Abstract
Antimicrobial peptides (AMPs) represent the largest group of endogenous compounds and serves as a novel alternative to traditional antibiotics for the treatment of pathogenic microorganisms. Moricin is an important α-helical AMP plays a crucial role in insect humoral defense reactions. The present study was designed to identify and characterize novel AMP moricin (Px-Mor) from diamondback moth (Plutella xylostella) and tested its activity against bacterial and fungal infection including the opportunistic human pathogen Aureobasidium pullulans. Molecular cloning of Px-Mor using rapid amplification of cDNA ends revealed a 482 bp full length cDNA with 198 bp coding region. The deduced protein sequence contained 65 amino acids, and the mature peptides contained 42 amino acid residues with a molecular mass of 4.393 kDa. Expression analysis revealed that Px-Mor was expressed throughout the life cycle of P. xylostella with the highest level detectable in the fourth instar and prepupa stage. Tissue specific distribution showed that Px-Mor was highly expressed in fat body and hemocyte. In vitro, antimicrobial assays indicated that Px-Mor exhibited a broad antimicrobial spectrum against Gram positive bacteria (GPB), Gram negative bacteria (GNB) and fungi. Moreover, scanning electron microscopy and transmission electron microscopy (TEM) revealed that Px-Mor can cause obvious morphological alterations in A. pullulans, which demonstrated its powerful effect on the mycelia growth inhibition. Taken together, these results indicate that Px-Mor plays an important role in the immune responses of P. xylostella and can be further exploited as an antimicrobial agent against various diseases including for the treatment of A. pullulans infection.
Highlights
Insect-pathogen association can be seen as an evolutionary arms race where pathogen evolves to optimize host infection and its dispersion; in turn, the host activates immune response involving humoral and cellular reaction to defense against the infection
A broad range of Antimicrobial peptides (AMPs) including cecropins, moricins, gloverins, attacins, lebocins, and defensins have been reported in Lepidopteran insects (Ponnuvel and Yamakawa, 2002; Cheng et al, 2006)
We report the characterization of a new antibacterial peptide moricin (Px-Mor) from the lepidopteran insect, P. xylostella
Summary
Insect-pathogen association can be seen as an evolutionary arms race where pathogen evolves to optimize host infection and its dispersion; in turn, the host (insect) activates immune response involving humoral and cellular reaction to defense against the infection. AMPs involved in insect humoral defense reactions and were rapidly secreted into the hemolymph upon microbial infection (Kanost et al, 2004) These AMPs can serve as novel alternatives to traditional antibiotics for the treatment of pathogenic microorganisms due to their broad spectrum of activity, less potential for resistance development, and capability to modulate the host immune response (Mohammad et al, 2015; Mohamed et al, 2016). Moricins are important α-helical cationic AMPs which play an important role in insect humoral defense reactions This type of peptide was initially isolated from the hemolymph of E. coli immunized Bombyx mori larvae (Bm-moricin A1) and contains 42-amino-acid peptide (Hara and Yamakawa, 1995). In-depth studies of the interaction between moricin with the fungal pathogen are not yet performed
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