Abstract
Antimicrobial peptides (AMPs) are effective against different plant pathogens and newly considered as part of plant defense systems. From prokaryotes to eukaryotes, AMPs can exist in all forms of life. SM-985 is a cationic AMP (CAMP) isolated from the cDNA library of Mexican teosinte (Zea mays ssp. mexicana). A computational prediction server running with different algorithms was used to screen the teosinte cDNA library for AMPs, and the SM-985 peptide was predicted as an AMP with high probability prediction values. SM-985 is an arginine-rich peptide and composed of 21 amino acids (MW: 2671.06 Da). The physicochemical properties of SM-985 are very promising as an AMP, including the net charge (+8), hydrophobicity ratio of 23%, Boman index of 5.19 kcal/mol, and isoelectric point of 12.95. The SM-985 peptide has amphipathic α-helix conformations. The antimicrobial activity of SM-985 was confirmed against six bacterial plant pathogens, and the MIC of SM-985 against Gram-positive indicators was 8 μM, while the MIC of SM-985 against Gram-negative indicators was 4 μM. The SM-985 interacting with the bacterial membrane and this interaction were examined by treatment of the bacterial indicators with FITC-SM-985 peptide, which showed a high binding affinity of SM-985 to the bacterial membrane (whether Gram-positive or Gram-negative). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the treated bacteria with SM-985 demonstrated cell membrane damage and cell lysis. In vivo antimicrobial activity was examined, and SM-985 prevented leaf spot disease infection caused by Pst DC3000 on Solanum lycopersicum. Moreover, SM-985 showed sensitivity to calcium chloride salt, which is a common feature of CAMPs.
Highlights
Antimicrobial peptides (AMPs), defined as small-molecular-weight proteins, are regarded as one of the substitutes for traditional antibiotics since they are small molecules and often have a wide range of antimicrobial activity, and AMPs have always been acknowledged for their low relative cytotoxicity
Breeding programs and germplasm classification reports have shown that, in general, cultivated plants have comparatively lower rates of resistance to abiotic and biotic stresses compared with their wild ancestors (Rosenthal and Dirzo, 1997). cDNA is a complementary DNA copy of mRNA that is generated by the enzyme reverse transcriptase. cDNA library construction is a powerful tool for determining celland tissue-specific gene expression. cDNA is prepared from mRNA, and it has no inverting sequences such as introns
Scanning Electron Microscopy (SEM) This experiment was performed on C. michiganesis ssp. michiganesis as a representative of other bacterial indicators
Summary
Antimicrobial peptides (AMPs), defined as small-molecular-weight proteins, are regarded as one of the substitutes for traditional antibiotics since they are small molecules and often have a wide range of antimicrobial activity, and AMPs have always been acknowledged for their low relative cytotoxicity. In recent years, many studies have used the cDNA library method to clone AMPs (Ronèeviæ et al, 2018; Wu et al, 2019; Tavares et al, 2020) due to its advantages such as enhanced fragments of efficiently transcribed genes and cloned AMPs from cDNA library, which can be actively manufactured via bacterial expression systems (Sharma et al, 2014) due to the lack of introns that might pose a problem when the target is manufactured as a eukaryotic protein in bacteria. The α-helical AMPs are potent agents in mediating plant defense due to the antibacterial effect (Montesinos, 2007; Keymanesh et al, 2009) Their primary mechanism is to destroy the outer and plasma pathogen membranes, prevent membrane invasion, or pore formation, leading to cell lysis (Holaskova et al, 2014). Bacterial plant diseases are responsible for major losses of crops and agricultural goods, and their protection relies primarily on chemical pesticides (Agrios, 2004). Because of the lack of active compounds, certain plant diseases of economic significance have faced management difficulties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
