Fig. 6. The regulation of the expression of dve. Anterior is to the left; ventral to the bottom. In all images, expression of Dve and Wg is revealed by antibody staining. (A-C) Vg is sufficient to initiate expression of dve in the wing area. (A) Expression of Dve (green) is lost in a vg^83b27R-mutant wing disc, indicating that the function of vg is required for the induction of expression of dve. Red staining shows the expression of wg. In vg^83b27R-mutant wing discs, only the weaker outer ring-like expression domain of Wg is present. The weak punctuate green staining is unspecific background staining. (B,C) A wing imaginal disc of the late third larval instar stage bearing Vg-expressing cell clones. The clones of UAS-vg expressing cells were induced with the help of the AyGal4-UAS-GFP chromosome during the second larval instar and are labelled by the green GFP marker in C. (B) Expression of Dve. The arrows indicate Vg-expressing clones located outside the normal Dve expression domain. (C) Pseudo-colour image of the same disc as in B, revealing the Vg-expressing cell clones in green and expression of Dve in red. The double staining reveals that Vg-expressing clones can induce ectopic expression of Dve in the PW (see arrows) and in the pleura (arrowhead). Note that Vg can induce expression of Dve in adjacent non-expressing cells (see clones highlighted by the arrows), indicating that the induction of Dve expression occurs in a non-autonomous manner. The ability of Vg to induce expression of Dve is restricted to certain regions of the wing, indicating that additional factors are required in other regions. (D-I) Negative regulation of dve expression by the Notch and wg pathways. (D) Expression of Dve in a wing imaginal disc where UAS-Nintra is activated by dpp-Gal4 in a medial band of cells perpendicular to the DV boundary (arrows). Expression of Dve is suppressed in the region where Nintra is expressed (highlighted by the arrows). (E) Expression of UAS-wg by dpp-Gal4 results in a similar suppression of the expression of Dve. (F-I) Expression of Dve in wing imaginal disc of the late third larval instar stage bearing arr²-mutant cell clones. (F,H) Dve expression. (G,I) Pseudo-colour image of the same wing discs as in F and H, respectively, including the green channel to reveal the mutant clones of mutant cells through the absence of GFP fluorescence. Expression of Dve is shown in red. The comparison of F,H with G,I shows that expression of Dve is elevated in arr²-mutant cells (arrows in F-I). The elevation is observable in cells of clones at the DV boundary (arrows in H,I) and also in mutant cells that are many cell diameters away from the Wg source at the DV boundary (arrows in F,G). (J-L) Expression of Dve and Wg in a nub¹-mutant wing imaginal disc. (J) Expression of Wg in a nub-mutant wing imaginal disc of the late third larval instar stage. (K) Expression of Dve in the same disc as shown in J. (L) Merged view of both channels shown in J and K, showing Wg expression in red and Dve expression in green. The double staining reveals that expression of dve at the DV boundary is not suppressed in most of the regions (arrow in J-L). This suggests that Nub is required to suppress the expression of Dve at the DV boundary. (M) Expression of Dve (green) is not affected in a spade^flg-mutant wing imaginal disc. Red shows the expression of Wg and reveals that the inner ring-like domain of expression is lost. (N) Expression of Nub is unaffected in dve^P1738-mutant wing imaginal discs.