Identification of odorant binding proteins and chemosensory proteins in red palm weevil, Rhynchophorus ferrugineus (Olivier)

Insect chemosensory gene families include a group of soluble secreted carrier proteins, odorant binding proteins (OBPs) and chemosensory proteins (CSPs), are thought to aid chemo-sensation by taking and conveying hydrophobic ligand molecules across the sensillum lymph of the antennae to the odorant receptors. The Red Palm Weevil (RPW) Rhynchophorus ferrugineus (Oliver) is one of the most important quarantine insect pest, is a serious threat to the palm trees all over the world. Here we report on the high throughput sequencing of the RPW antennal transcriptome and present a comprehensive catalogue of the OBPs and CSPs in R. ferrugineus antenna. We identified 38 putative OBPs and 12 transcripts encoding candidate CSPs from the R. ferrugineus antenna. The arrangement pattern of the conserved cysteine residues in the R. ferrugineus OBP and CSP family are similar to that in other insect. We found RPW antennal-specific OBP and CSP gene repertoires by comparing and analysing RPW antennal transcriptome dataset with whole body transcriptome. An RPKM value analysis revealed that three OBPs and 1 CSP (RPKM>4000) are greatly abundant transcripts in the R. ferrugineus antennal transcriptome, could be candidate genes involved in aggregation pheromone detection. We identified 26 Minus-C OBPs and 8 Plus-C OBPs and grouped R. ferrugineus OBPs into different OBP-subfamilies by phylogeny, which indicated significant species-specific expansion and divergence in R. ferrugineus. We also identified a diverse family of CSP proteins, as well as a Coleopteran-specific CSP lineage that diverged from the Diptera and Lepidoptera. The abundance of their diversity specifies that R. ferrugineus OBPs and CSPs play a fundamental role in R. ferrugineus odor detection and olfactory sensation.

Acknowledgments: Grant-aid from NPST-KACST 12-AGR2854-02.