A rough-eye assay shows a strong genetic interaction between BEAF and Sry-δ. Shown are SEM images from eyes of 3–5-day-old females. Negative control ey-GAL4/+; Sry-δSF2/+ flies have normal eyes. A mild rough-eye phenotype is seen in ey-GAL4/+; UAS-BID/+ flies expressing a dominant-negative form of BEAF. The rough-eye phenotype is much stronger when the Sry-δSF2 mutation is also present (ey-GAL4/+; UAS-BID/ Sry-δSF2). This phenotype is 100% penetrant. Sry-δ UAS RNAi transgenes give a clear rough-eye phenotype when heterozygous with ey-GAL4 (ey-GAL4/Sry-δ-RNAi1 and ey-GAL4/Sry-δ-RNAi2). The phenotype is more extreme in combination with heterozygous UAS-BID (ey-GAL4/Sry-δ-RNAi1; BID/+ and ey-GAL4/Sry-δ-RNAi2; BID/+). RNAi1: VDRC 41094; RNAi2: VDRC 102786. BEAF, Boundary Element-Associated Factor; RNAi, RNA interference; Sry-δ, Serendipity δ; UAS, upstream activating sequence; VDRC, Vienna Drosophila Resource Center.