Transgenic plants expressing cationic peptide chimeras exhibit broad-spectrum resistance to phytopathogens

Here we describe a strategy for engineering transgenic plants with broad-sp ectrum resistance to bacterial and fungal phytopathogens. We expressed a sy nthetic gene encoding a N terminus-modified, cecropin-melitiin cationic pep tide chimera (MsrA1), with broad-spectrum antimicrobial activity. The synth etic gene was introduced into two potato (Solanum tuberosum L,) cultivars, Desiree and Russet Burbank, stable incorporation was confirmed by PCR and D NA sequencing, and expression confirmed by reverse transcription (RT)-PCR a nd recovery of the biologically active peptide. The morphology and yield of transgenic Desiree plants and tubers was unaffected. Highly stringent chal lenges with bacterial or fungal phytopathogens demonstrated powerful resist ance. Tubers retained their resistance to infectious challenge for more tha n a year, and did not appear to be harmful when fed to mice. Expression of msrA1 in the cultivar Russet Burbank caused a striking lesion-mimic phenoty pe during leaf and tuber development, indicating its utility may be cultiva r specific. Given the ubiquity of antimicrobial cationic peptides as well a s their inherent capacity for recombinant and combinatorial variants, this approach may potentially be used to engineer a range of disease-resistant p lants.