Fig. 4. Arm is not stabilized in the DV boundary of tws^P/tws^P wing discs. (A) Wild-type wing disc stained with anti-Arm (red) and anti-Wg (green) antibodies. Note higher levels of Arm in cells adjacent to Wg-expressing DV boundary compared with distant non-DV cells. (B) tws^P/tws^P wing disc stained with anti-Arm (red) and anti-Wg (green) antibodies. Note reduction in the levels of Arm in cells adjacent to the Wg-expressing DV boundary. Also seen in B are large peripodial cells. In wild-type wing discs, they normally are not in the same focal plane as disc cells. A' and B' show x-z sections of the cells around the DV boundary of wild type (A') and tws^P/tws^P (B') wing discs. Although Arm is localized apically, owing to its stabilization in the cytoplasm of DV cells, it is seen all along the cross-section of the cells. However, in mutant cells, Arm is localized only to the apical adherens junctions. (C,D) Wild-type wing disc double-stained (but shown in single channels) with anti-Arm (C) and FITC-conjugated actin-phalloidin (D). Note that both Arm and Actin-phalloidin show intense staining in the cells surrounding the DV boundary (arrows in C,D). (E,F) tws^P/tws^P wing disc double-stained (shown in single channels) with anti-Arm (E) and FITC-conjugated actin-phalloidin (F). Note reduced levels of Arm in the DV boundary (arrow in E). However, actin-phalloidin staining is as intense as in the wild-type disc (arrow in F). (G) hsFLP; P[FRT]82 tws^P/P[FRT]82 arm-lacZ wing disc stained for Arm (green). tws^P/tws^P mitotic clones are marked with arm-lacZ (red), which is shown in single channel in G'. G'' is a merge of G and G'. A large clone abutting the DV boundary is shown. Note that levels of Arm are lower in tws^P/tws^P cells compared with neighboring tws⁺ cells. The viability of tws^P/tws^P cells were confirmed by DAPI staining (data not shown). (H,I) vg-GAL4; UAS-arm^S2 (H) and vg-GAL4; UAS-arm^S2 tws^P/tws^P (I) wing discs stained for Myc tag, which marks expression of only the overexpressed Arm. Note that Myc staining in I is significantly lower than in H, suggesting enhanced degradation of Arm in tws^P/tws^P discs. (J,K) UAS-arm^S10; vg-GAL4 (J) and UAS-arm^S10; vg-GAL4; tws^P/tws^P (K) wing discs stained for Myc tag. Levels of Myc in K are comparable with those in J, suggesting that tws^P/tws^P has no effect on degradation-resistant form of Arm.