Figure 2.

Cell clones lacking [Df(3L)iro^DFM3; A, D–F] and overexpressing (UAS–caup; C) Iro-C genes in late third instar wing discs. All discs are oriented anterior to the left and ventral to the top. (A) Mutant clone (*) delimited by an ectopic fold. The disc is stained with anti-Caup antibody. Apparent staining within the clone is due to flattening of the disc upon mounting. The arrowhead points at the notum/hinge fold. (B) Disc overexpressing UAS–caup driven by dpp–GAL4. An ectopic fold (arrowheads) appears on the side where cells with high levels of Caup abut cells without the protein, i.e., the A/P compartment border. (C) Confocal section of a disc with clones of cells overexpressing UAS–caup (anti-Caup antibody, red). Clones contact each other, their cells are arranged in filaments separating large, roundish islands of nonexpressing cells, and create ectopic folds (phalloidin staining, green) that surround the nonexpressing cells. Folds were visible with light transmission optics (not shown). (D–F) Confocal section of a clone in the notum–hinge region that reroutes the normal fold between these regions. The absence of anti-Myc antibody staining (E) marks the homozygous Df(3L)iro^DFM3 cells. The clone border is smooth along the fold (arrow) that separates it from notum cells and wiggly in the wing hinge region (arrowhead). Phalloidin staining (F) shows the smooth continuity between the extant (arrow) and ectopic (arrowhead) folds. (G) Clones (arrowed, absence of anti-Myc antibody staining, red) of homozygous Df(3L)iro^DFM3 cells in the notum region of a UAS–ara/ap–GAL4 disc. The absence of a fold surrounding these clones was evidenced by phalloidin (not shown) and Myc stainings (cf. with E) and transmission optics. (H) Similar clones stained with anti-Sc antibody (green and yellow). The presence of a clone did not disturb the extant Sc proneural clusters (arrowheads). It should be pointed out that the ubiquitous UAS–ara expression slightly modified the wild-type pattern of sc proneural clusters in the notum (Campuzano and Modolell 1992), but the clones did not modify it further. The UAS–ara expression did not prevent notum formation and bristle development, as observed in pharate individuals (data not shown).