Identification and functional characterization of galectin-3 in silver pomfret ( Pampus argenteus )

Galectin-3, as a unique member of the galectin family, exhibits a significant role in both extracellular and intracellular environments. In this study, the silver pomfret galectin-3 gene (SpGal-3) was cloned and functionally characterized. The open reading frame of SpGal-3 was found to be 843 base pairs in length, encoding a protein of 280 amino acids. Phylogenetic tree analysis indicated that SpGal-3 was highly conserved in fish species. The mRNA of SpGal-3 was expressed at various levels in all tested tissues, with the gill exhibiting the highest expression levels. Furthermore, infection with Photobacterium damselae subsp. damselae significantly changed the mRNA expression of SpGal-3 in liver and head kidney tissues. Subcellular localization analysis suggested that SpGal-3 was expressed in both the nucleus and cytoplasm. Purified recombinant protein of SpGal3, designated as rSpGal-3, showed binding ability to two classic pathogen-associated molecular patterns (peptidoglycan and lipopolysaccharide) and two sugars (D-mannose and D-galactose), with the highest affinity toward lipopolysaccharide. Additionally, rSpGal-3 demonstrated the capability to interact with various bacterial species. Taken together, our findings underscore the critical role of SpGal-3 as a key pattern recognition receptor in the immune response of the silver pomfret.