Properties of infectious ribonucleic acid preparations obtained from tobacco mosaic virus by a heat method

Abstract

A method is described for obtaining ribonucleic acid preparations from tobacco mosaic virus by a brief heat treatment. Such preparations are several times more infectious than previously reported tobacco mosaic virus ribonucleic acid preparations. This level of infectivity, nevertheless, is still low in comparison with natural or reconstituted tobacco mosaic virus. The infectious agent in these preparations differs from tobacco mosaic virus with respect to a number of physical, chemical, and biological characteristics which suggest that a high molecular weight ribonucleic acid is necessary for the infectivity of these preparations. Fractionation of ribonucleic acid preparations by elution from columns of Ecteola or by ultracentrifugation indicates that most of the infectivity in these preparations is associated with only a portion of the ribonucleic acid present. This, and the presence of about 0.5% protein in the RNA preparations, allows the possibility that ribonucleic acid may not be a self-sufficient agent of infection. The infectivity of both tobacco mosaic virus and ribonucleic acid preparations from the virus was found to depend on the total ionic strength of the inoculating medium, the pH, and the presence of phosphate. On the local lesion host Nicotiana glutinosa L., the optimum total ionic strength for infectivity of ribonucleic acid preparations was twice that for optimum tobacco mosaic virus infectivity.