The research team, led by scientists at Nanjing Agricultural University together with collaborators in Kenya, focused on IR75q.2, a member of the IR75 clade, in the cotton leafworm Spodoptera litura and the beet armyworm Spodoptera exigua. Both species are major agricultural pests with broad host ranges and formidable dispersal abilities, making them priority targets for novel pest management strategies. IR75q.2 had previously been characterized in a third species, the fall armyworm Spodoptera frugiperda, where it was shown to mediate avoidance of nonanoic acid. The central question of the new work was whether this ligand recognition profile, and the structural features underlying it, have been preserved across related moth lineages or whether evolutionary divergence has reshaped them.

To answer that question, the researchers assembled a multi-pronged analytical pipeline that combined phylogenetics, expression profiling, electrophysiology, structural modeling, molecular docking, and site-directed mutagenesis. Phylogenetic analysis of IR75 amino acid sequences from three Spodoptera species and two additional noctuid moths, Agrotis segetum and Helicoverpa armigera, revealed that the IR75 receptors form a highly conserved clade. Motif analysis using the MEME program identified ten conserved motifs arranged in nearly identical order across the sequences, with statistical significance values so extreme that the probability of chance occurrence fell below ten to the power of minus 170. This remarkable sequence conservation suggested that members of the IR75 clade share structural features tied to ligand recognition.

Transcriptome data added a functional dimension to this conservation story. Among all IR75 genes in the two Spodoptera species, IR75q.2 exhibited the highest expression in the antennae of both sexes, with no significant differences between males and females. Because antennae are the primary olfactory organs, this expression pattern pointed to an important role in odor detection. Sequence comparisons showed that the SlitIR75q.2 and SexiIR75q.2 proteins share 90.65 percent amino acid identity, both genes contain eleven exons, and both proteins possess three transmembrane domains. Evolutionary analysis using the PAML package revealed that while selective pressures vary across branches, all omega values were below one, indicating strong purifying selection has preserved the function of these orthologs over evolutionary time.

The functional core of the study came from experiments using the Xenopus oocyte expression system with two-electrode voltage clamp recording. The team co-expressed each IR75q.2 ortholog with its obligatory co-receptor IR8a and tested 59 odorant compounds in three mixtures. Both receptors responded primarily to just six compounds: three medium-chain fatty acids, namely octanoic acid, nonanoic acid, and decanoic acid, and their corresponding aldehydes, octanal, nonanal, and decanal. Nonanoic acid was by far the strongest ligand for both receptors, eliciting peak currents of 491.61 nanoamperes in SlitIR75q.2 and 347.70 nanoamperes in SexiIR75q.2. Dose-response assays yielded half-maximal effective concentrations of 7.596 times ten to the minus four molar for the cotton leafworm receptor and 4.052 times ten to the minus four molar for the beet armyworm receptor, confirming nearly identical sensitivities.

To probe the structural basis of this shared tuning, the researchers predicted three-dimensional structures of both receptors using AlphaFold 3.0 and docked nonanoic acid into the binding pockets using AutoDock Vina. The predicted binding energies were minus 6.04 kilocalories per mole for SlitIR75q.2 and minus 4.93 kilocalories per mole for SexiIR75q.2. In both receptors, a phenylalanine and an arginine residue within the S1 domain of the ligand-binding domain were predicted to form hydrogen bonds with the ligand: Phe285 and Arg290 in SlitIR75q.2, and Phe284 and Arg289 in SexiIR75q.2. Ten amino acid residues within four angstroms of nonanoic acid were conserved between the two receptors, underscoring the preservation of the binding pocket.

Site-directed mutagenesis put these structural predictions to a rigorous test. Substituting either Phe285 or Arg290 with alanine in SlitIR75q.2 completely abolished the response to nonanoic acid, preventing any estimate of sensitivity. In SexiIR75q.2, single alanine substitutions of Phe284 or Arg289 did not eliminate responses but increased the half-maximal effective concentration roughly four to five-fold, from 1.38 times ten to the minus four molar in the intact receptor to 6.3 and 6.2 times ten to the minus four molar in the mutants. These results establish Phe and Arg as conserved key residues for nonanoic acid recognition and suggest that subtle changes in binding-pocket chemistry can modulate ligand sensitivity across species. Docking of the remaining five ligands showed the same hydrogen-bonding anchors plus conserved hydrophobic contacts involving residues such as Ile230/229, Trp257/256, and Pro282/282.

