Figure 4.
Regional Regulation of Intestinal Tracheae by Multiple Ilp and Pdf Neuropeptides
(A) Expression of Ilp7 (green) and Pdf (red) neuropeptides in a 1st-instar VNC. Note the cell bodies in the posterior-most segments (to the right). DAPI (in blue) was used to visualize the CNS. Anterior is to the left.
(B) Higher magnification image of these posterior cell bodies: four of the eight Ilp7-expressing neurons (those located in the two posterior-most segments) coexpress Pdf. Pdf is also expressed by four additional neurons in these segments. Anterior is to the top.
(C) Regional expression of the Ilp7 and Pdf peptides produced by the neurons in (B) in a 2nd-instar hindgut. Anterior is to the left, and the visceral muscles are highlighted in blue with phalloidin. Both peptides are present in varicosities along the hindgut nerves, but the anterior-most nerve endings are only positive for Pdf.
(D–F) Representative hindgut tracheation in well-fed control larvae. The specific gut regions are boxed in the cartoons: anterior (D), mid- (E), and posterior hindgut (F).
(G–I) Ilp7 mutation does not affect branching in the anterior or posterior hindgut but results in mildly reduced branching in the mid-hindgut.
(J–L) A severe reduction in branching is apparent in the entire hindgut of mutants lacking Ilp7 as well the systemic Ilp2, Ilp3, and Ilp5 peptides.
(M–O) Pdf mutation does not affect branching in the anterior hindgut (M) or posterior hindgut (O) but leads to reduced tracheal growth in the mid-hindgut (N).
(P–R) Downregulation of the Pdf receptor specifically in tracheal terminal cells using DSRF-GAL4 does not affect branching in the anterior hindgut (P) or posterior hindgut (R) but leads to significantly reduced growth in the mid-hindgut (Q).
(S–U) The intestinal tracheal coverage in double mutants lacking both Pdf and Ilp7 peptides is indistinguishable from that of control flies in the anterior hindgut (S), but it is strongly reduced in both the mid-hindgut (T) and posterior hindgut (U).
See also Figure S5 for quantifications and Figure 7 for a summary of this regional regulation of tracheae by different peptides. Scale bars, 10 μm in all images except for (A), (B), and (C), 100 μm, 50 μm, and 100 μm, respectively.