Expression and antimicrobial characterization of rhamnose-binding lectin in Pinctada fucata martensii

Rhamnose-binding lectins (RBLs) are key components of pattern recognition molecules involved in pathogen clearance during non-specific immune responses and play an important role in the immune response of Mollusca. Pinctada fucata martensii is an essential species for artificial seawater pearl cultivation in China. With the increasing pollution of seawater, the study of the immune function of P. f. martensii has become increasingly urgent. Therefore, investigating the basic structural characteristics and immunological activity of RBL is of significant interest. This study employed RACE technology to clone and perform bioinformatics analysis on the RBL from P. f. martensii (PmRBL). Real-time quantitative fluorescence (qRT-PCR) technology was used to analyze gene expression following stimulation with pathogen-associated molecular patterns (PAMPs). In addition, a prokaryotic expression vector for PmRBL was constructed, followed by an evaluation of the antibacterial and hemolytic activities of the recombinant protein. The results revealed that the cDNA sequence of the PmRBL gene is 1045 bp in length, with its open reading frame (ORF) encoding 212 amino acids that include two D-galactoside-binding lectin domains. The expression of PmRBL across various tissues and in response to PAMP stimulation showed that PmRBL was most abundantly expressed in the gill tissue of P. f. martensii and exhibited a significant response to stimulation with lipopolysaccharides (LPS). From the perspective of antibacterial activity, PmRBL exhibited significant efficacy against Gram-negative bacteria. Overall, this study enhances our understanding of the functional characteristics of RBLs in Mollusca and provides new insights into the immune molecular polymorphism of P. f. martensii.