Some properties of infectious ribonucleic acid from broad bean mottle virus

Abstract

Ribonucleic acid (RNA) preparations, containing no more than 0.37% protein and selectively destroyed by snake venom phosphodiesterase, had specific infectivities up to 28% relative to that of RNA in intact broad bean mottle virus (BBMV). The infectivity of such RNA preparations sedimented in density gradient tubes with 17 S RNA not at the 83 S rate characteristic for the virus. Sedimentation-viscosity measurements showed a molecular weight of about 1 × 10 6 for the isolated infectious RNA. No infectivity could be associated with a 7 S RNA component which was isolated from part of the virus population from old infections. Labeling experiments indicated that the 7 S RNA did not result from the bentonite-phenol extractions, but rather originated inside particles inside the plant; a progressive loss of specific infectivity for both the isolated virus and its RNA resulted. This degradation may offer a general explanation for in vivo specific infectivity decrease, often associated with recovery from disease.