Figure 5. PNs require presynaptic innervation during development for their survival.

(A) Schematic of the experimental approach. OSNs on one side were laser ablated at stage 14, before OSN axons contact PNs. Animals were left to develop and hatch and PN morphology was examined in mid-first instar larvae. (B) Anterior part of a first instar larva in which OSNs have been unilaterally ablated. All sensory neurons are labelled using PO163-Gal4;UAS-CD8GFP, including taste neurons that appear as the most anteriorly located cluster of PO163 positive cells on both sides. OSNs labelled both with PO163 in green and with α-Orco antibody (magenta) are present on the control side (bottom) but not in the ablated side (top). (C) Quantification of the OSN ablation experiments. Number of PNs in the control (blue dots) and OSN ablated side (pink dots) for each animal are linked by a grey line. (D–D″) Z projection of a brain in which OSNs were unilaterally ablated (right side). PNs visible with GH146-QF;QUAS-mTomato on the control side are missing on the ablated side. The AL, visualized with Nc82 antibody staining in the control side (dashed line), is absent on the ablated side. (E–E″) Z projection of a brain in which OSNs were unilaterally ablated (right side). PNs (GH146-QF;QUAS-mTomato) can be seen innervating the AL in the control side. Some PN of the ablated side are missing, while surviving ones are found innervating the subesophageal ganglion (SOG). The AL, visualized in the control side as a gap with DAPI staining, is missing on the ablated side (see Figure S2).