Galectin is a kind of lectin that can promote the cell adhesion, proliferation, and phagocytosis and participates in immune regulation and destruction of microbes. In this study, a galectin-related protein (On-GRP) homolog was identified from Nile tilapia, and its expression level and antibacterial ability were studied. The Open Reading Frame, which encoded a 179 amino acid protein (GenBank accession no: XM_005733705.1), was 537 bp. The On-GRP possessed a carbohydrate recognition domain. qRT-PCR showed that the On-GRP was detected in the examined tissues in healthy Nile tilapia, and the highest expression levels was observed in the skin. After challenge with Streptococcus agalactiae, the On-GRP expression was up-regulated significantly (P < 0.05) in the whole blood, head kidney, gills and thymus. In addition, the recombinant On-GRP (rOn-GRP) could agglutinate and bind Streptococcus agalactiae and Aeromonas hydrophila. In vitro and in vivo bacteriostatic tests showed that the rOn-GRP could inhibit the growth of bacteria. Besides, the rOn-GRP could promote the phagocytic ability of macrophages to engulf bacteria. Over all, this study indicated On-GRP is involved in the immune responses of Nile tilapia against bacterial pathogens.

半乳糖凝集素是一种能促进细胞粘附、增殖和吞噬作用并参与免疫调节和破坏微生物的凝集素。本研究从尼罗罗非鱼中鉴定出一个半乳糖凝集素相关蛋白（On-GRP）同源物，并对其表达水平和抗菌能力进行了研究。编码 179 个氨基酸的蛋白质（GenBank 登录号：XM_005733705.1）的开放阅读框为 537 bp。将在-GRP拥有的碳水化合物识别区域。qRT-PCR 显示在健康尼罗罗非鱼的检查组织中检测到On-GRP，并且在皮肤中观察到最高表达水平。用无乳链球菌攻击后，On-GRP在全血、头肾、鳃和胸腺中表达显着上调（P < 0.05）。此外，重组On-GRP (rOn-GRP) 可以凝集和结合无乳链球菌和嗜水气单胞菌。体外和体内抑菌试验表明，rOn-GRP 可以抑制细菌的生长。此外，rOn-GRP 可以促进巨噬细胞吞噬细菌的吞噬能力。总的来说，这项研究表明On-GRP参与了尼罗罗非鱼对细菌病原体的免疫反应。