Figure 2

Female SG cells undergo an architectural transition to attain their final cup shape. Low magnification maximum intensity “Z” projection (MIP) confocal images of female SGs either (Ai) 12–36 hours post eclosion or (Bi) four days post eclosion stained with antibodies to newly synthesized alpha-tubulin (green) and the dyes WGA (red) and DAPI (blue). (Ai) By mid/late day one post eclosion, SG secretory cavities (SCs) are evident (Ai, insets). The thin red and blue lines (Ai inset, Bi inset, Bv) are positional markers added by the “Ortho” function in the Zen software. (Aii) In the PL, individual cells are cup-shaped with secretory cavities (SCs) of variable size. In many cells, the cell body at the base of the “cups” remains thick, and the nuclei are mostly round. The walls of the cup are sometimes bent (dashed arrow). (Aiii,iv) Similarly, DL cells are cup-shaped, with only moderately compressed cell bodies. The rims of the cup-shaped cells directly contact the WGA-positive secretory duct in all but the most distal DL cells where some cells also appear to have recently fused PACs. Arrowheads indicate apical WGA staining. Some cells were severed in Aiii during IHC processing. (Avi–vi″) Cells in the ML appear compressed with only slight indentations on the surface where the secretory cavities will eventually form. (Avi) Nuclei are smaller and are primarily located at the basal periphery. A confocal slice through the cell bodies reveals PACs (nearly round compartments depleted of alpha-tubulin staining) in nearly all cells (Avi–Avi”, arrows). (Bi) By day four post eclosion, SCs have completed maturation and expansion. In all lobes, SCs occupy a much larger volume than the surrounding cup-shaped cell bodies, WGA and alpha-tubulin are observed in cells, and nuclei are basally positioned. (Bii) A dense WGA stained duct is present in the PL. WGA signal is also seen along the lateral cytoplasmic extensions surrounding SCs in DL and PL lobes (Fig. 2Bii, iv, arrows). (Biii,iv) The WGA staining in the DL is less intense (Biii) with lower intensity at cell boundaries (Biv, arrowheads). Asterisk in Biii denotes acellular basement membrane. (Bv) In cross section, the rims of the cup-shaped DL cells make direct contact with the WGA positive duct. (Bvi,vii) Cells of the ML are cup-shaped with the walls of the cup showing low level WGA staining. There is no obvious secretory duct in the ML beyond the proximal tip. Individual channels are denoted “b”–blue, DAPI, “g”- green, tubulin, or “r”–red, WGA. Scale bar lengths are given in microns.