RNA interference (RNAi) is widely used for functional genomics and is an emerging eco-friendly alternative to chemical pesticides. Its success depends on the delivery of double-stranded RNA (dsRNA), which is processed into small interfering RNAs (siRNAs) that silence essential target genes. While design rules for siRNA are well studied in humans, their direct application to insects is limited. The study by Cedden et al. addressed this gap by systematically testing insect-specific siRNA features to improve dsRNA design for pest control.
Researchers tested 31 siRNAs inserted into a non-targeting dsRNA backbone and delivered them into Tribolium castaneum larvae. They analyzed larval survival outcomes and mapped RISC-bound siRNAs through small RNA sequencing. Predictive models including thermodynamic asymmetry, GC content, and sequence motifs were evaluated. In parallel, the team designed and compared full-length dsRNAs optimized with their new algorithm (dsRIP) across multiple essential insect genes and pest species.
- Key Features Identified: Insecticidal efficacy correlated with siRNA thermodynamic asymmetry, absence of secondary structures, adenine at the 10th antisense position, and high GC content (9–14 nt).
- Cross-Species Validation: Optimized dsRNAs showed higher lethality in T. castaneum, Psylliodes chrysocephala, and Leptinotarsa decemlineata.
- Mechanistic Insight: RISC-bound sRNA-seq revealed optimized dsRNAs produced significantly more antisense siRNAs, explaining higher knockdown efficiency.
- Practical Impact: dsRIP-designed dsRNAs outperformed commercial products such as Ledprona at lower concentrations, offering higher mortality and feeding inhibition.
Survival analysis of Psylliodes chrysocephala and Leptinotarsa decemlineata fed with dsRIP-optimized dsRNAs shows significantly higher insecticidal efficacy compared to previous or commercial dsRNA designs.
Cedden et al. demonstrated that dsRNA design rules derived from human systems are not fully transferable to insects. By experimentally identifying insect-specific sequence features and validating them across species, the authors established dsRIP, a web platform integrating target gene selection, dsRNA optimization, and off-target minimization. This resource improves both research applications and practical pest management, advancing the deployment of RNAi as a sustainable, species-specific pest control tool.