Molecular cloning and functional analysis of an orange-spotted grouper (Epinephelus coioides) secreted protein acidic and rich in cysteine (SPARC) and characterization of its expression response to nodavirus

Mammalian secreted protein acidic and rich in cysteine (SPARC) is the primary regulator of cell shape and cell adhesion to fibronectin. We, for the first time, report the complete sequencing of SPARC cDNA from orange-spotted grouper. Despite the difference in the lengths of the SPARC transcripts, all of the SPARC molecules encoded a signal peptide, follistain-like copper binding sequence (KGHK) domain, and extracellular domain. The grouper SPARC gene was differentially expressed in vivo and contributed differently to high-level expression of SPARC in muscle. Immunohistochemical staining demonstrated a decreased level of SPARC in nodavirus-infected grouper compared with healthy grouper. Comparative real-time polymerase chain reaction analyses of eye tissues of viral nervous necrosis grouper and healthy grouper were performed. Recombinant SPARC produced changes in grouper cell shape 24 h after treatment. The results provide new insight into the pathogenesis of nodavirus, and demonstrate an experimental rationale for SPARC characterization in nodavirus-infected grouper.