Fig. 1. The wing-blister genes piopio and papillote encode ZP-domain-containing transmembrane proteins. The genes piopio (pio, A) and papillote (pot, B) are shown with their closely flanking genes and their encoded proteins. Untranslated regions are white-filled boxes and coding regions are black. Genomic rescue constructs were generated with the segment of DNA between the restriction sites: BamHI for piopio and SpeI and EclXI for papillote. The position of the 1.7 kb deletion in the pio^V132 mutant allele, which removes the signal peptide, is shown in A. The schematic of the proteins show signal peptides (SP) and transmembrane domains (TM) as black boxes, the zona pellucida (ZP) domains as grey boxes, and the insertion points of the fluorescent protein tags (GFP and CFP). For Piopio, the sequence surrounding the potential furin cleavage site (underlined) at the end of the ZP domain is shown, as is the conservation of the short cytoplasmic domain, with identical residues shaded. For Papillote, the position of the frame shift caused by the 13 bp deletion in the pot^P53 mutant allele, which causes a truncation of the protein after residue 686, is indicated. (C) Pio but not Pot is proteolytically processed. Extracts of pupal wings from wild type (wt) or animals expressing GFP, Pio-GFP or Pot-CFP were analysed by western blotting and probed with an anti-GFP antibody. Two distinct bands were detected for the Pio-GFP fusion protein, with apparent molecular weights as predicted for the full-length fusion protein lacking the signal peptide (76 kDa), and a C-terminal fragment fused to GFP generated by cleavage at the potential furin recognition site (39 kDa), distinct from GFP alone (27 kDa). By contrast, a single band was observed for Pot-CFP of the size expected for the full-length fusion protein (131 kDa).