Replication of RNA-1 of tomato black ring virus independently of RNA-2

In hybridization experiments, using complementary DNA (cDNA) copies of the two genome parts of tomato black ring virus (TBRV RNA-I 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-L extracts made 24 or 48 h later contained RNA that had the same mobility as RNA- ~ in polyacrylamide-agarose gels, and that hybridized to cDNA copies of RNA-I. 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. Thegenome-linked protein of nepoviruses is probably virus-coded, and its production i protoplasts inoculated with bottom component particles therefore suggests hat RNA-t contains the gene for this protein