Fig. 4. Fat body (but not neuronal) AKHR expression substantiates observed metabolic phenotypes. (A–C) The axon projection pattern of akhr-Gal4-expressing gustatory neurons in the adult subesophageal ganglion. The dark region at the top of the picture (white arrow) is the esophagus. Shown from left to right, Gr5a-Gal4/UAS-GFP, Akhr-RFP, and the merged images, demonstrating co-expression of Gr5a and AKHR. (D–F) Double-labeling experiments with Gr66a-expressing neurons demonstrated exclusion of AKHR. Additional Akhr fibers likely represent axon projections of other attractive taste neurons. Single sections are displayed (1 µm); similar results were obtained through all projection layers in the subesophageal ganglion. (G) Genetic rescue experiments demonstrate that AKHR expression in the fat body of Akhr^null flies restores wild-type starvation resistance (Student's t-test, ^*P<0.05). All genetic rescue experiments were done in an Akhr^null background in 1-week-old male flies. R⁴-Gal4 was used as a fat body driver. Gr5a-Gal4 (which drives Gal4 expression in the majority of attractive-gustatory neurons) was used as the gustatory neuron driver. The results are average starvation resistances from separate experiments (N=4 for fat body rescue, with 16 flies for each experiment; N=3 for Gr5a rescue, with 16 flies for each experiment), and standard deviations are shown. The starvation resistance of neuronal rescue flies is indistinguishable from Akhr^null flies. (H) Expression of AKHR in the fat body (in an otherwise Akhr^null background) dramatically reduces total body triglyceride content; the triglyceride content of Akhr^null flies is shown for comparison.