Water-insoluble odorants and tastants must pass through cuticular pores and sensillar lymph before reaching the chemosensory receptors on receptor neuron membranes. This pathway is also assumed to be used by repellents that act on chemosensory receptors. For many years it was thought that odorant-binding proteins (OBPs) carried out the task of transporting odorants to the receptors, but recent experiments have raised questions about whether OBPs are necessary for insect olfaction. We carried out proteomics analyses of red imported fire ant antennae and stable fly tarsi, and we found these chemosensory tissues contain many tubular lipid-binding proteins (TULIPs). TULIPs are widely distributed in vertebrates, insects, and plants, and they have functions ranging from lipid transport to innate immunity. The roles of TULIPs in insect antennae and tarsi are not known. We will discuss how TULIPs could be involved in olfactory reception, and how they may be suitable as targets for repellents.
