Expression profile and ligand‐binding characterization of odorant‐binding protein 2 from Batocera horsfieldi (Hope)

Abstract

Odorant‐binding proteins (OBPs) are important components in insect olfactory systems that transport semiochemicals through the aqueous sensillum lymph to surface of olfactory receptor neurons. In this study, we cloned the cDNA of odorant‐binding protein 2 (BhorOBP2) in Batocera horsfieldi (Hope) and measured the level of the BhorOBP2 mRNA in a variety of tissues using quantitative reverse transcription and real‐time polymerase chain reaction. We found that the BhorOBP2 mRNA was primarily expressed in the antennae, the level of BhorOBP2 mRNA was higher in males than in females, and correlated with age and mating status. The BhorOBP2 mRNA was also expressed in the labial palps at relatively high level, suggesting that it might have a role in gestation as well. To better understand the functions of the BhorOBP2 protein in odorant reception, recombinant BhorOBP2 was expressed in Escherichia coli, and the binding specificity of the protein for 18 volatile developmentally relevant chemicals and host‐plant‐related metabolites were assessed using N‐phenyl‐1‐naphthylamine as a fluorescent probe. Competitive fluorescence binding assays showed that BhorOBP2 bound a broad range of host‐plant‐related odorants, including (E)‐2‐hexenal, 2‐methyl‐butanal, salicylaldehyde, (1S)‐(‐)‐verbenone, (Z)‐3‐hexen‐1‐ol, (E)‐2‐hexen‐1‐ol, β‐pinene and ethyl acetate. Our results imply that BhorOBP2 might play an important role in the selectivity and specificity of odorant reception.

Predicted structure of a Minus-C OBP from Batocera horsfieldi (Hope) suggests an intermediate structure in evolution of OBPs

“…After mating, the females travel back to Populus for oviposition under the bark of trees 29 30 31 . B. horsfieldi has a sensitive olfactory system that is essential for host location and mating, and a number of olfactory-related genes have been identified in B. horsfieldi 32 33 34 . Here, we cloned the cDNA of minus-C OBP2 (BhorOBPm2) from B. horsfieldi and expressed and purified the protein in vitro .…”

Antennal transcriptome analysis of olfactory genes and tissue expression profiling of odorant binding proteins in Semanotus bifasciatus (cerambycidae: coleoptera)

“…Therefore, we can infer SbifOBP15 plays an important role in finding suitable oviposition sites for females, but follow-up functional verification must be carried out. BhorPBP2 has male-biased expression and can bind a broad range of host-plant-related odorants [ 68 ]. In the phylogenetic tree constructed in this study, SbifOBP5 and BhorPBP2 were clustered into one branch with bootstrap support of 67, but the qPCR results showed that the SbifOBP5 was expressed not only both sexes in the antennae of but also male head.…”

Identification of odorant‐binding proteins and functional analysis of antenna‐specific BhorOBP28 in Batocera horsfieldi (Hope)

“…[33][34][35][36] Studies on olfactory mechanisms have identified a few OBP and CSP genes and evaluated the in vitro binding properties of two OBPs from B. horsfieldi. 32,[37][38][39][40] This shows a need for a deeper understanding of the olfactory recognition mechanism of B. horsfieldi, and it is unclear which OBPs are involved in the recognition of key chemical cues, for example, the kairomones for the adult and larval hosts for maturation feeding and oviposition, respectively.…”