<scp> <i>BmDll</i> </scp> regulates appendage morphogenesis in <scp> <i>Bombyx mori</i> </scp> and is a candidate target for <scp>RNA</scp> ‐based control of lepidopteran pests

BACKGROUND: Lepidopteran pests cause major agricultural losses, and overreliance on chemical pesticides raises environmental and health concerns. Genes controlling insect wing development offer promising targets for sustainable pest management. Here, we used the silkworm (Bombyx mori) as a model to investigate the transcription factor BmDll (BmDistal-less) in appendage development and to evaluate its potential as a target for RNA-based biopesticides. RESULTS: CRISPR/Cas9-mediated knockdown of BmDll caused severe defects in adult antennae, thoracic legs, and wings, including shortening, hardening, scale loss and complete wing malformation. Transcriptomic and quantitative real-time PCR (qPCR) analyses revealed that BmDll regulates cell differentiation and chitin assembly primarily through Hox and Notch signaling pathways. We developed chitosan (CS)/dsRNA (double-stranded RNA) nanoparticles targeting BmDll; oral delivery to silkworms and Spodoptera litura suppressed target gene expression and recapitulated the wing deformity phenotypes observed in the knockdown model. CONCLUSION: BmDll is a central regulator of lepidopteran appendage morphogenesis and a feasible target for dsRNA-based biopesticides. Nanoparticle-mediated delivery of BmDll-dsRNA provides a novel, environmentally friendly strategy to disrupt appendage development in pest insects. This work demonstrates the translation of fundamental developmental gene discovery into a potential agricultural application. © 2026 Society of Chemical Industry.