Plant defense peptides

Eight families of antimicrobial peptides, ranging in size from 2 to 9 kD, h ave been identified in plants. These are thionins, defensins, so-called lip id transfer proteins, hevein- and knottin-like peptides, MBPI, IbAMP, and t he recently reported snakins. All of them have compact structure es that ar e stabilized by 2-6 disulfide bridges. They ar-e part of both permanent and inducible defense barriers. Transgenic overexpression of the corresponding genes leads to enhanced tolerance to pathogens, and peptide-sensitive path ogen mutants have reduced virulence. (C) 1999 John Wiley & Sons, Inc.