Binding of Orysata lectin induces an immune response in insect cells

In mammals, plant lectinshave been shown to possess immunomodulatory properties, acting in both the innate and adaptive immune system to modulate the production of mediators of the immune response, ultimately improving host defences. At present, knowledge of immunomodulatory effects of plant lectins in insects is scarce. Treatment of insect cells with the Orysa sativa lectin, Orysata, was previously reported to induce cell aggregation, mimicking the immune process of encapsulation. In this project we investigated the potential immunomodulatory effects of this mannose-binding lectin using Drosophila melanogaster S2 cells. Identification of the Orysata binding partners on the surface of S2 cells through a pull-down assay and proteomic analysis revealed 221 putative interactors, several of which were immunity-related proteins. Subsequent qPCR analysis revealed the upregulation of Toll- and immune deficiency (IMD)-regulated antimicrobial peptides (Drs, Mtk, AttA, and Dpt) and signal transducers (Rel and Hid) belonging to the IMD pathway. In addition, the iron-binding protein Transferrin 3 was identified as a putative interactor for Orysata, and treatment of S2 cells with Orysata was shown to reduce the intracellular iron concentration. All together, we believe these results offer a new perspective on the effects by which plant lectins influence insect cells and contribute to the study of their immunomodulatory properties.