Broad-spectrum antimicrobial activity of synthetic peptides GV185 and GV187

Authors: Sweany, Rebecca; Cary, Jeffrey; JAYNES, JESSE - Tuskegee University; Rajasekaran, Kanniah - Rajah

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2023
Publication Date: 10/23/2023
Citation: Sweany, R.R., Cary, J.W., Jaynes, J.M., Rajasekaran, K. 2023. Broad-spectrum antimicrobial activity of synthetic peptides GV185 and GV187. Plant Disease. 107(10):3211-3221. https://doi.org/10.1094/PDIS-11-22-2572-RE.
DOI: https://doi.org/10.1094/PDIS-11-22-2572-RE

Interpretive Summary: Corn, peanuts, treenuts and cottonseed contaminated with poisonous and cancer-causing aflatoxin is a major concern for providing safe food and feed to humans and livestock. Aflatoxin contamination is managed by controlling the fungus that produces the toxin, Aspergillus flavus. One strategy is developing crops with resistance to the fungus either through traditional breeding or introducing resistance genes from other sources. Small proteins called peptides from several sources possess antimicrobial activities by lysing or breaking bacterial and fungal membranes and cell walls. We have demonstrated previously that antimicrobial peptides genetically engineered into corn and cotton provided enhanced resistance to the fungus and aflatoxin contamination. In this study we provide the efficacy of two new peptides with greater antimicrobial activity, especially against A. flavus. These will be introduced into corn plants for improved resistance to A. flavus and aflatoxin contamination.

Technical Abstract: Optimizing synthetic antimicrobial peptides for safe, enhanced activity against fungal and bacterial pathogens is useful for genetic engineering of plants for resistance to plant pathogens and contamination with mycotoxins. We assayed nine synthetic peptides modeled after lytic peptides tachyplesin 1, cecropin A and protegrin 1 for antimicrobial activity against fungal species Aspergillus flavus, Rhizopus stolonifer, Fusarium oxysporum f. sp. vasinfectum, F. verticillioides, F. graminearum, Claviceps purpurea, Verticillium dahliae and Thielaviopsis basicola and bacterial species Psuedomonas syringae p.v. tabaci and Xanthomonas campestris p.v. campestris. Peptides GV185 and GV187, modified from tachyplesin 1, had superior abilities to inhibit fungal and bacterial growth (50% inhibitory concentrations or IC50 ranging from 0.1 to 8.7 µM). Rhizopus stolonifer (IC50 = 8.1 µM) , A. flavus (IC50 = 3.1 µM) and F. graminearum (IC50 = 2.2 µM) were less inhibited than the remaining fungi (IC50 = 1.4 µM) and bacteria (IC50 = 0.1 µM). GV185 and GV187 had less hydrophobic and cationic residues than other tachyplesin 1 modified peptides, but still had unexpectedly high lytic activity. Germinated fungal spores exposed to these two peptides and D4E1 and AGM182 appeared wrinkled with perforations leading to cytoplasmic leakage, which provided evidence of plasma membrane and cell wall lysis. We conclude that peptides GV185 and GV187 are promising candidates for genetic engineering of crops for resistance to plant pathogenic bacteria and fungi including A. flavus and aflatoxin contamination.