Search Results (199)

Bacillus thuringiensis Cry toxins are well known for their high insecticidal activity against Lepidoptera, Diptera, and Coleoptera and have been widely used in Bt transgenic crops. However, their activity against Hemipteran aphids remains relatively low. Identifying novel Cry proteins and elucidating their action mechanisms can facilitate the development of effective aphid control strategies. In this study, we found that ingestion of Cry2Ab12 did not kill Myzus persicae adults but significantly reduced their offspring number and exerted a lethal effect on M. persicae nymphs. After identifying Cry2Ab12 toxin-binding proteins in M. persicae, we further characterized the interaction with Obg-like ATPase 1 (OLA1), a conserved protein involved in growth regulation. Bio-layer interferometry (BLI), ELISA, and enzyme activity assays revealed that Cry2Ab12 and OLA1 do not interact directly. Interestingly, heat shock protein 60 (HSP60) was shown to mediate the interaction among Cry2Ab12, HSP60, and OLA1, leading to inhibition of OLA1 enzymatic activity. Based on these findings and bioinformatics simulations, we proposed a mechanistic model for Cry2Ab12 toxicity against M. persicae: upon ingestion of a sufficient amount of Cry2Ab12, the formation of the Cry2Ab12–HSP60–OLA1 complex impairs the cellular stress response, disrupts normal OLA1 expression, and ultimately restricts larval growth and development, resulting in lethality. This study provides new insights into the action of Cry toxins in aphids and offers a basis for developing enhanced aphid biocontrol strategies. Full article

The Asian corn borer, Ostrinia furnacalis, is a major pest in China and across East and Southeast Asia, serving as the primary target of Bt maize expressing Cry proteins. Evolution of resistance to Bt toxins represents a critical challenge in plant protection. The high-dose/refuge strategy is more effective when resistance is recessively inherited and fitness costs are present. Here, we characterize the inheritance pattern and fitness costs of Cry1Ab resistance in O. furnacalis using a resistant strain exhibiting a resistance ratio of >1400-fold. The LC₅₀ values of F₁ hybrids from reciprocal crosses between resistant and susceptible strains were 2.44 (1.90–3.12) μg/g and 2.01 (1.53–2.61) μg/g, respectively, with no significant difference, indicating autosomal inheritance. The effective dominance (h) of F₁ offspring decreased with increasing concentration, suggesting that resistance was concentration-dependent. Analysis of observed versus expected mortality in backcross progeny (F₁ × resistant strain) indicated that Cry1Ab resistance is likely governed by more than one genetic locus. Compared with the susceptible strain, resistant individuals exhibited prolonged larval development (18.6 d vs. 17.2 d, p < 0.001), reduced pupation (42.5% vs. 60.8%, p < 0.001) and adult emergence rates (60.3% vs. 87.8%, p < 0.001), while fecundity was not significantly affected. These results verify the existence of fitness costs associated with Bt resistance. Our findings provide important insights into the mechanistic basis of Cry1Ab resistance and will assist in designing proactive management strategies to delay resistance evolution in field populations of O. furnacalis. Full article

To elucidate the mode of action of Mpp5Ab1 against Colaphellus bowringi Baly larvae, this study aimed to identify midgut proteins interacting with the toxin. A validated bait plasmid, pBT3-SUC-mpp5Ab1, was used to screen a larval midgut cDNA library via the split-ubiquitin yeast two-hybrid system. A total of 33 positive clones representing five distinct proteins were obtained, among which bioinformatic analyses prioritized three candidates: Cb-RP-L23e, Cb-CTSL, and Cb-TsetseEP. Subsequent bimolecular fluorescence complementation (BiFC) assays in Sf9 cells specifically confirmed interactions between Mpp5Ab1 and both Cb-CTSL and Cb-TsetseEP, whereas no fluorescence signal was observed for Cb-RP-L23e. Molecular docking further supported stable interactions between Mpp5Ab1 and the validated candidate proteins through hydrogen bonds, salt bridges, and hydrophobic interactions. These findings suggest that Cb-CTSL and Cb-TsetseEP may function as candidate interacting proteins associated with the activity of Mpp5Ab1 in the larval midgut of C. bowringi. Overall, this study provides new insight into the molecular interactions of Mpp5Ab1 and establishes a foundation for future functional studies on its insecticidal mechanism and receptor validation. Full article

