Molecular cloning and characterization of a C-type lectin from the cotton bollworm, Helicoverpa armigera

C-type lectins participate in pathogen recognition and other defense responses in innate immunity as well as in cell-cell interactions. A new cDNA encoding a 335-residue polypeptide containing two tandem C-type lectin domains was cloned from the haemocytes of Helicoverpa armigera (Ha-lectin). Northern hybridizations revealed that the mRNA of Ha-lectin was expressed constitutively in haemocytes, and was up-regulated following injections of bacteria, yeast, or virus. Ha-lectin expression was also induced in the fat body when larvae were injected with bacteria, yeast or 20-hydroxyecdysone and a non-steroidal ecdysone agonist, RH-2485. The Ha-lectin was detected in granular haemocytes. The recombinant protein (rHa-lectin) expressed in Escherichia coli had hemagglutinating and sugar-binding activities. The native Ha-lectin protein was identified in haemocytes and plasma using a polyclonal antiserum raised against rHa-lectin by immunoblotting techniques. All together, our results suggest that the Ha-lectin gene is involved in innate immunity, and may also participate in the molting process.