Fig. 6. Apical delivery of V-ATPase continues in karst mutant cells. All CCs shown are from third-instar guts; `red' and `green' refer to colors in the central merged image. (A) Staining for V-ATPase in a Shibire^2Ts (Shi^2Ts) mutant cell at the permissive temperature reveals a normal endosomal and apical localization (see Fig. 4G). (B) Staining for Rab5 in a Shi^2Ts cell at the permissive temperature reveals a normal distribution (see Fig. 4I). (C) Staining for V-ATPase in a Shi^2Ts/karst double-mutant cell at the permissive temperature reveals only the diffuse cytoplasmic staining characteristic for karst mutants. (D) Staining for Rab5 in a Shi^2Ts/karst double-mutant cell at the permissive temperature reveals only the diffuse cytoplasmic staining characteristic for karst mutants. (E-G) Staining for V-ATPase (E, red) and Rab5 (G, green) in a Shi^2Ts mutant cell at the restrictive temperature reveals a strong apical accumulation for both proteins (arrowheads). The inset shows a co-labeled endosomal compartment from another cell. Here, Rab5 is still present, but the signal appears weaker and somewhat patchy compared with the permissive temperature. (H-M) Staining for V-ATPase (H,K: V, red) and Rab5 (J,M: R5, green) in Shi^2Ts/karst double-mutant cells at the restrictive temperature. Both proteins co-accumulate at the apical membrane of CCs (H-J), although V-ATPase is weaker and is variable from larvae to larvae. No V-ATPase- or Rab5-positive endosomes are evident. Rab5 particles also accumulate near the apical membrane in interstitial cells (i), with no evident V-ATPase staining (K-M). Asterisk indicates a CC with apical Rab5 accumulation, but very weak V-ATPase accumulation. Bars, 20 µm.