Fig. 6. Brk induces low levels of apoptosis in the wing disc. (A) A wing disc of genotype nub-Gal4>UAS-brk UAS-GFP doubly stained for GFP (green) and caspase 3 activity (red). The green fluorescence marks where brk is expressed. (B) Low level of caspase 3 activity (red) in brk-expressing cells. (C,D) A disc of the same genotype but stained for GFP and TUNEL. Only a minority of brk-expressing cells undergo apoptosis (red in D). (E,F) Wing disc of genotype nub-Gal4>UAS-brk UAS-p35 UAS-GFP stained for GFP and TUNEL (red). The green fluorescence marks the cell containing brk and p35 activity. This disc (F) shows unusually high apoptotic levels, but was chosen to illustrate the effectiveness of p35 in suppressing cell death (absence of red staining in area corresponding to green staining in E).