No abstract

The management of forest pests has become a significant challenge, particularly for wood borers, because they spend most of the time in the trunks or cones. The coneworm, Dioryctria abietella, is a representative of cone borers as its larvae feed on the cones of Pinaceae plants. The molecular mechanisms underlying the interactions between this species and host plants or habitats can assist in developing strategies for pest control. In this study, we extended the expression profiles of 32 odorant binding proteins (OBPs) in the reproductive tissues of D. abietella, revealing the detectable transcription of 29 genes. Using two DabiOBPs highly expressed in antennae (DabiOBP5 and DabiOBP14) as targets, six compounds with high affinities (dissociation constants < 13 μM) were identified through a reverse chemical ecology strategy, including insecticides widely used for the control of lepidopteran pests. Of these compounds, a floral volatile β-ionone and a pear-produced ester ethyl-(2E,4Z)-decadienoate may serve as behaviorally active compounds in D. abietella. The strong binding of DabiOBPs to insecticides suggested their involvement in insecticide resistance, reflecting sophisticated detoxification mechanisms of this moth. In the molecular simulations, DabiOBP14 possessed stronger interactions with the six ligands compared to DabiOBP5, in which a few key residues within the binding pockets were involved in the formation of hydrogen bonds. This study provides some valuable reference active compounds for the development of lures or repellents in D. abietella and unravels the putative roles of two antenna-dominant DabiOBPs in the perception of plant-derived odorants and insecticides.

In this study, we annotated 49 odorant-binding proteins (OBPs) in Papilio xuthus, with four novel genes and seven improved sequences. Expression profiles identified numerous OBPs in antennae or reproductive tissues. Using two antenna-enriched general OBPs (PxutGOBP1 and PxutGOBP2) as targets, we screened three key compounds by a reverse chemical ecology strategy. Of these, an oviposition stimulant vicenin-2 could strongly interact with PxutGOBP1, representing a dissociation constant (K i ) value of 10.34 ± 0.07 μM. Molecular simulations and site-directed mutagenesis revealed the importance of His66, Thr73, and Phe118 between PxutGOBP1 and vicenin-2 interactions. Two other compounds, an ordinary floral scent β-ionone and a widely used insecticide chlorpyrifos, exhibited high affinities to PxutGOBPs (K i < 13 μM). Furthermore, two mutations His66Ala and Thr73Ala of PxutGOBP1 significantly reduced the binding to chlorpyrifos. Our study provides insights into the putative roles of PxutGOBPs in odorant perception and identifies key binding sites of PxutGOBP1 to vicenin-2 and chlorpyrifos.

Transferrins (Trfs) are multifunctional proteins with key functions in iron transport. In the present study, a Trf (PxTrf) from Plutella xylostella was identified and characterized. The PxTrf consisted of a 2046-bp open reading frame, which encoded a 681 amino acid protein with a molecular weight of 73.43 kDa and had an isoelectric point of 7.18. Only a single iron domain was predicted in the N-lobe of PxTrf. Although PxTrf was expressed ubiquitously, the highest levels of expression were observed in the fourth instar larvae. PxTrf transcript level was highest in fat bodies among various tissues. The PxTrf transcript levels increased significantly after the stimulation of pathogens. A decrease in PxTrf expression via RNA interference enhanced the susceptibility of P. xylostella to the Isaria cicadae fungus and inhibited hemocyte nodulation in response to the fungal challenge. In addition, a considerable increase in the pupation rate was observed in larvae treated with double-stranded PxTrf (dsPxTrf). Overall, according to the results, PxTrf may participate in P. xylostella immunity against fungal infection and insect development.

No abstract