Plant defense peptides.

Eight families of antimicrobial peptides, ranging in size from 2 to 9 kD, have been identified in plants. These are thionins, defensins, so-called lipid transfer proteins, hevein- and knottin-like peptides, MBP1, IbAMP, and the recently reported snakins. All of them have compact structures that are stabilized by 2-6 disulfide bridges. They are part of both permanent and inducible defense barriers. Transgenic overexpression of the corresponding genes leads to enhanced tolerance to pathogens, and peptide-sensitive pathogen mutants have reduced virulence.