Inducing partial protection in the host plantwith native virus protein

Abstract

A kind of partial protection was achieved by treating half-leaves of Nicotiana glutinosa with dilute native tobacco mosaic virus (TMV) protein solutions, and inoculating with TMV 4 days later. Treatment of leaves with TMV protein 1 day or less before inoculation with TMV did not reduce the number of lesions. A direct inhibiting effect of the dilute protein, therefore, does not seem to be the cause. In subsequent studies this local protection effect against TMV was observed in Datura stramonium. Reduced susceptibility of upper untreated leaves of N. glutinosa and D. stramonium plants whose lower leaves had been treated with TMV protein showed that this type of protection was systemic. A preliminary study with S 35-labeled TMV protein gave no indication of any translocation of the protein per se. TMV protein protected Gomphrena globosa and D. stramonium plants against potato virus X, but not against cucumber mosaic virus in Chenopodium amaranticolor. The effect of TMV protein does not seem to be associated with traces of RNase, which may occur in proteins and differs in its action from that of milk protein, egg albumin, hemoglobin, soya α-protein, and casein. These results suggest the formation of “protective substances” in the plant and their translocation, in analogy to the interferon-induced effect in animal virology.