Rab11 is also required for R-cell positioning. (A-C) Longitudal optic sectioning of third-instar larval eye discs double-stained with anti-Elav (blue) and anti-HRP (green) to visualize R-cell nuclei and R-cell surface, respectively. (A) In wild type, R-cell bodies localizes to the apical region, while their apical processes attach to the apical surface and their axons project basally. (B) The generation of clones of Rab11ex2 mutant cells caused R-cell nuclei to be mis-localized at the basal region. (C) In eye discs expressing a UAS-Rab11-RNAi transgene, R cells did not appear to be tightly associated clusters at the apical region and instead formed a long stretch along the apical-basal axis (20 out of 41 eye discs examined). Note that R-cell processes still attached to the apical surface in Rab11 mutants (B and C). (D) Basal localization of Rab11 mutant nuclei in Rab11ex2 mosaic eye disc. GFP (green) was used to label wild-type or Rab11 heterozygous ommatidia in Rab11 mosaic eyes. R-cell nuclei at the basal region were visualized with anti-Elav staining (red). In GFP-positive ommatidia, no R-cell nuclei were observed in the basal region. In the basal region of homozygous Rab11 mutant ommatidia or mosaic ommatida (GFP negative), mis-localized R-cell nuclei (red) were observed. Scale bar: A-C,10 μm; D, 5 μm.