Figure 1. JAK/STAT signaling is dynamically regulated in the wing imaginal disc.

In all panels dorsal is up and anterior is to the left.

(A) Schematic of the P/D axis in a third instar wing imaginal disc, showing notum (N), proximal hinge (PH), distal hinge (DH), lateral hinge (L) and wing pouch (P).

(B) A wild type adult wing showing P/D subdivisions. Labels are the same as in A, except for the wing blade (WB), to which pouch cells fate map.

(C) Schematic representation of gene expression domains along the P/D axis of the mature wing disc.

(D–F) upd-GAL4, UAS-GFP (upd>GFP, green) expression in mid-second instar (D), early third instar (E), and late third instar (F). upd>GFP is expressed in the medial hinge within Tsh-expressing cells but it is excluded from the Nub-expressing cells in the pouch. During mid-third instar, upd appears to be expressed within the gap domain, as well as in Tsh-positive cells. D′, E′, F′ are single channels for upd>GFP and D″, E″, F″ for Nub and D‴, E‴, F‴ for Tsh.

(G–M) JAK/STAT pathway activity, as monitored by the expression of the 10xSTAT-GFP reporter, in wing discs at various stages of development. Wg is red in G. JAK/STAT signaling as shown by the expression of the 10xSTAT-GFP reporter is initially detected throughout the wing primordium (G, G′). Subsequently, it becomes restricted to the proximal regions that give rise to the hinge. An early third instar (H), a mid-third instar (J) and late third instar disc (L). Regions outlined by a yellow box in H, J and L are shown at higher resolution in I, K and M, respectively. Robust activation of the JAK/STAT pathway takes place in the gap domain (I, K, M). Locations of z-sections are marked by a yellow line in I, K and M and shown in I′-I‴, K′-K‴ and M′-M‴. I′, K′ and M′ show all three channels. I″, K″ and M″ show single channels for 10xSTAT-GFP and I‴, K‴ and M‴ show Tsh (blue) and Nub (red) channels. Nub is red and Tsh is blue in D–F, H–M.