small wing encodes a phospholipase C-gamma that acts as a negative regulator of R7 development in Drosophila

Phospholipase C-gamma (PLC-gamma) is activated in many cell types following growth factor stimulation. Our understanding of the role of PLC-gamma in c ell growth and differentiation has been severely limited by the dearth of m utations in any organism. In this study, we show that the Drosophila gene s mall wing (sl), identified by Bridges in 1915, encodes a PLC-gamma. Mutatio ns of sl result in extra R7 photoreceptors in the compound eye, consistent with overactivation of the receptor tyrosine kinase pathways that control R 7 development. The data presented here provide the first genetic evidence t hat PLC-gamma is involved in Ras-mediated signaling and indicate that PLC-g amma acts as a negative regulator in such pathways in Drosophila.