Smell and taste perception in Drosophila melanogaster larva: Toxin expression studies in chemosensory neurons

GAL4-driven targeted expression of tetanus toxin light chain (UAS-TeTxLC) i n a subset of chemosensory neurons of the larval antennomaxillary complex ( AMC) and pharynx causes abnormal chemosensory behavior in Drosophila melano gaster. Consistent with strongest staining in the dorsal organ (DO), the pr esumed olfactory organ of the AMC, tetanus toxin-expressing larvae subjecte d to an olfactory preference assay show anosmic behavior to most volatile s ubstances tested. Furthermore, we observed reduced responses to sodium chlo ride, fructose, and sucrose in gustatory plate assays. Surprisingly, the en tire subset of labeled sensory neurons from the terminal (maxillary) organ (TO) of the AMC was found to project via the antennal nerve to the larval a ntennal lobe region. The maxillary nerve remained completely unstained. Hen ce, a subset of neurons from the TO builds an anatomical entity with projec tions from the DO. Our results suggest that the AMC contains both olfactory and gustatory sensilla, and that the DO is the main olfactory organ in lar vae.