Fig. 2. Expression of duf-lacZ in DVMs. (A) Diagram showing the position of the three DVM bundles (blue) relative to the DLM fibres (white) in the adult fly. (B) actin-lacZ pupal preparation (24-hour APF) showing the DVM fibre bundles. The DVM I fibres are marked by black asterisks; fibres of DVM II are marked by red asterisks. DVM III fibres are formed beneath the DLM fibres. In this figure, one of the two DVM III fibres (black arrow) can be observed. The DLM fibre most adjacent to the DVMs is indicated by the black arrowhead. (C-E) duf-lacZ-expressing DVM nuclei assayed by lacZ staining. The nuclei corresponding to DVM I are indicated by black asterisks, to DVM II by red asterisks and to DVM III by black arrows. (C) The three duf-lacZ-expressing nuclei of DVM I, and the two of DVM II, at 7 hours APF. The linear arrays of nuclei, indicated by an arrowhead, are duf-lacZ-expressing nuclei in the adjacent larval templates and are described in more detail in Fig. 4. (D,E) Twelve-hour APF pupae showing duf-lacZ-expressing nuclei of DVM I and DVM II (D), and of DVM II and DVM III (E). (F) Forty-hour APF preparation of duf-lacZ pupa double labeled with anti-MHC (red) and anti-ß-galactosidase (green) to mark the two myofibres (of DVM II) and duf-lacZ nuclei, respectively. One nucleus in each fibre (white arrow) expresses higher levels of lacZ than the rest. Anterior, top; dorsal midline, right. Scale bar: in C, 18 µm for C-E; in F, 20 µm.