Venom IMP-L2 from the Ectoparasitoid Scleroderma guani Regulates the IIS/TOR Pathway in Tenebrio molitor

Parasitoid venom significantly influences host physiology and development. Our previous research identified high levels of insulin-binding protein IMP-L2 in the venom of <i>Scleroderma guani</i>. IMP-L2 may inhibit the insulin/insulin-like growth factor signaling (IIS) cascade by competitively binding insulin-like peptides (ILPs) with insulin receptor (InR). However, how to regulate IIS transduction is unclear. We speculate that venom-derived IMP-L2 may bind ILPs to inhibit IIS transduction. Consequently, we investigated the regulation of the IIS/TOR pathway by venom-derived IMP-L2. An expression analysis of IIS/TOR pathway genes across various developmental stages of <i>Tenebrio molitor</i> demonstrated that this pathway governs the entire developmental process. By examining gene expression before and after parasitism, we determined that <i>S. guani</i> predominantly inhibits TOR pathway signaling in <i>T. molitor</i> post-parasitism. Bioinformatics and expression analyses revealed that IMP-L2 is critically involved in Hymenoptera insects, exhibiting high expression in the venom apparatus, and is upregulated in response to <i>S. guani</i> parasitism factors. Additionally, recombinant IMP-L2 was produced via eukaryotic expression. Finally, the recombinant IMP-L2 was found to inhibit the TOR and IIS/TOR signaling pathways at early (6 h) and late (24 h) stages post-injection. Knockdown of <i>IMP-L2</i> in <i>S. guani</i> parasitized <i>T. molitor</i> pupae, resulting in accelerated death of <i>T. molitor</i>. During parasitism, <i>S. guani</i> may suppress host growth and development by modulating the IIS/TOR signaling pathway through venom-derived IMP-L2, potentially affecting host lifespan.