TRPV channel nanchung and TRPA channel water witch form insecticide-activated complexes

Recent innovations in crop protection research

As the world's population continues to grow and demand for food increases, the agricultural industry faces the challenge of producing higher yields while ensuring the safety and quality of harvests, operators, and consumers. The emergence of resistance, pest shifts, and stricter regulatory requirements also urgently calls for further advances in crop protection and the discovery of new innovative products for sustainable crop protection. This study reviews recent highlights in innovation as presented at the 15th IUPAC International Congress of Crop Protection Chemistry held in New Delhi, in 2023. The following new products are discussed: the insecticides Indazapyroxamet, Dimpropyridaz and Fenmezoditiaz, the fungicides Mefentrifluconazole and Pyridachlomethyl, the nematicide Cyclobutrifluram, the herbicides Rimisoxafen, Dimesulfazet, and Epyrifenacil as well as the abiotic stress management product Anisiflupurin. In addition, the latest innovative research areas and discovery highlights in all areas of crop protection will be presented, including insecticidal alkyl sulfones and 1,3,4-trisubstituted pyrazoles, fungicidal picolinamides, herbicidal ketoenols, and trifluoromethylpyrazoles, as well as the latest advances in crop enhancement and green pest control research. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Taste detection of flonicamid in Drosophila melanogaster

Flonicamid, a widely used insecticide, presents an intriguing question: does it function as an antifeedant by directly activating bitter-sensing gustatory receptor neurons (GRNs) in Drosophila melanogaster. Here, we found that electrophysiological recordings revealed that S-type labellar sensilla exhibited strong neuronal responses to flonicamid, while inhibition of bitter-sensing GRNs nullified this response. Genetic screening identified Gr28b, Gr93a, and Gr98b as essential gustatory receptors for flonicamid detection. Isoform-specific rescue experiments confirmed that Gr28b.a is responsible for restoring sensory responses in Gr28b mutants. Proboscis extension response assays demonstrated that wild-type flies avoided flonicamid, whereas Gr28b, Gr93a, and Gr98b mutants failed to. Functional rescue of these mutants restored the behavioral response, confirming the involvement of these receptors in mediating gustatory aversion. Our findings uncover a novel sensory mechanism for detecting flonicamid through specific gustatory receptors and highlight their potential as molecular targets for insect control strategies.

Expression profiles analysis and roles in immunity of transient receptor potential (TRP) channel genes in Spodoptera frugiperda

BACKGROUND

Transient receptor potential (TRP) ion channels play crucial roles in mediating responses to environmental stimuli, as well as regulating homeostasis and developmental processes in insects. Several members of the TRP superfamily are potential molecular targets for insecticides or repellents, indicating their research value in pest control. This study focuses on Spodoptera frugiperda, an important invasive pest in China known for its wide host range and strong reproductive capacity. Currently, there is a lack of molecular research on the TRP channels of the invasive pest S. frugiperda.

RESULTS

In this study, we identified 15 TRP family genes in S. frugiperda, which were classified into six subfamilies. The TRPP subfamily gene was not identified, whereas the TRPA subfamily contained the highest number of members in this insect. Real-time quantitative polymerase chain reaction (RT-qPCR) experiments revealed widespread expression of TRP channel genes across various developmental stages of S. frugiperda. However, TRPM and TRPML were highly expressed only in eggs. Transcripts of TRP channel genes were detected in the sensory organs of mature adults, including the mouthparts, antennae, compound eyes, legs, wings, harpagones, and ovipositors, as well as in tissues of 5th instar larvae (hemocytes, central nervous system, midgut, fat body, and Malpighian tubules). To explore the potential role of TRP channels in immunity, we detected their levels in larvae 24 h after infection with Serratia marcescens. The expression levels of TRPML, TRPL, and the Pain genes were significantly up-regulated, suggesting their important roles in immune responses to S. marcescens.

CONCLUSIONS

The results of this study extend our knowledge of these critical sensory channels in S. frugiperda. This knowledge provides a basis for the future development of insecticides that target these channels, thereby promoting the safe and effective control of this key pest.

