Purification and partial characterization of a lectin from the midgut of the worker honeybee (Apis mellifera)

Isolation and characterization of a mid-gut derived lectin  from honeybee (Apis mellifera)

Abstract

Lectins are central components in the innate immune response of insects. They have been isolated from various insect tissues, including hemolymph, fat body, and gut, and their presence typically correlates with their specific immune or physiological functions. Although hemocyte-associated lectins, such as hemolectin (Hml), have been well characterized for their roles in clotting and encapsulation, the biological functions of midgut-derived lectins remain largely unknown in the honey bee (Apis mellifera). The midgut is one of the first lines of defence that regulates the molecular effectors of the immune system. Here, we report the isolation of a low-molecular-weight (~40 kDa) galactose/mannose-specific lectin from the midgut of the worker honey bee. Functional assays have shown that Apis lectin strongly binds to carbohydrate moieties, acts as a specific ligand for sugars, has a direct bacteriostatic effect on E. coli, and can induce bacterial aggregation. In particular, the melanization response in hemolymph was greatly upregulated after the treatment with lectin. This indicates the coordinating role of lectin in both cellular and humoral immunity. Our study provides the first evidence of functional activity for the gut-derived lectin in A. mellifera. These findings open new avenues for research on caste- and task-specific immune modulation, as foragers, nurse bees, and queens are subject to varying pathogen pressures.