The dual coding of a single sex pheromone receptor in regulating the mating behavior of Asian Honeybee Apis cerana

In honeybee society, a virgin queen usually mates only once with several drones before founding a colony. For the rest of her prolific life, she will not engage in subsequent mating events. In the Asian honeybee Apis cerana, the mechanisms controlling this reproductive strategy involves the queen-released mandibular pheromone (QMP). This pheromone blend regulates the physiology and reproductive behavior of workers and drones. Its main component, 9-oxo-(E)-2-decenoic acid (9-ODA), acts as a sex pheromone and attracts drones. However, how the QMP prevents additional mating later in the queens life remains elusive. Using behavioral and chemical analysis, we show that the QMP component methyl p-hydroxybenzoate (HOB) released by mated queens inhibits male attraction to 9-ODA. Furthermore, in vivo electroantennogram and single sensillum recording data indicated that HOB alone significantly reduces the spontaneous spike activity of 9-ODA-sensitive olfactory receptor neurons (ORNs). To explore the molecular mechanism underlying this inverse effect, we conducted qPCR and in situ hybridization assays. The results indicated that AcerOr11 is specifically expressed in sensilla placodea from the drones antennae, which are the sensilla that narrowly respond to both 9-ODA and HOB. We then cloned and expressed AcerOr11 in a Xenopus oocyte expression system, where AcerOr11 induced robust inward (regular) currents in response to 9-ODA. Intriguingly, HOB induced inverse currents in a dose-dependent manner. This suggests that HOB may act as an inverse agonist against AcerOr11, providing additional odor-coding information. Based on these findings, we propose a model in which AcerOr11 function as a dual modulators in regulating the mating behavior of A. cerana. The inverse agonist, HOB, can help manage the population dynamics of honeybees in apiculture.