Nucleotide sequence of the satellite of peanut stunt virus reveals structural homologies with viroids and certain nuclear and mitochondrial introns.

Abstract

Peanut stunt virus-associated RNA 5 (PARNA 5), the satellite of a plant cucumovirus, is a linear RNA of 393 nucleotides with a 5' cap and a 3' hydroxyl group. Determination of its nucleotide sequence has revealed two consecutive open reading frames that together extend most of its length. Sequences at the 5' and 3' ends are homologous with those of the satellite of the related cucumber mosaic virus, and the double-stranded forms of both satellites contain an unpaired guanosine at the 3' end of the minus strand. However, little other homology exists between the two satellites. In contrast, PARNA 5 has several regions of 90% sequence homology with various plant viroids, including sequences of the conserved central region of most viroids. Such homologies suggest a common origin with viroids coupled with specific adaptation as a linear RNA. The presence within PARNA 5 of conserved intron sequences essential to proper RNA processing suggests a possible origin from plant introns and/or involvement of such sequences in the processing of PARNA 5 multimers to monomers at some stage of replication.Two distantly related plant viruses of the cucumovirus group, cucumber mosaic virus (CMV) and peanut stunt virus (PSV) (1), each encapsidate a small, linear satellite RNA along with their own four major RNAs (2-4). Each satellite RNA is dependent upon its respective helper virus for replication, thus contrasting with plant viroids-circular molecules of similar size that replicate independently of a helper virus (5). The two satellite RNAs, CARNA 5 (CMV-Associated RNA 5) and PARNA 5 (PSV-Associated RNA 5), show little relationship to each other or to the RNAs of their respective helper viruses (3,4,6). This latter characteristic distinguishes satellite RNAs from defective interfering RNAs (7) and invites speculation on the question of their origin.Studies on the satellites of different strains of CMV have unveiled the existence of many different sequence variants. The biological effects of their presence range from exacerbation to attenuation of normal CMV symptoms, the latter often accompanied by a decrease in virus yield presumably due to interference with the CMV replicative machinery (8-10). Because of their ability to perturb both virus replication and symptom development, their small size (Mr 110,000), and their naturally occurring variability, the CMV satellites provide an excellent model system in which to explore structure-function relationships in RNA molecules. Accordingly, over a dozen already have been sequenced (refs. 11-14; un-published data).In contrast, PARNA 5 has received little attention beyond its characterization and a study of some of its replicative properties (15). However, its larger size (Mr 130,000), lack of relationship to CARNA 5, and replication specificity for PSV but not CMV predicted that comparison of its primary structure with that of CARNA 5 and other small pathogenic RNAs might provide clues into the origin and replication strategy of cucumovirus satellite RNAs. As reported here, the ...

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

“…The cytidylate could result from the incorporation of a nontemplate-encoded 3' residue. Unpaired extra guanidylates at the 3' ends of the (-)-strands of the double-stranded RNAs of two satellite RNAs from cucumoviruses have been detected (31). It is also possible that prior to the addition of the extra cytidylate, the 3' termini of sub-ASBVd(+) and sup-ASBVd(+) may have suffered some processing.…”

The Nucleotide Sequence of Satellite RNA in Grapevine Fanleaf Virus, Strain F13

“…Furthermore, no sequence homology was found with other satellite RNAs like cucumber mosaic virus RNA5 (Garcia-Arenal et al, 1987), peanut stunt virus RNA5 (Collmer et al, 1985), tobacco ringspot virus satellite RNA (Buzayan et al, 1986), panicum mosaic virus satellite RNA (Masuta et al, 1987), and satellite tobacco necrosis RNA (Ysebaert et al, 1980). It seems likely that a satellite RNA contains information or recognition signals for its replication by the helper virus and also for its encapsidation by the capsid protein encoded by the genomic RNAs.…”

Replication of cucumber mosaic virus satellite RNA in vitro by an RNA‐dependent RNA polymerase from virus‐infected tobacco

“…This is shown in Fig. 1 where I-CARNA 5 (334 nt [18]), Y-CARNA 5 (369 nt [19]), and PARNA 5 (393 nt [20]) were offered as templates, and the reaction products analyzed by • .…”