Involvement of NF-κB transcription factors in antimicrobial peptide gene induction in the red flour beetle, Tribolium castaneum

We previously demonstrated that Tribolium castaneum antimicrobical peptide (AMP) genes can be classified to IMD-dependent group I, Toll-dependent group III and co-dependent group II genes besides non-inducible group IV. Here, we focused on NF-kappa B transcription factor genes, Dill, Dip and Rel, and examined their functions in AMP gene induction as well as linkages to the Toll or IMD pathway. IMD-dependent group I and Toll-dependent group III genes were revealed to be Rel- and Dif-dependent respectively through knockdown experiments, indicating that the pathway specificity of NF-kappa B classes found in Drosophila is also conserved in T. castaneum. The Toll-Dif and IMD-Rel pathways of T. castaneum were activated concomitantly by single microbe species, which may represent a distinctive feature of its immune responses. In addition, Rel knockdown impaired host defense against two model bacterial pathogens. Finally, potential kappa B motifs were searched in the regulatory regions of AMP genes, and relevance to respective NF-kappa B transcription factors was discussed. (C) 2012 Elsevier Ltd. All rights reserved.