Chemosensory genes from Pachypeltis micranthus, a natural enemy of the climbing hemp vine

Abstract

The plant bug, Pachypeltis micranthus (Hemiptera: Miridae), is a natural enemy of the invasive alien weed Mikania micrantha with a widespread distribution in South China as well as other countries. The interactions of P. micranthus and its host M. micrantha, associated with a linkage of host recognition, are of great importance for its survival and reproduction. The identification of olfactory-related genes is undoubtedly the initially key step, to uncover how P. micranthus perceives and recognizes the specific host plant M. micrantha. Here, we constructed an antennal full length cDNA library from P. micranthus antennae. By sequencing, a total of 13 transcripts encoding chemosensory-related genes were identified, comprising nine odorant-binding proteins (OBPs), three chemosensory proteins (CSPs) and one odorant receptor (OR). All identified OBPs and CSPs shared classic characteristics of conserved cysteines and a signal peptide. Expression profiles by quantitative real time PCR (qPCR) revealed that as many as 12/13 chemosensory genes were expressed predominantly in the antennae at a sex-biased pattern, strongly linking to their specific olfactory functions. Notably, expression of all these genes was also differentially detected in legs of both sexes with an exception of PmicOBP7, indicative of their functional differentiation between female and male adults. Further, molecular docking of PmicOBP6 and CSP1 to behaviorally active compounds provided the potentially key residues for ligand-binding, which deserves further studies.