If PDFR is required for tPDF activity in the oenocytes, then loss of PDFR function would be predicted to block the phenotypic increase in sex pheromone expression. Surprisingly, the loss of PDFR did not mitigate phenotypic effects resulting from the

expression of tPDF ( Figure 5B). The expression of 7-T and 7-P remained significantly elevated in w, Pdfr5304; oe-Gal4/UAS-tPDF relative to negative control flies w, Pdfr5304; oe-Gal4/+; UAS-tPDF-scr/+. Although there remain unresolved questions, the relationship between PDF and PDFR may be more complex than a simple model for ligand-receptor interactions would suggest. Several populations of neurons express PDF in the adult fly. These include the 16 ventral lateral clock neurons (vLNs) in the VX-770 ic50 brain and a cluster of approximately eight abdominal ganglia neurons (AbNs) in the ventral nerve cord. To determine which population of PDF-expressing neurons is responsible for influencing oenocyte physiology, we utilized the Gal4/UAS system to knockdown Pdf expression by RNAi ( Shafer and Taghert, 2009). The Dorothy-Gal4 (Dot-Gal4)

and tim-Gal4 drivers were used to target RNAi to the AbNs and vLNs, respectively ( Figure S4). Using the desat1-luc 17-AAG clinical trial reporter, we asked which population of PDF-expressing neurons is involved in regulating the free-running rhythm of the oenocyte clock. Surprisingly, both the AbNs and the vLNs appear to play a role in modulating

the period of the oenocyte clock. Knockdown of PDF in either population of neurons resulted in a long period (∼29 hr) relative to negative controls (∼25–26 hr; Figure 6A and Figure S5), consistent with the phenotypes of Pdf01 and Pdfr5304 ( Figure 3). Using Vasopressin Receptor the same means to knockdown PDF expression, we also asked which population of neurons was necessary to support wild-type expression levels of male sex pheromones. Here, only PDF derived from the AbNs played a role in regulating oenocyte physiology. The PDF knockdown in the AbNs resulted in a significant decrease in the amount of 7-T, 5-T, and 7-P during both the subjective day and night on DD6 (Figure 6B and Table S8), whereas the vLN knockdown had no affect on pheromone levels (data not shown and Table S8). The extent of the decrease in the expression of these pheromones in response to the AbN PDF knockdown is consistent with that shown for both Pdf01 and Pdfr5304 ( Figure 4). Thus, it appears that while both the vLNs and the AbNs contribute to the regulation of the oenocyte clock, only the AbNs influence the physiological output of the oenocytes. The results above demonstrate that PDF signaling is involved in the regulation of the oenocyte clock, desat1 expression, and cuticular hydrocarbon production.