Apical actomyosin activation, but not apical cell area reduction, is critical for apical accumulation of Rab11 vesicles. (A) Ectopic expression of Fog results in Myosin II activation in dorsal cells but does not cause apical area reduction. N = 3 embryos. Scale bar, 10 μm. (B and C) Ectopic activation of Myosin II in dorsal cells by overexpression of Fog induces ectopic apical accumulation of Rab11 vesicles. (B) Enface view. (C) Cross-section view. N = 5 embryos for Fog overexpression; N = 4 embryos for control embryos. Scale bars, 5 μm. Scale bar for zoom-in view, 2 μm. (D and E) Comparison of YFP-Rab11 in the ventral furrow and dorsal fold. Yellow outlines: example cells displaying apical area reduction. Dorsal fold cells do not show apical Rab11 vesicle accumulation despite undergoing apical shrinking. N = 10 embryos for imaging the dorsal folds. (D and E) Cross-section view and en face view, respectively. Scale bar, 5 μm. Green arrows: Rab11 vesicles. Scale bar, 5 μm.