Strategies for insect population control are currently targeting chemical communication at the molecular level. The diamondback moth Plutella xylostella represents one of the most serious pests in agriculture, however detailed information on the proteins mediating olfaction in this species is still poor. This species is endowed with a repertoire of a large number of olfactory receptors and odorant binding proteins (OBPs). As a contribution to map the specificities of these chemical sensors in the moth and eventually unravel the complexity of chemodetection, we have measured the affinities of three selected OBPs to a series of potential odorants. Three proteins are highly divergent in their amino acid sequences and show markedly different expression profiles. In fact, PxylOBP3 is exclusively expressed in the antennae of both sexes, PxylOBP9 is male specific and present only in antennae and reproductive organs, while PxylOBP19, an unusual OBP with nine cysteines, is ubiquitously present in all the organs examined. Such expression pattern suggests that the last two proteins may be involved in non-chemosensory functions. Despite such differences, the three OBPs exhibit similar binding spectra, together with high selectivity. Among the 26 natural compounds tested, only two proved to be good ligands, retinol and coniferyl aldehyde. This second compound is particularly interesting being part of the chemical pathway leading to regeneration of lignin, one of the defense strategies of the plant against insect attack, and might find applications as a repellent for P. xylostella and other pests.

The polyphagous B-biotype of Bemisia tabaci (Gennadius) has demonstrated a high capacity to adapt to numerous hosts from diverse plant families. To illustrate induced responses by the host plant, biochemical research on eight plant-insect interaction correlative enzymes, representing detoxifying, antioxidant and digestive pathways, were investigated. Transferring whitefly adults to Zhongmian 23 from the pre-adapted host Zhongmian 41 induced activities of carboxylesterase (by 1.80-fold), glutathione S-transferase (by 3.79-fold), proteinase (by 1.62-fold) and amylase (by 2.41-fold) activities, but decreased polyphenol oxidase (by 1.89-fold) and peroxidase (by 1.88-fold). However, transferring whitefly adults to the favorite host abutilon from Zhongmian 41 was associated with increased activities of cytochrome P450 monooxygenase (by 1.61-fold) and amylase (by 1.42-fold), and decreased activities of polyphenol oxidase (by 2.96-fold) and peroxidase (by 2.07-fold). Our results, together with previous studies, proved that multiple pathways are involved in coping with host shifts by polyphagous herbivores, and the taxonomic status and preference of the host transferred would affect which pathway would be induced. These results would represent a key challenge in developing long-term sustainable insect control strategies.

The nicotinic acetylcholine receptors (nAchRs) are cholinergic receptors that form ligand-gated ion channels by five subunits in insect and vertebrate nervous systems. The insect nAChR is the molecular target of a class of insecticides, neonicotinoids. Here, we identified and cloned 11 candidate nAChR subunit genes in Acyrthosiphon pisum using genome-based bioinformatics combined modern molecular techniques. Most A. pisum nAChRs including α1, α2, α3, α4, α6, α8, and β1 show highly sequence identities with the counterparts of other insects examined. Expression profiles analysis showed that all subunit genes were expressed in adult head. At least two subunits have alternative splicing that obviously increase A. pisum nicotinic receptor diversity. This study will be invaluable for exploring the molecular mechanisms of neonicotinoid-like insecticides in sucking pests, and for ultimately establishing the screening platform of novel insecticides.