Supplementary Figure 1: AS and LE cell organization during dorsal closure.

(A) Apical surfaces of AS cells extend filopodia into the perivitelline space. The inset shows a magnification of bundled actin filaments (black arrow) in the selected filopodium. (B) Examples of cavities formed by LE cells around AS cell protrusions (black arrows). (C) Tomographic slices through the LE/AS adherens junction. The cross section is perpendicular and the longitudinal section parallel to the anterior/posterior embryonic axis. (D) Tomographic slice and rendered view showing lateral lamellipodia overlaps of neighbouring LE cells before zipping. Blue dots mark the dorsal most position of LE/AS adherens junctions (B and D).