title: Isolation of temperature-sensitive mutations of the tyrosine kinase receptor sevenless (sev) in Drosophila and their use in determining its time of action.
abstract: Loss-of-function mutations in the sevenless (sev) gene in Drosophila result in the failure to differentiate a specific photoreceptor cell type--namely, the R7 cell. The sev gene encodes a cell-surface receptor tyrosine kinase that functions in the presumptive R7 cell to transduce developmental cues from its neighbors, instructing it to differentiate along the R7 cell pathway. We have isolated temperature-sensitive alleles of sev and used them to show that Sev activity is required for several hours during the development of each R7 cell to specify R7 cell differentiation. Our data also suggest that the presumptive R7 cell remains for approximately 5 hr in an undetermined state in the absence of the Sev-mediated signal before committing to an alternative fate. We have determined the molecular lesions in four of the temperature-sensitive alleles. One of these mutations disrupts the Gly-Xaa-Gly-Xaa-Xaa-Gly consensus in the ATP-binding site of the kinase domain.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: M C
authors.initials: MC
authors.lastname: Mullins
authors.forename: G M
authors.initials: GM
authors.lastname: Rubin
mesh_terms: D000483:Alleles; D000818:Animals; D004252:DNA Mutational Analysis; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology*; D005136:Eye Proteins / Q000502:physiology*; D015870:Gene Expression; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000502:physiology*; D010786:Photoreceptor Cells / Q000196:embryology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases; D011956:Receptors, Cell Surface / Q000502:physiology*; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; C056737:sev protein, Drosophila