HL-TRP channel is required for various repellents for the parthenogenetic Haemaphysalis longicornis

BACKGROUND

Ticks can transmit a wide range of pathogens that endanger human and animal health. Although repellents are commonly used for tick control, understanding their mechanisms aren't  complete.

METHODS

The repellent effects of N, N-diethyl-meta-toluamide (DEET); sec-butyl 2-(2-hydroxyethyl) piperidine-1-carboxylate (icaridin); N, N-diethyl-3-methylbenzamide (IR3535); and cinnamaldehyde on the parthenogenetic tick Haemaphysalis longicornis at the nymph stage were assessed using Y-tubes. The involvement of transient receptor potential (HL-TRP) channel molecules in the repellent mechanism was investigated through in situ hybridization, subcellular localization, real-time fluorescence quantitative polymerase chain reaction (PCR), RNA interference, and electroantennography. In addition, the binding affinity of HL-TRP molecules to repellents was predicted using AlphaFold3.

RESULTS

DEET, icaridin, IR3535, and cinnamaldehyde have been shown to effectively repel nymphs. HL-TRP channel is shared among various arthropods, particularly several species of ticks. It is localized to the cell membrane and Haller's organ. Moreover, microinjection of double-stranded RNA elicited tick repellency behavior, and the electroantennogram responses to those repellents were significantly decreased. The TYR783 site was proposed as an essential binding site to establish hydrogen bonds with icaridin, DEET, and cinnamaldehyde.

CONCLUSIONS

This exploration of ticks and repellents found that HL-TRP channel functions as a chemosensory receptor for repellents and, thereby, mediates avoidance behavior.

The continuing significance of chiral agrochemicals

Chemical crop protection is one of the most cost-effective methods for agriculture, as crop failures can be prevented, and sustainable growth can be enabled regardless of the seasons. Agricultural production must be significantly increased in the future to meet the food needs of a growing world population. However, the continued loss of established active ingredients due to consumer perceptions, changing needs of farmers and ever-changing regulatory requirements is higher than annually new active ingredients introduced to the market. The development of innovative active ingredients is therefore essential to continuously improve the selectivity, efficacy and favorable environmental profile of agrochemicals. Molecules with stereogenic centers can be considered here, as they often have different properties than non-chiral molecules. Natural products and their congeners are still a valuable source of inspiration for chiral agrochemicals. However, only a few novel chiral agrochemicals are currently produced on an industrial scale as pure stereoisomers or in enriched form. As of 2018, around 43% of the 35 chiral products introduced to the market (herbicides, fungicides, insecticides, acaricides, and nematicides) contain one or more stereogenic centers in the molecule, and almost 69% of them have been marketed as racemic mixtures of enantiomers or stereoisomers. Surprisingly, the proportion of chiral agrochemicals is in the same order of magnitude as in the time frame from 2007 to 2017 with around 42%, respectively. This report therefore provides an overview of the continued importance of chiral agrochemicals brought to market in the last 6 years and describes the inherent related challenges of modern agrochemicals through the management of key aspects arising from innovative crop protection products. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparative assays revealed distinct toxicity characterizations between pymetrozine and flonicamid

Flonicamid is an insecticide with a unique mode of action, primarily inhibiting the feeding behavior of sap-sucking insects. However, its molecular target remains controversial. Reports indicate that both flonicamid and pymetrozine affect insect behavior and mobility. To investigate further, we compared the susceptibility of three insect species (Myzus persicae, Nilaparvata lugens, and Drosophila melanogaster) to flonicamid and pymetrozine under two different feeding postures. Results showed that feeding posture did not affect the survival curves or mean lifespans of the three insects. However, insect lifespans were significantly reduced under exposure to either insecticide compared to untreated controls. The effects of the two insecticides on susceptibility and lifespan under different feeding postures were markedly different: feeding posture significantly influenced the sensitivity of aphids, planthoppers, and fruit flies to pymetrozine but had minimal effects on the sensitivity of aphids and planthoppers to flonicamid. Flonicamid had only a minor impact on fruit flies' sensitivity. Survival curve analysis also revealed significant differences under pymetrozine stress, while no such differences were observed under flonicamid stress. These findings indicate that flonicamid exerts different toxicological effects on target insects (aphids and planthoppers) versus non-target insects (fruit flies), depending on feeding posture. This suggests that the toxicological mechanisms of flonicamid differ substantially between target and non-target organisms, with implications that findings in non-target insects may not directly apply to target pests. Our study provides valuable insights and directions for further research into flonicamid's mode of action, aiding in elucidating its underlying mechanisms.

