Effect of a novel antifungal peptide P852 on cell morphology and membrane permeability of Fusarium oxysporum.

P852, a novel cyclic peptide isolated from Bacillus amyloliquefaciens L-H15, showed potent antifungal activity against several major plant fungal pathogens including Fusarium oxysporum. To elucidate the antifungal mechanism, the impact of P852 on the cell morphology and membrane permeabilization of F. oxysporum was studied. By applying electron microscopy and fluorescent techniques, we showed that P852 treatment caused the morphological change of F. oxysporum cells and disrupted its cell structure, including formation of blebs, broken hyphae, deformation of membrane, intracellular organization disruption, pore formation, and cell lysis. Our findings provide insights into the mode of action of P852, which laying a foundation to develop P852 as a novel antifungal agent to control plant fungal pathogens.

[Roles of spermidine in induced resistance of cucumber seedlings to Botrytis cinerea Pers].

Under the conditions of root substrate injection and foliar spray of different concentration spermidine, this paper measured the disease index, defense enzyme activities, and contents of disease resistance-related substances in cucumber (Cucumis sativus L.) seedlings infected by Botrytis cinerea Pers., aimed to investigate the roles of spermidine in induced resistance of cucumber seedlings to B. cinerea. The results showed that after treated with spermidine, the disease index decreased by 25.4%, phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) activities increased by 48.4%, 635.9% and 38.9%, respectively, and total polyphenol, flavonoid and lignin contents increased significantly, compared with the control. All of these suggested that spermidine could induce the disease resistance of cucumber seedlings, and its optimum concentration was 150 mg L(-1).