Figure 4. A specific requirement of JAK/STAT signalling in P cells.

(a–e) Late third instar wing primordia from wild-type (a) larvae or from larvae expressing the indicated transgenes under the control of the sd-gal4 (b,c) or en-gal4 (e) drivers, or hemizygous for the hop²⁷ allele (d). Wing primordia were labelled to visualize expression of Engrailed (En, red, a–c,e), Ci (green) to label the posterior (P) and anterior (A) compartments, respectively, and Tsh (red, d). Note the reduction in the size of the P compartment upon depletion of the JAK/STAT signalling pathway (white arrows). (f,g,i) Representative examples of mature larval wing primordia with clones of cells lacking stat92E activity (g,i) or wild-type for stat92E (f) labelled by absence of GFP (green or white, f,g) or lacZ expression (antibody against β-gal, green or white, i) and induced at first instar (see Methods). Wing primordia were stained for Engrailed (En, red or white) and Ci (blue). In f,g, clones were generated by the Minute technique. In i, mutant clones and their corresponding twins (labelled with two copies of lacZ) can be monitored. (h) Scatter plot showing the percentage of the A or P compartments covered by stat92E mutant (red) or wild-type (black) clones. Wild-type clones, anterior=52±16%, posterior=59±21% (n=45 discs); stat92E clones, anterior=40±13%, posterior=21±17% (n=102 discs). Error bars (vertical lines) represent s.d. and long horizontal lines label the average values. P values: Student's t-test, ns, not significant; ***P<0.001. Each dot represents a wing disc. (j) G-TRACE mediated cell lineage analysis to irreversibly label all cells born in the P compartment upon JAK/STAT depletion in P cells. Wing disc was stained for Engrailed (En, red or white), Ci (blue and white) and GFP (green or white). Dashed red line marks the AP boundary. Scale bars, 50 μm.