Figure 7. State-dependent modulation of yeast taste neurons regulates specific yeast feeding behavior programs to support protein homeostasis.

Schematic depicting the regulation of yeast feeding by specific taste receptor neurons. GRNs in the proboscis that express Ir76b and Ir25a mediate yeast feeding. GRNs innervating taste sensilla on the labellum regulate proboscis extension in response to yeast, and subsequent extension and retraction cycles are regulated by taste peg GRNs. The response of each of these GRN subsets is modulated according to the fly’s internal amino acid state: after 3 or 10 days of deprivation from yeast, the response of these neurons is increased. This modulation provides a potential neuronal basis to increase both the number and duration of yeast feeding bursts when the fly is lacking amino acids, and thereby to maintain protein homeostasis.