Characterization of gene expression profiles and functional analysis of peptidoglycan recognition protein 2 from rock bream (Oplegnathus fasciatus).

Peptidoglycan recognition protein 2 (PGRP2) is a Zn2+-dependent peptidase that plays important roles in binding to microbial components of the cell membrane, inducing phagocytosis and antimicrobial activity. Rock bream (Oplegnathus fasciatus) PGRP2 (RbPGRP2) was identified in the intestine by next generation sequencing (NGS) analysis. The open reading frame (ORF) the RbPGRP2 cDNA (470 amino acid residues) contains a peptidoglycan recognition protein domain (residues 300 to 446). Alignment analysis revealed that RbPGRP2 shares 37.6-53.5% overall sequence identity with the PGRP2s of other species. Phylogenetic analysis revealed that RbPGRP2 clustered together with PGRP2s from teleosts. In healthy rock bream, RbPGRP2 was found to be ubiquitously expressed in all of the examined tissues, especially in the liver. RbPGRP2 expression was significantly upregulated in all of the examined tissues of rock bream after infection with Edwardsiella piscicida, Streptococcus iniae and red sea bream iridovirus (RSIV) compared with the control. Purified rRbPGRP2 interactions with bacteria and inhibited the growth of bacteria in the presence of Zn2+. These results indicate that RbPGRP2 plays an important role in the innate immune response against bacterial infection.