Fig. 7. Discontinuous levels of Brk give rise to JNK-mediated apoptosis. The activity of the JNK pathway is monitored by the expression of the puc-lacZ insert. (A,B) Control hh-Gal4>UAS-GFP disc showing normal JNK activity, which is restricted to the proximal thoracic region. pucZ expression is shown in red. (C,D) Disc of hh-Gal4>UAS-brk UAS-GFP. There is puc expression (red) at the border of the brk-expressing cells (green), along the AP compartment boundary (arrows). There appears to be puc expression at both sides of the border, suggesting a non-autonomous effect. (E,F) Clone of brk^– cells labelled by the loss of GFP (green) showing puc activity at the border (arrows). (G,H) Caspase 3 activity (red, arrows) in the border of a brk^– clone (shown by loss of green staining). There are also some scattered caspase-positive cells in the vicinity of other brk^– clones.