Steroid regulated programmed cell death during Drosophila metamorphosis.
During insect metamorphosis, pulses of the steroid hormone 20-hydroxyecdysone (ecdysone) direct the destruction of obsolete larval tissues and their replacement by tissues and structures that form the adult fly. We show here that larval midgut and salivary gland histolysis are stage-specific steroid-triggered programmed cell death responses. Dying larval midgut and salivary gland cell nuclei become permeable to the vital dye acridine orange and their DNA undergoes fragmentation, indicative of apoptosis. Furthermore, the histolysis of these tissues can be inhibited by ectopic expression of the baculovirus anti-apoptotic protein p35, implicating a role for caspases in the death response. Coordinate stage-specific induction of the Drosophila death genes reaper (rpr) and head involution defective (hid) immediately precedes the destruction of the larval midgut and salivary gland. In addition, the diap2 anti-cell death gene is repressed in larval salivary glands as rpr and hid are induced, suggesting that the death of this tissue is under both positive and negative regulation. Finally, diap2 is repressed by ecdysone in cultured salivary glands under the same conditions that induce rpr expression and trigger programmed cell death. These studies indicate that ecdysone directs the death of larval tissues via the precise stage- and tissue-specific regulation of key death effector genes.
Jiang
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Howard Hughes Medical Institute, Department of Human Genetics, University of Utah, Salt Lake City 84112, USA.
Baehrecke
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Thummel
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D000165:Acridine Orange; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D053938:DNA Fragmentation; D004064:Digestive System / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D004330:Drosophila / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D029721:Drosophila Proteins; D004441:Ecdysterone / Q000494:pharmacology / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D051034:Inhibitor of Apoptosis Proteins; D007814:Larva / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D008675:Metamorphosis, Biological; D008954:Models, Biological; D009479:Neuropeptides / Q000235:genetics; D010455:Peptides / Q000235:genetics; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology
D029721:Drosophila Proteins; C108880:HID protein, Drosophila; D051034:Inhibitor of Apoptosis Proteins; D009479:Neuropeptides; D010455:Peptides; D014764:Viral Proteins; C086430:inhibitor of apoptosis, Nucleopolyhedrovirus; C086973:rpr protein, Drosophila; D004441:Ecdysterone; D000165:Acridine Orange