The physiological findings translated into behavior for at least one of the two species. Electroantennogram recordings demonstrated that adults of both Spodoptera litura and Spodoptera exigua responded in a dose-dependent manner to nonanoic acid and the other five ligands, confirming that the antennal sensory system detects these compounds. In Y-tube olfactometer assays, nonanoic acid significantly repelled S. litura adults at doses of 50 and 100 micrograms. Behavioral testing of S. exigua proved unreliable because the beet armyworm adults showed extremely low locomotor activity in the olfactometer, but the electrophysiological evidence indicates the compound is detected by this species as well. Together, the behavioral and physiological data align with the earlier finding in the fall armyworm, reinforcing the idea that nonanoic acid serves as a conserved aversive cue across Spodoptera moths.

The broader evolutionary implications of the study are considerable. The ligands detected by IR75q.2 overlap partly with those sensed by certain odorant receptors, and nonanal in particular is known to attract females of S. frugiperda and S. litura through a conserved odorant receptor lineage. The authors propose that odorant receptors and ionotropic receptors do not simply duplicate one another but instead provide complementary information: the former tuned largely to neutral plant volatiles, the latter to acids, amines, and other polar ecological cues. This parallel coding may help moths discriminate chemically related compounds with different behavioral valences and broaden their detectable chemical space. At the same time, comparisons with the related IR75q.1 group, which prefers the aversive compound octanoic acid, suggest that subfunctionalization after gene duplication has shaped the ligand preferences of acid-sensing IRs in Lepidoptera. By pinpointing conserved binding residues and demonstrating functional conservation across two major pests, the study provides a molecular framework both for understanding how olfactory systems evolve and for designing targeted behavioral interventions, such as repellent formulations built around nonanoic acid analogs, that could exploit this preserved sensory channel in the fight against some of the world’s most destructive crop pests.

Subject of Research: Functional conservation of the ionotropic receptor IR75q.2 in detecting volatile acids and aldehydes across two Spodoptera moth species

Article Title: Functional conservation of IR75q.2 in the recognition of volatile acids and aldehydes in two Spodoptera species

Article References: Guo, J.-M., Wang, J.-X., He, Y., Luan, X.-P., Wei, Z.-Q., Liu, X.-L., Obiero, G. F., Yan, Q., Dong, S.-L., & Zhang, J. (2026). Functional conservation of IR75q.2 in the recognition of volatile acids and aldehydes in two Spodoptera species. Crop Health, 4(1), Article 20. https://doi.org/10.1007/s44297-026-00082-7

Image Credits: AI Generated

DOI: 10.1007/s44297-026-00082-7

Keywords: ionotropic receptors, IR75q.2, Spodoptera litura, Spodoptera exigua, nonanoic acid, insect olfaction, chemosensory receptors, Xenopus oocyte expression, molecular docking, site-directed mutagenesis, purifying selection, pest management

The newly identified nematode isolate was subjected to an in-depth morphological and molecular characterization to ascertain its identity and possible novelty compared to previously documented strains of S. abbasi. Morphological traits such as infective juvenile dimensions, body shape, and esophageal region specifics were meticulously measured and compared, while molecular analyses focused on sequencing particular ribosomal DNA regions. These combined approaches confirmed the isolate’s affiliation with Steinernema abbasi but highlighted distinctive genetic markers indicative of its unique biocontrol potential.

Understanding the biology and lifecycle of entomopathogenic nematodes is pivotal to maximizing their utilization. Steinernema species are renowned for their symbiotic relationship with bacteria belonging to the genus Xenorhabdus, which they release upon infecting insect hosts. The bacteria produce toxins that swiftly incapacitate the host, paving the way for nematode reproduction inside the cadaver, eventually perpetuating their lifecycle. This covert infection mechanism makes S. abbasi an invaluable ally against agriculturally detrimental lepidopteran larvae.

The tobacco cutworm, Spodoptera litura, inflicts substantial economic damage globally, affecting a broad spectrum of crops such as cotton, soybean, and various vegetables. Similarly, Mythimna separata is notorious for devastating cereal crops across Asia, posing serious threats to food security. Conventional chemical control methods often entail pesticide resistance development, environmental contamination, and non-target organism harm, underscoring the urgent need for viable biological alternatives. This newly isolated S. abbasi strain’s pathogenicity assays demonstrated a high mortality rate in both pest species, positioning it as a formidable candidate for biocontrol.

Laboratory bioassays involved treating larvae of both S. litura and M. separata with varying concentrations of infective juveniles (IJs) from the nematode isolate. Mortality outcomes exhibited a dose-dependent response, with substantial larval death recorded at relatively low nematode exposure levels. Notably, the infective juveniles showed rapid host-seeking behavior and robust penetration efficiency, critical attributes for effective field application. Furthermore, no adverse effects on non-target beneficial insects or soil microorganisms were observed in preliminary studies, emphasizing ecological safety.

