Plant Antimicrobial Peptides (PAMPs): Features, Applications, Production, Expression, and Challenges

Abstract

The quest for an extraordinary array of defense strategies is imperative to reduce the challenges of microbial attacks on plants and animals. Plant antimicrobial peptides (PAMPs) are a subset of antimicrobial peptides (AMPs). PAMPs elicit defense against microbial attacks and prevent drug resistance of pathogens given their wide spectrum activity, excellent structural stability, and diverse mechanism of action. This review aimed to identify the applications, features, production, expression, and challenges of PAMPs using its structure-activity relationship. The discovery techniques used to identify these peptides were also explored to provide insight into their significance in genomics, transcriptomics, proteomics, and their expression against disease-causing pathogens. This review creates awareness for PAMPs as potential therapeutic agents in the medical and pharmaceutical fields, such as the sensitive treatment of bacterial and fungal diseases and others and their utilization in preserving crops using available transgenic methods in the agronomical field. PAMPs are also safe to handle and are easy to recycle with the use of proteases to convert them into more potent antimicrobial agents for sustainable development.

Keywords: PAMPs; biotechnology; drug; engineering; modelling; structure.

Figure 1

Relative gene expression of Snakin-2 in Solanum lycopersicum plants. (A) Diagram of a Solanum lycopersicum plant (Tomato) at the fruit-bearing stage. (B) Relative gene expression levels of SN2, using qRT-PCR, in healthy adult S. lycopersicum plant. SN2 recorded the highest expression in the leaves and flowers, respectively; therefore, further analysis of SN2 activity was conducted on the leaves [70]. (C) Relative gene expression levels of SN2, using qRT-PCR, after infection of tomato plant with pathogenic F. solani. The heatmap represents an upregulation of SN2 expression over 24 h, with the expression of SN2 being highest at the 24 h. This illustrates that the presence of F. solani in the tomato plants strongly increases the expression of the SN2 gene as a defense against pathogenic attack [70].

Figure 2

Schematic diagram of the mode of action of SN2 peptide on Fusarium solani pathogen. (A) The cationic SN2 peptide has a high affinity for the negatively charged cell wall of F. solani, diffusing through the cell wall to initiate pore formation on the biomembrane. This ultimately results in the rupture of the biomembrane, releasing the intracellular contents of the pathogenic cell, killing the F. solani pathogen [71,72]. (B) Cell viability assay conducted on F. solani pathogen treated with SN2 peptide. Trypan Blue dye (0.5%) was used to test the cell viability by infiltrating pathogenic cells with damaged biomembranes and staining these cells. This microscopic image represents that after 10 min of exposing F solani to the SN2 peptide, most of the SN2-treated cells were stained blue compared with the control, indicating SN2 disrupted the biomembrane allowing the dye to penetrate the SN2-treated cells, killing the pathogenic cells [71].

Figure 3

Kinetically control enzymatic peptide synthesis. FE: free enzyme, Acyl-X: acyl donor substrate, E., Acyl-X: acyl-enzyme complex, HX: released group, Acyl-E: acyl-enzyme intermediate, HN: nucleophiles, Acyl-N: target peptide, Acyl-OH: product of hydrolysis.

Figure 4

SUMO fusion protein. A: fusion tag 1, B: fusion tag 2, C: cleavage site, D: PAMP. For example, four interacting SUMO motif domains on the SUMO-ubiquitin E3 ligase RNF4 identify more than 300 peptides in HeLa cells using heat-shock treatment [107].