Presentation Details
Neural Circuitry Underlying Negative Valuation of Sweetness in Drosophila

Dorsa Motevalli1, Sydney Fogleman1, Robert Alfredson1, Ulrich Stern1, Will Silander2, Kaiyu Wang4, Barry Dickson3, Toshihide Hige2, Rebecca Chung-Hui Yang1.

1Duke University, Durham, NC, USA.2University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.3Queensland Brain Institute, Brisbane, Australia.4Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China

Abstract


Sugar is a well-known appetitive tastant for feeding in flies. However, recent evidence suggests that it can also decrease option value in a non-feeding decision-making task. Specifically, flies accept a sugary agarose for egg-laying when it is the sole option but reject it when a sugar-free agarose is available. The neural mechanism by which sugars devalue option for egg-laying is not well understood, but input from the leg sweet neurons has been shown to be critical. Here we identified a circuit that converts input from the leg sweet neurons into a negative value signal for decision-making. First, we found a group of SEZ-targeting projection neurons in the VNC that are post-synaptic to the leg sweet neurons; these neurons respond to sugars and are required to devalue sweet options for egg-laying. Next, we found that these SEZ-targeting VNC neurons synapse onto specific SLP-targeting projection neurons in the brain, and, like their presynaptic partners, these SLP-targeting neurons also respond to sugars and are required to devalue sweet options for egg-laying. Notably, these neurons are GABAergic and can inhibit the egg-laying command neurons (oviDNs). This devaluing circuit (from legs -> VNC -> SEZ -> SLP -> oviDNs) is task specific and does not regulate feeding. Lastly, analysis of an African natural variant that prefers sugary agarose for egg-laying identified a single gene whose expression change in this circuit drives this variant’s altered sugar preference. In conclusion, we have uncovered a circuit that uniquely confers a negative value to sugars and showed how its genetic modification can diversify flies’ sugar valuation for egg-laying in nature. This discovery lays the groundwork for determining the circuit and genetic basis for sensory-value transformation.

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