Molecular Cloning and Functional Characterization of Galectin-1 in Yellow Drum (Nibea albiflora)

Galectins are proteins that are involved in the innate immune response against pathogenic microorganisms. In the present study, the gene expression pattern of galectin-1 (named as NaGal-1) and its function in mediating the defense response to bacterial attack were investigated. The tertiary structure of NaGal-1 protein consists of homodimers and each subunit has one carbohydrate recognition domain. Quantitative RT-PCR analysis indicated that NaGal-1 was ubiquitously distributed in all the detected tissues and highly expressed in the swim-bladder of Nibea albiflora, and its expression could be upregulated by the pathogenic Vibrio harveyi attack in the brain. Expression of NaGal-1 protein in HEK 293T cells was distributed in the cytoplasm as well as in the nucleus. The recombinant NaGal-1 protein by prokaryotic expression could agglutinate red blood cells from rabbit, Larimichthys crocea, and N. albiflora. The agglutination of N. albiflora red blood cells by the recombinant NaGal-1 protein was inhibited by peptidoglycan, lactose, D-galactose, and lipopolysaccharide in certain concentrations. In addition, the recombinant NaGal-1 protein agglutinated and killed some gram-negative bacteria including Edwardsiella tarda, Escherichia coli, Photobacterium phosphoreum, Aeromonas hydrophila, Pseudomonas aeruginosa, and Aeromonas veronii. These results set the stage for further studies of NaGal-1 protein in the innate immunity of N. albiflora.