Evolution of vertebrate olfactory receptor repertoires and their function

Chemosensation is evolutionarily ancient but has split into separate taste and smell channels only much later in vertebrates and insects. Here, we focus on recent advances in understanding vertebrate olfaction. Progress has been made on several fronts, from establishing an ever more complete picture of olfactory receptor repertoires, including their allelic polymorphisms, to a better understanding of their evolutionary dynamics in various branches of the vertebrate phylogenetic tree. The ongoing deorphanization of olfactory receptors begins to allow investigations into evolution of their function. Mechanistic understanding of the highly specific, monogenic expression of olfactory receptors has seen large advances. Finally, internal sensing of metabolites by ectopically expressed olfactory receptors is an active field of research. • First structures of olfactory receptors were solved with cryo-electron microscopy. • From olfactory receptor activation to behavior: one receptor may be enough. • Molecular mechanism of monogenic expression comes close to being understood. • A plethora of receptor repertoires enables fine-grained correlation with lifestyle. • Potentially widespread role of olfactory receptors as endogenous metabolite sensors.