A novel antifungal peptide from foxtail millet seeds

Abstract

Antifungal proteins (AFP) help plants to combat phytopathogenic fungi and thus protect plants from the devastating damage caused by fungal infections and prevent massive economic losses. To date, several proteins with antibacterial and/or antifungal properties have been isolated and characterized from different plant species and tissues; however, there are no reports concerning the antifungal peptide from foxtail millet seeds. An antifungal peptide with a molecular mass of 26.9 kDa was isolated from dry seeds of the foxtail millet (Setaria italica (L.) Beauv.), using a procedure that involved four chromatographic steps. The antifungal peptide was adsorbed on CM-Sepharose, Affi-gel blue gel and Superdex 75. It was further purified by C(18) reverse-phase high-performance liquid chromatography and submitted for analysis of peptide mass fingerprint. The Mascot peptide mass fingerprint of the isolated protein hit no existing protein (score >60), and it was proved to be a novel antifungal peptide. It inhibited mycelial growth in Alternaria alternate with an IC(50) of 1.3 µmol L(-1) , and it also exhibited antifungal activity against Trichoderma viride, Botrytis cinerea and Fusarium oxysporum. Transmission electron microscopy of mold forms of Alternaria alternate after incubation with 20 µg mL(-1) of the antifungal protein for 48 h revealed marked ultrastructural changes in the fungus. A novel antifungal peptide with high potency was isolated from foxtail millet seeds.