Characterization of a C-Type Lectin Domain-Containing Protein with Antibacterial Activity from Pacific Abalone ( Haliotis discus hannai ).

Genes that influence the growth of Pacific abalone ( Haliotis discus hannai ) may improve the productivity of the aquaculture industry. Previous research demonstrated that the differential expression of a gene encoding a C-type lectin domain-containing protein (CTLD) was associated with a faster growth in Pacific abalone. We analyzed this gene and identified an open reading frame that consisted of 145 amino acids. The sequence showed a significant homology to other genes that encode CTLDs in the genus Haliotis . Expression profiling analysis at different developmental stages and from various tissues showed that the gene was first expressed at approximately 50 days after fertilization (shell length of 2.47 ± 0.13 mm). In adult Pacific abalone, the gene was strongly expressed in the epipodium, gill, and mantle. Recombinant Pacific abalone CTLD purified from Escherichia coli exhibited antimicrobial activity against several Gram-positive bacteria ( Bacillus subtilis , Streptococcus iniae , and Lactococcus garvieae ) and Gram-negative bacteria ( Vibrio alginolyticus and Vibrio harveyi ). We also performed bacterial agglutination assays in the presence of Ca ²⁺ , as well as bacterial binding assays in the presence of the detergent dodecyl maltoside. Incubation with E . coli and B . subtilis cells suggested that the CTLD stimulated Ca ²⁺ -dependent bacterial agglutination. Our results suggest that this novel Pacific abalone CTLD is important for the pathogen recognition in the gastropod host defense mechanism.