Identification and expression analysis of carboxylesterases and cytochrome P450 gene families in red palm weevil, Rhynchophorus ferrugineus (Olivier)

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus listed as major invasive pest, is a destructive worldwide pest of palm trees. RPWs affecting more than 60,000 date palm trees in Saudi Arabia every year, with 30,000 having to be destroyed. RPWs locate palm trees by means of plant volatile cues and use an aggregation pheromone to coordinate a mass-attack, often leads to the death of the palm tree. The insect chemoreception involve the odorant molecule binds to odorant receptors, and finally the signal termination is accomplished by odorant-degrading enzymes (ODEs), including carboxyl esterases (cxe) and cytochrome P450 monooxygenases, which occur in major chemosensory tissues, including the antenna. Here we report on the high throughput sequencing of the RPW antennal transcriptome and present a comprehensive catalogue of cxes and CYP450 genes in the R. ferrugineus. We identified 44 putative cxe genes and 182 transcripts encoding candidate cytochrome P450 from the R. ferrugineus antenna. We found antennal-specific cxe and CYP450 repertoires by comparing and analysing RPW antennal transcriptome dataset with whole body transcriptome, and through tissue specific gene expression analysis. Phylogenetic analysis of the insect cxes and CYP showed order-specific gene diversification and species-specific conservation of this multigene family. We found many cxes and CYP450 were expressed in different body parts, consistent with functions in detoxification, and some were also found exclusively expressing in antennae, suggesting a role in odorant deactivation. Quantitative PCR analysis data of antennal specific cxes and CPY40 identified highly expressed candidates ODEs in the antennae, could be candidate genes involved in aggregation pheromone degradation. The study provides strong background information on novel ODE multi-gene families and our study will be fundamental for future functional characterization studies and that ultimately facilitate a better understanding of the odorant deactivation of the R. ferrugineus, and it may provide potential targets for novel pest control strategies of the RPW that inflicts significant damage every year on palm trees throughout the world.  Acknowledgments: Grant-aid from NPST-KACST 12-AGR2854-02.