PBP1 plays key roles in sex pheromone reception of the fall armyworm

Strategic Analysis of Collaborative Networks in Spodoptera frugiperda (Lepidoptera: Noctuidae) Research for Improved Pest Management Strategies

The fall armyworm (FAW) poses a significant global threat to food security, and economics. Timely detection is crucial, and this research explores innovative techniques like data analysis, remote sensing, satellite imagery, and AI with machine learning algorithms for predicting and managing outbreaks. Emphasizing the importance of community engagement and international collaboration, social network analysis (SNA) is employed to uncover collaborative networks in FAW management research. The study analyzes a decade of research, revealing trends, influential institutions, authors, and countries, providing insights for efficient FAW management strategies. The research highlights a growing interest in Spodoptera frugiperda (Smith and Abbott 1797) research, focusing on biological control, chemical insecticides, plant extracts, and pest resistance. Co-Citation analysis identifies key research concepts, while collaboration analysis emphasizes the contributions of actors and institutions, such as China, the USA, and Brazil, with international collaboration playing a vital role. Current research trends involve evolving resistance, insecticidal protein gene discovery, and bio-control investigations. Leveraging insights from collaborative networks is essential for formulating effective strategies to manage fall armyworm and ensure global food security. This comprehensive analysis serves as a valuable resource for researchers and stakeholders, guiding efforts to combat this pervasive agricultural pest.

EsigPBP3 Was the Important Pheromone-Binding Protein to Recognize Male Pheromones and Key Eucalyptus Volatiles

Pheromone-binding proteins (PBPs) are specific odorant-binding proteins that can specifically recognize insect pheromones. Through transcriptional analysis of the antennae of adult Endoclita signifer, EsigPBP3 was discovered and identified, and EsigPBP3 was found to be highly expressed in the antennae of male moths. Based on the binding characteristics and ability of EsigPBP3, we can find the key ligands and binding site to consider as a target to control the key wood bore E. signifier. In this study, the fluorescence competitive binding assays (FCBA) showed that EsigPBP3 had a high binding affinity for seven key eucalyptus volatiles. Molecular docking analysis revealed that EsigPBP3 had the strongest binding affinity for the sexual pheromone component, (3E,7E)-4,7,11-trimethyl-1,3,7,10-dodecatetraene. Furthermore, same as the result of FCBA, the EsigPBP3 exhibited high binding affinities to key eucalyptus volatiles, eucalyptol, α-terpinene, (E)-beta-ocimene, (-)-β-pinene, and (-)-α-pinene, and PHE35, MET7, VAL10, PHE38, ILE52, and PHE118 are key sites. In summary, EsigPBP3 exhibits high binding affinity to male pheromones and key volatile compounds and the crucial binding sites PHE35, MET7, VAL10, PHE38, ILE52, and PHE118 can act as targets in the recognition of E. signifier pheromones.

Molecular mechanism of sex pheromone perception in male Mythimna loreyi revealed by in vitro system

BACKGROUND

Mythimna loreyi is an important agricultural pest with a sensitive sex pheromone communication system. To clarify the pheromone binding proteins (PBPs) and pheromone receptors (PRs) involved in sex pheromone perception is important for both understanding the molecular olfactory mechanism and developing a new pest control strategy in M. loreyi.

RESULTS

First, the electroantennogram (EAG) assay showed that male M. loreyi displayed the highest response to the major sex pheromone component Z9-14:Ac, and higher responses to two minor components, Z7-12:Ac and Z11-16:Ac. Second, the fluorescence competition binding assay showed that PBP1 bound all three pheromones and other tested compounds with high or moderate affinity, while PBP2 and PBP3 each bound only one pheromone component and few other compounds. Third, functional study using the Xenopus oocyte system demonstrated that, of the six candidate PRs, PR2 was weakly sensitive to the major pheromone Z9-14:Ac, but was strongly sensitive to pheromone analog Z9-14:OH; PR3 was strongly and specifically sensitive to a minor component Z7-12:Ac; PR4 and OR33 were both weakly sensitive to another minor component, Z11-16:Ac. Finally, phylogenetic relationship and ligand profiles of PRs were compared among six species from two closely related genera Mythimna and Spodoptera, suggesting functional shifts of M. loreyi PRs toward Spodoptera PRs.

