Galectin-1 from blunt snout bream (Megalobrama amblycephala) participates in anti-bacterial immune response through mediating pathogen recognition

Galectins are involved in immune response against pathogenic microorganisms. Here, a prototypic galectin-1 (MaGal-1) from blunt snout bream (Megalobrama amblycephala) was identified and characterized. MaGal-1 comprises an open reading frame spanning 405 bp and encodes a deduced protein of 134 amino acids, containing one single carbohydrate recognition domain, in which two strictly conserved motifs were detected. MaGal-1 transcript was ubiquitously detected in detected tissues with higher expression in muscle, liver and spleen, and its expression was up-regulated in head-kidney liver and spleen after injection with LPS and Aeromonas hydrophila. Sublocalization analysis revealed that MaGal-1 was mainly distributed in the cytoplasm and nucleus of EPC cells. The rMaGal-1 agglutinated markedly Staphylococcus aureus, Escherichia coli and A. hydrophila. Notably, rMaGal-1 bound five different bacteria, which was inhibited by LPS, glucose and trehalose. Besides that, rMaGal-1 could remarkably inhibit the growth of three types of bacteria in vitro. Furthermore, rMaGal-1 destroyed bacterial cell membrane as confirmed by PI staining and SEM observation. Collectively, these findings indicated that MaGal-1 recognized and killed a wide range of microbes and played the vital role in innate immune, which sets the stage for further studies of antibacterial functions of galectins in teleost fish.