Cloning and Characterization of Serum Amyloid A (SAA) from Sea Cucumber, Apostichopus japonicus

摘要

Serum amyloid A (SAA) was identified as a specific product of pathogen-induced skin ulcer syndrome in sea cucumber. Up-regulation of SAA transcription was detected in coelomocytes, which exhibits numerous variants of innate recognition and effector molecules. SAA plays an important role in acute responses; however, studies of the role of SAA in acute responses in sea cucumber remain limited. In the present study, the SAA gene was first cloned and characterized from coelomocytes of the sea cucumber Apostichopus japonicus; this species was cultured along the coast of southern China (Yunxiao, Fujian, China). The full-length cDNA of SAA is 983 bp, and it contains a 369 bp open reading frame that encodes 122 amino-acid peptides. SAA mRNA expression in the sea cucumber increased significantly after treatment with the pathogen Vibrio pomeroyi for 24 h and then decreased dramatically after 48 h. The results showed that SAA was one of the major acute-phase reactants following an acute-phase stimulus in the sea cucumber, similar to vertebrates. Tissue distribution analysis revealed that SAA mRNA expression was the highest in the coelomocytes of challenged sea cucumber. These data suggested that SAA might play vital roles in the innate immune system of sea cucumber.