In <i>Drosophila</i>, Gr64f promotes feeding.

(A) Refeeding after 24h starvation decreases Gr64f transcript. ****p t test. (B) The sugar blind mutant (all eight known sugar receptors mutated) show almost no motivation to feed in proboscis extension reflex (PER). n = 10 trials. ***p C) Gr64f mutant (Gr64fLexA) flies show less motivation to feed in PER. n = 10 trials. ***p p D) Silencing Gr64f-GAL4 neurons by expressing the hyperpolarizing channel Kir2.1 also caused loss of motivation to feed in PER. n = 10 trials. ***p p p E) Silencing the Gr64f gene using the Gr5a-GAL4 driver leads to decreased food consumption compared to wildtype flies in the CAFE essay. *p t test. Food intake is the estimated food consumption (μl) of one female per day. (F) Gr64f mutant (Gr64fLexA) flies show decreased food consumption compared to wildtypes in the CAFE essay. **p t test. (G) Silencing Gr64f-GAL4 neurons by expressing the hyperpolarizing channel Kir2.1 also leads to decreased food consumption in the CAFE assay. ****p H) Dynamics of light-induced proboscis extension after photoactivation in a fly expressing Gr64f-Gal4, UAS-CsChrimson. (I) Relationship between the intensity of the stimulating light and PER rate using the indicated flies. A fly immobilized in a pipet tip was stimulated with red light at the indicated intensity and the light-induced proboscis extension of the fly was recorded. We used two values to score the PER assay. A score of 1.0 indicates a fly that extended its proboscis after being presented with the light. The score was 0 if the fly failed to extend its proboscis. n = 8 trials. **p p J) Increasing the baseline activity of sweet GRNs (UAS-Chrimson (X)/+;; +/Gr5a-GAL4) by photo-activation with 0.78 μW/mm2 of red light increases the probability that the fly shows PER upon sugar stimulation (1 mM sucrose) compared with either red light stimulation (0.78 μW/mm2) or 1 mM sucrose alone. *p K) Simplified model showing that Gr64f promotes feeding.