Fig. 7. Phosphorylation of Cos2 on Ser572 impairs its regulation of Ci stability. (A) 71BGal4;UAS-GFP; (B) yw,hs-flp; FRT42D cos2^W1/FRT42D armlacZ, (C) yw,hs-flp; FRT42D cos2^W1/FRT42D armlacZ; 71BGAL4/UAS cos2-WT-myc, (D) yw,hs-flp; FRT42D cos2^W1/FRT42D armlacZ; 71BGAL4/UAS cos2-572A-myc and (E) yw,hs-flp; FRT42D cos2^W1/FRT42D armlacZ; 71BGAL4/UAS cos2-572D-myc imaginal discs are stained for Ci (2A1; red), Myc (blue) and ß-galactosidase (green), except in A where GFP is in green. (A,A') Ci is stabilised in 10-15 cells in the anterior compartment near the anteroposterior (AP) border, as in a wild-type disc. The 71B line drives the expression of Gal4 in a large domain centred in the wing pouch indicated by a broken line. (B,B') In cos2^W1 clones, the Ci155 isoform is stabilised, as revealed by the 2A1 antibody (arrow in B'). (C-F) Examples of rescue experiments with UAS-cos2-WT (C), UAS-cos2-572A (D) and UAS-cos2-572D (E,F) driven by 71BGal4. The rescue domain is visualised by Myc staining (encircled). cos^WI loss-of-function clones are identified by a loss of ß-galactosidase staining (C'-F'). In C''-F'', all the anterior clones outside of the wing pouch are encircled by an unbroken line. The inhibition efficiencies of the wild-type (WT) and mutant cos2 transgenes were quantified in each disc by comparing Ci155 levels in cos2^W1 clones situated inside the rescue domain (marked by arrows) with clones outside of this domain (asterisk). Inhibition efficiencies were calculated using data obtained from 8-12 different clones for each Cos2 variant and are indicated as percentages in C''-F''. When compared with the surrounding tissues within the driver domain, the Ci level was increased in mutant clones expressing Cos2-WT, Cos2-572A and Cos2-572D by 10.6, 22 and 38.5%, respectively.