Figure 1: Serotonergic SE0PG neurons innervate the PG.
(a) The third instar larva expressing RFP using phantom–GAL4 (phm>RFP). The anterior side is at the top. RFP is expressed in the prothoracic gland (PG, arrow). The boxed area is illustrated in b. (b) The pharyngeal muscles (PM), oesophagus (EP), ring gland (RG), brain (Br), ventral nerve cord (VNC) and proventriculus (PV). The RG contains the PG, the corpora allata (CA) and the corpora cardiaca (CC). (c) The Br–RG complex from a phm>RFP third instar larva was immunostained for serotonin (green). Serotonergic neurons directly innervate the PG (arrows). The neurites pass through the oesophagus foramen (arrowhead, outlined circle). (d,e) The PG-projecting neurons were visualized with DsRed and nSyb::GFP using TRH–GAL4. (f) A TRH>GFP third instar larva was dissected from the lateral side. PG-projecting neurons (green, yellow arrow) passed through the oesophagus foramen (arrowhead, see also c), extending towards the frontal nerve junction (FJ). The blue arrow indicates the ‘SE0’ cluster in the ventral side of the brain. Magenta is used as a background colour to show the shapes of the tissues. (g) A TRH>GFP third instar larva was dissected from the dorsal side and immunostained for serotonin (magenta) and GFP (green). The SE0 neurons (blue arrows) innervated the PG as well as the PM and the PV (yellow arrows). The boxed area is magnified in the inset. At the FJ, the neural tracts bifurcated to PM and PG (green and orange). (h) Four pairs of SE0 cells (circles). The boxed area is shown in i. (i) The TRH>GFP third instar larva was immunostained for GFP (green) and a suboesophageal ganglion (SOG) marker PBAN (magenta). The SE0 neurons (arrows) are located anterior to the SOG cells (bracket). The inset is a single-cell clone of SE0 neurons. (j) The anterior half of a larva and the tracts of SE0 neurons (green lines) are illustrated. The scale bar depicted in i corresponds to 481 μm (a), 18.7 μm (c), 20.0 μm (d,e), 32.7 μm (f), 50 μm (g), 28.4 μm (g, inset), 28.1 μm (i) and 24.4 μm (i, inset).
