Molecular and neural mechanisms of sex pheromone reception and processing in the silkmoth Bombyx mori

Abstract

Male moths locate their mates using species-specific sex pheromones emitted by conspecific females. One striking feature of sex pheromone recognition in males is the high degree of specificity and sensitivity at all levels, from the primary sensory processes to behavior. The silkmoth Bombyx mori is an excellent model insect in which to decipher the underlying mechanisms of sex pheromone recognition due to its simple sex pheromone communication system, where a single pheromone component, bombykol, elicits the full sexual behavior of male moths. Various technical advancements that cover all levels of analysis from molecular to behavioral also allow the systematic analysis of pheromone recognition mechanisms. Sex pheromone signals are detected by pheromone receptors expressed in olfactory receptor neurons in the pheromone-sensitive sensilla trichodea on male antennae. The signals are transmitted to the first olfactory processing center, the antennal lobe (AL), and then are processed further in the higher centers (mushroom body and lateral protocerebrum) to elicit orientation behavior toward females. In recent years, significant progress has been made elucidating the molecular mechanisms underlying the detection of sex pheromones. In addition, extensive studies of the AL and higher centers have provided insights into the neural basis of pheromone processing in the silkmoth brain. This review describes these latest advances, and discusses what these advances have revealed about the mechanisms underlying the specific and sensitive recognition of sex pheromones in the silkmoth.

Antennal-lobe tracts in the noctuid moth, Heliothis virescens: new anatomical findings

“…Due to the male moth's amazing sense of smell, demonstrated by its ability to seek a potential mate from a distance of more than 1 km (Priesner et al 1986), a number of moth species have served as model organisms for exploring olfactory coding mechanisms responsible for reproductive behavior (reviewed by Sakurai et al 2014;Berg et al 2015). The sexual behavior is initially based on recognition of a few female-produced molecules by a distinct neuronal arrangement in the male.…”

Dendritic Eph organizes dendrodendritic segregation in discrete olfactory map formation in Drosophila

“…Although Drosophila shows an opposite pattern of Eph/Ephrin (Eph in the pheromone-sensing circuit and Ephrin in the adjacent region), the same signaling machinery seems to have a conserved role in glomerular boundary formation across species. Interestingly, the mouse accessory olfactory bulb receiving input from the VNO, the moth MGC, and the Drosophila pheromone sensory glomeruli are all clustered and located dorsally to the other ordinary glomeruli in the mouse main olfactory bulb and the moth/ Drosophila ALs, respectively (Kaneko and Nighorn 2003;Fishilevich and Vosshall 2005;Sakurai et al 2014). This conserved anatomical feature also suggests a notion that a unique signaling pathway is playing a role to secure the strict segregation between the pheromone-sensing circuits and the other olfactory circuits.…”

Olfactory Signaling in Insects

“…The processing of olfactory information is linked to the physiological and intentional state of an individual. 43,57,86 Fine tuning of olfactory information processing is, for example, mediated by neuropeptides. 87 In summary, the detection and processing of volatile information in insects involve ionotropic as well as metabotropic mechanisms.…”

“…37,38 Various models of OR function have been extensively discussed. [39][40][41][42][43] The odorant specificity is determined by the OrX partner. 9,44 An exchange of only a few amino acids can lead to a shift in agonist specificity as observed for Or22a in Drosophila melanogaster versus Drosophila sechellia.…”