Involvement of Inwardly Rectifying Potassium (Kir) Channels in the Toxicity of Flonicamid to Drosophila melanogaster

Inwardly rectifying potassium (Kir) channels regulate essential physiological processes in insects and have been identified as potential targets for developing new insecticides. Flonicamid has been reported to inhibit Kir channels, disrupting the functions of salivary glands and renal tubules. However, the precise molecular target of flonicamid remains debated. It is unclear whether flonicamid directly targets Kir channels or acts on other sites involved in the activation of transient receptor potential vanilloid (TRPV) channels. In this study, we observed that flonicamid is more toxic to flies than its metabolite, flumetnicam. This higher toxicity is difficult to reconcile if nicotinamidase is the active target, as flonicamid does not inhibit nicotinamidase. An alternative explanation is that flonicamid and flumetnicam may have distinct targets or act on multiple targets. Furthermore, reducing the expression of three individual Kir genes in the salivary glands of D. melanogaster significantly decreased the flies' susceptibility to both flonicamid and flumetnicam. The double knockdown of Kir1 with Kir3 or Kir2 with Kir3 further reduced the flies' sensitivity to both compounds. These findings confirm the involvement of Kir channels in mediating the toxic effects of flonicamid on flies. Overall, this study offers new insights into the physiological roles of insect Kir channels and flonicamid toxicity.

The Synergistic Effect of Lemongrass Essential Oil and Flometoquin, Flonicamid, and Sulfoxaflor on Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae): Insights into Toxicity, Biochemical Impact, and Molecular Docking

The whitefly, Bemisia tabaci (Genn.), is one of the most dangerous polyphagous pests in the world. Eco-friendly compounds and new chemical insecticides have gained recognition for whitefly control. In this study, the toxicity and biochemical impact of flometoquin, flonicamid, and sulfoxaflor, alone or combined with lemongrass essential oil (EO), against B. tabaci was studied. In addition, a molecular docking study was conducted to assess the binding affinity of the tested compounds to AchE. Based on the LC values, the descending order of the toxicity of the tested compounds to B. tabaci adults was as follows: sulfoxaflor > flonicamid > flometoquin > lemongrass EO. The binary mixtures of each of the tested compounds with lemongrass EO exhibited synergism in all combinations, with observed mortalities ranging from 15.09 to 22.94% higher than expected for an additive effect. Sulfoxaflor and flonicamid, alone or in combination with lemongrass EO, significantly inhibited AchE activity while only flonicamid demonstrated a significant impact on α-esterase, and none of the tested compounds affected cytochrome P450 or GST. However, the specific activity of P450 was significantly inhibited by the lemongrass/sulfoxaflor mixture while α-esterase activity was significantly inhibited by the lemongrass/flometoquin mixture. Moreover, the lemongrass EO and all the tested insecticides exhibited significant binding affinity to AchE with energy scores ranging from -4.69 to -7.06 kcal/mol. The current findings provide a foundation for utilizing combinations of essential oils and insecticides in the integrated pest management (IPM) of B. tabaci.