Beyond immediate pest mortality, the nematode’s ability to persist in soil environments and establish enduring populations was investigated. The isolate displayed notable resilience under varying soil moisture and temperature ranges, which suggests potential for sustained control across diverse agroecological zones. This environmental adaptability could enable deployment in regions where fluctuating climatic conditions hinder the utility of other biocontrol agents, broadening the scope of integrated pest management.

Advancements in molecular techniques allowed researchers to delve deeper into the isolate’s symbiotic bacterial profile. Sequencing and phylogenetic analysis of the Xenorhabdus bacteria associated with this S. abbasi strain revealed unique secondary metabolite gene clusters. These genetic features are likely responsible for the potent insecticidal activity observed, hinting at previously untapped biochemical pathways. Unlocking such microbial chemical arsenals not only enhances understanding of host-pathogen interactions but also lays groundwork for biopesticide development.

Field trials conducted in controlled crop environments substantiated laboratory findings, where plots treated with the nematode isolate exhibited significantly reduced pest infestations compared to untreated controls. Crop damage assessments demonstrated preservation of leaf area and improved overall plant vigor. Importantly, these naturally derived nematode applications showed no phytotoxic effects or environmental detriments, underscoring the method’s sustainability and farmer acceptability.

This research addresses critical challenges hindering entomopathogenic nematode commercialization, including production scalability, delivery mechanisms, and field persistence. Optimization efforts reported include formulating nematode-containing bio-products capable of maintaining viability during storage and transportation. The development of aqueous suspensions and granular formulations optimized for easy application further enhance user adoption potential in diverse farming systems.

The success of the novel S. abbasi isolate also provides insights into evolutionary adaptation within nematode populations subjected to selective pressures in pest-rich environments. Its enhanced virulence and stress tolerance may stem from genetic exchanges or local environmental adaptation, offering a model system for studying nematode-pathogen evolution and co-adaptive dynamics.

Importantly, the integration of this entomopathogenic nematode into existing pest management strategies could reduce reliance on synthetic pesticides, diminishing environmental contamination and human health risks. Widespread adoption could lead to restored biodiversity in agroecosystems, bolstered populations of natural enemies, and improved ecosystem resilience, essential components for sustainable agriculture.

Looking forward, researchers advocate for the expansive screening of native nematode populations to uncover additional isolates with superior biocontrol attributes. Collaborative efforts between molecular biologists, entomologists, and agronomists are poised to refine delivery systems, tailor nematode formulations, and evaluate long-term ecological impacts under diverse agroclimatic scenarios.

The promising findings concerning this Steinernema abbasi isolate underscore the critical role of biodiversity explorations in uncovering practical solutions to pressing agricultural challenges. Employing such natural, environmentally harmonious tools aligns with global goals for pesticide reduction and sustainable food production, offering a beacon of hope in combating resilient crop pests.

Ultimately, this study exemplifies how bridging classical taxonomy with contemporary molecular biology and applied field research can yield impactful innovations. As the agricultural sector intensifies efforts to reconcile productivity with environmental stewardship, biological control agents like the newly characterized S. abbasi isolate represent a vital arsenal in the quest for agroecological balance and global food security.

Subject of Research: Biological characterization and pest control efficacy of a newly isolated Steinernema abbasi nematode against key lepidopteran pests affecting agriculture.

Article Title: Characterization and Biocontrol Efficacy of a New Isolate of Steinernema abbasi (Elawad Ahmad & Reid, 1997) Against Spodoptera litura (Fabricius) and Mythimna separata (Walker).

Article References:
Mallikarjun, G., Keshari, N., Mahboob, M. et al. Characterization and Biocontrol Efficacy of a New Isolate of Steinernema abbasi (Elawad Ahmad & Reid, 1997) Against Spodoptera litura (Fabricius) and Mythimna separata (Walker). Acta Parasit. 70, 205 (2025). https://doi.org/10.1007/s11686-025-01143-7

Image Credits: AI Generated

Viral replication and transmission depend heavily on the virus’s ability to hijack host cellular components. In recent years, membraneless organelles, or biomolecular condensates, have emerged as essential sites where numerous cellular processes converge. Unlike traditional membrane-bound organelles, BMCs form through LLPS, a reversible process allowing the concentration of biomolecules in dynamic compartments, thereby creating specialized microenvironments critical for diverse biological functions. CGMMV, a notorious pathogen among cucurbitaceae crops causing significant agricultural losses worldwide, adeptly commandeers this cellular mechanism by engaging host factors, primarily the enzyme fructose-1,6-bisphosphatase (FBPase), to establish replication niches.

Central to this mechanism is the interaction between the viral capsid protein (CGMMV-CP) and the host cytosolic FBPase, especially the NbFBPase isoform found in Nicotiana benthamiana, a model plant species. The capsid protein specifically binds to NbFBPase, initiating LLPS-driven formation of BMCs within host cells. This intimate interaction promotes the condensation of viral and host factors into concentrated droplet-like structures, providing a protective and efficient hub for viral genome replication and particle assembly. Experimental overexpression of NbFBPase significantly enhances CGMMV propagation, while RNA interference-mediated silencing of NbFBPase markedly restricts viral load, underscoring this host enzyme’s indispensable role.

