Knockout of ABC Transporter ABCG4 Gene Confers Resistance to Cry1 Proteins in Ostrinia furnacalis

Global distribution and sustainable management of Asian corn borer (ACB), Ostrinia furnacalis (Lepidoptera: Crambidae): recent advancement and future prospects

The Asian corn borer (ACB), Ostrinia furnacalis (Guenée, 1854), is a serious pest of several crops, particularly a destructive pest of maize and other cereals throughout most of Asia, including China, the Philippines, Indonesia, Malaysia, Thailand, Sri Lanka, India, Bangladesh, Japan, Korea, Vietnam, Laos, Myanmar, Afghanistan, Pakistan and Cambodia. It has long been known as a pest in South-east Asia and has invaded other parts of Asia, Solomon Islands, parts of Africa and certain regions of Australia and Russia. Consequently, worldwide efforts have been increased to ensure new control strategies for O. furnacalis management. In this article, we provide a comprehensive review of the ACB covering its (i) distribution (geographic range and seasonal variations), (ii) morphology and ecology (taxonomy, life-history, host plants and economic importance) and (iii) management strategies (which include agroecological approaches, mating disruption, integrated genetic approaches, chemical as well as biological control). Furthermore, we conclude this review with recommendations to provide some suggestions for improving eco-friendly pest management strategies to enhance the sustainable management of ACB in infested areas.

Full-length transcriptome-referenced analysis reveals developmental and olfactory regulatory genes in Dermestes frischii

Dermestes frischii Kugelann, 1792 is a storage pest worldwide, and is important for estimating the postmortem interval in forensic entomology. However, because of the lack of transcriptome and genome resources, population genetics and biological control studies on D. frischii have been hindered. Here, single-molecule real-time sequencing and next-generation sequencing were combined to generate the full-length transcriptome of the five developmental stages of D. frischii, namely egg, young larva, mature larva, pupa and adult. A total of 41,665 full-length non-chimeric sequences and 59,385 non-redundant transcripts were generated, of which 42,756 were annotated in public databases. Using the weighted gene co-expression network analysis, gene co-expression modules related to the five developmental stages were constructed and screened, and the genes in these modules were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The expression patterns of the differentially expressed genes (DEGs) related to olfaction and insect hormone biosynthesis were also explored. Transcription of most odorant binding proteins was up-regulated in the adult stage, suggesting they are important for foraging in adults. Many genes encoding for the ecdysone-inducible protein were up-regulated in the pupal stage, may be mainly responsible for the tissue remodelling of metamorphosis. The results of the quantitative real-time polymerase chain reaction (qRT-PCR) were consistent with the RNA-seq results. This is the first full-length transcriptome sequencing of dermestids, and the data obtained here are vital for understanding the stage-specific development and olfactory system of D. frischii, providing valuable resources for storage pest and forensic research.

Mismatch between lab-generated and field-evolved resistance to transgenic Bt crops in Helicoverpa zea

Transgenic crops producing crystalline (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) have been used extensively to control some major crop pests. However, many populations of the noctuid moth Helicoverpa zea, one of the most important crop pests in the United States, have evolved practical resistance to several Cry proteins including Cry1Ac. Although mutations in single genes that confer resistance to Cry proteins have been identified in lab-selected and gene-edited strains of H. zea and other lepidopteran pests, the genetic basis of field-evolved resistance to Cry proteins in H. zea has remained elusive. We used a genomic approach to analyze the genetic basis of field-evolved resistance to Cry1Ac in 937 H. zea derived from 17 sites in seven states of the southern United States. We found evidence for extensive gene flow among all populations studied. Field-evolved resistance was not associated with mutations in 20 single candidate genes previously implicated in resistance or susceptibility to Cry proteins in H. zea or other lepidopterans. Instead, resistance in field samples was associated with increased copy number of a cluster of nine trypsin genes. However, trypsin gene amplification occurred in a susceptible sample and not in all resistant samples, implying that this amplification does not always confer resistance and mutations in other genes also contribute to field-evolved resistance to Cry1Ac in H. zea. The mismatch between lab-generated and field-evolved resistance in H. zea is unlike other cases of Bt resistance and reflects challenges for managing this pest.

