Figure 4.

Role of ecdysterone signaling in remodeling of the CSD neuron. (a, c, d) CSDn profiles visualized in RN2-Flp, Tub-FRT-CD2-FRT-Gal4, UAS-mCD8GFP/UAS-EcR^W650A animals at different developmental stages. (b) RN2-Flp, Tub-FRT-CD2-FRT-Gal4, UAS-mCD8GFP/+ control at 20 hours APF; scale bar for all images = 30 μm. (a) In the larvae, branching within the antennal lobe (red arrow), the ipsilateral higher centers (arrowhead) and the terminals are comparable to that of the wild type (Figure 1b). Branches at the contralateral higher centers (yellow arrows) appear more elaborate than that of normal controls (Figure 1b). Staining with antibodies against the EcR-B1 isoform (red in inset) and anti-GFP (green in inset) demonstrated that the CSDn soma (arrows in inset) expressed EcR-B1. At 20 hours APF, pruning has occurred in the normal CSDn (b) and branching within the antennal lobes (demarcated with dotted lines), the ipsilateral (arrowheads) and contralateral (arrows) are greatly reduced. CSDn expressing a DN-EcR transgene (c) does not undergo pruning and the neuronal architecture resembles that of the larva. In the adult (d), the pattern continues to be 'larva-like'. However, the footprint of the terminal arbors occupies a larger area than in the larva (demarcated with yellow dots) and many of the arbors appear blebby (arrowheads in inset in (d)).