The nucleotide sequence and genomic organization of grapevine virus B.
Grapevine virus B (GVB) is a tentative member of the genus Trichovirus. The 5'-terminal region of the RNA genome of GVB comprises 5437 nucleotides and has been sequenced by the dideoxynucleotide chain termination method. Evidence was obtained that the RNA is capped. Two putative open reading frames (ORFs) were identified. ORF 1 coded for a 194.7 kDa polypeptide with conserved motifs of replication-related proteins of positive-strand RNA viruses (i.e. methyltransferase, helicase and RNA-dependent RNA polymerase, in that order from the N to the C terminus). ORF 2 encoded a 20 kDa polypeptide that did not show any significant sequence homology with protein sequences from the databases. The biological function of this polypeptide was not determined. Although the 20 kDa product was expressed as a fusion protein with glutathione S-transferase in Escherichia coli and an antiserum produced, it could not be identified in GVB-infected plant tissue extracts. The GVB genome had the same size as that of apple chlorotic leaf spot virus (ACLSV), the type species of the genus Trichovirus, but differed substantially in the number (five compared to three), size and order of genes. Differences existed also in the extent of sequence homology between polymerases, which did not cluster together in tentative phylogenetic trees. The results of this study show that definitive and tentative trichovirus species differ molecularly to an extent that may warrant a taxonomic revision of the genus.
Dipartimento di Protezione delle Piante, Università degli Studi and Centro di Studio del CNR sui Virus e le Virosi dell Colture Mediterranee, Bari, Italy.
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Martelli
D000595:Amino Acid Sequence; D001483:Base Sequence; D004926:Escherichia coli / Q000378:metabolism; D005638:Fruit / Q000821:virology*; D015870:Gene Expression; D016679:Genome, Viral; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D010942:Plant Viruses / Q000235:genetics*; D012328:RNA Viruses / Q000235:genetics*; D012367:RNA, Viral; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D012367:RNA, Viral; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins