Expression Patterns of Four Candidate Sex Pheromone Receptors in Honeybee Drones (Apis mellifera)

In honeybee (Apis mellifera), odorant receptors (Ors) play a crucial role in special recognition of sex pheromones in honeybee mating activities. Four candidate sex pheromone Ors (AmOr10, AmOr11, AmOr18 and AmOr170) have been identified and found to be preferentially expressed in drone antennae. However, few studies have investigated the regulation of these four drone Ors on drone mating behaviour. This study characterised the expression patterns of these Ors across different sexual developmental stages (immature and sexually mature) and different physiological statuses (flying and crawling), using both the antennae and brains of drones. qRT-PCR results indicated that the expression of four Ors were not significantly different in drone antennae between flying and crawling statuses at immature stage. However, all four Ors expression levels in brains of flying drones were significantly higher than those of crawling drones at mature stage. Moreover, only the expression level of Or170 was significantly higher in antennae of mature flying drones than crawling ones. Therefore, this study demonstrated a link between four candidate sex pheromone Ors transcriptional expression in the brains of honeybee drones and behaviour associated with sexual maturity and mating flight. In addition, Or170 might be involved in the maturation of honeybee drones' olfactory system, and in the organisation of odour-mediated mating behaviours.