CONCLUSION

Functional differentiations were revealed among three PBPs and six PRs in sex pheromone perception, laying an important basis for understanding the molecular mechanism of sex pheromone perception and for developing new control strategies in M. loreyi. © 2023 Society of Chemical Industry.

Characterization and transcriptomic analyses of the toxicity induced by toosendanin in Spodoptera frugipreda

The fall armyworm, Spodoptera frugiperda, is a destructive agricultural pest that seriously threatens global food security. Insecticide resistance of this pest has gradually formed in recent years due to improper usage, and alternative methods are badly needed. Toosendanin (TSN) is a botanical compound with broad-spectrum insecticidal activities against many pests. However, the effects of TSN on S. frugiperda are still unclear. In this study, the growth inhibition phenomenon, including weight loss and prolonged developmental duration, in the larvae with TSN exposure was clearly observed. Compared to the control group, a total of 450 and 3314 differentially expressed genes (DEGs) were identified by RNA-Seq in the larvae groups treated with 10 and 20 mg/kg TSN, respectively. Furthermore, the DEGs involved in the juvenile hormone and ecdysone signal pathways and downstream processes, including detoxifying enzyme genes, chitin synthesis and metabolism genes, and cuticular protein genes, were found. Our findings suggest that TSN regulates the expression of key genes in juvenile hormone and ecdysone signal pathways and a series of downstream processes to alter the hormone balance and cuticle formation and eventually inhibit larval growth, which laid the foundation for the molecular toxicological mechanism research of TSN on S. frugiperda larvae.

Binding Properties of Odorant-Binding Protein 7 to Host Volatiles in Larvae of Spodoptera frugiperda

The chemosensory system is crucial during the growth and development of the moths. Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the most destructive insect pests. However, there is little functional research on odorant-binding proteins (OBPs) in the larval stage of S. frugiperda. Here, we obtained SfruOBP7 from transcriptomics and conducted the sequence analysis. We used quantitative real-time PCR to explore the expression profiles of SfruOBP7. The function identification showed that SfruOBP7 has a binding ability to 18 plant volatiles. Further molecular docking and site-directed mutant assay revealed that Lys45 and Phe110 were the key binding sites for SfruOBP7 interacting with linalool. In the behavior assays, linalool could attract the larvae, and dsOBP7-treated larvae lost their attraction to linalool. Our results help to reveal the essential molecular mechanism of the olfactory perception in the larvae and design an attractant based on the host volatiles.

The effects of carvacrol on development and gene expression profiles in Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a highly polyphagous agricultural pest that is widely distributed around the world and causes severe crop yield loss. Carvacrol showed adverse effects on many pests, such as larval death and growth inhibition. While the effects of carvacrol on S. frugiperda larvae are not yet known. In this study, the effects of carvacrol on S. frugiperda, including larval growth inhibition and mortality induction, were observed. The detoxification and digestive enzyme activities of larvae with 1.0 and 2.0 g/kg carvacrol treatments were analyzed. Carvacrol boosted the enzyme activities of carboxylesterase (CarE) and glutathione S-transferase (GST) while decreasing the activities of α-amylase (AMS), lipase (LIP), and trypsin. A total of 3422 differentially expressed genes were identified in the larvae treated with 2.0 g/kg carvacrol, of which the DEGs involved in xenobiotic detoxification, food digestion, and insecticidal targets were further examined. These results suggest that carvacrol could regulate growth and development by affecting the process of food digestion, and exert its toxicity on the larvae through interaction with a variety of insecticidal targets. While the altered expressions of detoxification enzymes might be related to the detoxification and metabolism of carvacrol. Our findings offer a theoretical foundation for the use of carvacrol for S. frugiperda control in the field.

