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SUMMARYThe sequence of the 4662 nucleotides [excluding poly(A)] of RNA-2 of tomato black ring virus (TBRV) has been determined. Most of the sequence (4074 nucleotides) encodes a polypeptide of mol. wt. 150000 (150K). The 5' and Y non-coding sequences are 287 and 301 nucleotides in length, differ from the coding sequence in base composition, and contain repeated sequences, some of which resemble oligonucleotides in the 3' non-coding sequence of M-RNA of cowpea mosaic virus (CPMV). From its amino acid composition, the coat protein of TBRV was tentatively located in the Cterminal third of the 150K polypeptide. The amino acid sequence of the 150K polypeptide immediately N-terminal to the putative coat protein sequence was found to resemble parts of the 30K polypeptides of tobamoviruses and, to a lesser extent, part of the 105K polypeptide translation product of CPMV M-RNA.

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SUMMARYIn 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. The genome-linked protein of nepoviruses is probably virus-coded, and its production in protoplasts inoculated with bottom component particles therefore suggests that RNA-t contains the gene for this protein.

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