Fig. 3. Overexpression of lines in the PE replaces the PE with DP. (A,C,D) Wild type; (B,E-G) Ubx-GAL4 UAS-Lines (Ubx>Lines); arrowheads in A,B,D,E indicate plane of z-section in A', B', D'-D''' and E'-E''', respectively. (A-B') Armadillo (Arm); cellular outlines are detected in apical sections; bright dots reveal adherence junctions in z-sections. Images in A and B are at the same magnification. (A-A') Wild type; (B-B') Ubx>Lines; the PE was replaced with a mirror image duplication of the pseudostratified CE and the disc was severely reduced in size. (C-E''') Dapi (blue); Nub (red) is restricted to the DP. (C,D) Wild type; optical sections at the level of the PE (C), and the DP (D). (D'-D''') The DP (left layer) expresses Nub and apposes the PE (right layer). (E-E''') Ubx>Lines; the PE (right layer) was replaced with a mirror-image duplication of the DP. Nub was detected symmetrically in both layers of these discs. (F) Ice (red) accumulated in clusters of apoptotic cells (arrows in F). Apoptosis is minimal in wild-type discs (data not shown). (G) Phospho-Histone H3 (PH3; red) stain reveals homogenous distribution of actively dividing cells in experimental discs.