Fig. 5. Ubx-mediated inhibition of Arm stabilization is downstream of Sgg function. All discs in this figure are stained with anti-Arm antibodies. (A) vg-GAL4/UAS-Dsh-haltere disc. Overexpression of Dsh does not enhance Arm levels at the haltere DV boundary, suggesting that Ubx functions downstream of Dsh. (B,C) vg-GAL4/UAS-APC/CBD-wing (B) and -haltere (C) discs. Misexpression of human APC sequesters Arm only in cells where Sgg is inactive (Bhandari and Shashidhara, 2001): for example, at the DV boundary of the wing disc (B). In haltere discs, APC sequesters Arm only in the anterior compartment (C). This suggests that Sgg is inactive in the anterior compartment and active in the posterior compartment. (D) vg-GAL4/UAS-Dsh; UAS-APC/CBD-haltere disc. Overexpression of both Dsh and APC together causes sequestration of Arm in both anterior and posterior compartments. This is owing to the Dsh-mediated inhibition of Sgg activity followed by APC-mediated sequestration of Arm.