title: Overexpression of zeste white 3 blocks wingless signaling in the Drosophila embryonic midgut.
abstract: The extracellular signals encoded by the Wnt family of genes regulate growth and differentiation in several developmental processes in both vertebrates and invertebrates. Genetic studies of the signaling pathway of the Drosophila Wnt homologue, Wingless, have identified a number of genes, including zeste white 3, which function to transduce the Wingless signal. zeste white 3 encodes a serine/threonine kinase. We have previously proposed that the Wingless signal is mediated by repression of this kinase activity [E. Siegfried, E.L. Wilder, and N. Perrimon (1994) Nature 367, 76-80]. Here we have tested this hypothesis by overexpressing zeste white 3 in a tissue-specific fashion using the UAS/GAL4 binary expression system. We demonstrate that elevated levels of zeste white 3 in the ectoderm and mesoderm result in phenotypes that resemble a loss of wingless. Overexpression of zeste white 3 in the mesoderm disrupts several Wingless-dependent processes including the specification of a unique cell type in the larval midgut, the formation of the second midgut constriction, and the expression of Wingless target genes Ultrabithorax and decapentaplegic in the mesoderm and labial in the endoderm. Zeste white 3 regulates the stability of Armadillo which is essential for transducing the Wingless signal to the nucleus. We show that zeste white 3 overexpression blocks Wingless signaling through the modulation of Armadillo since expression of a constitutively active form of Armadillo, which is independent of Zeste white 3 regulation, is epistatic to overexpression of zeste white 3.
authors.affiliation: Department of Biology and Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park 16802, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Steitz
authors.forename: J K
authors.initials: JK
authors.lastname: Wickenheisser
authors.forename: E
authors.initials: E
authors.lastname: Siegfried
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D004064:Digestive System / Q000196:embryology; D004330:Drosophila / Q000196:embryology* / Q000235:genetics* / Q000254:growth & development; D029721:Drosophila Proteins; D004817:Epidermis / Q000196:embryology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D018398:Homeodomain Proteins / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics / Q000502:physiology; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008297:Male; D008648:Mesoderm / Q000166:cytology; D008954:Models, Biological; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors; D051155:Wnt1 Protein
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; D051155:Wnt1 Protein; C064196:dpp protein, Drosophila; C074622:wg protein, Drosophila; C060849:z protein, Drosophila