Replication of RNA-1 of Tomato Black Ring Virus Independently of RNA-2

Abstract

SUMMARY In hybridization experiments, using complementary DNA (cDNA) copies of the two genome parts of tomato black ring virus (TBRV RNA-1 and RNA-2), no sequence homology between the two RNA species was detected. When tobacco mesophyll protoplasts were inoculated with purified middle component particles, which contain only RNA-2, no replication of TBRV RNA could be detected. However, when they were inoculated with purified bottom component particles, which contain only RNA-1, extracts made 24 or 48 h later contained RNA that had the same mobility as RNA-1 in polyacrylamide-agarose gels, and that hybridized to cDNA copies of RNA-1. Thus RNA-1 can replicate in protoplasts that do not contain RNA-2. Moreover, this RNA-1 was capable, when mixed with nucleoprotein particles containing RNA-2, of inducing the formation of local lesions in Chenopodium amaranticolor leaves, and therefore was intact and attached to the genome-linked protein. The genome-linked protein of nepoviruses is probably virus-coded, and its production in protoplasts inoculated with bottom component particles therefore suggests that RNA-1 contains the gene for this protein.