TmTRAF6 acts as a potential negative modulator of antimicrobial defense in Tenebrio molitor

Tumor necrosis factor receptor-associated factor (TRAF) proteins function as key signaling adaptors in innate immune pathways; however, their regulatory roles in coleopteran insects remain largely unexplored. Here, we identified and characterized a TRAF6 homolog from Tenebrio molitor ( Tm TRAF6) and examined its role in antimicrobial defense. Sequence analysis revealed conserved RING and MATH domains, and phylogenetic clustering grouped Tm TRAF6 with insect TRAF6 orthologs. Upon systemic challenge with Escherichia coli , Staphylococcus aureus , or Candida albicans , Tm TRAF6 transcripts were dynamically induced across multiple tissues, indicating a broad immune responsiveness. Functional analysis using RNA interference demonstrated that silencing of Tm TRAF6 markedly elevated antimicrobial peptide gene expression and significantly enhanced larval survival following infection. These findings contrast with the canonical positive regulatory role of TRAF6 described in other insect models and instead suggest that Tm TRAF6 may operate as a potential pathogen- and tissue-dependent negative regulator of antimicrobial defense. Our results highlight potential evolutionary divergence in TRAF-mediated immune modulation and provide new insight into the plasticity and homeostatic control of innate immune signaling in beetles.