title: Phenotypic suppression of empty spiracles is prevented by buttonhead.
abstract: Unlike the trunk segments, the anterior head segments of Drosophila are formed in the absence of pair-rule and HOX-cluster gene expression, by the activities of the gap-like genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd). The products of these genes are transcription factors, but only EMS has a HOX-like homeodomain. Indeed, ems can confer identity to trunk segments when other HOX-cluster gene activities are absent. In trunk segments of wild-type embryos, however, ems activity is prevented by phenotypic suppression, in which more posterior HOX-cluster genes inactivate the more anterior without affecting transcription or translation. ems is suppressed by all other Hox-cluster genes and so is placed at the bottom of their hierarchy. Here we show that misexpression of EMS in the head transforms segment identity in a btd-dependent manner, that misexpression of BTD in the trunk causes ems-dependent structures to develop, and that EMS and BTD interact in vitro. The data indicate that this interaction may allow ems to escape from the bottom of the HOX-cluster gene hierarchy and cause a dominant switch of homeotic prevalence in the anterior-posterior direction.
authors.affiliation: Max-Planck-Institut für Biophysikalische Chemie, Abt. Molekulare Entwicklungsbiologie, Göttingen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Schöck
authors.forename: J
authors.initials: J
authors.lastname: Reischl
authors.forename: E
authors.initials: E
authors.lastname: Wimmer
authors.forename: H
authors.initials: H
authors.lastname: Taubert
authors.forename: B A
authors.initials: BA
authors.lastname: Purnell
authors.forename: H
authors.initials: H
authors.lastname: Jäckle
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004330:Drosophila / Q000196:embryology* / Q000502:physiology; D029721:Drosophila Proteins; D018398:Homeodomain Proteins / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D016335:Zinc Fingers; D000099260:Empty Spiracles Homeobox Proteins
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C084801:btd protein, Drosophila; C093054:ems protein, Drosophila; D000099260:Empty Spiracles Homeobox Proteins