Replication of grapevine fanleaf virus satellite RNA transcripts in Chenopodium quinoa protoplasts

A set of full-length cDNA clones of the satellite RNA of grapevine fanleaf nepovirus isolate F13 (GFLV-F13) was constructed with a variable number of additional, non-viral nucleotides at the 5' and 3' ends. The biological activity of the RNAs transcribed from these constructs was tested in Chenopodium quinoa protoplasts using a helper virus. When inoculated with arabis mosaic virus S (ArMV-S) RNA as helper, transcripts with 33 non-viral nucleotides at the 5' end (tr45p4) did not replicate, whereas transcripts with only one non-viral nucleotide at the 5' end (tr3S and tr3M) did replicate. Capping of the transcripts enhanced their replication. On the other hand, the presence of extra nucleotides at the 3' end had little influence on the biological activity of the in vitro transcripts. In contrast with ArMV-S, GFLV isolate 24 was not a helper for tr3M transcripts, indicating a specific interaction between the helper strain and the satellite RNA.