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

Author(s): Daròs JA, Marcos JF, Hernández C, Flores R

Abstract

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.

Similar Articles

Potato spindle tuber "virus"

Author(s): Diener TO

Inhibition of potato spindle tuber viroid (PSTVd) infection with DNA oligonucleotides

Author(s): Matousek J, Trnena L, Arnold L, Dedic P, Rakousky S, et al.

Behavior of a hammerhead ribozyme in aqueous solution at medium to high temperatures

Author(s): El-Murr N, Maurel MC, Rihova M, Vergne J, Hervé G, et al.

The revised classification of eukaryotes

Author(s): Adl SM, Simpson AG, Lane CE, Lukes J, Bass D, et al.

Improving the coverage of the cyanobacterial phylum using diversity-driven genome sequencing

Author(s): Shih PM, Wu D, Latifi A, Axen SD, Fewer DP, et al.

Accurate strand-specific quantification of viral RNA

Author(s): Plaskon NE, Adelman ZN, Myles KM

Self-cleavage of plus and minus RNA transcripts of avocado sunblotch viroid

Author(s): Hutchins CJ, Rathjen PD, Forster AC, Symons RH