Cno regulates coupling of AJs to contractile network. Embryos, stage 6–8, antigens, and genotypes are indicated. (A–A’’, C–C’’, G, J, and M–O) Ventral views are shown. (B, D–F’, H, I, and K) Cross sections are shown. (A–A”, B, and E) Wild-type (WT) ventral furrow. Myosin (Myo) covers cell apices (arrows and insets). Constriction coupled to actomyosin contraction. (C–C’’, D, and F–F’’) cno^MZ is shown. Myosin condensed into balls that are not contiguous with AJs (arrows and insets). Cell shape change is not completed. (G) cno^MZ is shown. Myosin balls visualized live with zipper-GFP (Zip-GFP). (H) Wild type is shown. Actin accumulates evenly at the apical surface (arrow). (I) cno^MZ is shown. Actin condenses into balls that are not contiguous with actin at AJs. Constriction arrests (arrow and inset) are shown. (J) cno^MZ is shown. F-actin balls visualized live with moe-GFP. (K) Probable cno maternal mutant. Balls of actin (inset) observed even in embryos initiating invagination. (L) Model of alterations in actin, myosin and constriction in cno^MZ. (M–O) Rap1^MZ is shown. (M and N) Similar balls of Myo form and separate from AJs. (O) Balls of actin. Bars: (A–A” and C–C”) 30 µm; (B and D–O) 10 µm.