Purification and cDNA cloning of a defensin in Brassica juncea, its functional expression in Escherichia coli, and assessment of its antifungal activity

Abstract

We describe the purification, cDNA cloning, and characterization of a defensin, AFP1, in Brassica juncea, which shares 100% amino acid sequence identity with Raphanus sativus defensin (Rs-AFP1) and has a high antifungal activity against Magnaporthe oryzae. The recombinant AFP1 synthesized in Escherichia coli showed thermostability and antifungal activity against a broad spectrum of rice pathogenic fungi. The changes of a negative to positive charge at the surface of AFP1 derived by amino acid substitutions showed more enhanced antifungal activities than the wild-type AFP1.