SYNTHETIC ANTIMICROBIAL PEPTIDE DESIGN

To guide the design of potential plant pathogen-resistance genes, synt hetic variants of naturally occurring antimicrobial gene products were evaluated. Five 20-amino acid (ESF1, ESF4, ESF5, ESF6, ESF13), one 18 -amino acid (ESF12), and one 17-amino acid (ESF17) amphipathic peptide sequences were designed, synthesized, and tested with in vitro bioass ays. Positive charges on the hydrophilic side of the peptide were show n to be essential for antifungal activity, yet the number of positive charges could be varied with little or no change in activity. The size could be reduced to 18 amino acids, but at 17 amino acids a significa nt reduction in activity was observed. ESF1, 5, 6, and 12 peptides wer e inhibitory to the germination of conidia from Cryphonectria parasiti ca, Fusarium oxysporum f. sp, lycopersici, and Septoria musiva but did not inhibit the germination of pollen from Castanea mollissima and Sa lix lucida, ESF12 also had no effect on the germination of Malus sylve stris and Lycopersicon esculentum pollen, but inhibited the growth of the bacteria Agrobacterium tumefaciens, Erwinia amylovora, and Pseudom onas syringae, The minimal inhibitory concentrations of the active ESF peptides were similar to those of the naturally occurring control pep tides, magainin II and cecropin B. The significant differential in sen sitivity between the microbes and plant cells indicated that the activ e ESF peptides are potentially useful models for designing plant patho gen-resistance genes.