EFFECT OF CECROPIN-B ON PEACH PATHOGENS, PROTOPLASTS, AND CELLS

The aim of this study was to determine the effect of cecropin B on peach cells and bacterial pathogens of peach for assessing the feasibility of introducing the cecropin gene into peach for pathogen protection. Cecropin B, a lytic peptide, caused depolarization of the plasmalemma, as determined by the change in fluorescence of cells and protoplasts stained with merocyanine 540, and impaired the integrity of the plasmalemma, as determined by fluorescein diacetate staining. Both protoplasts and cells were more affected by cecropin B when isolated in highly osmotic solutions of the non-penetrating osmoticum mannitol or in solutions containing low calcium. Cells were more sensitive than protoplasts to cecropin B under increased osmoticum, but less sensitive under low calcium. Under conditions of high calcium and low osmotic potential, cells were unaffected by 10 mu M cecropin B but were rendered non-viable by about 100 mu M. Lethal concentrations of cecropin B on peach pathogens Xanthomonas campestris pv. pruni and Pseudomonas syringae pv. syringae were at 0.1-0.5 mu M. These findings suggest that it will be feasible to introduce the gene for cecropin B into peach cells for enhancing the resistance against bacterial pathogens.