PNNL

Abstract

The introduction of chemical fungicides for agricultural use initially revolutionized fungal disease control in crops. However, escalating fungal resistance to many of these single-site fungicides calls for the development of new antifungal agents with novel modes of action (MoA). The sequence-divergent cysteine-rich antifungal defensins with multiple MoA are promising starting templates for design of novel biofungicides. Here, we have designed a set of potent 17-amino acid antifungal peptides based on the previously reported antifungal plant defensin MtDef4. These peptides exhibit antifungal properties different from those of MtDef4. The lead peptide GMA4CG_V6 is a random coil in solution with potent cation-tolerant antifungal activity against a plant fungal pathogen Botrytis cinerea. Its multi-site MoA involves disruption of the fungal cell plasma membrane, rapid entry into the vacuole and cytoplasm, and promiscuous binding to phosphoinositides. Topical spray-application of GMA4CG_V6 on Nicotiana benthamiana and tomato plants provides robust preventative and curative suppression of gray mold disease symptoms. Our findings identify short defensin-derived peptides as promising candidates for development as biofungicides.