Putative carboxylesterase gene identification and their expression patterns in Hyphantria cunea (Drury)

The olfactory system of insects is important for behavioral activities as it recognizes internal and external volatile stimuli in the environment. Insect odorant degrading enzymes (ODEs), including antennal-specific carboxylesterases (CXEs), are known to degrade redundant odorant molecules or to hydrolyze important olfactory sex pheromone components and plant volatiles. Compared to many well-studied Type-I sex pheromone-producing lepidopteran species, the molecular mechanisms of the olfactory system of Type-II sex pheromone-producing Hyphantria cunea (Drury) remain poorly understood. In the current study, we first identified a total of ten CXE genes based on our previous H. unea antennal transcriptomic data. We constructed a phylogenetic tree to evaluate the relationship of HcunCXEs with other insects’ CXEs, and used quantitative PCR to investigate the gene expression of H. cunea CXEs (HcunCXEs). Our results indicate that HcunCXEs are highly expressed in antennae, legs and wings, suggesting a potential function in degrading sex pheromone components, host plant volatiles, and other xenobiotics. This study not only provides a theoretical basis for subsequent olfactory mechanism studies on H. cunea, but also offers some new insights into functions and evolutionary characteristics of CXEs in lepidopteran insects. From a practical point of view, these HcunCXEs might represent meaningful targets for developing behavioral interference control strategies against H. cunea.

Identification and Functional Characterization of Two Putative Pheromone Receptors in the Potato Tuber Moth, Phthorimaea operculella

Pheromones are a kind of signal produced by an animal that evoke innate responses in conspecifics. In moth, pheromone components can be detected by specialized olfactory receptor neurons (OSNs) housed in long sensilla trichoids on the male antennae. The pheromone receptors (PRs) located in the dendrite membrane of OSNs are responsible for pheromone sensing in most Lepidopteran insects. The potato tuber moth Phthorimaea operculella is a destructive pest of Solanaceae crops. Although sex attractant is widely used in fields to monitor the population of P. operculella, no study has been reported on the mechanism the male moth of P. operculella uses to recognize sex pheromone components. In the present study, we cloned two pheromone receptor genes PopeOR1 and PopeOR3 in P. operculella. The transcripts of them were highly accumulated in the antennae of male adults. Functional analysis using the heterologous expression system of Xenopus oocyte demonstrated that these two PR proteins both responded to (E, Z)-4,7–13: OAc and (E, Z, Z)-4,7,10–13: OAc, the key sex pheromone components of P. operculella, whilst they responded differentially to these two ligands. Our findings for the first time characterized the function of pheromone receptors in gelechiid moth and could promote the olfactory based pest management of P. operculella in the field.

Effect of Pheromones, Plant Volatiles and Spinosad on Mating, Male Attraction and Burrowing of Cadra cautella (Walk.) (Lepidoptera: Pyralidae)

Mating disruption of Cadra cautella (Walk.) (Lepidoptera: Pyralidae) using its sex pheromone components, (Z, E)-9,12-tetradecadienyl acetate (ZETA) and (Z)-9-tetradecadien-1-yl acetate (ZTA), is successful in its population management. In addition, botanical oils have extensively been investigated in stored product pest management, but the effect of synthetic sex pheromones on the mating of C. cautella in the presence of plant volatiles is still unknown. Spinosad is used in food facilities as a contact insecticide but, if C. cautella larvae burrow into food, they may escape from spinosad. Importantly, the impact of spinosad on burrowing ability of C. cautella remains unknown. Therefore, the objectives of this study were to determine the effects of sex pheromone components ZETA and ZTA in the presence of botanical oils on the mating of C. cautella and the burrowing ability of C. cautella larvae in different types of flour treated with spinosad. In the first study, male and female moths were introduced into the cubicle having botanical oils and pheromone components. The mating status of female moths and male moth attraction to the trap was determined. The control experiments had only the botanical oils or pheromones. In the second study, burrowing ability of C. cautella larvae through different flour types was evaluated over 10 d. The flour was sprayed with spinosad (treatments) or water (controls). The mating success was higher with botanical oils alone but declined with exposure to pheromone either alone or combined with botanical oils. No differences in male attraction to traps were observed in botanical only, pheromone only or pheromone + botanical oil treatments. The burrowing of C. cautella larvae differed with flour type and spinosad altered burrowing ability. Thus, we conclude that the mating and burrowing of C. cautella is influenced by its pheromone and by exposure to botanicals and spinosad.