Figure 3. Neighbor exchanges leading to tube seam formation.

(A-I) Rearrangements of the floor cells and their neighbors, visualized in live egg chambers expressing E-cad:GFP; numbers indicate time from the beginning of imaging, rounded to the nearest minute. Orientations in different panels are adjusted to keep the floor cells in the plane of the figure. See also Movie S1.

(A-C) 3D reconstructions of the floor cells and their neighbors, viewed from the oocyte. The floor cells are distinguished by their straight borders (see text); the roof, floor, and midline cells are positioned from top to bottom. As the floor side of the floor-midline border contracts, the marked pair of floor cells (yellow and blue dots) initially borders nonadjacent midline cells, but both eventually contact the same midline cell (pink dot).

(D-I) 3D reconstruction of the floor cells, with the roof cells cropped out. Constriction of floor cell edges bordering the midline continues until several floor cells form a multicellular rosette (G, arrow), which then resolves perpendicularly to its initial configuration (H,I), resulting in new floor-floor borders. See also Movie S2.

(J-M') Summary of dorsal appendage morphogenesis, putting the changes in floor cells geometry (see Figure 2E) into the context of their roof and midline neighbors. Panels J-M show the floor cells (red) with the roof domain (blue). Panels J'-M' add the midline cells (orange). Again, the green line marks the outer border of the floor cells, which initially contacts midline cells, but then rearranges to form the new floor-floor border.