Genome-Wide Identification of Hsp40 in Channel Catfish and Their Involvement in Disease Defense Response

Heat shock proteins (HSPs) consist of a large group of chaperone proteins which can be triggered by exposure to various stress conditions, such as infection, hypoxia, and high temperature. Among all the HSPs, Hsp40 encodes the largest HSP family binding to Hsp70 ATPase domain to assist protein folding and stress release. In this study, we identified 57 Hsp40s genes in channel catfish (Ictalurus punctatus) through in silico analysis using RNA-Seq and genome databases. All these genes can be classified into three different subfamilies, DnaJa, DnaJb and DnaJc, based on their structural similarities. Orthologies were established through phylogenetic and syntenic analyses. Meta-analyses of RNA-Seq datasets were conducted to determine expression profiles of the Hsp40 genes following bacterial infection in channel catfish. Strikingly, a total of 27 Hsp40s were found up- or down- regulated in the liver after E. ictaluri infection, 20 Hsp40s were found regulated in intestine after E. ictaluri infection, and 19 Hsp40s were found regulated in gill following F. columnare infection. These results suggest the involvement of Hsp40 genes in disease defenses in catfish. This is the first systematic analysis of Hsp40 genes and their involvement in disease defense process in channel catfish.