Bradysia odoriphaga is a devastating soil pest of Allium tuberosum (Chinese chive), and current control relies heavily on chemical insecticides. Cry39Ab1 toxins from Bacillus thuringiensis (Bt), which are highly toxic to B. odoriphaga, offer an environmentally friendly alternative. However, its mechanism of action remains unclear. In this study, we identified the involvement of vacuolar H⁺-ATPase subunit A (V-ATPase A) in Cry39Ab1 insecticidal activities. The full-length cDNA sequences of BoV-ATPase A was contained 1659 bp open reading frame (ORF), encoding a protein of 552 amino acids with a calculated molecular weight of 59 kDa and an isoelectric point of 9.11. Successful expression and purification of BoV-ATPase A (with GST and His tags) and Cry39Ab1 (with GST and His tags) proteins were achieved. GST pull-down assays demonstrated a direct interaction between recombinant BoV-ATPase A and activated Cry39Ab1 toxin in vitro. Heterologous expression of BoV-ATPase A in Cry-insensitive Sf9 cells conferred susceptibility to Cry39Ab1, resulting in a significant increase in cytolysis compared with control cells. Finally, RNAi-mediated knockdown of BoV-ATPase A in larvae significantly decreased their susceptibility to Cry39Ab1, as evidenced by a marked decrease in mortality. This is the first report that BoV-ATPase A is a key protein required for Cry39Ab1 toxicity, revealing its insecticidal mechanism and establishing BoV-ATPase A as a potential target for pest control. Full article

Immature ladybeetles and lacewings can thrive by feeding on eggs of lepidopteran pests, such as Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae). However, considering that the survival and fitness performances of generalist predators are heavily dependent on their ability to select suitable prey, we first evaluated whether eggs of S. frugiperda strains with differential susceptibilities to Bacillus thurigiensis (Bt) toxins would affect the food preference of larvae of the ladybeetle Coleomegilla maculata DeGeer (Coleptera: Coccinellidae) and the lacewing Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae). We further determined, for the first time, the functional responses of all immature phases of both predator species when fed with S. frugiperda eggs. In our choice bioassays, predator larvae were individually offered 25 eggs of each S. frugiperda strain. The number of consumed eggs was recorded hourly and replenished during each evaluation. For the functional responses, increasing densities of S. frugiperda eggs were offered to the larvae of lacewings and ladybeetles, and the number of consumed eggs was recorded 24 h after the release of the predator. Ch. externa larvae had a generalized preference for Bt-susceptible strains of eggs, while Co. maculata exhibited such a preference only during the first evaluation hour. Both predators displayed type II functional responses, and their consumption substantially increased during larval development. By demonstrating that lacewing and ladybeetle larvae can satisfactorily consume S. frugiperda eggs, including eggs from Bt-resistant individuals, our findings reinforce the potential of these predatory insects for the ecological management of S. frugiperda. Full article

Low Bt toxin concentration in seeds results in low insecticidal efficacy in transgenic Bt cotton. In order to improve the insecticidal efficacy of seeds, two treatments with different amino acid combinations (5 amino acids comprising aspartic acid, glutamic acid, proline, methionine, and arginine; and 21 amino acids) were applied to two Bt cotton cultivars at peak boll stages in 2021 and 2022. The results showed that the amino acid treatments enhanced the seeds’ Bt toxin concentration by 13.5–34.2% compared with the untreated control in a two-year study. However, the difference for the Bt toxin was not significant between the two amino acid treatments. In the seeds, Bt toxin levels correlated positively with amino acid and soluble protein contents, as well as Glutamic-Pyruvic Transaminase (GPT) and Glutamate Oxaloacetate Transaminase (GOT) activities. Conversely, negative correlations were observed between the Bt toxin and the activities of protease and peptidase. Compared with the control, hazard boll rates were also reduced following application of the two amino acid combinations, while no difference was observed between the two amino acid treatments. Because the two treatments performed similarly, these results suggest that applying a simpler combination of five amino acids is an effective and efficient strategy for enhancing the insecticidal efficacy of cotton seeds. Full article

