It is well known that insect larval midgut cadherin protein serves as a receptor of Bacillus thuringiensis (Bt) crystal Cry1Ac or Cry1Ab toxins, since structural mutations and downregulation of cad gene expression are linked with resistance to Cry1Ac toxin in several lepidopteran insects. However, the role of Spodoptera frugiperda cadherin protein (SfCad) in the mode of action of Bt toxins remains elusive. Here, we investigated whether SfCad is involved in susceptibility to Cry1Ab or Cry1Fa toxins. In vivo, knockout of the SfCad gene by CRISPR/Cas 9 did not increase tolerance to either of these toxins in S. frugiperda larvae. In vitro cytotoxicity assays demonstrated that cultured insect TnHi5 cells expressing GFP-tagged SfCad did not increase susceptibility to activated Cry1Ab or Cry1Fa toxins. In contrast, expression of another well recognized Cry1A receptor in this cell line, the ABCC2 transporter, increased the toxicity of both Cry1Ab and Cry1Fa toxins, suggesting that SfABCC2 functions as a receptor of these toxins. Finally, we showed that the toxin-binding region of SfCad did not bind to activated Cry1Ab, Cry1Ac, nor Cry1Fa. All these results support that SfCad is not involved in the mode of action of Cry1Ab or Cry1Fa toxins in S. frugiperda.

ARG1 catalyzes the conversion of L-arginine to L-ornithine, urea, polyamines, and L-proline, thereby balancing nitrogen detoxification with tissue-specific roles in proliferation and immunity. This review delineates the context-dependent functions of ARG1 across diverse cell types—including tumor cells, immune cells, endothelial cells, keratinocytes, and stem cells. In tumors, ARG1 drives immunosuppression and metabolic reprogramming but can paradoxically suppress tumorigenesis. Immune modulation via ARG1-polyamine crosstalk regulates T cell differentiation, macrophage polarization, and microbiota interactions, influencing infection and autoimmunity. Endothelial ARG1 exacerbates obesity-related vascular dysfunction, while keratinocyte ARG1 impacts wound healing and psoriasis. Emerging therapies—such as ARG1 inhibitors, engineered extracellular vesicles, and microbiome interventions—show preclinical promise in cancer, cardiovascular, and neurodegenerative diseases. By mapping ARG1’s spatiotemporal metabolic networks, this work highlights its dual roles and positions ARG1 as a central player for precision medicine in complex pathologies.

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.

The fall armyworm Spodoptera frugiperda is a globally invasive pest that severely threatens major crops such as maize. Although RNAi holds great promise for pest control, its efficiency in Lepidoptera is often limited by rapid degradation of dsRNA mediated by gut dsRNases. Here, we identified and functionally characterized a key dsRNA-degrading nuclease, SfdsRNase3, from the midgut digestive fluid of S. frugiperda. SfdsRNase3 exhibited strong midgut-enriched expression and robust dsRNA degradation activity, indicating its central role in RNAi inefficiency. To overcome this barrier, we developed a chitosan-based nanoparticle system to enhance dsRNA stability and delivery. Chitosan encapsulation significantly improved dsRNA protection, cellular uptake, and the duration of gene silencing in both in vitro and in vivo assays. Moreover, co-RNAi and CRISPR/Cas9-mediated knockout of SfdsRNase3 markedly reduced gut dsRNA degradation and significantly enhanced RNAi efficiency against target genes such as SfCHS, resulting in increased larval mortality and severe developmental defects. Overall, this study reveals the pivotal role of SfdsRNase3 in limiting RNAi efficiency in S. frugiperda and proposes a synergistic strategy combining nuclease targeting with nanocarrier-mediated dsRNA delivery. These findings provide both mechanistic insights and practical approaches for improving RNAi-based pest control in Lepidoptera.