Identification of Nod like receptor C3 (NLRC3) in Asian seabass, Lates calcarifer: Characterisation, ontogeny and expression analysis after experimental infection and ligand stimulation.

Abstract

Nod like receptors (NLRs) are a large group of cytoplasmic PRRs believed to play an important role in bacterial recognition in higher vertebrates. In this study, a novel Nod like receptor C3 (AsNLRC3) has been identified, cloned and characterised from Asian seabass, Lates calcarifer. The full-length AsNLRC3 transcript composed of a 4142bp nucleic acid sequence encode for a protein of 1134 deduced amino acids. Three signature domains identified are conserved NACHT-domain, C-terminal LLR domain and N-terminal CARD effector domain. From the domain architecture and phylogenetic analysis, it was quite evident that AsNLRC3 is different from the NLR subfamily C of other teleosts. AsNLRC3 expressed in all the 11 tissues tested but highly expressed in tissues facing external environment such as gill, hindgut and midgut. The ontogenic expression profile of this receptor showed constitutive expression throughout the embryonic and larval developmental stages, which could be an innate immune strategy against different marine pathogens for larval survival. Infection with Vibrio alginolyticus and poly I:C induction showed an alteration of expression pattern in different tissues but did not show significant alteration in expression with Staphylococcus aureus infection. Invitro study in Asian seabass kidney cell line (SISK) stimulated with different ligands such as LPS, PGN and poly I:C showed considerable up-regulation at some of the time-points tested. These results suggest that AsNLRC3 can be a pivotal cytosolic innate immune receptor for recognizing wide array of pathogens in a euryhaline teleost model like Asian seabass in diverse environmental conditions.