With the large-scale cultivation of transgenic Bacillus thuringiensis (Bt) crops, the Bt toxin released from Bt crops is continuously introduced into the soil. Its environmental fate represents a key indicator for assessing the ecological safety of transgenic crops. However, the persistence of Bt toxin in soil is influenced by both biotic and abiotic processes, and their respective contributions under natural conditions remain unclear. This study measured water-dissolved Bt toxin concentrations in paddy soil (PS) and red soil (RS) to compare the influence of biotic and abiotic factors on the dynamic retention of exogenous Bt toxin under different sterilization methods: no sterilization, heat sterilization (HT), and irradiation sterilization (IS). The water-dissolved Bt toxin exhibited a dynamic decrease–increase–decrease trend across all three treatments in both soil types during the 30 day experimental period. Bt toxin displayed rapid adsorption during the initial 2 h stage in RS, but subsequently showed a high desorption, whereas PS probably achieved more stable bonding through soil organic matter (SOM). Different sterilization methods significantly influenced the results by altering abiotic factors: Compared to CK, HT affected soil physicochemical properties and enhanced adsorption resilience, whereas IS caused minimal impact on the soil physicochemical properties, thereby providing a more accurate reflection of abiotic processes. And microbial, as biotic facters, also influence the reduction process of Bt toxin by participating in the adsorption–desorption–degradation equilibrium process. Therefore, we infer that over time, the concentration of water-soluble Bt proteins in the soil will tend toward zero. Additionally, the initial Bt toxin concentration influenced dynamic balance by adjusting adsorption site saturability, with more pronounced desorption reversibility at 500 ng/g concentrations. Overall, this study systematically reveals the effects of soil properties, microorganisms, and sterilization methods on Bt toxin persistence. The findings underscore the importance of selecting and justifying sterilization methods in related environmental behavior studies, while providing essential guidance for the scientific assessment of environmental risks posed by transgenic crops. Full article

Insecticidal proteins derived from Bacillus thuringiensis (Bt) have been effectively employed in controlling lepidopteran pests, notably in transgenic crops targeting Spodoptera species. However, concerns have arisen regarding the long-term efficacy due to the emergence of tolerant and resistant insect populations. Prior research suggested that repeated exposures to Bt, which contains a mixture of spores and crystals, may contribute to the development of tolerance; however, the specific effects of sequential exposure to purified Cry1 and Vip3Aa proteins remain unclear. This study aimed to assess whether prior exposure of Spodoptera exigua neonate larvae to sublethal concentrations of Cry1Ab, Cry1Ca or Vip3Aa proteins would heighten their tolerance upon subsequent exposure, and whether such effects would extend to their offspring. Pre-exposure to Cry1Ab or Vip3Aa did not affect larval responses to the toxin. For Cry1Ca, a slight increase was observed under one treatment condition, but the effect was not considered biologically relevant. Transgenerational analysis revealed no enhancement of tolerance; rather, there was a negative impact on the offspring’s response in some cases. These findings indicate that although previous studies have documented that sublethal contact with bacterial preparations may significantly affect insect tolerance, exposure to sublethal doses of purified Cry1 and Vip3Aa proteins is unlikely to lead to the development of tolerance in S. exigua. Full article

Bacillus thuringiensis (Bt) is one of the most extensively used microbial insecticides, attributed to the action of insecticidal crystal proteins (ICPs), primarily Cry toxins, which mediate damage to the insect midgut epithelium. Recent evidence suggests that Bt toxicity is also strongly influenced by its physiological state and interactions with the host gut environment. Biofilm formation represents an important adaptive strategy that enhances bacterial stress tolerance and may modulate insecticidal performance, although the underlying mechanisms remain unclear. However, it is still unclear how Bt in the biofilm state alters host responses at the structural and transcriptomic levels. Using the tea plantation pest Ectropis grisescens as a model, we systematically evaluated the insecticidal efficacy of biofilm-state Bt formulations and their synergistic effects with a biofilm inducer system composed of Tween-80, tea saponin, matrine, and tea polyphenols. Bioassays showed that the biofilm-state Bt supplemented with composite inducers achieved the highest corrected mortality and reduced the LC₅₀ against neonate larvae by 2.88-fold compared with conventional planktonic Bt. Histopathological, biochemical, and transcriptomic analyses further revealed that biofilm-state Bt caused more severe midgut damage and induced extensive remodeling of detoxification- and stress-response-related pathways. These findings highlight Bt physiological state as a critical determinant of formulation efficacy and provide a novel framework for Bt optimization through microbial physiological regulation. Full article

