BIOLOGICALLY-ACTIVE TRANSCRIPTS FROM CLONED CDNA OF GENOMIC GRAPEVINE FANLEAF NEPOVIRUS RNAS

Transcripts were produced in vitro by run-off transcription from full-length cDNA of RNA1 and RNA2 of grapevine fanleaf nepovirus (GFLV; isolate Fl 3) cloned downstream from a bacteriophage RNA polymerase promoter. These transcripts, which possess a 5' terminal cap structure and a non-viral G residue instead of the naturally occurring genome-linked viral protein (VPg), are infectious to Chenopodium quinoa protoplasts when inoculated by electroporation. Synthetic RNA1 alone replicated in protoplasts. Inoculation of C quinoa plants with synthetic RNA1 plus RNA2 produced symptoms similar to, but weaker, than those observed in plants infected with natural GFLV 6 to 8 days post-inoculation. Co-inoculated RNA1 and RNA2 were able to replicate and spread systemically in plants but RNA1 alone produced no symptoms and was not detected in non-inoculated leaves, suggesting that virus spread requires RNA2. Analysis of the genomic RNAs in plants infected with transcripts showed that the non-viral G at their 5' ends was not retained in the progeny.