Fig. 3. Sdt is required for correct localization of Crb and Dlt. (A-C) Dlt (B, green) is absent (arrowheads) in sdt^- clones marked by the absence of GFP (C, blue) or Sdt (A, red) staining. Arrows show the presence of Dlt in Sdt⁺ cells in a mosaic photoreceptor cluster, indicating cell-autonomous function of Sdt. (D-F) Crb (D, red) is absent or strongly reduced in the stalk (arrows in F) of sdt^- cells marked by the absence of Dlt (E, green) or GFP (F, blue). (G) Top view of a three-dimensional reconstruction of sdt^- clones marked by the absence of Sdt staining (green). Arm staining indicates that AJ was expanded basolaterally and mispositioned in sdt^- clones marked by the absence of Sdt (green). (H) DE-cad (red), another marker of AJs is expanded basolaterally. Mutant clones were marked by the absence of GFP staining (blue). (I) F-actins (phalloidin, red) are diffused (arrowheads) and/or displaced from the apical to the lateral position of the photoreceptors (arrows). sdt^- mutants are marked by the absence of GFP (blue). (J) Longitudinal section of sdt^- clones containing wild-type (right) and sdt^- cells (left) marked by the absence of Sdt staining (green). Arm staining is fragmented and widely mispositioned to the lateral positions. (K,L) An oblique (K) and a longitudinal section (L) of w^- sdt^- adult eye clones marked by the absence of red pigments (labeled with brackets). The oblique section (K) shows arrays of ommatidia from the distal end to the proximal end at the floor of the retina. sdt^- ommatidia in the distal region show rhabdomeres, whereas mutant ommatidia in the proximal region show severe disruption. The longitudinal section (L) shows continuous elongated rhabdomeres in sdt⁺ ommatidia and discontinuous disrupted rhabdomeres in sdt^- ommatidia. (M,N) Transmission electron micrographs of a wild-type (M) and a sdt^- photoreceptor cluster (N) from a mosaic adult eye. These tangential sections were made at the distal region of the eye. The rhabdomeres are bulky and fused in the sdt^- photoreceptors (N) compared with the wild type (M).

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