Field-evolved resistance of Helicoverpa zea to crops expressing Cry insecticidal proteins from Bacillus thuringiensis (Bt) is widespread across the United States. To comparatively evaluate physiological factors associated with Bt susceptibility, we analyzed two laboratory strains (Benzon and SIMRU) and one field colony obtained from a commercial corn field near Pickens, Arkansas. Biochemical assays of larval midgut extracts showed that Pickens exhibited significantly altered activities of chymotrypsin-like proteases, aminopeptidase N (APN), and alkaline phosphatase (ALP) compared with the SIMRU or Benzon colonies, with differences varying by larval instar. In contrast, trypsin-like protease activities did not differ significantly among the three colonies. Gene expression analyses of ten serine protease genes and seven candidate Cry receptor genes (including cadherin, ATP-binding cassette family C2, ALP, and four APN genes) revealed significant transcriptional differences in the Pickens relative to the lab colonies. Collectively, these results suggest that chymotrypsin-like proteases may play an important role in the activation of Cry toxins in H. zea. Altered chymotrypsin and APN activities, together with differential gene expressions in the Pickens population, likely contribute to reduced Bt susceptibility. The biochemical and molecular differences provide insight into potential physiological factors underlying reduced Bt susceptibility and may inform future Bt resistance monitoring and management strategies. Full article

Bt Cry toxins remain the cornerstone of transgenic crop protection against Lepidopteran pests, yet field-evolved resistance, particularly in invasive species such as Spodoptera frugiperda and Helicoverpa armigera, can threaten their long-term efficacy. This review presents a comprehensive and unified mechanistic framework that synthesizes current understanding of Bt Cry toxin modes of action and the complex, multilayered regulatory mechanisms of field-evolved resistance. Beyond the classical pore-formation model, emerging evidence highlights signal transduction cascades, immune evasion via suppression of Toll/IMD pathways, and tripartite toxin–host–microbiota interactions that can dynamically modulate protoxin activation and receptor accessibility. Resistance arises from target-site alterations (e.g., ABCC2/ABCC3, Cadherin mutations), altered midgut protease profiles, enhanced immune regeneration, and microbiota-mediated detoxification, orchestrated by transcription factor networks (GATA, FoxA, FTZ-F1), constitutive MAPK hyperactivation (especially MAP4K4-driven cascades), along with preliminary emerging findings on non-coding RNA involvement. Countermeasures now integrate synergistic Cry/Vip pyramiding, CRISPR/Cas9-validated receptor knockouts revealing functional redundancy, Domain III chimerization (e.g., Cry1A.105), phage-assisted continuous evolution (PACE), and the emerging application of AlphaFold3 for structure-guided rational redesign of resistance-breaking variants. Future sustainability hinges on system-level integration of single-cell transcriptomics, midgut-specific CRISPR screens, microbiome engineering, and AI-accelerated protein design to preempt resistance trajectories and secure Bt biotechnology within integrated resistance and pest management frameworks. Full article

Plant nutrient content is spatially and temporally dynamic, exposing insect herbivores to substantial nutritional variability. Such variability can constrain insects to feeding on sub-optimal diets, but it can also allow them to regulate their intake towards an optimal nutrient balance. Nutrient regulation is important in pest management, as the nutritional state of insects may alter their susceptibility to insecticides. Diet macronutrient balance has been shown to significantly affect the susceptibility of Helicoverpa zea larvae to endotoxins produced by transgenic crops containing Bacillus thurigiensis (Bt) genes. However, this was demonstrated using a highly inbred laboratory strain, limiting extrapolation to field populations. Here, we test the impact of field-relevant macronutrient variability on the efficacy of two Bt toxins across three field populations to increase the relevance to resistance monitoring and management. While differences in susceptibility were limited across populations, dietary effects were highly population specific. The Bt toxin that was most affected by diet and the diet that supported optimal survival and performance varied across populations. These findings indicate that nutrition can strongly influence Bt susceptibility, but these effects are influenced by population-level differences. To accurately assess Bt susceptibility in the field, bioassay diets should be tailored to the nutritional ecology of local populations. Full article

