IDENTIFICATION, CHARACTERIZATION AND EXPRESSION PROFILE OF SERUM AMYLOID P-COMPONENT FROM THE BIG-BELLY SEAHORSE (Hippocampus abdominalis)

Pentraxins (PTXs) are humeral lectins which are evolutionarily conserved pattern-recognition molecules in tissue homeostasis and innate immunity. PTXs are divided into the two groups: short pentraxins and long pentraxins. Serum amyloid P component (SAP) is a member of short pentraxin family that play crucial roles in innate immune system which is specified to recognize and eliminate the invading pathogens. Herein, Serum amyloid P-component(SAP) was identified and molecularly characterized from the big-belly seahorse (Hippocampus abdominalis) (designated as ShSAP). The full cDNA sequence of ShSAP was identified from Seahorse cDNA database. In silico analysis was performed to determine the conserved domains and evolutionary position between other orthologs. Quantitative Real-Time PCR (qPCR) was performed to determine the tissue specific distribution and expression profile of ShSAP in response to the pathogenic stress.The full-length ShSAP was 829 bp consisting of 666 bp open reading frame which encodes the polypeptide with 222 amino acids. The deduced ShSAP protein contained pentraxin domain and signal peptide. The phylogenetic result showed that the ShSAP shared significant homology with other SAP orthologs. The ShSAP mRNA was abundantly expressed in liver tissue among the tissues tested, whereas the lowest expression level was observed in heart tissue. After immune challenge experiment with Streptococcus iniae, Edwardsiella tarda and polyinosinic:polycytidylic (poly I:C), the ShSAP mRNA expression levels were significantly up-regulated in liver. Collectively, our investigations suggest that the ShSAP plays an essential role in post immune responses upon the invasion of pathogens.