(A-A”) Lateral view of a stage 11 PrdG4;UAS-Ato;RhoAAA-lacZ embryo immunostained for β-gal (green) and Ato (red). Ectopic Ato has a small affect on RhoAAA activity in the thoracic segment (T2), and occasionally enhances RhoAAA activity in additional cells of the abdomen (arrow). (B-B”) Lateral view of a stage 11 PrdG4;UAS-Sens;RhoAAA-lacZ Drosophila embryo immunostained for β-gal (green) and Sens (purple). Ectopic Sens does not alter the number of RhoAAA-positive cells within either the thorax or the abdomen. (C-C”) Lateral view of a stage 11 PrdG4;UAS-Ato UAS-Sens;RhoAAA-lacZ Drosophila embryo immunostained for β-gal (green) and Sens (purple). Co-expression of Ato and Sens significantly stimulates the number of RhoAAA-positive cells within the abdomen but not the thorax. (D-D”) Lateral view of the same embryo in C immunostained for phospho-ERK (red) and β-gal (green). Close-up view of PrdG4-On and PrdG4-Off abdominal segments reveals that the co-expression of Ato and Sens induces additional phospho-ERK (arrows) compared to a control abdominal segment. (E-E”) Lateral view of a stage 11 PrdG4;UAS-Abd-A;RhoAAA-lacZ Drosophila embryo immunostained for β-gal (green) and Abd-A (blue). Ectopic Abd-A expression enhances RhoAAA activity in the thoracic segment (T2), but has no additional affect on β-gal expression in the abdomen. (F-F”) Lateral view of a stage 11 PrdG4;UAS-Ato,UAS-AbdA;RhoAAA-lacZ Drosophila embryo immunostained for β-gal (green) and Abd-A (blue). Co-expression of Ato and AbdA activates RhoAAA activity in multiple cells of both the thoracic (T2) and abdominal segments (arrows). (G-G”) Lateral view of a stage 11 PrdG4;UAS-Ato,UAS-AbdA;RhoAAA-lacZ Drosophila embryo immunostained for phospho-ERK (red), Abd-A (blue), and β-gal (green, in G’). Close-up view of PrdG4-On and PrdG4-Off segments reveals that the co-expression of Ato and Abd-A induces phospho-ERK (arrows) surrounding the β-gal-positive cells within thoracic and abdominal segments.