This study systematically evaluated insect resistance in transgenic poplar lines carrying three distinct Bacillus thuringiensis (Bt) gene vector architectures: a single-gene pb vector (Cry1Ac), a reverse-oriented double-gene n19 vector (Cry1Ac-Cry3A), and a forward-oriented double-gene n5 vector (Cry3A-Cry1Ac). The transgenic lines were accordingly designated as pb8/pb9, n19a/n19b, and DB7/DB16, respectively. Molecular analyses confirmed stable Bt gene integration, with the expression of Cry3A being consistently higher than that of Cry1Ac expression. Bioassays showed that dual-gene lines conferred broader insect resistance to pests than that of single-gene lines against both lepidopteran (Hyphantria cunea) and coleopteran (Plagiodera versicolora, Anoplophora glabripennis) pests. In contrast, the single-gene line pb9 exhibited specialized, high efficacy against H. cunea, achieving 100% mortality. Transcriptomic analysis of P. versicolora larvae fed the double-gene high-resistance n19a line and low-resistance DB16 line revealed multi-level molecular responses to Bt stress, including up-regulation of toxin-activating proteases, altered receptor expression, and suppression of growth-related genes. These changes were associated with significant developmental delay (8.33–20.83% reduction in the molting index). Our findings characterize the insect resistance and molecular profiles of the six transgenic poplar lines, as follows: multi-gene lines (n19a/n19b and DB7/DB16) confer broad-spectrum pest resistance, whereas single-gene lines (pb8/pb9) exhibit targeted efficacy. These results support the utility of these lines for pest-specific poplar breeding programs. Full article

In cervical dystonia (CD), balance and gait impairments can compromise daily activities and negatively affect quality of life. However, interventions addressing these deficits remain poorly investigated. A 54-year-old woman with CD, presenting balance and gait difficulties that interfered with work-related motor tasks, underwent a four-month training program. Sessions (40 min, three times per week) combined lower-limb strengthening, proprioceptive and balance exercises, and integrated motor–cognitive tasks. Pre- and post-intervention assessments included gait speed (GS), stride length (SL), and stance time (ST) under usual (UW), fast (FW), and dual-task (DT) walking conditions, measured with an inertial sensor (BTS G-Walk). DT cost was calculated for GS and SL. Balance was evaluated with the Mini-BEST and Four-Square Step Test (FSST), while fear of falling was measured with the Falls Efficacy Scale-International (FES-I). Of note, both assessment sessions were conducted in the absence of botulinum toxin effects, whereas the training was performed, at least in part, under its influence. After training, increase were observed in GS and SL, with reductions in ST across all gait conditions. DT cost decreased for both GS and SL. Balance performance increased, and fear of falling was reduced. Importantly, the patient reported a marked improvement in work-related performance. This case suggests that a specific training program may effectively ameliorate balance and gait in CD, with positive effects on functional mobility. Further studies on larger samples are warranted to confirm efficacy. Full article

Bradysia difformis is a notorious pest in mushroom production in China. Biological control using Bacillus thuringiensis (Bt) offers an environmentally friendly and effective strategy against this pest. Here, we show that the complete genome of strain JW-1 consists of one circular chromosome and seven circular plasmids. JW-1-Plasmid 4 comprises 127,921 bp with a GC content of 33.9%, and is predicted to contain 131 genes, including six insecticidal genes: cry4Aa, cry4Ba, cry10Ab, cry11Aa, cyt1Aa, and cyt2Ba. A 3542-bp fragment containing the cry4Aa gene was amplified from this strain. Phylogenetic analysis based on Cry4 toxin sequences showed that JW-1 Cry4 toxin belongs to the Cry4Aa toxin cluster. A Cry4Aa fusion protein was subsequently expressed in E. coli and purified using Ni-IDA affinity chromatography. A larval feeding assay showed that purified Cry4Aa was toxic to B. difformis larvae, with an LC₅₀ of 2.71 ng/mL. These results confirmed the identity and bioactivity of Cry4Aa from strain JW-1, offering a promising biological control agent against this major pest. Full article