Figure 1. Receptor-to-neuron maps of taste organs.

(A) Schematic of sensillar classes in the labellum, defined by receptor expression patterns and functional analysis (left). Tables indicating identified neurons (center) or sensilla (right) with their receptor expression patterns. Maps created from expression studies along with, in some instances, functional studies; with the exception of Gr64a, which is mapped to labellar sweet neurons by functional studies [59,60]. Receptors marked with an asterisk are not expressed in every sensillum of the indicated class. Sweet receptors in italics have been mapped by knock-in reporter analysis but not by transgenic reporter experiments. Receptors in bold are broadly expressed in bitter neurons. Expression of ppk23 and ppk29 has been assigned to S sensilla based on observed pairing of ppk23⁺ cells with Gr66a⁺ cells. (B) Schematic of sensilla in the female fore tarsi (left) and tables indicating identified neurons (center) or sensilla (right) with their receptor expression patterns. (C) Schematic indicating the location of oral taste pegs and the labral sense organ (LSO; chemosensory sensilla in lilac, mechanosensory sensilla in black) and ventral cibarial sense organ (VCSO) in the pharynx. Tables indicating identified neurons (right) with their receptor expression patterns in the LSO and VCSO (center) and the taste pegs (right).