Network toxicology and molecular docking to investigative the non-acetylcholinesterase mechanisms and targets of cardiotoxicity injury induced by organophosphorus pesticides

BACKGROUND

Organophosphorus pesticides (OPPs) are widely used in the world, however, OPP poisoning often occurs because of improper use and lack of protective measures. Cardiotoxicity injury induced by OPPs is insidious, and it does not receive attention until the end stage of OPP poisoning. Heart failure or arrhythmia gradually becomes the main lethal cause of OPP poisoning patients.

METHODS

In this study, network toxicology and molecular docking were employed to investigate the non-acetylcholinesterase targets and mechanisms of cardiotoxicity injury induced by OPPs.

RESULTS

One hundred twenty-three targets of dichlorvos, 205 targets of methidathion, and 337 targets of malathion were searched from SwissTargetPreict, STITCH and PharmMapper database. Additionally, 1379 targets related to cardiotoxicity injury were acquired from GeneCards and OMIM database. Ninety-six mutual targets between OPPs and cardiotoxicity injury were considered as the potential cardiotoxicity injury targets induced by OPPs. The protein-protein interaction (PPI) network was constructed using STING database, and 21 core targets were identified by Cytoscape software, such as AKT1, ESR1, HSP90AA1, MAPK1, MMP9, and MAPK8. Gene ontology and KEGG enrichment analysis revealed that cell migration, apoptotic process, protein phosphorylation and signal transduction were the major biological functions associated with OPPs-induced cardiotoxicity injury, and OPPs-induced cardiotoxicity injury might be regulated by MAPK, PI3K-Akt, VEGF signaling pathway. Docking results manifested that the best binding target for dichlorvos, methidathion and malathion were MAPK9 (-7.1 kcal/mol), MAPK1 (-8.1 kcal/mol) and HSP90AA1 (-8.6 kcal/mol) with the lowest affinity, respectively.

CONCLUSION

The core targets and non-AchE mechanisms were explored by network toxicology and molecular docking, providing a theoretical basis for the treatment of OPP-induced cardiotoxicity injury.

Insights into the Detoxification of Spruce Monoterpenes by the Eurasian Spruce Bark Beetle

Plant defence mechanisms, including physical barriers like toughened bark and chemical defences like allelochemicals, are essential for protecting them against pests. Trees allocate non-structural carbohydrates (NSCs) to produce secondary metabolites like monoterpenes, which increase during biotic stress to fend off pests like the Eurasian spruce bark beetle, ESBB (Ips typographus). Despite these defences, the ESBB infests Norway spruce, causing significant ecological damage by exploiting weakened trees and using pheromones for aggregation. However, the mechanism of sensing and resistance towards host allelochemicals in ESBB is poorly understood. We hypothesised that the exposure of ESBB to spruce allelochemicals, especially monoterpenes, leads to an upsurge in the important detoxification genes like P450s, GSTs, UGTs, and transporters, and at the same time, genes responsible for development must be compromised. The current study demonstrates that exposure to monoterpenes like R-limonene and sabiene effectively elevated detoxification enzyme activities. The differential gene expression (DGE) analysis revealed 294 differentially expressed (DE) detoxification genes in response to R-limonene and 426 DE detoxification genes in response to sabiene treatments, with 209 common genes between the treatments. Amongst these, genes from the cytochrome P450 family 4 and 6 genes (CP4 and CP6), esterases, glutathione S-transferases family 1 (GSTT1), UDP-glucuronosyltransferase 2B genes (UDB), and glucose synthesis-related dehydrogenases were highly upregulated. We further validated 19 genes using RT-qPCR. Additionally, we observed similar high expression levels of detoxification genes across different monoterpene treatments, including myrcene and α-pinene, suggesting a conserved detoxification mechanism in ESBB, which demands further investigation. These findings highlight the potential for molecular target-based beetle management strategies targeting these key detoxification genes.

