A Novel Defensin Encoded by a Mungbean cDNA Exhibits Insecticidal Activity against Bruchid

A cDNA encoding a small cysteine-rich protein designated VrCRP was isolated from a bruchid-resistant mungbean. VrCRP encodes a protein of 73 amino acids containing a 27 amino acid signal peptide and 8 cysteines. On the basis of the amino acid sequence similarity and conserved residues, it is suggested that VrCRP is a member of the plant defensin family. VrCRP protein was obtained by overexpression of VrCRP with a truncated signal peptide in an IMPACT system. Artificial seeds containing 0.2% (w/w) of the purified VrCRP-TSP were lethal to larvae of the bruchid Callosobruchus chinensis. VrCRP is apparently the first reported plant defensin exhibiting in vitro insecticidal activity against C. chinensis.