Novel defensin‐like antimicrobial peptides as promising targets for the control of Bactrocera dorsalis

BACKGROUND: Bactrocera dorsalis (Diptera: Tephritidae), a globally invasive agricultural pest, demonstrates remarkable adaptive resilience and invasive capacity. These traits are closely linked to its robust immune mechanisms, particularly through antimicrobial peptides (AMPs), which directly combat microbial pathogens. RESULTS: Based on a newly assembled B. dorsalis genome, we identified six novel defensin-like AMP genes, collectively designated BdDef-212s. We comprehensively characterized their structural features, spatiotemporal expression patterns, and functional roles in microbial defense and associated immune signaling pathways. Sequence validation confirmed their coding integrity, and motif analysis revealed conserved defensin-like structural signatures. Spatiotemporal expression profiling demonstrated dynamic, pathogen-responsive transcriptional induction of BdDef-212s across developmental stages and tissues. Notably, infections by distinct pathogens consistently upregulated BdDef-212s expression in B. dorsalis. RNA interference (RNAi)-mediated silencing of BdDef-212.1052 significantly impaired immune responses during pathogen exposure. Furthermore, mechanistic exploration identified nuclear transcription factors BdRelish of the immune deficiency (Imd) pathway and BdDif of the Toll pathway as key regulators of BdDef-212s. Intriguingly, cross-activation between these two factors was observed, suggesting a layered regulatory interplay fine-tuning defensin-like AMP expression in B. dorsalis. CONCLUSION: Our findings advance the understanding of dipteran AMPs, provide insights for novel antibiotic discovery and offer promising targets for the biological control of B. dorsalis. © 2026 Society of Chemical Industry.