(A–H) Comparison of wild-type discs (A, C, E, G) to discs lacking endogenous Dpp in the pouch and expressing weak uniform Dpp instead (B, D, F, H). Uniform Dpp allows discs to reach a relatively normal size, although with a variably deformed shape (representative examples are shown). Omb is expressed in experimental discs, an indication of active Dpp signaling, but at a relatively lower level than in control discs (samples shown in A and B were stained and imaged under identical conditions). Note also the repression of Brinker and the loss of pMad expression in experimental discs. In contrast to their relatively normal size, experimental discs show abnormal vein patterning, with only two vein territories recognizable instead of the normal five (marked by the absence of DSRF immunoreactivity) (G, H). (I–K) pH3 immunoreactivity shows that, in control and rescued discs, proliferation is sustained seemingly normally (I, J) while proliferation in the pouch of non-rescued discs is depressed (K) Quantification show in L is based on 14 rescued discs, 9 controls and 11 unrescued discs. Statistical significance was assessed with a Student’s t-test, assuming equal variance and a Gaussian distribution. Mitotic density (pH3 spots/area) was determined for each individual disc using a code written in Fiji (see Figure 5—source data 1). (M–O) Wings from the above genotypes. A majority of examined experimental wings (15/20) had excess vein tissue (O) while the remainder (5/20) had one central vein around the position of the A/P boundary and another (not visible) along the margin (I). Each micrograph is representative of 7–10 discs. Scale bar = 50 μm.