Fig. 5. Comparison of the expression domain of dve with that of other genes involved in the patterning of the Drosophila wing along the PD axis. In C,D,F,G,I, anterior is to the left; ventral to the bottom. In A,B,E,H,J, discs of the early pupal phase are shown where the wing has everted, revealing the PD axis. In these images anterior is up; distal to the right. The everted wing helps to clarify the limits of the examined expression domains in relation to the expression of Wg. The arrow highlights the inner (IR) and the arrowhead the outer (OR) ring-like domain of Wg expression in the PW. (A) Persistent ß-galactosidase activity in adult flies carrying a P-lacZ insertion in the wg locus. The staining allows the determination of the structures that arise from the regions of Wg expression. It reveals that the ring-like domains of wg expression at the late third larval instar stage (arrow and arrowhead in Fig. 4H) label the anlagen of the proximal and medial regions of the PW (compare also with B). These observations suggest that the region between the IR and the actual wing pouch is the anlage of the distal region of the PW. (B) A dve^P1738/+ wing imaginal disc of the early pupal phase, stained with anti-ß-Gal antibody, to reveal the expression of dve (green), and anti-Wg antibody, to reveal the expression of Wg (red). The expression domain of dve reaches close to the IR. (C) Expression of vg-QE (green), revealed by anti-ß-Gal, and Dve (red), revealed by anti-Dve antibody staining. The expression domain of Dve is larger than that of the vg-QE. (D,E) Expression of the vg-QE (green) relative to that of Wg (red). The expression domain of vg-QE is restricted to the wing pouch and a broad band of non-expressing cells separates it from the IR (arrow). (F) Anti-Nub (red) anti-Dve (green) double-antibody staining of a wing imaginal disc of the late third larval instar stage. The double staining reveals that the disc-like expression domain of Nub is larger and includes that of Dve. (G,H) Anti-Nub anti-Wg double staining. (G) A wing imaginal disc of the late third larval instar stage, showing Wg (green) and Nub (red) expression. (H) A wing imaginal disc in the early pupal phase stained with anti-Wg (red) and anti-Nub (green) antibodies. G and H reveal that the border of the Nub expression domain lies between the two ring-like domains of Wg expression. (I) Expression of fj, revealed by anti-ß-Gal staining (green), and Wg, revealed by anti-Wg antibody staining (red). fj is expressed in the wing pouch in a similar domain to Vg and is not expressed in the distal region of the PW. Thus, the expression domain is smaller than that of Dve. (J) A wing imaginal disc of the early pupal stage containing an rn-lacZ insertion to reveal the expression of rn. Anti-ß-Gal (green) anti-Wg (red) double staining reveals that the boundary of the rn expression domain is identical to that of the IR. Thus, the expression domain of rn is larger than that of Dve. (K) Summary of the comparison. The proximodistal extent of the expression domains are depicted as follows: Vg/Fj, turquoise; Dve, blue; Rn, red; the IR, pink; Nub, green; and the outer ring-like domain of Wg, mauve. The cartoon highlights the fact that the tested genes are expressed in ring-like (Wg) or disc-like (Dve, Nub, Fj and Vg) domains of different sizes. The size of the domain increases from Vg/Fj to Dve to Rn, and from the inner ring-like domain of Wg to Nub to the outer ring-like domain of Wg. The result of these different expression domains is the definition of concentric regions with different combinations of gene activities that probably define the different regions of the PW.

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