A potent antifungal protein from Helianthus annuus flowers is a trypsin inhibitor

A 16-kDa protein was isolated from Helianthus annuus flowers by its ability to inhibit the germination of fungal spores. This protein, SAP16, displays an associated activity of trypsin inhibitor and was further purified to ap parent homogeneity by affinity chromatography on trypsin-agarose. SAP16 cau ses the complete inhibition of Sclerotinia sclerotiorum ascospores germinat ion at a concentration of 5 mug.mL(-1) (0.31 muM) and a clear reduction of mycelial growth at lower concentrations, indicating a strong antifungal pot ency against this natural pathogen of sunflower. Our data suggest that the antifungal ability of SAP16 would not be the result of the inhibition of a fungal protease. This study contributes to the characterization of the emer ging family of antifungal proteins with an associated activity of trypsin i nhibition and emphasizes their role in plant resistance against fungal atta ck. (C) 2000 Editions scientifiques et medicales Elsevier SAS.