Genome-wide analysis of TRAF gene family and its response to bacterial infection in noble scallop Chlamys nobilis with different carotenoids content

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are multifunctional adaptor proteins in the immune system, which play significant roles in the regulation of Toll-like receptor and RIG-I-like receptor signaling pathway in animals. Although many TRAF genes have been identified in mollusks, the systematic identification of the TRAF gene family in noble scallop Chlamys nobilis has not been reported, and very little is known about its roles in scallop innate immunity. In this study, four TRAF genes (CnTRAF 2, CnTRAF3, CnTRAF4 and CnTRAF6) were identified and characterized from C. nobilis. Sequence and phylogenetic analysis revealed that CnTRAFs contain typical conserved domains closely related to TRAFs of other mollusks. The motifs analysis of C. nobilis CnTRAFs also showed that the conserved motifs were identical to other mollusks and vertebrates. The expression pattern of CnTRAF genes in tissues of brown and golden scallops (the carotenoid content of golden scallops is significantly higher than that of brown scallops) were not statistically significant, but in hemolymph of scallops challenged with bacteria, the expression of CnTRAF genes was significantly higher than that of control, suggesting that the CnTRAF genes play vital roles in the immunity of mollusks. Furthermore, at several time points after bacteria challenge, the expression level of CnTRAF genes in golden scallops were significantly higher than that of brown scallops, indicating that carotenoids may enhance CnTRAF genes expression and immunity. The systematic analysis of the roles of TRAFs in C. nobilis provides valuable information for the further researches of CnTRAF genes.

Automated summary

This study identified and characterized four TRAF genes in noble scallops, revealing their important roles in scallop innate immunity. The expression levels of CnTRAF genes in golden scallops were significantly higher than those in brown scallops, indicating carotenoids may enhance CnTRAF gene expression and immunity. The systematic analysis of the roles of TRAFs in C. nobilis provides valuable information for further research on CnTRAF genes.