Adult Drosophila aversion to caffeine requires a unique TrpA1 isoform and the PLC signaling cascade

Taste in Drosophila melanogaster is crucial to survival, influencing feeding, mating, and egg-laying behaviors. Taste organs are located on various parts of the body, including the legs, proboscis, wings, and ovipositor. Taste neurons detect chemicals via receptors like gustatory receptors, ionotropic receptors, and transient receptor potentials, with bitter and sweet tastes linked to specific neurons (Gr66a+ and Gr5a+). Bitter substances such as caffeine activate neurons, resulting in rejection behavior. TrpA1 channels, associated with aversive responses, are involved in complex behaviors and could interact with taste receptors. Our results show that caffeine mixed with sucrose reduces proboscis extension in flies compared to sucrose alone, a response that requires only the TrpA1-E isoform out of the 5 possible ones. Furthermore, our data demonstrate that this avoidance requires TrpA1 and signaling via phospholipase C and inositol trisphosphate receptors in adult Gr66a+ neurons.