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On the basis of sequence homology a model is proposed for five structural and functional domains in viroids. These domains include (i) a conserved central region capable of forming two alternative structures that may regulate two phases of the viroid replication cycle, (ii) a region associated with pathogenicity, (iii) a domain with high sequence(More)
We recently identified a new cucumovirus-specific gene (2b) which is encoded by RNA 2 of the cucumber mosaic cucumovirus (CMV) tripartite RNA genome and whose coding sequence overlaps the C-terminal 69 codons of ORF 2a encoding the RNA polymerase protein. We have now found that although a CMV mutant lacking ORF 2b accumulated in the inoculated cotyledons of(More)
Cucumber mosaic virus (CMV) contains three genomic RNAs (RNAs 1, 2, and 3) and a subgenomic RNA (RNA 4), a shared feature of the Bromoviridae family which includes cucumoviruses, bromoviruses, alfalfa mosaic virus, and ilarviruses. We describe in this paper the molecular characterization of a novel subgenomic RNA of the Q strain of CMV (Q-CMV), RNA 4A,(More)
Full-length double-stranded cDNA was prepared from purified circular RNA of two new Australian field isolates of citrus exocortis viroid (CEV) using two synthetic oligodeoxynucleotide primers. The cDNA was then cloned into the phage vector M13mp9 for sequence analysis. Sequencing of nine cDNA clones of isolate CEV-DE30 and eleven cDNA clones of isolate(More)
Virusoids are circular single-stranded RNAs dependent on plant viruses for replication and encapsidation. Virusoid replication appears to involve longer-than-unit-length plus and minus RNAs, indicating that unit-length plus RNA is generated by specific cleavage reactions. Here, we synthesize plus and minus partial-length RNAs of the 324-nucleotide virusoid(More)
Self-cleavage of both plus and minus RNA transcripts of the 247-residue avocado sunblotch viroid (ASBV), prepared from tandem dimeric cDNA clones, occurs specifically at two sites in each transcript to give monomeric plus and minus species. The cleavage reaction occurs both during transcription and on incubation of purified transcripts at pH 8 and 37(More)
The sequence of the 356 nucleotide residues of chrysanthemum stunt viroid (CSV) has been determined. Overlapping linear viroid fragments were obtained by partial ribonuclease digestion, radiolabelled in vitro at their 5'-ends, and sequenced using partial enzymic cleavage methods. Of the CSV sequence, 69% is contained in the published sequence of potato(More)
Sequence variants from field isolates of citrus exocortis viroid (CEV) that cause either mild or severe symptoms on tomato plants have previously been classified into two groups, A and B. These groups differ primarily in two domains, P(L) and P(R), of the proposed native structure. Infectivity studies with full-length cDNA clones of variants from each class(More)
RNA-RNA recombination is an important pathway in virus evolution and has been described for many viruses. However, the factors driving recombination or promoting the selection of recombinants are still unclear. Here, we show that the small movement protein (2b) was able to promote selection of RNA 1/2-RNA 3 recombinants within a chimeric virus having RNAs 1(More)
Virusoids are circular single-stranded RNAs dependent on plant viruses for replication and encapsidation. Recently, we showed that an in vitro-synthesized RNA containing 273 nucleotides of the 324-nucleotide virusoid of lucerne transient streak virus self-cleaves at a unique site. The reaction requires heating and snap cooling of the RNA and the subsequent(More)