Environmental-related doses of afidopyropen induced toxicity effects in earthworms (Eisenia fetida)

Afidopyropen has high activity against pests. However, it poses potential risks to the soil ecology after entering the environment. The toxicity of afidopyropen to earthworms (Eisenia fetida) was studied for the first time in this study. The results showed that afidopyropen had low level of acute toxicity to E. fetida. Under the stimulation of chronic toxicity, the increase of reactive oxygen species (ROS) level activated the antioxidant and detoxification system, which led to the increase of superoxide dismutase (SOD) and glutathione S-transferase (GST) activities. Lipid peroxidation and DNA damage were characterized by the increase of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents. Meanwhile, the functional genes SOD, CAT, GST, heat shock protein 70 (HSP70), transcriptionally controlled tumor protein (TCTP), and annetocin (ANN) played a synergistic role in antioxidant defense. However, the comprehensive toxicity of high concentration still increased on the 28th day. In addition, strong histopathological damage in the body wall and intestine was observed, accompanied by weight loss, which indicated that afidopyropen inhibited the growth of E. fetida. The molecular docking revealed that afidopyrene combined with the surface structure of SOD and GST proteins, which made SOD and GST become sensitive biomarkers reflecting the toxicity of afidopyropen to E. fetida. Summing up, afidopyropen destroys the homeostasis of E. fetida through chronic toxic. These results provide theoretical data for evaluating the environmental risk of afidopyropen to soil ecosystem.

Identification of amino acid residues that are crucial for afidopyropen binding to the TRPV channel of Myzus persicae (Sulzer)

Afidopyropen is highly effective against sucking insects, including the Myzus persicae, that modulates the transient receptor potential vanilloid (TRPV) channel. However, the action mechanisms of afidopyropen to the TRPV channel remain unknown. In this study, the genes encoding the Nanchung (MpNan) and Inactive (MpIav) subunits of the TRPV channel of M. persicae (MpTRPV) were cloned, and their spatiotemporal expression profiles were investigated. Then, MpTRPV was functionally expressed in Xenopus laevis oocytes, and the AA residues crucial for afidopyropen binding were identified using the two-electrode voltage clamp (TEVC) technique. The results showed that both MpNan and MpIav exhibited the highest expression in the antennae and were most abundant in the 4th instar nymphs and adults. Knockdown of these two genes by RNAi greatly increased the toxicity of afidopyropen to the aphids. Moreover, the AA residues involved in afidopyropen binding to MpNan were predicted and L412 was further identified as the key residue for binding by TEVC analysis. The results also showed that afdopyropen and pymetrozine share the same binding site. These findings lay a foundation not only for exploring the mechanisms of pest target resistance to afidopyropen and pymetrozine but also for developing new insecticides targeting the TRPV channels of pests.

Insect transient receptor potential vanilloid channels as potential targets of insecticides

Chordotonal organs are miniature sensory organs present in insects. Chordotonal organs depend on transient receptor potential (TRP) channels. Transient receptor potential vanilloid (TRPV) channels are the only TRPs identified that can act as targets of insecticides. By binding with TRPV channels, insecticides targeting the chordotonal organs trigger the inflow of calcium ions, resulting in abnormal function of the chordotonal organ to achieve the goal of eliminating pests. TRPV channels are highly expressed in various developmental stages and tissue parts of insects and play an important role in the whole life history of insects. In this review, we will discuss the structure and types of TRPV channels as well as their genetic relationships in different species. We also systematically reviewed the recent progress of TRPV channels as insecticide targets, demonstrating that TRPV channels can be used as the target of new high-efficiency insecticides.

Reverse genetic study reveals the molecular targets of chordotonal organ TRPV channel modulators

