Overexpression of DrefScer\UAS.cSa in the developing eye (under the control of Scer\GAL4GMR.PS) induces ectopic DNA synthesis and apoptosis and inhibits photoreceptor cell differentiation in eye imaginal discs, such that adult flies exhibit a mild rough eye phenotype.
Flies expressing DrefScer\UAS.cSa under the control of Scer\GAL4ptc-559.1 show ectopic macrochaetae in the scutellum and a notching wing phenotype and reduction in the distance between the L3 and L4 wing veins.
Expression of DrefScer\UAS.cSa in the developing eye under the control of Scer\GAL4GMR.PS leads to an adult eye which is severely rough in appearance and with most bristles missing. The organised array of each ommatidium is destroyed and some ommatidia are fused to each other. The number and shape of the photoreceptor cells in each ommatidia is also abnormal. Pigment cells are found to be missing in all ommatidia, and some remaining tissues are vacuolated.
No significant difference is seen between control and DrefScer\UAS.cSa-expressing flies (under the control of Scer\GAL4GMR.PS) in the region anterior to the morphogenetic furrow, where the GMR promoter is inactive. In control discs, a 30-min pulse of BrdU incorporation leads to labeling of cells in one or two columns posterior to the morphogenetic furrow, while imaginal discs of transgenic flies expressing DrefScer\UAS.cSa labels the equivalent of five columns. Therefore expression of DrefScer\UAS.cSa expands the S phase or induces an extra S phase. Most of the nuclei of cells with BrdU incorporated occupy a more apical position in the imaginal discs than do nuclei in the synchronous S-phase cells posterior to the morphogenic furrow and in uncommitted cells, suggesting that DrefScer\UAS.cSa expression causes ectopic S phase in some cells that are normally postmitotic.
Expression of DrefScer\UAS.cSa in the developing eye under the control of Scer\GAL4GMR.PS inhibits the differentiation of R1, R6 and R7 photoreceptor cells.
Transgenic flies expressing DrefScer\UAS.cSa in the developing eye under the control of Scer\GAL4GMR.PS exhibit an increase in apoptotic cells in the region posterior to the morphogenetic furrow. Apoptosis seems to begin in the imaginal disc cells in the region where commitment to R1/R6 cells takes place, suggesting that failure of differentiation in to R1/R6 may induce apoptosis.