Molecular identification and expression analysis of two distinct BPI/LBPs (bactericidal permeability-increasing protein/LPS-binding protein) from rock bream, Oplegnathus fasciatus

Abstract

We identified two cDNAs designated as RbBPI/LBP-1 and RbBPI/LBP2, respectively, which were identified by expressed sequence tag (EST) analysis of a lipopolysaccharide (LPS)-stimulated rock bream liver cDNA library. The two cDNA displayed 36.9% identity at the translated amino acid level. Despite the low level of identity between the two genes, high conservation was seen in the BPI/LBP/CETP N-terminal, LPS-binding, the proline-rich central and the BPI/LBP/CETP C-terminal domains. The full-length RbBPI/LBP-1 cDNA (1945 bp) contained an open reading frame (ORF) of 1431 bp encoding 476 amino acids. The full-length RbBPI/LBP-2 cDNA was 2652 bp in length and contained an ORF of 1422 bp encoding 473 amino acids. RbBPI/LBP-1 was significantly expressed in the spleen, liver, intestine and gill. On the other hand, RbBPI/LBP-2 showed significant expression in the kidney, peripheral blood leukocytes, and spleen. Real-time RT-PCR was used to examine RbBPI/LBP-1 and RbBPI/LBP-2 mRNA expression in kidney under conditions of bacterial and viral challenge. Experimental infection of rock bream with Streptococcus iniae, Edwardsiella tarda, and red sea bream iridovirus resulted in significant increases in RbBPI/LBP-1 and RbBPI/LBP-2 mRNA levels in the kidneys, however, the increases in transcription was seen at different time points.