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. 2014 Jan 16;156(1-2):69–83. doi: 10.1016/j.cell.2013.12.008

Figure 3.

Figure 3

Two Subsets of Insulin-Producing Neurons Regulate the Growth of Different Tracheal Subsets

(A–C) Representative terminal tracheation in well-fed control larvae. The specific body wall/gut areas are boxed in the cartoons: body wall (A), midgut (B, anterior), and hindgut (C, posterior).

(D–F) Reduced branching is apparent in equivalent areas of the body wall (D), midgut (E), but not hindgut (F) in well-fed and genetically matched Ilp2,3,5 mutants. p < 0.0001 for both body wall and anterior midgut. n = 16–35/set.

(G–I) Representative terminal tracheation in the same body regions of well-fed control larvae upon silencing of the hindgut-innervating Ilp7 neurons. No effect is apparent in body wall (G) or anterior midgut (H), but the tracheal branching in the posterior hindgut is significantly reduced (I). For body wall: p = 0.048 (Ilp7 > kir2.1 versus UAS control), but not significant versus GAL4 control. For posterior hindgut: p < 0.0001 (Ilp7 > kir2.1 versus GAL4 control) and p < 0.0001 (Ilp7 > kir2.1 versus UAS control). n = 12–18/set for body wall, 22–27/set for guts.

(J) Larval neuroanatomy of the two subsets of insulin-producing neurons: Ilp2, Ilp3, and Ilp5 (in green) are released from the brain mNSCs into the circulation. Ilp7-producing neurons located in the posterior segments of the VNC (in red) send long axons that exit in the posterior nerves that innervate both sides of the hindgut.

(K) The two hindgut nerves (labeled in red with the broad neuronal marker 22C10) are found in close proximity to the posterior visceral tracheal branches in the posterior hindgut of a 1st-instar larva (visualized using a membrane-tagged GFP expressed from the pan-tracheal driver btl-GAL4). Phalloidin (in blue) was used to highlight the visceral muscles.

(L) Transmission electron microscopy of a posterior hindgut cross-section highlighting the proximity between the hindgut nerve axons (highlighted in red) and tracheae (in green).

Scale bars, 10 μm in all images except for (A), (D), and (G), 100 μm and (L), 2,000 nm. See also Figure S4.