title: Flight muscle myofibrillogenesis in the pupal stage of Drosophila as examined by X-ray microdiffraction and conventional diffraction.
abstract: In the asynchronous flight muscles of higher insects, the lattice planes of contractile filaments are strictly preserved along the length of each myofibril, making the myofibril a millimetre-long giant single multiprotein crystal. To examine how such highly ordered structures are formed, we recorded X-ray diffraction patterns of the developing flight muscles of Drosophila pupae at various developmental stages. To evaluate the extent of long-range myofilament lattice order, end-on myofibrillar microdiffraction patterns were recorded from isolated quick-frozen dorsal longitudinal flight muscle fibres. In addition, conventional whole-thorax diffraction patterns were recorded from live pupae to assess the extent of development of flight musculature. Weak hexagonal fluctuations of scattering intensity were observed in the end-on patterns as early as approximately 15 h after myoblast fusion, and in the following 30 h, clear hexagonally arranged reflection spots became a common feature. The result suggests that the framework of the giant single-crystal structure is established in an early phase of myofibrillogenesis. Combined with published electron microscopy results, a myofibril in fused asynchronous flight muscle fibres is likely to start as a framework with fixed lattice plane orientations and fixed sarcomere numbers, to which constituent proteins are added afterwards without altering this basic configuration.
authors.affiliation: Research and Utilization Division, Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan. iwamoto@spring8.or.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Iwamoto
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Inoue
authors.forename: Tatsuhito
authors.initials: T
authors.lastname: Matsuo
authors.forename: Naoto
authors.initials: N
authors.lastname: Yagi
mesh_terms: D008841:Actin Cytoskeleton / Q000000981:diagnostic imaging* / Q000648:ultrastructure; D000818:Animals; D004331:Drosophila melanogaster / Q000254:growth & development* / Q000648:ultrastructure; D005426:Flight, Animal; D024510:Muscle Development; D009132:Muscles / Q000000981:diagnostic imaging / Q000648:ultrastructure; D011679:Pupa / Q000254:growth & development / Q000502:physiology; D011859:Radiography; D014961:X-Ray Diffraction