Isolation and characterization of an inducer protein (Crip-31) from Clerodendrum inerme leaves responsible for induction of systemic resistance against viruses

A novel protein Crip-31 responsible for systemic induced resistance (SIR) against CMV, PVY and ToMV infection in susceptible host Nicotiana tabacum, was purified from the leaves of Clerodendrum inerme, The inducer molecule Crip-31 is proteineous, basic in nature, having hydrophobic residues and 31 kDa in molecular mass. Minimum amount of purified preparation sufficient for systemic resistance induction was similar to 25 mug ml(-1). Treatment of plants with purified Crip-31 induced a very high degree of localized, as well as systemic resistance against CMV, PVY and ToMV infection. Resistance induction was detectable between 40 and 60 min after challenge inoculation with viruses on the systemic host (N, tabacum). The resistance inducing activity of this biomolecule was not affected with the proteinase K treatment. Its properties are close to ribosome inactivating proteins (RIPs) possessing antiviral properties. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.