Fig. 5. Hipk is required to stabilize Arm in vivo. The expression of Arm protein was examined in third instar wing discs. (A) Wild type. Small panels beside and above show z-sections through the disc. (B) omb-Gal4/+; UAS-hipk/+ discs show expansion of the Arm domain. (C) omb-gal4/+; UAS-GFP/+ staining shows that omb-gal4 expression domain. (D) omb-gal4/+; UAS-Myc-Arm^S2 wing discs were stained with anti-Myc antibody to monitor the stabilization of exogenous wild-type Arm. Myc-Arm^S2 is stabilized in response to high Wg activity. (E) This effect was suppressed in hipk mutant discs, omb-gal4/+; UAS-Myc-Arm^S2, hipk³/hipk⁴. Arrow indicates reduced stabilization of Arm^S2 compared with D. (F) omb-gal4/+; UAS-Myc-Arm^S10/+. Expression of a degradation resistant form of Arm was visualized with an anti-Myc antibody. Myc-Arm^S10 was stabilized throughout the omb-Gal4 expression domain. (G) omb-gal4/+; UAS-Myc-Arm^S10/+; hipk³/hipk⁴. Reducing hipk activity did not affect the stabilization of constitutively active Arm.