Identification and functional characterization of a short-type peptidoglycan recognition protein, PGRP-S in the orange-spotted grouper, Epinephelus coioides

Peptidoglycan recognition proteins (PGRPs) are a family of pattern recognition receptors (PRRs) mediating the recognition of peptidoglycan. In the present study, a short-type PGRP gene named Eco-PGRP-S was identified in the orange-spotted grouper (Epinephelus coioides), a major commercial marine fish cultured in Asia. Eco-PGRP-S gene was constitutively expressed in all tissues examined, with the highest expression level observed in gill and skin. As a typical PRR, Eco-PGRP-S is inducible following the stimulation of peptidoglycan, and has an ability to bind peptidoglycan. Importantly, Eco-PGRP-S has been proven to have Zn2+-dependent amidase activity and direct antibacterial activity against Vibrio Harveri and Edwardsiella tarda. In addition, Eco-PGRP-S is mainly localized in cytoplasm and nucleus, and is able to significantly trigger the activation of NF-κB signalling. The present research thus contributes to a better understanding of the molecular mechanism of antibacterial defense and the containment of infectious bacterial diseases in grouper.