Insecticides have been widely used for the control of insect pests that have a significant impact on agriculture and human health. A better understanding of insecticide targets is needed for effective insecticide design and resistance management. Pymetrozine, afidopyropen and flonicamid are reported to target on proteins that located on insect chordotonal organs, resulting in the disruption of insect coordination and the inhibition of feeding. In this study, we systematically examined the susceptibility of six Drosophila melanogaster mutants (five transient receptor potential channels and one mechanoreceptor) to three commercially used insecticides, in order to identify the receptor subunits critical to the insect's response to insecticides. Our results showed that iav1, nan36aand wtrw1 mutants exhibited significantly reduced susceptibility to pymetrozine and afidopyropen, but not to flonicamid. The number of eggs produced by the three mutant females were significantly less than that of the w1118 strain. Meanwhile, the longevity of all male mutants and females of nan36a and wtrw1 mutants was significantly shorter than that of the w1118 strain as the control. However, we observed no gravitaxis defects in wtrw1 mutants and the anti-gravitaxis of wtrw1 mutants was abolished by pymetrozine. Behavioral assays using thermogenetic tools further confirmed the bioassay results and supported the idea that Nan as a TRPV subfamily member located in Drosophila chordotonal neurons, acting as a target of pymetrozine, which interferes with Drosophila and causes motor deficits with gravitaxis defects. Taken together, this study elucidates the interactions of pymetrozine and afidopyropen with TRPV channels, Nan and Iav, and TRPA channel, Wtrw. Our research provides another evidence that pymetrozine and afidopyropen might target on nan, iav and wtrw channels and provides insights into the development of sustainable pest management strategies.

The modes of action of ion-channel-targeting neurotoxic insecticides: lessons from structural biology

Insecticides are indispensable tools for plant protection in modern agriculture. Despite having highly heterogeneous structures, many neurotoxic insecticides use similar principles to inhibit or deregulate neuronal ion channels. Insecticides targeting pentameric ligand-gated channels are structural mimetics of neurotransmitters or manipulate and deregulate the proteins. Those binding to (pseudo-)tetrameric voltage-gated(-like) channels, on the other hand, are natural or synthetic compounds that directly block the ion-conducting pore or prevent conformational changes in the transmembrane domain necessary for opening and closing the pore. The use of a limited number of inhibition mechanisms can be problematic when resistances arise and become more widespread. Therefore, there is a rising interest in the development of insecticides with novel mechanisms that evade resistance and are pest-insect-specific. During the last decade, most known insecticide targets, many with bound compounds, have been structurally characterized, bringing the rational design of novel classes of agrochemicals within closer reach than ever before.

Genome-Wide Characterization and Gene Expression Analysis of TRP Channel Superfamily Genes in the Migratory Locust, Locusta migratoria

The TRP channel superfamily was widely found in multiple species. They were involved in many extrasensory perceptions and were important for adapting to the environment. The migratory locust was one of the worldwide agricultural pests due to huge damage. In this study, we identified 13 TRP superfamily genes in the locust genome. The number of LmTRP superfamily genes was consistent with most insects. The phylogenetic tree showed that LmTRP superfamily genes could be divided into seven subfamilies. The conserved motifs and domains analysis documented that LmTRP superfamily genes contained unique characteristics of the TRP superfamily. The expression profiles in different organs identified LmTRP superfamily genes in the head and antennae, which were involved in sensory function. The expression pattern of different life phases also demonstrated that LmTRP superfamily genes were mainly expressed in third-instar nymphs and male adults. Our findings could contribute to a better understanding of the TRP channel superfamily gene and provide potential targets for insect control.

Natural Product-Based Crop Protection Compounds─Origins and Future Prospects

The continuing need to protect food and fiber production to address the demands of an expanding global population requires new pest management tools for crop protection. Natural products (NPs) have been and continue to be a key source of inspiration for new active ingredients (AIs) for crop protection, accounting for 17% of all crop protection AIs. However, potentially 50% of all crop protection compounds have or could have a NP origin if NP synthetic equivalents (NPSEs, synthetic compounds discovered by other approaches but for which a NP model also happens to exist) are also considered. The real and hypothetical NPs have their greatest impact as insight for new classes of crop protection compounds. Among the different product areas, NPs have their largest influence on the discovery of new insecticides, while herbicides have been the least affected by mining NPs for new AIs. While plants have historically been the largest (60% of the total) source of NPs of AIs for crop protection, in the last 30 years, bacterial NPs have become the largest source (42% of the total) of new classes (first in class) of NP-inspired crop protection AIs. Interest in NPs for crop protection continues, an aspect that is highlighted by the notable rise in the numbers of publications and patents on this topic, especially in the last 20 years. The present analysis further illustrates the continuing interest and value in NPs as sources of and inspiration for new classes of crop protection compounds.