... which express the gene sevenless ( sev ). When a constitutively active form of Ras1 (Ras1 V12 ) is expressed in the R7 equivalence group cells using the sev promoter ( sev-Ras1 V12 ), additional cone cells are formed in the ommatidium. Expression of Ras1 N17 , a dominant negative form of Ras1, results...

...John D. Allard; Henry C. Chang; Ronald Herbst; Helen McNeill; Michael A. Simon ABSTRACT The sevenless gene encodes a receptor tyrosine kinase which is required for the development of the R7 photoreceptor cell in each ommatidium of the Drosophila eye. We have previously used a sensitized genetic...

..., R3/R4/R1/R6. We show that misexpression of seven-up in any of the other cell types within the developing ommatidium interferes with their differentiation. Each cell type responds differently to seven-up misexpression. For example, ectopic expression in the non-neuronal cone cells using the sevenless...

...Fernando J. Diaz-Benjumea; Ernst Hafen ABSTRACT In Drosophila , Drk, an SH2 adaptor protein, Sos, a putative activator of Ras1, Ras1, raf and rolled/MAP kinase have been shown to be required for signalling from the sevenless and the torso receptor tyrosine kinase. From these studies, it was unclear...

...E. Hafen; B. Dickson; T. Raabe; D. Brunner; N. Oellers; A. van der Straten ABSTRACT The specification of tlie R7 photoreceptor cell fate in the devloping eye of Drosophila depends on the local activation of the sevenless (sev) receptor tyrosine kinase (RTK) by boss, a protein expressed...

....). References Banerjee , U. , Renfranz , P. J. , Hinton , D. R. , Rabin , B. A. and Benzer , S. ( 1987a ). The sevenless + protein is expressed apically in cell membranes of developing Drosophila retina; it is not restricted to cell R7 . Cell 51 , 151 – 158 . 10.1016...

... and is dependent on the sevenless gene. In this study, we used a heat-shock-inducible sevenless gene as a conditional allele to determine the exact temporal requirements of sevenless gene expression and to reveal the stages of ommatidial development during which the presumptive R7 cell can respond to the presence...