Intercalation/closure of the int5 ring.

<p>(A) Transverse view of the reconstructed primordium showing the int5 and int6 cells during int5 intercalation/closure. The nascent apical surface is indicated at 265 and 305 minutes [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005950#pgen.1005950.ref006" target="_blank">6</a>]. (B) Heat-map representation of GFP fluorescence intensity (red = high) at the leading edge of 5L during intercalation. The increased signal at the leading edge is seen with both of the membrane reporters used in this study, and precedes cytoplasmic flow into the same region (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005950#pgen.1005950.s007" target="_blank">S3 Video</a>). We interpret the increased signal as resulting from the transient presence of four membranes (protrusion plus flanking cells), relative to the signal from two membranes at other cell contacts between intestinal cells. (C) Image sequence showing the left side of the E16 primordium during int5 intercalation. The dorsal surface of 3L constricts (purple, inverted double arrow) as 5L begins to shift dorsally. After reaching the roof, 5L expands longitudinally (orange double arrow) as the dorsal surface of 4L constricts (blue, inverted double arrow); see also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005950#pgen.1005950.s007" target="_blank">S3 Video</a>. (D, E) Image sequences of a wild-type embryo (D) and an <i>efn-4</i> mutant embryo (E) during int5 intercalation, imaged at an optical plane near the roof of the primordium. Note the constriction of 3L and 3R in both embryos. In the <i>efn-4</i> mutant, 3R partially separates from 3L, and detaches entirely from the roof of the primordium; 3R rejoined the roof 64 minutes later. Panels = B,C,D [JJ2360]. E, [JJ2486]. Bars = 5 microns.