Antennal transcriptome analysis of odorant-binding proteins and characterization of GOBP2 in the variegated cutworm Peridroma saucia

Odorant-binding proteins (OBPs) are expressed at extremely high concentrations in the chemo-sensilla lymph of insects and have long been thought to be crucial for delivering the semiochemicals to the odorant receptors. They are represented by multiple classes: general odorant-binding proteins (GOBP1 and GOBP2) and pheromone-binding proteins. In the current study, we identified a total of 35 OBPs in the antennal transcriptome of Peridroma saucia, a worldwide pest that causes serious damage to various crops. A gene expression value (TPM, transcripts per million) analysis revealed that seven OBPs (PsauPBP1/2/3, PsauGOBP1/2, PsauOBP6, and PsauOBP8) were highly abundant in the antennae. Next, we focused on the expression and functional characterization of PsauGOBP2. Real-time quantitative-PCR analysis demonstrated that PsauGOBP2 was predominantly expressed in the antennae of both sexes. Fluorescence binding assays showed that the recombinant PsauGOBP2 strongly binds to the female sex pheromone components Z11-16: Ac (Ki = 4.2 μM) and Z9-14: Ac (Ki = 4.9 μM) and binds moderately (6 µM ≤ Ki ≤ 13 µM) to the host plant volatiles phenylethyl acetate, β-myrcene, and dodecanol. Further 3D structural modeling and molecular docking revealed that several crucial amino acid residues are involved in ligand binding. The results not only increase our understanding of the olfactory system of P. saucia but also provide insights into the function of PsauGOBP2 that has implications for developing sustainable approaches for P. saucia management.

Expression, affinity, and binding mode analysis of antennal-binding protein X in the variegated cutworm Peridroma saucia (Hübner)

The variegated cutworm Peridroma saucia (Hübner) is a worldwide pest that causes serious damage to many crops. Odorant-binding proteins (OBPs) are small soluble proteins involved in the first step of odorant reception. In moths, antennal-binding protein Xs (ABPXs) represent a main subfamily of classic OBPs. However, their functions remain unclear. Here, we cloned the ABPX gene from the antennae of P. saucia. RT-qPCR and western-blot analyses showed that PsauABPX is antenna-predominant and male-biased. Further temporal expression investigation indicated that the expression of PsauABPX started 1 day before eclosion and reached the highest 3 days after eclosion. Next, fluorescence binding assays revealed that recombinant PsauABPX had high binding affinities with P. saucia female sex pheromone components Z11-16: Ac and Z9-14: Ac. Then, molecular docking, molecular dynamics simulation, and site-directed mutagenesis were employed to identify key amino acid residues involved in the binding of PsauABPX to Z11-16: Ac and Z9-14: Ac. The results demonstrated that Val-32, Gln-107 and Tyr-114 are essential for the binding to both sex pheromones. This study not only give us insight into the function and binding mechanism of ABPXs in moths, but could also be used to explore novel strategies to control P. saucia.

A novel volatile deterrent from symbiotic bacteria of entomopathogenic nematodes fortifies field performances of nematodes against fall armyworm larvae

The core elements of entomopathogenic nematode toxicity towards the fall armyworm Spodoptera frugiperda are associated with symbiotic bacteria. These microbes provide independent control effects and are reported to have repellency to insect pests. However, the ecological background of this nematode-bacteria-insect communication module is elusive. This work aims to identify key chemical cues which drive the trophic interactions through olfactory reception of S. frugiperda, and to inspire implementations with these isolated behavioral regulators in the corn field. A total of 657 volatiles were found within 13 symbiotic bacterial strains, and five of them induced significant electrophysiological responses of S. frugiperda larvae. 2-Hexynoic acid was demonstrated to exhibit a dominant role in deterring S. frugiperda larvae from feeding and localization. Field implementations with this novel volatile deterrent have resulted in fortified nematode applications. 2-Hexynoic acid acts as an excellent novel deterrent and presents remarkable application potential against fall armyworm larvae. Emissions from symbiotic bacteria of entomopathogenic nematodes are key players in chemical communication among insects, nematodes, and microbes. The olfactory perceptions and molecular targets for this volatile are worthy of future research.