Effects of bentonite on infectivity and stability of TMV-RNA

Abstract

Bentonite in sufficient concentration almost completely inhibits the action of pancreatic ribonuclease and permits the near-quantitative removal of the enzyme by centrifugation. In the presence of sufficient bentonite, tobacco mosaic virus ribonucleic acid (TMV-RNA) is completely resistant toward pancreatic ribonuclease, and it is only very slowly inactivated by plant nucleases. TMV-RNA prepared in the presence of bentonite or subsequently treated with bentonite is much more stable when incubated with 0.1 M phosphate in the absence of bentonite than is the untreated RNA. The infectivity of viral RNA is increased about tenfold by addition of bentonite to the test solution or to the leaf surface prior to application of the RNA solution to be assayed. No such potentiating effect is found when the intact virus is used as inoculum. This effect of bentonite is attributed to the in situ inhibition of plant nuclease, the presence of which is believed to limit the infectivity of the exposed viral RNA.