Fig. 7. ozd mesoderm is Shh-responsive, but cannot express Shh. The ozd mutant wing phenotype (A) was completely rescued by a ZPA graft (B). The ZPA graft was of leg origin and contributed a leg digit marked here as 3^*. (C) Application of an Shh-N-soaked bead to posterior st. 20 ozd wing buds restores zeugopod development. (D) Two sequential applied SHH beads rescues both zeugopod and autopod formation in ozd wings. (E) Reduction of Shh expression 24 hours after application of an RA bead to the posterior border of a wild-type wing bud. (F) ozd posterior mesoderm does not express Shh 24 hours after RA application. (G) Induction of Shh at the anterior border of a wild-type leg bud 24 hours after implantation of a RA bead. (H) RA application at the anterior border of ozd leg buds does not induce ectopic Shh expression. (I-L) RA application induces ectopic anterior dHAND expression in both normal (I) and mutant (J) wing buds. dHAND expression in the unmanipulated contralateral wild-type (K) and ozd (L) limb buds. The position of the RA bead is indicated by the red arrow.