fl y eyes which displayed a severe rough eye phenotype, most ommatidia were fo und to be fused and irregular shapes of rabdomeres were observed. In additi on, many pigment cells were lost. In the developing eye imaginal disc, phot oreceptor cell differentiation was initiated normally despite the ectopic e xpression of p53, However, expression of p53 inhibited cell cycle progressi on in eye imaginal disc cells and the S phase zone (the second mitotic wave ) behind the morphogenetic furrow was almost completely abolished. Furtherm ore, expression of p53 induced extensive apoptosis of eye imaginal disc cel ls, and co-expression of baculovirus P35 in the eye imaginal disc suppresse d the p53-induced rough eye phenotype, These results are consistent,vith th e known functions of human p53 and indicate the existence of signaling syst ems with elements corresponding to human p53 in Drosophila eye imaginal dis c cells. Genetic crosses of transgenic flies expressing p53 to a collection of Drosophila deficiency stocks allowed us to identify several genomic reg ions, deletions of which caused enhancement or suppression of the p53-induc ed rough eye phenotype, The transgenic flies established in this study shou ld be useful to identify novel targets of p53 and its positive or negative regulators in Drosophila.