Fig. 1. Proximodistal domains of the Drosophila wing imaginal disc. (A,A') vg (green) and wg (red) expression patterns in wing discs of early (A) and late (A') third instar larvae. In the early third instar the inner ring (IR) of wg expression abuts on vg expression in the wing pouch, but in the late third instar the two domains are several cells apart. (B,C) Wing disc (B) and adult wing (C) showing the expression domains of genes involved in proximodistal patterning relevant to this work. vg (green), rn (blue) and nub (yellow) are expressed in concentric domains, and wg (red) is expressed in a stripe that defines the wing margin (not shown) and in two rings - the IR and the outer ring (OR). Bars in B represent the extension of the domains on the proximodistal axis. The color scheme in C shows the corresponding expression domains in the adult wing. (D) nubGal4/+; EP#13/+ wing. Note that the wing hinge (arrow) is deleted. (E) Molecular organization of nab. The domains NCD1 and NCD2 and the sites of insertion of the alleles used in this work are shown. (F-F'') Wing imaginal discs of second instar (F) and early (F') and late (F'') third instar larvae labeled with Nab (green, here shown as white in combination with blue), Wg (red) and Rn (ß-galactosidase, blue). The right-hand panel shows separately the different channels of a view on the z-axis. Note how from the initial situation in the early third instar (F'), nab expression abuts on wg expression in the IR. Scale bars show the relative sizes of the discs (white bars) and wings (black bars). Hereafter, imaginal discs are always shown in the same orientation: dorsal up and anterior to the left.