Fig. 5. tkv reverts the extended Dpp activity caused by Ubx loss. (A-A'') Two clones merged at the A/P boundary of the haltere disc (as revealed by hh-lacZ expression, not shown), and marked by the absence of GFP expression (in green in A), show wider P-Mad signal (A') and non-cell-autonomous expression both anteriorly and posteriorly to the clones (arrowheads in A'). A'', merged image. (B-B''') Clones mutant for Ubx and that simultaneously express tkv. The clones are marked by GFP expression (in green in B). Note that P-Mad (in red in B') and omb (in blue in B'') signals are restricted to a few cells within the clones (compare with Fig. 2E' and Fig. 5A'). Merged image in B'''. (C,D) P-Mad expression in dpp-Gal4/UAS-tkv (C) and dpp-Gal4/UAS-Ubx (D) wing discs. In both cases the extent of P-Mad signal is reduced, but the level of expression in AB cells is increased, compared with that of wild-type wing discs (Fig. 4A).