Fig. 2. Myosin localization in embryos misexpressing fog. (A-F) Staining for Fog protein in control embryos expressing just the mat67;mat15 driver line (A-C) and this line driving UASfog⁶ expression (D-F). At the onset of cellularization (A,D), little fog expression is seen, but early in cellularization, before nuclear elongation (B,E), there is high fog expression throughout UASfog embryos. At the onset of gastrulation, there is low fog expression in the ventral furrow of control embryos (asterisk in C) and high expression throughout the UASfog embryos (F). (G-L) Control (G-I) and UASfog-expressing (J-L) embryos stained for myosin II. Myosin localizes normally to the basal cellularization front and decreases normally in ventral cells, which show the usual increase in cell depth (G,J). At the onset of gastrulation, myosin continues to be localized basally and now also localizes to the apical side of ventral cells in both control (H) and UASfog (K) embryos. Apical myosin is more intense in UASfog embryos and is no longer restricted to the ventral furrow, occurring in dorsal and lateral cells (arrow) too. This continues through later stages of gastrulation (comparing arrow in I and L). (M-O) Quantification of myosin intensity in driver-line control (blue) and UASfog-expressing (pink) embryos. Measurements were taken from the apical and basal sides of ventral and lateral cells at three different stages: (M) end of cellularization (see G,J), (N) onset of gastrulation (see H,K) and (O) later gastrulation (see I,L). No difference is seen between control and UASfog embryos at the end of cellularization (M) but during gastrulation (N,O) myosin increases on the apical side of both ventral and lateral cells in UASfog embryos with no corresponding decrease from the basal side. Error bars indicate s.e.m.