Isolation of a virus inhibitor from plants with localized infections

Abstract

Systemic resistance was induced in the leaves of Datura stramonium L., Nicotiana glutinosa, Phaseolus vulgaris var. Prince, and Chenopodium amaranticolor by localized infection with tobacco mosaic or necrosis viruses (TMV, TNV). Crude extracts prepared from the resistant leaves were more inhibitory to TNV infection on Phaseolus than were extracts from non-resistant (control) leaves. Subsequently, crude extracts were fractionated into protein and ribonucleic acid (RNA) and inhibitory activity from resistant areas was retained in the RNA preparation. The RNA from resistant and non-resistant leaves was purified and separated into three fractions (about 27 S, 17 S, and 3 S), by gel filtration on Sephadex G-200. The 27-S and 17-S fractions from both treatments inhibited TNV infection by similar amounts. However, the 3-S RNA from resistant leaves reduced lesion number to a greater extent when compared to both the 3-S RNA from control leaves and the 27-S and 17-S RNA from either treatment. The lowest molecular weight RNA isolated from systemic-induced resistant areas gave positive tests with orcinol reagent and had an absorption spectrum characteristic of a nucleic acid. When treated with pancreatic ribonuclease and mixed with TNV, inhibition no longer occurred.