Identification of the active component of an antiviral factor isolated from virus-infected plants

Abstract

Tests were carried out in order to define the active component of an antiviral factor (AVF) produced in Nicotiana glutinosa plants infected with tobacco mosaic virus. This previously described AVF, in a partially purified form, consisted of protein and ribonucleic acid (RNA). Paper electrophoretic analyses of purified, as well as crude, AVF material showed that antiviral activity was associated with the presence of RNA. The nucleic acid fraction of the crude AVF material, or of the purified AVF preparation, was extracted with phenol and found to be RNA. This RNA fraction always exhibited a pronounced antiviral activity, as compared to similar fractions derived from normal, noninoculated N. glutinosa plants. The phenolic extracts of AVF still contained traces of protein, but when treated with trypsin or pronase, their antiviral activity was not affected. Ribonuclease digestion of the phenol-treated AVF preparation resulted in complete loss of the antiviral activity. It was thus concluded that the active component of AVF is RNA.