The γ-Core Motif Peptides of AMPs from Grasses Display Inhibitory Activity against Human and Plant Pathogens

Abstract

Antimicrobial peptides (AMPs) constitute an essential part of the plant immune system. They are regarded as alternatives to conventional antibiotics and pesticides. In this study, we have identified the γ-core motifs, which are associated with antimicrobial activity, in 18 AMPs from grasses and assayed their antimicrobial properties against nine pathogens, including yeasts affecting humans, as well as plant pathogenic bacteria and fungi. All the tested peptides displayed antimicrobial properties. We discovered a number of short AMP-derived peptides with high antimicrobial activity both against human and plant pathogens. For the first time, antimicrobial activity was revealed in the peptides designed from the 4-Cys-containing defensin-like peptides, whose role in plant immunity has remained unknown, as well as the knottin-like peptide and the C-terminal prodomain of the thionin, which points to the direct involvement of these peptides in defense mechanisms. Studies of the mode of action of the eight most active γ-core motif peptides on yeast cells using staining with propidium iodide showed that all of them induced membrane permeabilization leading to cell lysis. In addition to identification of the antimicrobial determinants in plant AMPs, this work provides short candidate peptide molecules for the development of novel drugs effective against opportunistic fungal infections and biopesticides to control plant pathogens.

Transcriptome-Wide Identification and Expression Analysis of Genes Encoding Defense-Related Peptides of Filipendula ulmaria in Response to Bipolaris sorokiniana Infection

“…In our previous work, we showed that the γ-cores of wheat and tomato defensins with RGFRRR sequence display strong antimicrobial activity against a broad spectrum of plant and human fungal and bacterial pathogens [83,84]. For example, the IC 50 for pathogen inhibition by the wheat DEFL1-16 γ-core with RGFRRR sequence was 4.4 µM for Cryptococcus neoformans, 14.6 µM for Candida albicans, 12.1 µM for Fusarium oxysporum, 20.7 µM for Fusarium culmorum and 14.6 µM for Clavibacter michiganensis [84]. From these data on RGFRRR-sequence-containing defensins we can conclude that F. ulmaria FuDEFL1-2 and FuDEFL1-3 are indeed antimicrobial peptides.…”