A novel antifungal hevein-type peptide from Triticum kiharae seeds with a unique 10-cysteine motif

Two forms of a novel antimicrobial peptide (AMP), named WAMP-1a and WAMP-1b, that differ by a single C-terminal amino acid residue and belong to a new structural type of plant AMP were purified from seeds of Triticum kiharae Dorof. et Migusch. Although WAMP-1a and WAMP-1b share similarity with hevein-type peptides, they possess 10 cysteine residues arranged in a unique cysteine motif which is distinct from those described previously for plant AMPs, but is characteristic of the chitin-binding domains of cereal class I chitinases. An unusual substitution of a serine for a glycine residue in the chitin-binding domain was detected for the first time in hevein-like polypeptides. Recombinant WAMP-1a was successfully produced in Escherichia coli. This is the first case of high-yield production of a cysteine-rich plant AMP from a synthetic gene. Assays of recombinant WAMP-1a activity showed that the peptide possessed high broad-spectrum inhibitory activity against diverse chitin-containing and chitin-free pathogens, with IC50 values in the micromolar range. The discovery of a new type of AMP active against structurally dissimilar microorganisms implies divergent modes of action and discloses the complexity of plant-microbe interactions.