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Antifungal activity of gallerimycin encoded in the beet armyworn, Spodoptera exigua
Antimicrobial peptides (AMPs) are a group of immune proteins that protect the host from microial infection. Gallerimycin is one of the AMPs most commonly found in Galleria mellonella and Spodoptera frugiperda. In this paper, we found Gallereimycin in Spodoptera exigua by expressed sequence tag library 0analysis. The gallerimycin of S. exigua gene is 332 bp long and the predicted open reading frame contains 75 amino acids with a signal peptide. After removing signal peptide, S. exigua gallrimycin was estimated to be 5.9 kDa and pI at 8.53. The gallerimycin of S. exigua shared maximum sequence homology with that of S. frugiperda. In naive S. exigua larvae, not much gene expression was detected, but strongly induced in fat body and hemocytes following immune challenge with entomopathogenic bacteria and fungus. A recombinant gallerimycin was prepared using a bacterial expression system and showed significant antibacterial and antifungal activities. RNA interference using double stranded RNA could knock down the expression of gallerimycin and significantly suppressed immune capacity.
