Plant defensin peptides have antifungal and antibacterial activity against human and plant pathogens

Authors: SATHOFF, ANDREW - University Of Minnesota; VELIVELLI, SIVA - Danforth Plant Science Center; SHAH, DILIP - Danforth Plant Science Center; Samac, Deborah - Debby

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2018
Publication Date: 3/9/2019
Citation: Sathoff, A.E., Velivelli, S., Shah, D.M., Samac, D.A. 2019. Plant defensin peptides have antifungal and antibacterial activity against human and plant pathogens. Phytopathology. 109:402-408. https://doi.org/10.1094/PHYTO-09-18-0331-R.
DOI: https://doi.org/10.1094/PHYTO-09-18-0331-R

Interpretive Summary: One of the most destructive and yield limiting diseases of alfalfa is crown rot, caused by a complex of fungal and bacterial pathogens. The lack of cultural and chemical management practices for this disease severely limits alfalfa production across the U.S. Thus, innovative methods are needed to manage crown rot for enhanced alfalfa persistence and yields. Plant defensins, small antimicrobial peptides, with known broad activity were tested to identify those with activity against crown rot pathogens. Short, core regions of the defensin peptides predicted activity of full-length native peptides. Two defensins from barrel medic, a plant closely related to alfalfa, showed the greatest activity against crown rot pathogens but did not inhibit growth of nitrogen fixing microsymbionts. Surprisingly, these defensins showed activity against a range of bacterial pathogens from plants and animals. The genes for these peptides can be used to engineer plants for enhanced resistance to multiple pathogens. Plant antimicrobial peptides represent an untapped resource for combating bacteria with resistance to conventional antibiotics and for protection of plants against diseases.

Technical Abstract: Plant defensins are small, cysteine-rich antimicrobial peptides. These peptides have previously been shown to primarily inhibit the growth of fungal plant pathogens. Plant defensins have a gamma-core motif, defined as GXCX(3-9)C, which is required for their antifungal activity. To evaluate plant defensins as a potential control for a problematic agricultural disease, alfalfa crown rot, short chemically synthesized peptides containing gamma-core motif sequences were screened for activity against numerous crown rot pathogens. These peptides showed both antifungal and, surprisingly, antibacterial activity. Core motif peptides from Medicago truncatula defensins (MtDef4 and MtDef5) displayed high activity against both plant and human bacterial pathogens in vitro. Full-length defensins had higher antimicrobial activity compared to the peptides containing their predictive gamma-core motifs. These results show the promise for controlling a wide array of economically important fungal and bacterial plant pathogens through the transgenic expression of a plant defensin. They also suggest that plant defensins may be an untapped reservoir for development of therapeutic compounds for combating human and animal pathogens.