title: A neuropeptide hormone cascade controls the precise onset of post-eclosion cuticular tanning in Drosophila melanogaster.
abstract: A neuropeptide hormone-signalling pathway controls events surrounding eclosion in Drosophila melanogaster. Ecdysis-triggering hormone, eclosion hormone and crustacean cardioactive peptide (CCAP) together control pre-eclosion and eclosion events, whereas bursicon, through its receptor rickets (RK), controls post-eclosion development. Cuticular tanning is a convenient visible marker of the temporally precise post-eclosion developmental progression, and we investigated how it is controlled by the ecdysis neuropeptide cascade. Together, two enzymes, tyrosine hydroxylase (TH, encoded by ple) and dopa decarboxylase (DDC, encoded by Ddc), produce the dopamine that is required for tanning. Levels of both the ple and Ddc transcripts begin to accumulate before eclosion, coincident with the onset of pigmentation of the pharate adult bristles and epidermis. Since DDC activity is high before the post-eclosion onset of tanning, a different factor must be regulated to switch on tanning. Transcriptional control of ple does not regulate the onset of tanning because ple transcript levels remain unchanged from 24 hours before to 12 hours after eclosion. TH protein present before eclosion is degraded, and no TH activity can be detected at eclosion. However, TH protein rapidly accumulates within an hour of eclosion and we provide evidence that CCAP controls this process. Furthermore, we show that TH is transiently activated during tanning by phosphorylation at Ser32, as a result of bursicon signalling. We conclude that the ecdysis hormone cascade acts as a regulatory switch to control the precise onset of tanning by both translational and activational control of TH.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
authors.forename: Monica M
authors.initials: MM
authors.lastname: Davis
authors.forename: Sandra L
authors.initials: SL
authors.lastname: O'Keefe
authors.forename: David A
authors.initials: DA
authors.lastname: Primrose
authors.forename: Ross B
authors.initials: RB
authors.lastname: Hodgetts
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D029721:Drosophila Proteins; D007301:Insect Hormones; D009479:Neuropeptides; C058620:crustacean cardioactive peptide; D012313:RNA; C042645:eclosion hormone; D014446:Tyrosine 3-Monooxygenase