Identification and functional characterization of Tenebrio molitor inhibitor of apoptosis protein 2 (TmIAP2) in the innate immune response.

In Tenebrio molitor, the inhibitor of apoptosis protein 2 (TmIAP2) regulates immune responses; however, the role of TmIAP2 in the induction of antimicrobial peptides (AMPs) remains unexplored. Therefore, this study aimed to dissect the immunomodulatory function of TmIAP2 using RNAi-mediated silencing across whole body and five immune-relevant tissues following infection with Escherichia coli, Staphylococcus aureus, Candida albicans, and Listeria monocytogenes. Transcriptomic profiling revealed pathogen- and tissue-specific upregulation of AMP-related genes coupled with robust activation of NF-κB transcription factors (TmRelish, TmKayak, TmDorX1/2), particularly in response to fungal and Gram-negative challenges. Hemocytes, the gut, and Malpighian tubules emerged as key immunological hotspots. Intriguingly, Gram-positive bacteria elicited muted AMP responses, highlighting differential pathway engagement. Our study identified TmIAP2 as a central immune rheostat, which fine-tunes NF-κB-driven AMP expression to ensure compartmentalized, microbe-specific defense. These findings reveal a conserved IAP-NF-κB axis in insect immunity and provide mechanistic insights into an apoptosis-immune crosstalk pathway that is relevant to pest immunobiology.