Identification and Antimicrobial Characterization of Galectin-2 in Miichthysmiiuy

Galectin-2, a member of the galectin family, functions as an immunoregulatory molecule and plays significant roles in inflammatory responses, apoptosis, and the maintenance of immune homeostasis. In this study, we identified and characterized a galectin from a commercially important marine teleost Miichthys miiuy, designated mmiGal-2. We selected this species for its susceptibility to diverse aquaculture pathogens, rendering it suitable for teleost innate immunity studies. Distinct from mammalian galectins, mmiGal-2 exhibits structural and functional features linked to teleost antimicrobial defenses. Analysis of its gene sequence, structure, and evolutionary pattern revealed conserved functional domains and characteristic phylogenetic relationships. In vitro antibacterial assays demonstrated that the recombinant protein mmiGal-2 displayed differential inhibitory effects on bacterial growth: it showed pronounced activity against Gram-negative bacteria (Vibrio parahaemolyticus, Escherichia coli), whereas only a marginal inhibitory effect was detected against the Gram-positive bacterium Staphylococcus aureus. The expression of mmiGal-2 exhibited significant tissue specificity, with the highest and lowest levels detected in muscle and liver, respectively. Furthermore, RT-qPCR analysis showed that its expression was upregulated over time in the kidney and cells of Miichthys miiuy following immune challenge with lipopolysaccharide (LPS). Using SDS-PAGE and Western Blot, we determined the favorable conditions for the production of the recombinant mmiGal-2 protein: induction with 0.5 mM IPTG at 30 °C for 16 h in a weakly acidic environment (pH 6). This study expands the knowledge on the galectin family in fish and provides new insights and a basis for developing novel antimicrobial agents in aquaculture.