Abstract
Antimicrobial peptides (AMPs) are small molecules consisting of less than fifty residues of amino acids. Plant AMPs establish the first barrier of defense in the innate immune system in response to invading pathogens. The purpose of this study was to isolate new AMPs from the Zea mays L. inbred line B73 and investigate their antimicrobial activities and mechanisms against certain essential plant pathogenic bacteria. In silico, the Collection of Anti-Microbial Peptides (CAMPR3), a computational AMP prediction server, was used to screen a cDNA library for AMPs. A ZM-804 peptide, isolated from the Z. mays L. inbred line B73 cDNA library, was predicted as a new cationic AMP with high prediction values. ZM-804 was tested against eleven pathogens of Gram-negative and Gram-positive bacteria and exhibited high antimicrobial activities as determined by the minimal inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs). A confocal laser scanning microscope observation showed that the ZM-804 AMP targets bacterial cell membranes. SEM and TEM images revealed the disruption and damage of the cell membrane morphology of Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato (Pst) DC3000 caused by ZM-804. In planta, ZM-804 demonstrated antimicrobial activity and prevented the infection of tomato plants by Pst DC3000. Moreover, four virulent phytopathogenic bacteria were prevented from inducing hypersensitive response (HR) in tobacco leaves in response to low ZM-804 concentrations. ZM-804 exhibits low hemolytic activity against mouse red blood cells (RBCs) and is relatively safe for mammalian cells. In conclusion, the ZM-804 peptide has a strong antibacterial activity and provides an alternative tool for plant disease control. Additionally, the ZM-804 peptide is considered a promising candidate for human and animal drug development.
Highlights
Antimicrobial peptides (AMPs) are short peptides, usually among 12 and 50 amino acids in length, with broad-spectrum activities against microorganisms
Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) studies have demonstrated that dysfunction of the cell membrane can contribute to ion and metabolite leakage, depolarization, and cell death. These results show that the ZM-804 peptide can kill Gram-positive and Gram-negative bacteria via disrupting the cell membrane, and this is in agreement with most of the previous studies [21,53,58]
minimal inhibitory concentrations (MICs) were determined as the lowest concentration of ZM-804 peptide, which led to the inhibition of 80% growth of bacterial control [83]
Summary
Antimicrobial peptides (AMPs) are short peptides, usually among 12 and 50 amino acids (aa) in length, with broad-spectrum activities against microorganisms. Host defense peptides (HDPs) indicate the vital role of AMPs in preventing most disease infections before any symptoms are induced [3]. Plants’ AMPs are the first barrier defense component in the innate immune system; they are usually generated upon attack by microorganisms and play a vital role in the innate immune system [4,5]. In recent years, emerging AMPs from plants have become a huge challenge to predict their antimicrobial activities against pathogens using computational methods that utilize several algorithms based on strictly defined parameters. Several in silico resources have integrated a wide range of AMPs for many species, such as the Collection of Anti-Microbial Peptides (CAMPR3 ) which presently holds data of 10,247 AMP sequences, 757 structures, and
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