Molecular Genetic Basis of Lab- and Field-Selected Bt Resistance in Pink Bollworm

Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) control some important insect pests. However, evolution of resistance by pests reduces the efficacy of Bt crops. Here we review resistance to Bt cotton in the pink bollworm, Pectinophora gossypiella, one of the world's most damaging pests of cotton. Field outcomes with Bt cotton and pink bollworm during the past quarter century differ markedly among the world's top three cotton-producing countries: practical resistance in India, sustained susceptibility in China, and eradication of this invasive lepidopteran pest from the United States achieved with Bt cotton and other tactics. We compared the molecular genetic basis of pink bollworm resistance between lab-selected strains from the U.S. and China and field-selected populations from India for two Bt proteins (Cry1Ac and Cry2Ab) produced in widely adopted Bt cotton. Both lab- and field-selected resistance are associated with mutations affecting the cadherin protein PgCad1 for Cry1Ac and the ATP-binding cassette transporter protein PgABCA2 for Cry2Ab. The results imply lab selection is useful for identifying genes important in field-evolved resistance to Bt crops, but not necessarily the specific mutations in those genes. The results also suggest that differences in management practices, rather than genetic constraints, caused the strikingly different outcomes among countries.

Transcriptional response and functional analysis of ATP-binding cassette transporters to tannic acid in pea aphid, Acyrthosiphon pisum (Harris)

Although tannins are widely distributed in broad beans and alfalfa, the pea aphid (Acyrthosiphon pisum) can still destroy them. The ATP binding cassette (ABC) transporters participate in the metabolism of plant secondary metabolites and pesticides in insects. However, whether ABC transporter genes play a role in the metabolism of tannins in the pea aphid is unclear. Here, we found that verapamil (an ABC transporter inhibitor) significantly increased the mortality of tannic acid to pea aphid, which indicated that ABC transporter gene was related to the metabolism of tannic acid by pea aphid. Then, we identified 54 putative ABC transporter genes from the genome database of A. pisum. These genes were divided into eight subfamilies, ApABCA to ApABCH, of which subfamily G has the largest number of genes with 19, followed by the subfamily C with 14. RT-qPCR results show that the expression levels of ApABCA2, ApABCC7, ApABCG2, and ApABCG3 were highly expressed in the first instar, while those of ApABCA3, ApABCG6, ApABCG7, ApABCH3, and ApABCH4 were highly expressed in adults. Furthermore, transcription levels of many ABC transporter genes were induced by tannic acid. Especially, ApABCG17 and ApABCH2 were obviously induced after being exposed to tannic acid. Meanwhile, knockdown of ApABCG17 by RNA interference resulted in increased sensitivity of pea aphid to tannic acid. These results suggest that ApABCG17 may be involved in tannic acid metabolism in pea aphid. This study will help us to understand the mechanism of tannic acid metabolism in pea aphid, and provides a basis for further research on the physiological function of ABC transporter genes in pea aphid.

Cyclosporin A as a Potential Insecticide to Control the Asian Corn Borer Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae)

The long-term use of chemical insecticides has caused serious problems of insect resistance and environmental pollution; new insecticides are needed to solve this problem. Cyclosporin A (CsA) is a polypeptide produced by many fungi, which is used to prevent or treat immune rejection during organ transplantation. However, little is known about the utility of CsA as an insecticide. Therefore, this study evaluated the insecticidal activity of CsA using Ostrinia furnacalis as a model. The results demonstrated that CsA was toxic to O. furnacalis with LC₅₀ values of 113.02 μg/g and 198.70 μg/g for newly hatched neonates and newly molted third-instar larvae, respectively. Furthermore, CsA treatment had sublethal effects on the development of O. furnacalis, and significantly reduced the fecundity of adults; this suggests that CsA has great potential to suppress O. furnacalis populations. Further analysis revealed that CsA suppressed calcineurin activity in larvae. CsA had independent or synergistic toxic effects on O. furnacalis when combined with β-cypermethrin, indoxacarb, emamectin benzoate, azadirachtin, and the Bacillus thuringiensis toxin Cry1Ac, which suggests that CsA can help prevent or manage resistance. Our study provides detailed information on the potential of CsA as an insecticide for controlling lepidopterans.