Rhamnose-binding lectins (RBLs), a Ca²⁺-independent lectin family, are able to recognize varieties of pathogens and involve in the innate immune response. In this study, an L-rhamnose-binding lectin-like (OnRBL-1) was identified and functionally characterized from Nile tilapia (Oreochromis niloticus). The open reading frame of OnRBL-1 is 702 bp encoding 233 amino acids. The sequence of OnRBL-1 has relatively conservative characteristic peptide motifs, including YGR, DPC, and KYL-motif. Expression analysis showed that OnRBL-1 was abundantly distributed in liver tissue, and widely existed in all detected tissues. Meanwhile, the expressions of OnRBL-1 increased significantly in vivo (liver, spleen, head kidney, intestine, gills and peripheral blood) and in vitro (hepatocytes) following challenges with two important tilapia pathogenic bacteria Streptococcus agalactiae and Aeromonas hydrophila. Moreover, the recombinant OnRBL-1 was expressed and purified, which was found to bind and agglutinate S. agalactiae and A. hydrophila. Overall, This study indicated that OnRBL-1 may function as an important pattern recognition molecule, possessing recognition and agglutination activity to bacterial pathogens, thus involving in the innate immune defense of O. niloticus.

鼠李糖结合凝集素 (RBL) 是一种不依赖 Ca ^{2+ 的}凝集素家族，能够识别多种病原体并参与先天免疫反应。在这项研究中，从尼罗罗非鱼 ( Oreochromis niloticus ) 中鉴定了一种 L-鼠李糖结合凝集素样 (OnRBL-1) 并对其进行了功能表征。OnRBL-1的开放阅读框是 702 bp，编码 233 个氨基酸。OnRBL-1 的序列具有相对保守的特征肽基序，包括 YGR、DPC 和 KYL-基序。表达分析表明OnRBL-1在肝脏组织中大量分布，广泛存在于所有检测到的组织中。同时，OnRBL-1在体内的表达显着增加(肝、脾、头肾、肠、鳃和外周血) 和体外(肝细胞) 两种重要的罗非鱼病原菌无乳链球菌和嗜水气单胞菌的挑战。此外，所述重组OnRBL-1中表达并纯化，发现其结合和凝集无乳链球菌和嗜水气。总体而言，本研究表明OnRBL-1可能作为一种重要的模式识别分子，对细菌病原体具有识别和凝集活性，从而参与O. niloticus的先天免疫防御。