Journal
INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY
Volume 118, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ibmb.2020.103314
Keywords
C-type lectin; Encapsulation; Aggregation; Hemocytes; CRISPR/Cas9; Ostrinia furnacalis
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Funding
- National Key R&D Program of China [2017YFD200400]
- National Natural Science Foundation of China [31272091]
- International Foundation for Science [C3680-2]
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C-type lectins participate in hemocytic encapsulation as pattern recognition receptors; however, the molecular mechanisms underlying their function remain unknown. In this study, we determined that the encapsulationpromoting function of a C-type lectin, IML-10, may be related to its interaction with hemocytes in the agricultural pest Ostrinia furnacalis. IML-10 possesses two carbohydrate-recognition domains (CRDs) containing EPN and QPD motifs with 4 and 6 conserved cysteine residues, respectively. IML-10 was found to mainly be secreted by the fat body into the larval plasma, and its expression was induced by Sephadex A-25 beads. Anti-IML-10 antibodies inhibited encapsulation-promoting function of IML-10 in the larval plasma. The encapsulation rate of Sephadex A-25 beads decreased from approximately 90%-30% when expression of IML-10 in O. furnacalis larvae was inhibited by RNAi. Moreover, the Sephadex bead-encapsulating ability of hemocytes decreased to almost zero in O. furnacalis larvae with IML-10 knocked out by CRISPR/Cas9, with IML-10 expression clearly decreasing compared to that of the control. Similar to the larval plasma, recombinant IML-10 promoted Sephadex bead encapsulation by hemocytes. Immunohistochemistry analysis showed that IML-10 was able to bind to the surface of both granulocytes and plasmatocytes but not to Sephadex beads as foreign objects. Furthermore, recombinant IML-10 promoted hemocyte aggregation but not adhesion. Therefore, we speculate that IML-10 binds to the surface of hemocytes to promote their aggregation and further improve their encapsulation capacity. These results contribute to clarifying the function of insect C-type lectins in encapsulation.
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