A steroid-triggered transcriptional hierarchy controls salivary gland celldeath during Drosophila metamorphosis

The steroid hormone ecdysone signals the stage-specific programmed cell dea th of the larval salivary glands during Drosophila metamorphosis. This resp onse is preceded by an ecdysone-triggered switch in gene expression in whic h the diap2 death inhibitor is repressed and the reaper (rpr) and head invo lution defective (hid) death activators are induced. Here we show that rpr is induced directly by the ecdysonereceptor complex through an essential re sponse element in the rpr promoter. The Broad-Complex (BR-C) is required fo r both rpr and hid transcription, while E74A is required for maximal levels of hid induction. diap2 induction is dependent on beta FTZ-F1, while E75A and E75B are each sufficient to repress diap2. This study identifies transc riptional regulators of programmed cell death in Drosophila and provides a direct link between a steroid signal and a programmed cell death response.