Identification and expression profile of odorant-binding proteins in Halyomorpha halys (Hemiptera: Pentatomidae).

The brown marmorated stink bug, Halyomorpha halys, is a devastating invasive species in the USA. Similar to other insects, olfaction plays an important role in its survival and reproduction. As odorant-binding proteins (OBPs) are involved in the initial semiochemical recognition steps, we used RNA-Sequencing (RNA-Seq) to identify OBPs in its antennae, and studied their expression pattern in different body parts under semiochemical stimulation by either aggregation or alarm pheromone or food odorants. Thirty full-length putative HhalOBPs were identified, corresponding to 22 'classic' OBPs and eight 'Plus-C' OBPs. The similarity amongst them ranged from 4.95-70.92%, and with another 325 hemipteran OBPs similarity ranged from 1.94-91.51%, the highest levels being with other stink bug OBPs. Phylogenetic analysis confirmed the monophyly of seven groups of stink bug and other hemipteran OBPs. All 30 HhalOBPs were expressed and about 2/3 were expressed primarily in antennae. The expression of 21 HhalOBPs was higher in the antennae under alarm pheromone stimulus, indicating that multiple OBPs may be responding to this pheromone. Two were highest in antennae under aggregation pheromone stimulus. These findings should provide a basis for understanding the physiological functions of HhalOBPs and the chemosensory perception of this pest, which may help to uncover new control targets for behavioural interference.