BIRC7 gene in channel catfish (Ictalurus punctatus): identification and expression analysis in response to Edwardsiella tarda, Streptococcus iniae and Channel catfish Hemorrhage Reovirus.

Abstract A family member of inhibitor of apoptosis protein (IAP) termed baculoviral IAP repeat-containing 7 ( BIRC7 ) from channel catfish ( Ictalurus punctatus ) was identified, the full length cDNA sequence of channel catfish BIRC7 ( CcBIRC7 ) was 1686 bp, containing a 5′UTR of 93 bp, a 3′UTR of 399 bp with a poly (A) tail and an ORF of 1194 bp encoding a putative protein of 398 amino acids. The putative CcBIRC7 protein contains two BIR super-family conservative domains and a C-terminal RING finger motif. Phylogenetic analysis showed that catfish CcBIRC7 was moderately conserved with other BIRC7 . Quantitative real-time PCR was conducted to examine the expression profiles of CcBIRC7 in healthy tissues and responding to different pathogens ( Edwardsiella tarda , Streptococcus iniae and Channel catfish Hemorrhage Reovirus (CCRV)). CcBIRC7 was widely expressed in healthy tissues of channel catfish and with the highest 37.28-fold expression in blood. E. tarda and S. iniae could induce CcBIRC7 gene expression drastically in head kidney, liver and spleen, which the peak value reached 31.6-fold, 613.9-fold and 34.4-fold increase by E. tarda infection, and 248.3-fold, 1540.3-fold and 120.4-fold increase post S. iniae challenge, respectively. While, CCRV virus could slightly induce CcBIRC7 expression in head kidney and liver but reduce it in spleen. The result suggested BIRC7 may play a potential role in channel catfish innate immune system against bacterial and virus infections, especially as the anti-bacteria immune gene. This is the first report of BIRC7 gene identification and its expression in fish.