Dynamic RLC phosphorylation is not required to trigger basal to apical relocalization of Myo-II. (A) Wild-type Myo-II localizes to the apical surface and is reduced basally during ventral furrow formation. Images are fixed embryo cross sections during sequential stages of apical constriction stained for Zipper (myosin heavy chain) and neurotactin (membrane). (B and C) Sqh phosphomutants do not alter the basal–apical Myo-II redistribution. Embryo preparation was the same as in A, except germline clones expressing sqh-AE (B) and sqh-TA (C) were fixed. Bars, 20 µm.