Topics in current chemistry

The sense of smell enables insects to recognize and discriminate a broad range of volatile chemicals in their environment originating from prey, host plants and conspecifics. These olfactory cues are received by olfactory sensory neurons (OSNs) that relay information about food sources, oviposition sites and mates to the brain and thus elicit distinct odor-evoked behaviors. Research over the last decades has greatly advanced our knowledge concerning the molecular basis underlying the reception of odorous compounds and the mechanisms of signal transduction in OSNs. The emerging picture clearly indicates that OSNs of insects recognize odorants and pheromones by means of ligand-binding membrane proteins encoded by large and diverse families of receptor genes. In contrast, the mechanisms of the chemo-electrical transduction process are not fully understood; the present status suggests a contribution of ionotropic as well as metabotropic mechanisms. In this review, we will summarize current knowledge on the peripheral mechanisms of odor sensing in insects focusing on olfactory receptors and their specific role in the recognition and transduction of odorant and pheromone signals by OSNs.

Access to the odor world: olfactory receptors and their role for signal transduction in insects.

Recently, two alternative targets in insect periphery nerve system have been explored for environmentally-friendly approaches in insect pest management, namely odorant-binding proteins (OBPs) and odorant receptors (ORs). Located in insect antennae, OBPs are thought to be involved in the transport of odorants to ORs for the specific signal transduction of behaviorally active odorants. There is rich information on OBP binding affinity and molecular docking to bioactive compounds as well as ample 3D crystal structures due to feasible production of recombinant proteins. Although these provide excellent opportunities for them to be considered as pest control targets and a tool to design pest control agents, the debates on their binding specificity represent an obstacle. On the other hand, ORs have recently been functionally characterized with increasing evidence for their specificity, sensitivity and functional roles in pest behaviors. However, a major barrier to use ORs for semiochemical discovery is the lack of 3D crystal structures. Thus, OBPs and ORs have not been analyzed comparatively together so far for their feasibility as pest control targets. Here, we summarize the state of OBPs and ORs research in terms of its application in insect pest management. We discuss the suitability of both proteins as pest control targets and their selection toward the discovery of new potent semiochemicals. We argue that both proteins represent promising targets for pest control and can be used to identify new super-ligands likely present in nature and with reduced risk of resistance development than insect pesticides currently used in agriculture. We discuss that with the massive identification of OBPs through RNA-seq and improved binding affinity measurements, these proteins could be reconsidered as suitable targets for semiochemical discovery.

/pdf/odorant-receptors-and-odorant-binding-proteins-as-insect-2tu2xus9oe.pdf

Odorant Receptors and Odorant-Binding Proteins as Insect Pest Control Targets: A Comparative Analysis.

The vast majority of lepidopterans, about 90%, are moths. Some moths, particularly their caterpillars, are major agricultural and forestry pests in many parts of the world. However, some other members of moths, such as the silkworm Bombyx mori, are famous for their economic value. Fire et al. in 1998 initially found that exogenous double-stranded RNA (dsRNA) can silence the homolog endogenous mRNA in organisms, which is called RNA interference (RNAi). Soon after, the RNAi technique proved to be very promising not only in gene function determination but also in pest control. However, later studies demonstrate that performing RNAi in moths is not as straightforward as shown in other insect taxa. Nevertheless, since 2007, especially after 2010, an increasing number of reports have been published that describe successful RNAi experiments in different moth species either on gene function analysis or on pest management exploration. So far, more than 100 peer-reviewed papers have reported successful RNAi experiments in moths, covering 10 families and 25 species. By using classic and novel dsRNA delivery methods, these studies effectively silence the expression of various target genes and determine their function in larval development, reproduction, immunology, resistance against chemicals, and other biological processes. In addition, a number of laboratory and field trials have demonstrated that RNAi is also a potential strategy for moth pest management. In this review, therefore, we summarize and discuss the mechanisms and applications of the RNAi technique in moths by focusing on recent progresses.

RNA Interference in Moths: Mechanisms, Applications, and Progress

With well over 700 species, the Tribe Dacini is one of the most species-rich clades within the dipteran family Tephritidae, the true fruit flies. Nearly all Dacini belong to one of two very large genera, Dacus Fabricius and Bactrocera Macquart. The distribution of the genera overlap in or around the Indian subcontinent, but the greatest diversity of Dacus is in Africa and the greatest diversity of Bactrocera is in south-east Asia and the Pacific. The monophyly of these two genera has not been rigorously established, with previous phylogenies only including a small number of species and always heavily biased to one genus over the other. Moreover, the subgeneric taxonomy within both genera is complex and the monophyly of many subgenera has not been explicitly tested. Previous hypotheses about the biogeography of the Dacini based on morphological reviews and current distributions of taxa have invoked an out-of-India hypothesis; however this has not been tested in a phylogenetic framework. We attempted to resolve these issues with a dated, molecular phylogeny of 125 Dacini species generated using 16S, COI, COII and white eye genes. The phylogeny shows that Bactrocera is not monophyletic, but rather consists of two major clades: Bactrocera s.s. and the ‘Zeugodacus group of subgenera’ (a recognised, but informal taxonomic grouping of 15 Bactrocera subgenera). This ‘Zeugodacus’ clade is the sister group to Dacus, not Bactrocera and, based on current distributions, split from Dacus before that genus moved into Africa. We recommend that taxonomic consideration be given to raising Zeugodacus to genus level. Supportive of predictions following from the out-of-India hypothesis, the first common ancestor of the Dacini arose in the mid-Cretaceous approximately 80 mya. Major divergence events occurred during the Indian rafting period and diversification of Bactrocera apparently did not begin until after India docked with Eurasia (50–35 mya). In contrast, diversification in Dacus, at approximately 65 mya, apparently began much earlier than predicted by the out-of-India hypothesis, suggesting that, if the Dacini arose on the Indian plate, then ancestral Dacus may have left the plate in the mid to late Cretaceous via the well documented India–Madagascar–Africa migration route. We conclude that the phylogeny does not disprove the predictions of an out-of-India hypothesis for the Dacini, although modification of the original hypothesis is required.

