Chemical Proteomics\nReveals That Camptothecin Weakens\nInsect Immunity against Bacteria by Suppressing Antimicrobial Peptide\nExpression

Plant natural products are crucial in defending against\nherbivorous\ninsects and are widely used in pest control, yet their mechanisms\nremain complex and insufficiently studied. This study employed a reverse\nstrategy to investigate the mechanism of camptothecin (CPT), a botanical\npesticide. By using a CPT-based chemical probe coupled with proteomic\nanalysis, immune-related proteins, including those involved in prophenoloxidase\n(PPO) activation and antimicrobial peptide (AMP) synthesis, were identified\nin the Asian corn borer, Ostrinia furnacalis. The findings demonstrated that CPT weakens insect immunity, primarily\nby inhibiting AMP synthesis rather than affecting PPO activation.\nSpecifically, CPT downregulated the expression of genes in the IMD\npathway and those encoding AMPs (attacin and gloverin). Additionally,\nCPT-fed insects exhibited reduced antibacterial activity. This research\nuncovers a novel mechanism of CPT as an insect immunosuppressant,\noffering new insights that may enhance the application of CPT in pest\ncontrol.