Identification of Galectin 9 and its antibacterial function in yellow drum (Nibea albiflora)

Galectins are a family of evolutionarily conserved lectins that contain carbohydrate recognition domains (CRDs) specifically recognizing beta-galactoside. Galectin-9 plays a crucial role in various biological processes during pathogenic infections. In a previous study, galectin-9 was identified as a candidate gene for resistance to Vibrio harveyi disease in yellow drum using a genome-wide association study (GWAS) analysis. In this study, a galectin-9 gene was identified from Nibea albiflora and named YdGal-9. The mRNA transcripts of YdGal-9 were distributed in all the detected tissues and the highest level was found in the kidney. The subcellular localization of YdGal-9-EGFP proteins was observed in both nucleus and cytoplasm in the kidney cells of N. albiflora. The expression of YdGal-9 in the brain increased significantly after infection with Vibrio harveyi. The red blood cells from rabbits, Larimichthys crocea, and N. albiflora were agglutinated by the purified recombinant YdGal-9 proteins. The results of the agglutination activity of deletion mutants of YdGal-9 proved that the conserved sugar binding motifs (H -NPR and WG-EE-) were critical for YdGal-9's agglutination activity. In addition, YdGal-9 killed some gram -negative bacteria by inducing cell wall destruction including Pseudomonas plecoglossicida, Aeromonas hydro-phila, Escherichia coli, V. parahemolyticus, V. harveyi, and V. alginolyticus. Taken together, these results suggested that the YdGal-9 protein of N. albiflora played a vital role in fighting bacterial infections.

Automated summary

In this study, a galectin-9 gene named YdGal-9 was identified from Nibea albiflora and its role in fighting bacterial infections was examined. The gene was found to be expressed in various tissues, with the highest level in the kidney. The YdGal-9 protein showed agglutination activity on red blood cells and had the ability to kill gram-negative bacteria. These findings suggest that YdGal-9 plays a vital role in the immune response against bacterial infections.