Fig. 4. Vari is required for the assembly rather than stability of SJs. (A-F) In wild-type animals, Cor localizes predominantly to SJs during stage 14, and then continues to accumulate in SJs during stages 15 and 16 (A-C). In vari^F033 null mutants SJs do not assemble, as indicated by the failure of Cor to localize specifically to the SJ region (D-F). Instead, Cor shows diffuse basolateral and basal localization at all stages. Abnormal accumulations of Cor at the basal surface are visible during stages 15 and 16 (arrows in E and F). (G-L) In vari^F033 null homozygotes expressing either the short (G-I) or long (J-L) isoforms of Vari, SJ junction barrier function is restored (data not shown) and the Vari isoforms (green) and Cor (red) show their normal localization to SJs. G-L are stage 16 animals of genotype vari^F033 UAS::Vari-isoform/vari^F033 da-Gal4. Hindgut shown in all images. Blue lines, apical cell surface; white lines, basal cell surface. Scale bar: in L, 5 µm for A-L.