Buckwheat Antifungal Protein with Biocontrol Potential To Inhibit Fungal (Botrytis cinerea) Infection of Cherry Tomato

A 11 kDa antifungal protein FEAP was purified from buckwheat (Fagopyrum esculentum) seed extract with a procedure involving (NH4)(2)SO4 precipitation and chromatography on SP-Sepharose, Affi-gel blue gel, Mono S, and Superdex peptide. Its N-terminal sequence was AQXGAQGGGAT, resembling those of buckwheat peptides F alpha-AMP1 and F alpha-AMP2. FEAP exhibited thermostability (20-100 degrees C) and acid resistance (pH 1-5). Its antifungal activity was retained in the presence of 10-150 mmol/L of K+, Mn2+, or Fe3+ ions, 10-50 mmol/L of Ca2+ or Mg2+ ions, and 50% methanol, 50% ethanol, 50% isopropanol, or 50% chloroform. Its half-maximal inhibitory concentrations toward spore germination and mycelial growth in Botrytis cinerea were 79.9 and 236.7 mu g/mL, respectively. Its antifungal activity was superior to the fungicide cymoxanil mancozeb (248.1 mu g/mL). FEAP prevented B. cinerea from infecting excised leaves, intact leaves, and isolated fruits of cherry tomato. Its mechanism involved induction of an increase in cell membrane permeability and a decrease in mitochondrial membrane potential.