Delving deeper into the molecular interface, the amino acid residue tyrosine at position 18 (Tyr18) within the CGMMV-CP has emerged as a pivotal determinant for viral pathogenicity. Tyr18 is instrumental not only in mediating capsid assembly but also in driving the biophysical process of LLPS, facilitating the nucleation of BMCs. Mutational analyses reveal that disruption of Tyr18 severely compromises condensate formation and subsequent virion production. This finding unravels a precise viral vulnerability — a potential “Achilles’ heel” — exploitable for antiviral intervention.

Leveraging this molecular insight, the team designed and synthesized compound C1, an innovative benzo[d]oxazol derivative, which targets Tyr18 specifically. Compound C1 exhibits superior inhibitory efficacy against CGMMV compared to established antiviral agents like Ningnanmycin, effectively interrupting the condensate formation by obstructing the crucial Tyr18-driven LLPS pathway. The compound’s mode of action demonstrates a promising antiviral strategy based on perturbing the fundamental biophysical processes essential for viral proliferation, rather than merely inhibiting enzymatic activity or viral entry.

Further transcriptomic analyses illuminate how CGMMV infection, orchestrated via Tyr18, extends its influence beyond viral replication by modulating host photosynthetic pathways. The viral capsid protein alters expression of genes integral to the Calvin cycle, especially the glpX-SEBP locus, which is closely associated with photosynthetic carbon assimilation. Such modulation likely facilitates the reprogramming of host metabolism to optimize conditions conducive to viral replication, illustrating a sophisticated viral strategy to reshape cellular physiology on multiple fronts.

Significantly, evidence indicates that the interaction network centered on Tyr18 and FBPase homologs is conserved across diverse cucurbitaceae species, including economically vital hosts such as cucumber and melon. This broad applicability suggests a universal viral strategy within this plant family, heightening the agricultural relevance of these findings and expanding the potential utility of compound C1 or similar analogues across multiple crops.

Beyond illuminating fundamental virology, these discoveries hold immense potential for green pesticide innovation. By targeting a defined molecular node essential for viral lifecycle progression, this research opens pathways to more sustainable, environmentally responsible disease management methods, reducing reliance on conventional broad-spectrum chemical controls. The specialized specificity of compound C1 minimizes off-target effects and environmental impact, aligning with global efforts to foster agricultural sustainability and food security.

The State Key Laboratory of Green Pesticides at Guizhou University, renowned for its expertise in eco-friendly pest control strategies, spearheaded this experimental study integrating molecular biology, biochemistry, and plant pathology. Their multidisciplinary approach exemplifies cutting-edge science aimed at addressing pressing challenges in agriculture through innovative mechanistic exploration coupled with applied chemical design.

This seminal work not only enriches our conceptual framework of virus-host interactions via biomolecular condensate dynamics but also pioneers a translational research pathway by bridging fundamental mechanistic insights with tangible agrochemical solutions. Given the ever-increasing threat posed by plant viruses to global food supplies, the implications of such targeted antiviral strategies resonate far beyond academic interest, signifying a pivotal advance in crop protection technologies.

In essence, the elucidation of CGMMV’s exploitation of host FBPase through Tyr18-mediated LLPS formation of biomolecular condensates marks a watershed moment in phytovirology. This intricate viral maneuver co-opts a host metabolic enzyme to assemble functional viral factories, a discovery that challenges traditional views of plant-virus interaction paradigms. The successful design of compound C1 ushering in effective inhibition of this process underscores the power of fundamental scientific discovery translated into practical innovation.

As future directions unfold, expanding the structural characterization of these condensates and exploring the full spectrum of CGMMV-host interactomes will further refine antiviral targeting strategies. Additionally, broad-spectrum testing of compound C1 across different cultivars and environmental conditions will validate its field applicability. Collectively, this pioneering research embodies a visionary integration of biophysical virology and chemical biology aimed at safeguarding crop health and resilience.

Subject of Research: Virus-host interaction mechanisms in plants

Article Title: (Information not provided)

News Publication Date: (Information not provided)

Web References:
http://dx.doi.org/10.1016/j.scib.2025.05.012

References:
(Information not provided)

Image Credits:
©Science China Press | Runjiang Song

Keywords:
CGMMV, biomolecular condensates, liquid-liquid phase separation, FBPase, capsid protein, Tyr18, antiviral compound C1, benzo[d]oxazol derivative, plant virology, photosynthesis modulation, cucurbitaceae viruses, green pesticides