Fig. 6. Effects of reduction or elimination of PKA activity on the death of wing epidermal cells. Ectopic expression of a dominant-negative form of the regulatory subunit of PKA (R*) inhibited cell death at 2 hours (A) or even at 8 hours (B) after wing spreading in en-Gal4 UAS-GFPN /+; UAS-R*/+ flies. Mutant clones of DC0 were marked by the stc^– phenotype of smaller hairs or of tufts of hairs (C, enclosed by white lines). Cells of the clones remained 2 hours after wing spreading, although neighboring cells had died (D). Effects of ectopic expression of a constitutively active form of the PKA catalytic subunit (mC*) in en-Gal4 UAS-GFPN /UAS-mC* flies (E-G). Ectopic expression of mC* caused wing blisters (E, arrows). Precocious cell death had occurred in blistered wings by the time of wing spreading (F). The arrow (F) indicates GFP in vein cells. Precocious cell death induced by ectopic expression of mC* was examined at various stages of pharate adult (G). Black and gray bars indicate the percentage of flies showing cell death extensively or in restricted domains of the wing, respectively. The number of flies examined is shown in parentheses.