LAUSR

ABSTRACT Tumor necrosis factor receptor‐associated factor 6 (TRAF6) is a key cytoplasm signal adaptor that mediates signals activated by tumor necrosis factor receptor (TNFR) superfamily and the Interleukin‐1 receptor/Toll‐like receptor (IL‐1/TLR) superfamily. The full‐length 2492 bp TRAF6 (Sp‐TRAF6) from Scylla paramamosain contains 1800 bp of open reading frame (ORF) encoding 598 amino acids, including an N‐terminal RING‐type zinc finger, two TRAF‐type zinc fingers and a conserved C‐terminal meprin and TRAF homology (MATH) domain. Multiple alignment analysis shows that the putative amino acid sequence of Sp‐TRAf6 has highest identity of 88% with Pt‐TRAF6 from Portunus trituberculatus, while the similarity of Sp‐TRAF6 with other crustacean sequences was 54–55%. RT‐PCR analysis indicated that Sp‐TRAF6 transcripts were predominantly expressed in the hepatopancreas and stomach, whereas it was barely detected in the heart and hemocytes in our study. Moreover, Sp‐TRAF6 transcripts were significantly up‐regulated after Vibrio parahemolyticus and LPS challenges. RNA interference assay was carried out used by siRNA to investigate the genes expression patterns regulated by Sp‐TRAF6. The qRT‐PCR results showed that silencing Sp‐TRAF6 gene could inhibit SpALF1, SpALF2, SpALF5 and SpALF6 expression in hemocytes, while inhibit SpALF1, SpALF3, SpALF4, SpALF5 and SpALF6 expression in hepatopancreas. Taken together, the acute‐phase response to immune challenges and the inhibition of SpALFs gene expression indicate that Sp‐TRAF6 plays an important role in host defense against pathogen invasions via regulation of ALF gene expression in S. paramamosain. HighlightsA novel signal adaptor in the Toll/TLR signaling pathways, Sp‐TRAF6, was characterized from the mud crabs.Be highly induced upon bacterial challenges.Sp‐TRAF6 plays an important role in host defense via regulation of ALFs gene expression.