Fig. 7. The role of adherens junctions in response to fog signaling. (A-G) Staining of ventral (A-D,F) or lateral (E,G) cells showing the position of adherens junctions (zona adherens, ZA) and basal junctions (BJ) stained with anti-ARM antibody (red) and anti-myosin II antibody (M, green). (A-C) Movement of junctions in Ore-R embryos: ZA are located subapically in all cells at the end of cellularization (A) and this subapical position is maintained in lateral cells, while ZA move to the very apical edge of ventral cells at the onset (B) and during (C) gastrulation. (D,E) Control embryos from mat67;mat15 mothers show the same dynamics of ZA movement as seen in Ore-R, with junctions located at the very apical edge of ventral cells (D) and subapically in lateral cells (E) and at the onset of gastrulation. (F,G) Embryos expressing UASfog⁶ from the mat67;mat15 driver line show an apical shift of junctions in all cells both ventral (F) and lateral (G). Inset in E and G: non-specific background staining has been amplified in the blue channel to reveal the cell outline. (H-M) Localization of myosin II (green) to the cellularization front of wild-type embryos, and embryos in which junction formation has been disrupted (by expression of UASnullo, or by germline clone reduction of arm protein). Neurotactin staining is shown in red (except the arm panel in H where red staining is non-specific cell surface stain). (H) Myosin localizes normally to the cellularization front of wild-type, UASnullo and arm germline clone embryos. (I,J) Myosin localizes normally to the apical surface of ventral cells (arrow) at gastrulation in wild-type (I) and UASnullo (J) embryos. (K-M) Images of the apical surface of ventral cells. Cells are outlined by Nrt staining (red). Myosin (green) is localized throughout the apical surface of wild-type cells (K) but is constricted to a tight ball (arrow) within the cells of UASnullo (L) and arm germline clones (M), leaving large black (non-stained) areas without myosin that are not seen in wild type.