Tumor necrosis factor receptor-associated factor 6 (TRAF6) participates in peroxinectin gene expression in Fenneropenaeus penicillatus

Abstract

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an important 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. In the study, the full-length cDNA of a TRAF6 homolog (FpTRAF6) was identified from Fenneropenaeus penicillatus. The full-length cDNA of FpTRAF6 is 2033 bp long, with an open reading frame (ORF) encoding a putative protein of 594 amino acids, including a RING type Zinc finger, two TRAF-type Zinc fingers, and a conserved C-terminal meprin and TRAF homology (MATH) domain. The overall amino acid sequence identity between FpTRAF6 and other TRAF6s ranged from 62.7 to 94.1% for crustaceans and from 45.6 to 59.3% for mollusca. Real-time qRT-PCR indicated that FpTRAF6 was constitutively expressed in various tissues of F. penicillatus. The temporal expression patterns of FpTRAF6 mRNA were different in the different tissues after microbial challenge. FpTRAF6 was downregulated in the heart, no obvious changes in the gill, intestine and hemocytes, and upregulated in other tested tissues after WSSV challenge. After V. alginolyticus injection, FpTRAF6 was downregulated in the heart and intestine, upregulated in the gill, lymphoid organ and hematopoietic organ, and no obvious changes in other tested tissues. RNAi assay was carried out to investigate the function of FpTRAF6. The results showed that silencing FpTRAF6 gene could inhibit peroxinectin expression in vivo, and enhance the sensitivity of shrimps to WSSV and V. alginolyticus challenge, suggesting FpTRAF6 could play a positive role against bacterial and viral pathogens. In conclusion, the results of the study provide some insights into the function of FpTRAF6 in activating TLRs signaling pathway and the host defense against invading pathogens.