In vitro transcripts of a full-length cDNA of a naturally deleted RNA2 of barley mild mosaic virus (BaMMV) replicate in BaMMV-infected plants.
The RNA2 of a German isolate of the bipartite barley mild mosaic bymovirus (BaMMV-ASL1) is 3524 nucleotides long excluding the 3'-terminal poly(A) tail. The isolate was propagated by mechanical inoculation for several years. Electrophoretic comparison of viral nucleic acids during this period revealed that a spontaneous reduction in the length of the RNA2 occurred, resulting in the isolate BaMMV-ASL1a. The deleted RNA2 of BaMMV lacked a fragment that was 630 nucleotides long. The deletion occurred in the 3' half of the single open reading frame (ORF) found in RNA2; this ORF encodes a polyprotein that has a molecular mass of 98 kDa, which is assumed to be processed autocatalytically into proteins of 25 kDa and 73 kDa. A full-length cDNA of the deleted RNA2 was synthesized and cloned under the control of the phage T7 promoter. In vitro transcripts of the BaMMV-ASL1a clone replicated in barley plants after co-inoculation with a wild-type-like isolate of BaMMV. The deletions in RNA2 of BaMMV-ASL1a and those of a number of other isolates that were examined were found to affect a domain of the putative 73 kDa protein that is obviously not essential for replication but may be important for the transmission of BaMMV by its natural vector Polymyxa graminis.
Timpe
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Federal Centre for Breeding Research on Cultivated Plants, Institute for Resistance Research, Aschersleben, Germany.
Kühne
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D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics; D001467:Hordeum / Q000821:virology; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D017800:Potyvirus / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics* / Q000302:isolation & purification; D017384:Sequence Deletion; D014779:Virus Replication / Q000235:genetics*
D018076:DNA, Complementary; D004274:DNA, Recombinant; D012333:RNA, Messenger; D012367:RNA, Viral