Fig. 3. Expression of duf-lacZ in abdominal muscles. (A-E) duf-lacZ expression in developing dorsal muscles of the abdomen. (A-C) One hemisegment of a 24-hour APF duf-lacZ pupa double labeled with anti-ß-galactosidase (green) and 22C10 (red). (A) Single cells with duf-lacZ expression in their nuclei. (B) The same preparation as shown in A showing the duf-lacZ-expressing cells stained by 22C10. The nerve to which the myoblasts remain attached initially is also labeled by 22C10 and is indicated by the white arrowhead. (C) Merged image of A and B. (D) A 28-hour APF duf-lacZ pupa similarly double labeled as in C, showing the duf-lacZ-expressing cells stretching out at positions where future muscle fibres will form. (E) A 50-hour APF duf-lacZ pupa double labeled with anti-MHC (red) and anti-ß-galactosidase (green), showing a subset of dorsal muscles. By this stage, formation of the multi-nucleate fibres is largely complete. Each fibre has one prominent duf-lacZ-expressing nucleus (white arrows), presumably belonging to the single cell that preceded the multi-nucleate fibre. The remaining nuclei express duf-lacZ at a lower level. (F-H) duf-lacZ expression in developing lateral muscles of the abdomen. (F,G) duf-lacZ pupa double labeled with anti-ß-galactosidase (green) and 22C10 (red). (F) Twenty-four hours APF. Single cells expressing duf-lacZ are present in the region where the future lateral muscles will form. These cells, like the cells in the dorsal region, are labeled by 22C10. (G) The developing lateral myotubes at 36 hours APF. The fibres, labeled by 22C10, are now multi-nucleate. (H) Lateral muscles at 41 hours APF, labeled by anti-ß-galactosidase (green) and anti-MHC (red). In both G and H, each fibre contains a single nucleus with high levels of duf-lacZ expression (white arrows), against a backdrop of fainter expression in the other nuclei. For some fibres in H, nuclei with higher duflacZ expression are not present in the field of view. In A-E, anterior is to the top, dorsal midline to the right; in F-H, anterior is to the right, dorsal midline to the bottom. Scale bar: 50 µm.