Broad-spectrum antimicrobial activity of synthetic peptides GV185 and GV187

• Published in: Plant disease
• Main Authors: Sweany, Rebecca Ruth, Cary, Jeffrey, Jaynes, Jesse M, Rajasekaran, Kanniah
• Format: Journal Article
• Language: English
• Published: United States 01.10.2023
• Subjects: synthetic peptides; Aspergillus flavus; Disease management; aflatoxin; Subject Areas; antimicrobial peptides
• ISSN: 0191-2917
• DOI: 10.1094/PDIS-11-22-2572-RE

Optimizing synthetic antimicrobial peptides for safe and enhanced activity against fungal and bacterial pathogens is useful for genetic engineering of plants for resistance to plant pathogens and their associated mycotoxins. Nine synthetic peptides modeled after lytic peptides tachyplesin 1, D4E1 from cecropin A and protegrin 1 were added to germinated spores of fungal species , , f. sp. , , , , , and bacterial cultures of p.v. and p.v. at different doses and inhibitory dose response curves were modeled to assess antimicrobial activity. 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). (IC50 = 8.1 µM), (IC50 = 3.1 µM) and (IC50 = 2.2 µM) were less inhibited by GV185 and GV187 than all the remaining fungi (IC50 = 1.4 µM) and bacteria (IC50 = 0.1 µM). Of the remaining peptides, GV193, GV195 and GV196 (IC50 range 0.9 to 6.6 µM) inhibited fungal growth of , and less than GV185 and GV187 (IC50 range 0.8 to 3.9 µM), followed by GV197 (IC50 range 0.8 - 9.1 µM) whereas GV190 and GV192 inhibited poorly (IC50 range 28.2 to 36.6 µM and 15.5 to 19.4 µM, respectively) and GV198 stimulated growth. GV185 and GV187 had slightly weaker hydrophobic and cationic residues than other tachyplesin 1 modified peptides, but still had unexpectedly high lytic activity. Germinated fungal spores of and exposed to these two peptides and D4E1 and AGM182 appeared wrinkled with perforations near potential 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 and aflatoxin contamination.