In invertebrates, innate immunity was the crucial defending pattern against pathogenic microorganisms. For the past few years, Toll or Toll like receptors (TLRs) signaling pathway was studied extensively in crustaceans. Among the components of Toll or Toll like receptors (TLRs) signaling pathway, tumor necrosis factor receptor-associated factor 6 (TRAF6) acted as an important cytoplasmic adaptor, which was conserved from Drosophila to human. In this study, a new traf6 like gene was cloned from hepatopancreas of P. clarkii. After challenged respectively by S. aureus or E. ictaluri, the expression profiles were studied. And the results showed that the mRNA transcript of Pc-traf6 like gene was up-regulated significantly in the hemocytes, hepatopancreas, gills, and intestine of crayfish. After Pc-traf6 like gene was knocked down, the expression levels of transcription factor (Dorsal) and some crucial immunity effectors (ALF 3, Lysozyme 1, Lectin 1, and Crustin 2) in TLRs signaling pathway were dramatically suppressed. Simultaneously, the survival rate of crayfish challenged respectively by S. aureus or E. ictaluri was significantly decreased in RNAi assay. All these results indicated that Pc-traf6 like gene played an important role in regulating the expression of downstream effectors in the TLRs signaling pathway of crayfish.

Keywords: Antibacterial innate immune; Procambarus clarkii; RNAi; Toll like receptors signaling pathway; Tumor necrosis factor receptor associated factor 6 (TRAF6).