Fig.6.

Spatial relationship between primary and secondary neurons. A–D: Z-projections of confocal sections of part of third instar brain labeled with antibody Nc82 (white; labels neuropile). Secondary neurons (only) of the engrailed-positive DPLam lineage are visualized by MARCM where heat shock to induce recombination was given shortly after larval hatching. Panels show focal planes at different depth, indicated in schematic shown in panel I. A shows section near the cortex (cx) surface, containing the somata of secondary neurons. B represents deep cortex, C superficial neuropile, and D central neuropile. In B–D, secondary axon tract formed by secondary neurons of DPLam lineage is indicated by white arrow. Note branching of SAT in central neuropile (D). E–H, J–L: Z-projections of confocal sections of third instar brain hemisphere triple labeled with anti-DNcadherin (white in E–H; labels neuropile), anti-Neurotactin (secondary neurons; red in E–H, white in J–L), and anti-GFP to image the primary and secondary neurons of the DPLam lineage in which UAS mCD8-GFP is driven by engrailed-Gal4. These panels show brain slices at similar levels as adjoining panels A–D; levels indicated in schematic of panel I. Superficial panel (E) shows secondary DPLam neurons (sn), expressing both GFP and Neurotactin. In deep cortex (F, J) the primary neurons (pn), labeled with GFP but not neurotactin, are visible. In superficial neuropile (G, K), the primary axon tract (PAT) and secondary axon tract (SAT; white arrow) can be seen side by side. The PAT expresses only GFP. The SAT expresses both Neurotactin and GFP. In deep neuropile (H, L), labeling of SAT is faint, but still visible (see L). Primary axons have diverged to form primary axonal arborization (par).

Bar: 10µm