title: Prepattern in the developing Drosophila eye revealed by an activated torso--sevenless chimeric receptor.
abstract: Induction of the R7 photoreceptor cell fate in the developing eye of Drosophila depends on the activation of the sevenless receptor tyrosine kinase in the R7 precursor cell. The sevenless protein is expressed transiently in 8 of the 20 precursors of an ommatidium. Activation of the sevenless kinase in these eight cells indicates that six of them are competent to become R7 cells. To test the competence of all 20 ommatidial precursors in a temporally unrestricted manner we have used a constitutively activated sevenless kinase created by fusing the extracellular domain of a mutant torso protein, another Drosophila receptor tyrosine kinase, to the sevenless kinase. Our results show that competence to develop as neuronal cells in response to sevenless activity is spatially and temporally limited to the cells expressing sevenless. Therefore, the expression of sevenless marks a preexisting pattern of developmental potential in the disc epithelium.
authors.affiliation: Zoologisches Institut, Universität Zürich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Dickson
authors.forename: F
authors.initials: F
authors.lastname: Sprenger
authors.forename: E
authors.initials: E
authors.lastname: Hafen
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins; D004742:Enhancer Elements, Genetic; D005123:Eye / Q000196:embryology* / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics / Q000502:physiology*; D008024:Ligands; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010858:Pigmentation / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases; D011956:Receptors, Cell Surface / Q000502:physiology*; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction; D013696:Temperature; D014170:Transformation, Genetic
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D004247:DNA; D020794:Receptor Protein-Tyrosine Kinases; C056737:sev protein, Drosophila