Fig. 1. Identification of the Ser minimal wing enhancer. (A) Molecular map of the Ser region. Top horizontal line shows a restriction map of the Ser locus. B, BamHI; E, EcoRI; H, HindIII; X, XbaI. Polymorphic restriction sites are placed in parentheses. White boxes represent UTRs; black boxes represent exons in the transcription unit. For simplicity, the middle regions of the restriction map and the Ser transcript are omitted. The rescue experiments were carried out by expressing UAS-Ser under the control of Gal4 fused to constructs 1 to 7 in a Ser mutant (Bd^G/Ser^+r83k) background. The rescue efficiencies are indicated on the right (++, partial rescue; N/S, not shown; N/D, not determined). (B-F) Adult wing cuticle preparation; (G) schematic representation of the wing imaginal disc; (H,I) ß-galactosidase antibody staining; (J) GFP expression in late third instar wing imaginal discs. Dorsal is up, anterior to the left for all imaginal wing discs in this paper, if not indicated otherwise. (C) Bd^G/Ser^+r83k animals display little wing tissue compared with wild type (B). (D) Ser expression under construct 3 can partially restore the wing from the posterior to around L2 (L, longitudinal vein) in Bd^G/Ser^+r83k animals. Constructs 5 and 7 can fully rescue the wing phenotype with margin defects (arrowheads in E and F, respectively), which is identical to the phenotype when UAS-Ser is expressed under constructs 5 and 7 in a wild-type background (not shown). (G) The DV border (red band) is located between the dorsal and ventral compartments; the AP border (blue band) is located between the anterior and posterior compartments. The wing pouch, which gives rise to the adult wing blade, is demarcated by an oval. (H) UAS-nuc-lacZ expression under construct 2 is observed near the AP border (arrowheads) as well as in the pleura (arrow). (I) UAS-lacZ under construct 3 is expressed exclusively in the dorsal compartment, and mostly in the posterior. (J) UAS-GFP expression under construct 4 was detected at the DV border and in the cells flanking the DV border. Construct 5 recapitulates endogenous Ser expression during larval development (see Fig. 2 for details).