Sequence variability in avocado sunblotch viroid (ASBV)

Pallás, Vicente; García-Luque, Isabel; Domingo, Esteban; Flores, Ricardo

doi:10.1093/nar/16.20.9864

Cited by 18 publications

(15 citation statements)

References 4 publications

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“…1 shows the ASBVd RNAs separated in urea gels and detected by hybridization with ASBVd probes. mc-and ml-ASBVd(+), previously characterized by sequencing (15) and primer extension (28), respectively, were the most abundant species. dc-and dl-ASBVd(+) RNAs were also present at a high level.…”

Section: Resultsmentioning

confidence: 95%

Replication of avocado sunblotch viroid: evidence for a symmetric pathway with two rolling circles and hammerhead ribozyme processing.

Daròs

Marcos

Hernández

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

148

123

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The structure of a series of RNAs extracted from avocado infected by the 247-nt avocado sunblotch viroid (ASBVd) was investigated. The identification of multistranded complexes containing circular ASBVd RNAs of (+) and (-) polarity suggests that replication of ASBVd proceeds through a symmetric pathway with two rolling circles where these two circular RNAs are the templates. This is in contrast to the replication of potato spindle tuber viroid and probably of most of its related viroids, which proceeds via an asymmetric pathway where circular (+)-strand and linear multimeric (-)-strand RNAs are the two templates. Linear (+) and (-) ASBVd RNAs of subgenomic length (137 nt and about 148 nt, respectively) and one linear (+)-strand ASBVd RNA of supragenomic length (383-384 nt) were also found in viroid-infected tissue. The two linear (+)-strand RNAs have the same 5'-and 3'-terminal sequences, with the supragenomic species being a fusion product of the monomeric and subgenomic (+)-strand ASBVd RNAs. The 3' termini of these two (+)-strand molecules, which at least in the subgenomic RNA has an extra nontemplate cytidylate residue, could represent sites of either premature termination of the (+)-strands or specific initiation of the (-)-strands. The 5' termini of sub-and supragenomic (+)-strand and the 5' terminus of the subgenomic (-)-strand ASBVd RNA are identical to those produced in the in vitro self-cleavage reactions of (+) and (-) dimeric ASBVd RNAs, respectively. These observations strongly suggest that the hammerhead structures which mediate the in vitro self-cleavage reactions are also operative in vivo.Viroids are independently replicating circular RNAs capable of causing disease in infected plants. Replication of viroids has been proposed to occur through a rolling circle mechanism (1), because of the detection of multimeric negative (-)-strand RNAs [complementary to the predominant infectious (+)-strand] in tomato infected by the potato spindle tuber viroid. Other authors have come to similar conclusions (2, 3) and have also identified multimeric (+)-strand viroid RNAs in avocado infected by avocado sunblotch viroid (ASBVd) (4, 5) and in other viroid-host combinations (5-8).To accommodate these observations, two pathways were offered (ref. 6; see ref. 9 for a review). In the first pathway, the circular (+)-strand viroid RNA is transcribed into linear multimeric (-)-strands, which then act as the template for the generation of the linear multimeric (+)-strands; this pathway is termed asymmetric since it has a single rolling circle. In the second pathway, the linear multimeric (-)-strands are processed and ligated to monomeric circular (-)-strand RNA, which serves as the template for synthesis of the linear multimeric (+)-strand RNAs. This is the symmetric pathway, with two rolling circles. In both cases the multimeric (+)-strands resulting from the second round of RNA-RNA transcription are cleaved to unit-length molecules which are then ligated to the mature circular (+)-strand RNA. Evidence has been...

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Section: Resultsmentioning

confidence: 95%

Replication of avocado sunblotch viroid: evidence for a symmetric pathway with two rolling circles and hammerhead ribozyme processing.

Daròs

Marcos

Hernández

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

148

123

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“…The predominant sites of sequence heterogeneity in ASBVd are the terminal loops (Pallas et al, 1988;Rakowski & Symons, 1989) and the nucleotide differences that were found in the three variants reflect this. However, this is unlike the more conserved sequences in the T1 and T2 domains of other viroids (Keese et aL, 1988).…”

Section: Discussionmentioning

confidence: 91%

“…The primers used to generate full-length cDNA clones of the three ASBVd variants were made using the sequences of regions complementary (residues 161 to 179) and homologous (residues 180 to 198) to ASBVd SB-1 (Symons, 1981) in which no nucleotide exchanges have previously been reported (Pallas et al, 1988;Rakowski & Symons, 1989). The three full-length cDNA clones of each ASBVd variant were found to have lengths of between 247 and 250 nucleotides.…”

Section: Nucleotide Sequence Of Asbvd Variantsmentioning

confidence: 99%

“…The existence of ASBVd variants has been inferred from differences in the nucleotide sequence and molecular size estimates of ASBVd isolates (Palukaitis et al, 1981;Spiegel et al, 1984;Pallas et al, 1988;Rakowski & Symons, 1989). However these proposed strains have never been positively characterized as distinct variants by differences in their biological properties.…”

Section: Introductionmentioning

confidence: 99%

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Avocado sunblotch disease: a persistent viroid infection in which variants are associated with differential symptoms

Semancik

Szychowski

1994

Journal of General Virology

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“…The in vivo role of the hammerhead ribozymes is also supported by the sequence heterogeneity patterns found in members of the Avsunviroidae family. Although many sequence variants have been reported for ASBVd (Symons, 1981;Pallas et al, 1988;Rakowski and Symons, 1989;Semancik and Szychowski, 1994), PLMVd Shamloul et al, 1995;AmbrSs et al, , 1999 and CCh-MVd (Navarro and Flores, 1997;De la Pefia et al, 1999), the nucleotide changes detected in the regions corresponding to the hammerhead structures do not affect their stability, either because they are located in loops or because the mutations are compensatory. In one particular variant of PLMVd in which a mutation in the hammerhead catalytic pocket was observed, the RNA still showed significant in vitro self-cleavage, the corresponding cDNA was infectious, and the mutation was retained in a fraction of the progeny, indicating a sequence flexibility of the hammerhead structure higher than anticipated (AmbrSs and .…”

Section: Self-cleavage Of Oligomeric Rnas: Role Of Hammerhead Ribomentioning

confidence: 95%

Avsunviroidae family: Viroids containing hammerhead ribozymes

Flores

Daròs

Hernández

2000

Advances in Virus Research

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Sequence variability in avocado sunblotch viroid (ASBV)

Cited by 18 publications

References 4 publications

Replication of avocado sunblotch viroid: evidence for a symmetric pathway with two rolling circles and hammerhead ribozyme processing.

Replication of avocado sunblotch viroid: evidence for a symmetric pathway with two rolling circles and hammerhead ribozyme processing.

Avocado sunblotch disease: a persistent viroid infection in which variants are associated with differential symptoms

Avsunviroidae family: Viroids containing hammerhead ribozymes

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