A molecular phylogeny for the Tribe Dacini (Diptera: Tephritidae) : systematic and biogeographic implications

The genus Dacus is one of the most economically important tephritid fruit flies. The first complete mitochondrial genome (mitogenome) of Dacus species – D. longicornis was sequenced by next-generation sequencing in order to develop the mitogenome data for this genus. The circular 16,253 bp mitogenome is the typical set and arrangement of 37 genes present in the ancestral insect. The mitogenome data of D. longicornis was compared to all the published homologous sequences of other tephritid species. We discovered the subgenera Bactrocera, Daculus and Tetradacus differed from the subgenus Zeugodacus, the genera Dacus, Ceratitis and Procecidochares in the possession of TA instead of TAA stop codon for COI gene. There is a possibility that the TA stop codon in COI is the synapomorphy in Bactrocera group in the genus Bactrocera comparing with other Tephritidae species. Phylogenetic analyses based on the mitogenome data from Tephritidae were inferred by Bayesian and Maximum-likelihood methods, strongly supported the sister relationship between Zeugodacus and Dacus.

https://openresearch-repository.anu.edu.au/bitstream/1885/146281/1/01%20Jiang%20F%20et%20al%20The%20first%20complete%202016.pdf

The first complete mitochondrial genome of Dacus longicornis (Diptera: Tephritidae) using next-generation sequencing and mitochondrial genome phylogeny of Dacini tribe

The invention relates to the field of biological attractants, and specifically discloses an attractant for dendroctonus. The attractant comprises Frontalin (F), exo-Brevicomin (xB) and (S)-cis-Verbenol (cV). The attractant provided by the invention has the advantages of low cost, wide spectrum and extremely strong attractive effect to a variety of adult insects of dendrotonus; highly-efficient attractive effect is simultaneously exerted on a variety of dendrotonus in different working environment, wherein a part of the attracted dendrotonus is not yet clarified in pheromone thereof; meanwhile, the attractant provided by the invention has strong attracting action to a variety of insects like long-horned beetles, snout beetles and ground beetles.

Attractant for dendroctonus

The invention relates to a platypodidae insect attractant.The platypodidae insect attractant comprises active components including 6-methyl-5-hepten-2-ol, n-hexanol, 6-methyl-5-hepten-2-one and ethyl alcohol, wherein all the active components are put in independent slow-release carriers respectively.The invention further provides a preparation method and application of the platypodidae insect attractant.The platypodidae insect attractant can have efficient trap capacity on platypodidae insects of different genuses, the harms of foreign platypodidae to precious imported timber can be greatly reduced by means of the attractant, and wide application prospects are achieved.

Platypodidae insect attractant and preparation method and application thereof

The present invention relates to the field of biological attractants, and specifically discloses a xyleborus eichhoff attractant, which comprises alpha-pinene, beta-pinene, camphene, myrcene, 3-carene, and ethanol. According to the present invention, the attractant has characteristics of low cost and broad spectrum, provides extremely strong attracting effects for the imago of a variety of xyleborus eichhoff insects, can simultaneously provide efficient attracting effects for a variety of xyleborus eichhoff in different working environments, and further provides extremely strong attracting effects for platypodidae, chrysomelidae and other insects, wherein even the pheromone of the partial attracted xyleborus eichhoff is not clear.

Xyleborus eichhoff attractant

The gypsy moth, Lymantria dispar, is an important economic pest that causes large-scale damage to forests worldwide. Because of its important role in initiating and controlling insect behavior, olfaction-and olfaction-based pest management-has drawn increasing attention from entomologists. In this study, we identified the gene that encodes the olfactory receptor co-receptor (OrCo). Through amino acid sequence alignment, we found that LdisOrCo shares high identity with other OrCo proteins from different insect orders. Next, we performed RNA-interference (RNAi) to assess the role of OrCo in olfaction. Electroantennographic assays showed that after RNAi, the average value of males' response to sex pheromones was 0.636 mV, significantly lower than that of the positive control (average = 1.472 mV). Females showed no response to sex pheromones before or after RNAi. Finally, quantitative PCR showed a strong decrease in the expression of OrCo after RNAi, by ~74% in males and by 23% in females relative to the positive controls. These results indicate that OrCo is not only critical to odor recognition, but it may also represent a new target for development of semiochemicals that can influence insect behavior.

/pdf/identification-and-knockdown-of-the-olfactory-receptor-orco-ci86tkrokr.pdf

Identification and Knockdown of the Olfactory Receptor (OrCo) in Gypsy Moth, Lymantria dispar.

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