Characterization and expression analysis of BCA2 gene in large yellow croaker, Larimichthys crocea

BCA2, as an E3 ubiquitin ligase, is an important anti-virus immune factor in mammals. Up to date, there are not any related reports on BCA2 protein in fishes yet. In the present investigation, BCA2 in large yellow croaker Larimichthys crocea (named as LcBCA2) was identified and characterized. The full-length cDNA of LcBCA2 was 1571 bp, including an ORF of 888 bp encoding a polypeptide of 295 amino acids. The putative LcBCA2 protein contained a RING-H2 motif at C terminal. The LcBCA2 transcripts were broadly distributed in all detected tissues, with high expression in muscle, moderate in blood, skin, heart, liver and spleen, weak in other tissue as indicated by qPCR analysis. Significant increases were observed in skin, gill and spleen after infection of Cryptocaryon irritans, and in spleen and head-kidney after inactivated Vibrio. parahaemolyticus, LPS and Poly I:C stimulations. Tissue localization by in-situ hybridization showed that LcBCA2 mainly expressed in the spleen of the fish in the test group. Our findings showed that LcBCA2 inclined to sharply increase in immune organs, especially in head-kidney after bacterial and viral stimulations, while in locations (skin and gill) of parasites infections, suggesting that BCA2 may play an important role in fish defense against bacteria, virus and parasites infections, but the immune mechanisms is are different.