Figure 8. Cellular requirement for OBP49a-t, and testing for interactions between OBP49a and bitter tastants and GR64a.

(A–C) Tip-recordings were performed using the indicated sensilla and genotypes. Shown are representative traces and the mean numbers of action potentials (n=8—11) induced by 10 mM sucrose plus the indicated bitter tastant. (A) 10 µM berberine. (B) 10 µM denatonium. (C) 10 µM quinine. The asterisks indicate statistically significant differences between Obp49a^D+/UAS-Obp49a-t and Obp49a^D;Gr5a-GAL4/UAS-Obp49a-t flies (**p<0.01). (D–G) Sensorgrams showing binding between bitter tastants and OBP49a using the BIAcore system. The indicated concentrations of tastants were allowed to interact with the OBP49a, which was bound to CM5 chips. (R.U., relative resonance units). (H–K) Protein complementation assay using the split YFP approach. Labella were dissected from transgenic flies expressing the indicated YFP(1) and YFP(2) fusion proteins in Gr5a GRNs, under control of the GAL4/UAS system. In come cases, 100 µM berberine was applied to sensilla for 1 minute before dissection. The scale bar in (H) represents 10 µm, and applies to all panels in (H–K) (see also Figure S4).