Molecular Identification and mRNA Expression Profiles of Galectin-9 Gene in Red Sea Bream (Pagrus major) Infected with Pathogens

SIMPLE SUMMARY: We identified the sequence encoding galectin-9 from Pagrus major and subsequently investigated the molecular characteristics and changes in gene expression patterns in response to artificial infection with major pathogens. Overall, our data suggest that galectin-9 plays a pivotal role in the immune system of P. major. The findings of this study can potentially serve as a reference for understanding the function of galectin-9 in the P. major immune system; moreover, galectin-9 has been identified as a potential candidate for use as a disease-related molecular marker. ABSTRACT: Galectin (Gal) is a member of a family of β-galactoside-binding lectin. The members of this family play important roles in the recognition of carbohydrate ligands and in various other biological processes. In this study, we identified the gene encoding Gal-9 in Pagrus major (PmGal-9) and analyzed its expression in various tissues after pathogen challenge. Alignment analysis revealed that the two galactose-binding lectin domains of the deduced protein were highly conserved among all the teleosts. Phylogenetic analysis revealed that PmGal-9 is most closely related to the Gal-9 gene of gilthead sea bream. PmGal-9 was ubiquitously expressed in all tissues analyzed but was predominantly expressed in the spleen, head kidney, and intestine. After challenges with major microbial pathogens (Edwardsiella piscicida, Streptococcus iniae, or red sea bream iridovirus) of red sea bream, PmGal-9 mRNA expression was significantly regulated in most immune-related tissues. These results suggested that PmGal-9 not only plays an important role in the immune system of red sea bream but is also a possible inflammatory marker for pathogenic diseases.