Fig. 1. The autonomy of amnioserosa morphogenesis. (A-L) Wild-type embryos. Stage 7-8 (A) and stage 8-9 (B). AS is bracketed. (C) Stage 10-11. Fully extended AS (bracketed) is present between folded germband. (D-L) Embryo surface views at the level of AJs. (D-F) Stage 6. (D) DE-Cadherin. Two hexagonal AS cells are outlined. Inset shows a cross-section. (E) Lateral MT bundles in cross-section (arrows). (F) F-actin, AS cells are outlined. (G-I) Stage 8. (G) DE-Cadherin. Two AS cells elongating along DV axis are outlined. (H) MTs along cell elongation axis (arrows). (I) Actin, AS cells are outlined. (J-L) Stage 10. (J) DE-Cadherin. Two fully elongated AS cells are outlined. Inset shows a cross-section. (K) MT bundles along cell elongation axis (arrows). (L) Actin, AS cells are outlined. (M) Cell dimensions pre/post-elongation. (N,O) Stage 9-10 zen mutant. (N) Non-elongated dorsal cells are bracketed. (O) Projection. The germband ventral midline (arrow) extended beneath dorsal surface. (P,Q) arm^m/z mutant. Elongated dorsal cells are bracketed. (P) After cellularization. (Q) Stage 9-10. (R,S) bcd nos tsl mutant. Elongated dorsal cells are bracketed. (R) Stage 7-8. (S) Stage 9-10. (T) Higher magnification wild-type, zen mutant, arm^m/z mutant and bcd nos tsl mutant cells. Two cells are outlined in each. (U) Quantification of stage 10 wild-type, zen mutant, arm^m/z mutant and bcd nos tsl mutant cell lengths. (V) Bright-field timelapse imaging. Early bcd nos tsl mutant AS morphogenesis. Two cells are outlined. (W,X) dl mutant. DE-Cadherin. AS is bracketed. Ectopic furrows are indicated by arrows. (W) Stage 7-8. (X) Stage 9-10. (Y) Stage 9-11 AS cell orientations. bcd nos tsl mutants, white; dl mutants, red. White scale bar, 5 µm; gray scale bar, 50 µm.