CONTROL OF DROSOPHILA PHOTORECEPTOR CELL FATES BY PHYLLOPOD, A NOVEL NUCLEAR-PROTEIN ACTING DOWNSTREAM OF THE RAF KINASE

The phyllopod (phyl) gene regulates the fates of a subset of cells in the developing Drosophila eye; in the absence of phyl function, the R1 , R6, and R7 photoreceptors are transformed into additional cone cells , whereas ectopic phyl expression in the cone cell precursors transfor ms these cells into additional R7 cells. Within this group of cells, p hyl expression thus mimics activation of the Raf pathway in its abilit y to induce photoreceptor rather than cone cell development. Furthermo re, the transformation of cone cells into R7 cells in response to Raf activation is both accompanied by and dependent upon ectopic phyl expr ession. phyl thus represents a possible target gene of the Raf pathway during eye development, controlling the fates of a novel subset of ph otoreceptors.