| Invertebrates use pattern recognition receptors (PRRs) to recognize conserved pathogen-associated molecular patterns (PAMPs) and trigger the innate immunity. C-type lectins, as a PRR, is believed to mediate pathogen recognition and the clearance of pathogens. In the current study, we mainly try to explore the functions and mechanisms of C-type lectin 3 (HaCTL3) involved in innate immune response in the cotton bollworm, Helicoverpa armigera.1. rHaCTL3 can specifically recognize and bind to 3 Gram-positive bacteria (Staphylococcus aureus, Microbacterium pumilum, Cellulosimicrobium funkei) and 3 Gram-negative bacteria (Escherichia coli, Vibrio anguillarum, Ochrobactrum cytisi). In addition, the binding activity of rHaCTL3 to S. aureus could be inhibited by peptidoglycan (PGN) and Xylose.2. The expression of HaCTL3 in the fat body of H. armigera could be induced by beads challenge, which suggests HaCTL3 may be involved in encapsulation. Beads coated with rHaCTL3 enhance hemocytes mediated encapsulation and melanization. Besides, both endogenous HaCTL3 protein and exogenous rHaCTL3 could recognize and bind to the surface of eukaryotic Caenorhabditis elegans.3. Western blot demonstrated that HaCTL3 is expressed in the fat body and hemocytes. Meanwhile, HaCTL3 could be detected in plasma during the Wandering stage, which suggests that HaCTL3 protein may be serected into hemolymph to function. Immunocytochemistry showed that HaCTL3 is mainly distributed in granulocytes and oenocytoids. Further, rHaCTL3 could bind to granulocytes, oenocytoids and plasmatocytes.These results indicate that HaCTL3 may play important roles in defending against external pathogens, such as bacteria and parasite. HaCTL3 could recognize and bind to the invading pathogens through some PAMPs, recruit granulocytes, oenocytoids and plasmatocytes, and trigger the cellular response (such as hemocytes-mediated encapsulation and melanization) to kill the pathogens. |
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