Ectopic expression of <i>dysf</i> induces fold formation and Rho1 activation.

<p>(A-D) Apical view (A and C) and Z-section (B and D) of a region of the wing pouch (blue square in the schematic wing disc). The <i>ptc-Gal4</i> driver is used to express different UAS constructs in a band of cells of the anterior compartment of the wing pouch. Control <i>ptc>GFP</i> (A and B) or <i>ptc</i>><i>Rho1RBD-GFP</i> (C and D) and different time points of <i>ptc>dysf</i> expression, using the <i>tubulin-Gal80</i>^<i>ts</i> system. The <i>ptc</i> domain is marked with GFP (green and dotted lines). Phal is in red and separate grey channel where indicated. (A) The <i>dysf</i>-expressing cells undergo apical constriction and consequently the <i>ptc</i> domain becomes narrower. By 48 hrs, accumulation of F-actin is clearly visible. (B) Z-sections of the genotypes and time points described above. Note the progressive narrowing of the GFP positive cells in their apical region and the formation of a fold that is visible by 48h. (C) The <i>ptc</i>><i>Rho1RBD-GFP</i> cells undergo apical constriction and accumulate F-actin after 48 hrs of <i>dysf</i> expression. (D) Note that the formation of the ectopic fold in <i>ptc>dysf</i> wing pouch is accompanied by an apical accumulation of F-actin and enhanced Rho1 activity in the apical region of the cells that undergo apical constriction.