A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster

Salt is a crucial for survival, while excessive NaCl can be detrimental. In the fruit fly, Drosophila melanogaster, an internal taste organ, the pharynx, is a critical gatekeeper impacting the decision to accept or reject a food. Currently, our understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. Here, we found that a member of the ionotropic receptor family, IR60b, is exclusively expressed in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion, we demonstrate that IR60b and two coreceptors IR25a and IR76b, are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. Our findings highlight the critical role for IRs in a pair of pharyngeal GRNs to control ingestion of high salt.