A genetic screen to identify components of the sina signaling pathway in Drosophila eye development.

Specification of the R7 photoreceptor cell in the developing Drosophila eye requires the seven in absentia (sina) gene. We demonstrate that ectopic expression of sina in all cells behind the morphogenetic furrow disrupts normal eye development during pupation, resulting in a severely disorganized adult eye. Earlier events of cell fate specification appear unaffected. A genetic screen for dominant enhancers and suppressors of this phenotype identified mutations in a number of genes required for normal eye development, including UbcD1, which encodes a ubiquitin conjugating enzyme; SR3-4a, a gene previously implicated in signaling downstream of Ras1; and a Drosophila homolog of the Sin3A transcriptional repressor.