Silencing the Olfactory Co-Receptor RferOrco Reduces the Response to Pheromones in the Red Palm Weevil, Rhynchophorus ferrugineus

Abstract

The red palm weevil (RPW, Rhynchophorus ferrugineus), one of the most widespread of all invasive insect pest species, is a major cause of severe damage to economically important palm trees. RPW exhibits behaviors very similar to those of its sympatric species, the Asian palm weevil (R. vulneratus), which is restricted geographically to the southern part of Southeast Asia. Although efficient and sustainable control of these pests remains challenging, olfactory-system disruption has been proposed as a promising approach for controlling palm weevils. Here, we report the cloning and sequencing of an olfactory co-receptor (Orco) from R. ferrugineus (RferOrco) and R. vulneratus (RvulOrco) and examine the effects of RferOrco silencing (RNAi) on odorant detection. RferOrco and RvulOrco encoding 482 amino acids showing 99.58% identity. The injection of double-stranded RNA (dsRNA) from RferOrco into R. ferrugineus pupae significantly reduced RferOrco gene expression and led to the failure of odor-stimulus detection, as confirmed through olfactometer and electroantennography (EAG) assays. These results suggest that olfactory-system disruption leading to reduced pheromone detection holds great potential for RPW pest-control strategies.

Silencing the Odorant Binding Protein RferOBP1768 Reduces the Strong Preference of Palm Weevil for the Major Aggregation Pheromone Compound Ferrugineol

“…Such attempts have confirmed the role of OBPs in olfaction, as carriers of hydrophobic odorants and pheromones through the aqueous environment of the sensillum lymph to ORs (Leal, 2013 ). Regardless, no RNAi studies to date related to the role of OBPs have been reported in beetles, though several studies have been performed to characterize odorant co-receptors by RNAi and electrophysiological approaches (Soffan et al, 2016 ; Zhang et al, 2016 ). To the best of our knowledge, the current study is the first attempt to specifically characterize aggregation pheromone-specific OBPs using a gene silencing approach in a beetle.…”

“…Rhynchophorus ferrugineus has recently received greater attention due to its invasiveness and quarantine pest status. Conventional methods have proven ineffective for the management of palm weevil, leading to proposals of synthetic biology approaches intended at disrupting pheromone communication, given that olfaction interference has the potential to interrupt critical behaviors such as host and mate selection, ultimately disrupting reproductive success and causing weevil population decline (Antony et al, 2016 ; Soffan et al, 2016 ). We previously reported RferOrco silencing, and together with OBP silencing in R. ferrugineus via dsRNA injection, this approach is promising for the disruption of pheromone communication in R. ferrugineus (Soffan et al, 2016 ).…”

“…The SMARTer rapid amplification of cDNA ends technique (SMARTer RACE Kit, Clontech, CA, USA) was used to obtain the full-length sequences of candidate OBPs by amplifying both cDNA ends (5′ and 3′ ends). The 5′ and 3′ RACE cDNAs were prepared from total RNA of adult R. ferrugineus antennae, as described (Soffan et al, 2016 ). Gene-specific primers (GSPs) for 5′- and 3′-RACE were designed based on partial RferOBP23, RferOBP107, RferOBP1768 , and RferOBPu1 nucleotide sequences (Table S1 ).…”

“…We selected 10-day-old R. ferrugineus pupae for RNAi experiments, and 40 ng/μL dsRNA (in 20 μL) was injected at a depth of 0.5 cm into the first dorsal segment of the abdomen, close to the thorax, using a 0.5-mL BD Micro-FineTM PLUS syringe (Becton, Dickinson Co., NJ, USA). dsRNA-injected RPW pupae were maintained as previously described (Soffan et al, 2016 ). As two separate controls, RPW pupae were injected with nuclease-free water (hereafter referred to as “NFW”) or not injected (hereafter referred to as “NI”).…”

Volatile allosteric antagonists of mosquito odorant receptors inhibit normal odor-dependent behaviors

“…In view of these results and given the previously demonstrated importance of ORco for the functionality of OR heteromers and ORdependent behaviors (36)(37)(38)(39)(40)(41)(42)(43), we have employed the lepidopteran insect cell-based assay toward the rapid detection of potential agonists and antagonists of AgamORco. This system relies on the stable expression of homomeric AgamORco in cells constitutively expressing a luminescence emitting calcium biosensor reporter protein.…”