Figure 4. Axonal projections of different classes of pharyngeal GRNs in the subesophageal zone (SEZ).

(A–D) Images of the SEZ showing axonal termini (green) labeled by indicated Gr- or Ir-GAL4 drivers in wild type (w¹¹¹⁸, top) and poxn (poxn^ΔM22-B5/poxn⁷⁰, bottom) flies. Four main classes of pharyngeal neuronal projections are presented: sweet pharyngeal GRNs (A), putative water pharyngeal GRNs (B), putative bitter pharyngeal GRNs (C), and Ir-GAL4 expressing pharyngeal GRNs (D). Bright field images of the proboscis show GFP cells (green) labeled by indicated GAL4 driver in the LSO (closed arrowhead), VCSO (open arrowhead) and DCSO (arrow) in poxn mutants. Asterisks point to representative long, bent mechanosensory bristles, which are present in place of external taste hairs in poxn mutants. Scale bar: 100 μm. Neuropil is stained with anti-nc82 (magenta). Subsets of pharyngeal GRNs labeled by GAL4 drivers named in bottom left corners. Also see Figure 1F, J, N for nomenclature. Note the presence of a small subset of taste peg projections labeled by Gr64e-/Ir76b-/Ir25a-GAL4 in the SEZ, and Ir76b-/Ir25a-GAL4 labeled olfactory projections to antennal lobes in poxn mutants.