Molecular cloning and analysis of a C-type lectin from silkworm Bombyx mori

C-type lectins (CTLs) play a variety of roles in plants and animals. They are involved in animal development, pathogen recognition, and the activation of immune responses. CTLs carry one or more non-catalytic carbohydrate-recognition domains (CRDs) to bind specific carbohydrates reversibly. Here, we report the molecular cloning and functional analysis of a single-CRD CTL, named C-type lectin-S2 (BmCTL-S2) from the domesticated silkmoth Bombyx mori (Lepidoptera: Bombycidae). The ORF of CTL-S2 is 666 bp, which encodes a putative protein of 221 amino acids. BmCTL-S2 is expressed in a variety of immune-related tissues, including hemocytes and fat body among others. BmCTL-S2 mRNA level in the midgut and the fat body was significantly increased by bacterial challenges. The recombinant protein (rBmCTL-S2) bound different bacterial cell wall components and bacterial cells. rBmCTL-S2 also inhibited the growth of Bacillus subtilis and Staphylococcus aureus. Taken together, we infer that BmCTL-S2 is a pattern-recognition receptor with antibacterial activities.