Lnc40766-TLR6-miR14-3p Regulation Pathway Mediates the Immunity of Plutella xylostella against Entomopathogenic Fungus Isaria cicadae.

The diamondback moth Plutella xylostella is a major agricultural pest with severe insecticide resistance. Entomopathogenic fungi (EPF) serve as eco-friendly biocontrol. Insects rely on immunity to resist fungal invasion, while the regulatory mechanism of long non-coding RNAs (lncRNAs) in insect antifungal immunity remains unclear. Here, lncRNA-mediated immune responses of P. xylostella against EPF Isaria cicadae were explored. RNA-seq identified 33,402 lncRNAs, 97 of which were predicted to cis-regulate 72 immune genes. The lnc40766 targets Toll-like receptor 6 (TLR6); both were upregulated post-fungal infection, whereas miR14-3p was downregulated. Biochemical assays verified the binding relationships among lnc40766, TLR6, and miR14-3p. RNA interference (RNAi) assays indicate that TLR6 plays an important role in the Toll pathway, and lnc40766 enhances host antifungal defense, whereas miR14-3p negatively regulates immunity via TLR6. This study reveals a novel lnc40766-TLR6-miR14-3p regulatory pathway, providing promising targets for optimizing the EPF-based pest biocontrol.