Drosophila proboscis extension response and GCaMP imaging for assaying food appeal based on grittiness

Fruit flies sense the features of food that are driven by particle size, including smoothness versus grittiness, by deflection of sensilla decorating the labellum, and md-L neurons. We describe adaptation of the Drosophila proboscis extension response assay, including steps to perform the taste tests and score behavioral responses, to determine preferences to foods with different sized particles. We also describe calcium imaging in GCaMP-expressing flies to assess the responses of md-L neurons to different levels of taste sensilla deflection. For complete details on the use and execution of this protocol, please refer to Li and Montell. (2021).