Galectin-8 gene belongs to the agglutinin family, which can specifically recognize β-galactoside bonds and play essential roles in many biological processes. In this study, we researched the sequence characteristics and immune-related function of Galectin-8 gene in Japanese flounder Paralichthys olivaceus, named PoGalectin-8. The results showed that the open reading frame of PoGalectin-8 was 891 bp, which encoding a protein with 296 amino acid residues and containing typical HXNPR and WGXEE motifs in the N-terminal and C-terminal CRD domains. Sequence alignment showed that PoGalectin-8 was conserved in different aquatic animals and exhibited the highest similarity (95.27%) with Seriola dumerili. PoGalectin-8 expressed in all detected tissues and exhibited the highest expression level in spleen, followed by skin and kidney. After infected by Edwardsiella tarda, the expression of PoGalectin-8 was down-regulated in the spleen and skin tissues of P. olivaceus. Further to study its immune-related functions, the recombinant PoGalectin-8 (rPoGalectin-8) was expressed and purified. The rPoGalectin-8 can specifically bind to lipopolysaccharide and peptidoglycan, the main components of cell walls from Gram-negative and Gram-positive bacteria. Bacteria binding and the microbial agglutinating experiments showed that the rPoGalectin-8 could bind and agglutinate all examined Gram-positive and Gram-negative bacteria. This study implied that PoGalectin-8, as a pattern recognition receptor, may play important roles during immune responses against bacterial infection, which laid a foundation for further functional identification of Galectin-8 in aquatic animal immunity.

Galectin-8基因属于凝集素家族，可以特异性识别β-半乳糖苷键，并在许多生物学过程中起重要作用。在这项研究中，我们研究了日本比目鱼（Paralichthys olivaceus）GaGalectin-8基因的Galectin-8基因的序列特征和免疫相关功能。结果表明，PoGalectin-8的开放阅读框为891 bp，编码一个具有296个氨基酸残基的蛋白质，在N端和C端CRD域中含有典型的HXNPR和WGXEE基序。序列比对显示PoGalectin-8在不同的水生动物中均被保存，并且与杜氏蚕Seriola dumerili的相似性最高（95.27％）。PoGalectin-8在所有检测到的组织中表达，并在脾脏中表现出最高的表达水平，其次是皮肤和肾脏。在感染爱德华氏菌爱德华氏菌后，PoGalectin-8在橄榄假单胞菌的脾脏和皮肤组织中的表达下调。。为了进一步研究其免疫相关功能，表达并纯化了重组PoGalectin-8（rPoGalectin-8）。rPoGalectin-8可以特异性结合脂多糖和肽聚糖，这是革兰氏阴性和革兰氏阳性细菌细胞壁的主要成分。细菌结合和微生物凝集实验表明，rPoGalectin-8可以结合和凝集所有检查的革兰氏阳性和革兰氏阴性细菌。这项研究表明，PoGalectin-8作为模式识别受体，可能在抵抗细菌感染的免疫反应中起重要作用，这为Galectin-8在水生动物免疫中的进一步功能鉴定奠定了基础。