Characterization of candidate odorant-binding proteins and chemosensory proteins in the tea geometrid Ectropis obliqua Prout (Lepidoptera: Geometridae)

Insects rely heavily on their sophisticated chemosensory systems to locate host plants and find conspecific mates. Although the molecular mechanisms of odorant recognition in many Lepidoptera species have been well explored, limited information has been reported on the geometrid moth Ectropis obliqua Prout, an economically important pest of tea plants. In the current study, we first attempted to identify and characterize the putative olfactory carrier proteins, including odorant-binding proteins (OBPs) and chemosensory proteins (CSPs). By analyzing previously obtained transcriptomic data of third-instar larvae, five OBPs and 14 CSPs in E. obliqua were identified. Sequence alignment, conserved motif identification, and phylogenetic analysis suggested that candidate proteins have typical characteristics of the insect OBP or CSP family. The expression patterns regarding life stages and different tissues were determined by quantitative real-time PCR. The results revealed that four transcripts (OBP2, OBP4 and CSP8, CSP10) had larvae preferential expression profiles and nine candidate genes (PBP1, OBP1 and CSP2, CSP4, CSP5, CSP6, CSP7, CSP11, and CSP13) were adult-biased expressed. Further specific tissue expression profile evaluation showed that OBP1, OBP2, OBP4, and PBP1 were highly expressed at olfactory organs, implying their potential involvement in chemical cue detection, whereas CSPs were ubiquitously detected among all of the tested tissues and could be associated with multiple physiological functions. This study provided a foundation for understanding the physiological functions of OBPs and CSPs in E. obliqua and will help pave the way for the development of a new environmental friendly pest management strategy against the tea geometrid moth.