(Downloading may take up to 30 seconds.
If the slide opens in your browser, select File -> Save As to save it.)
Click on image to view larger version.


Figure 1


Fig. 1. Posterior spiracle cell invagination involves apical constriction and basolateral membrane elongation. (A) Stills of a movie showing the A8 segment (bracket) of a DE-Cad-GFP-expressing embryo. At stage 11 (t=0 minutes), spiracular chamber cells (dashed line) are superficial and localise posteriorly to the A8 tracheal pit (arrow). Later, notice apical constriction and inward cell movement to form a lumen (arrow). (B) Spiracle cells are expressing {alpha}-Catenin-GFP (green), using the ems-GAL4 driver (spiracle-specific); Armadillo (ß-Catenin) is in red. All images are top views. (i,ii) Initial lumen formation (stage 11) involves rearrangement of the most anterior cells (arrowheads) around the tracheal opening (arrow). (iii) the more posterior cells (left from white outline) constrict apically and invaginate later (iv), to form the complete chamber (v). (C) Stills of a live embryo expressing GFP-Actin in the spiracle invaginating cells. t=0 minutes corresponds to end of stage 12. Notice apical enrichment of GFP-Actin and elongation of the basolateral cell domain, with the cell nuclei (black) remaining basally localised. (D) Phalloidin staining (red) in the spiracular chamber cells expressing GFP (green). Notice the accumulation of F-Actin at the apical/luminal side of the spiracular chamber cells (lateral view). (E) Diagram showing invagination of the posterior spiracle cells (lateral view). The cells belonging to the spiracle primordium (red and green) constrict apically (i,ii); the more anterior cells (red) rearrange around the A8 tracheal dorsal branch (DB) (iii) and invaginate first, occupying deeper positions in the spiracle. These are followed by the most posterior cells (green), which then occupy more superficial positions. The invaginated cells form a multicellular tube (spiracular chamber) in continuity with the tracheal dorsal trunk. During invagination, cells also elongate their basolateral membrane, acquiring a bottle shape (iv). Anterior is to the left in all panels; note that in the extended germ band stage (stage 11) the anterior cells are on the right side because the embryo is folded. Scale bars: 20 µm in A; 10 µm in B-D. DT, tracheal dorsal trunk; SC, spiracular chamber.