Fig. 3. Actin isoform incorporation into cortical actin and stress-fibre-like assemblies. Using the CY2-Gal4 driver all six actins were ectopically expressed in the follicular epithelium during oogenesis. (A) Diagram illustrating the level of the confocal sections in B-G' and H-N'. (B-G') Confocal sections through the follicle epithelium; the apical surface of the epithelium facing the oocyte is up, basal surface is down, as depicted in A. In the colour panels, GFPactins are green, labelling with phalloidin is red (B-G), the individual GFPactin channels are also shown as black and white images (B'-G'). The arrows in B,C,F,G indicate phalloidin-labelling of the muscle sheet surrounding the egg chambers, the arrowhead in B indicates the strong phalloidin labelling within the oocyte. Both structures were not labelled with the GFPactins as the CY2-Gal4 driver is only expressed in the follicle cells. Different actins varied in the level of their incorporation into the apical terminal web and microvilli [e.g. strong incorporation for actin5C (B') and actin42A (C')] and incorporation into the cortical actin cytoskeleton lining the lateral sides of follicle cells [e.g. strong labelling for actin87E (F')]. (H-N') Confocal scans of a basal face-on view of the follicle cells (with the muscle sheath removed), showing the basal actin stress fibres as depicted in A. In the colour panels, GFPactins are green, labelling with phalloidin is red (H-N) and the individual GFPactin channels are shown as black and white images (H'-N'). Levels of incorporation into the bundles vary, with actin42A being highly concentrated (I') and actin79B being only weakly incorporated (L') into the fibres.