Innervation is required for Drosophila tracheogenesis. The RicinA subunit was driven under the pan-neural driver elav to lesion neurogenesis in Drosophila embryos. FasII staining labels longitudinal tracts of the CNS and some motor axons (magenta). Tracheal structure is stained for lumen protein (cyan). (A) shows neural and tracheal structure in wild type embryos. (B) Neural nuclei are labeled by activity of the elav promoter to visualise the cells affected by RicinA. (C-F) show examples of RicinA-mediated neural depletion and its effects on airway development. Longitudinal tracts are often almost eliminated (C,E open arrowheads) or occasionally reduced to single disordered and broken tracts (D, open arrowheads) or merged with disordered peripheral projections (F, open arrowheads). Sections of dorsal tracheal trunk do form but show breaks (C-E, arrows). In (C), the tracheal cells that appear to be forming segments of a dorsal trunk are seen improperly on the ventral side of the embryo. Smaller tubes are largely absent by lumen staining, and those that remain are incomplete (E, closed arrowheads). In (F), the tracheal cells form severely disorganised balls of lumenised tube (arrows). (G-I) show labeling of tracheal lumen (G) and tracheal epithelium (H) with the merged image shown in (I) to test if the discontinuous tubule staining simply represents a lumenisation problem or if there are true gaps in the epithelial tubes. Sections of stained lumen (G) are surrounded by epithelial cells (H,I) (example indicated by arrowheads). Where gaps in the lumen exist, epithelial cells are absent (G-I, arrow). Scale bars =50 μm. CNS, central nervous system.