A Satellite RNA in Grapevine Fanleaf Virus Strain F13

Abstract

SUMMARYThe F 13 isolate of grapevine fanleaf virus (GFLV) differs from other isolates in that it induces severe symptoms on Chenopodium quinoa. We show here that its particles contain three RNA species with sizes, estimated by electrophoresis in agarose gels containing formaldehyde, of 6800 nucleotides (RNA 1), 3900 nucleotides (RNA2) and 1150 nucleotides (RNA3). The three RNA species are polyadenylated and probably have a genome-linked protein at their 5' end. RNA1 and RNA2 are known to be genomic RNAs. Evidence for the satellite nature of RNA3 came from Northern blot analysis with DNA probes. A probe originating from the 3' end region of RNA3 and corresponding to one-third of the molecule did not hybridize with either RNA1 or RNA2. Conversely 3'-terminal cDNA probes of RNA1 and RNA2 did not hybridize significantly to RNA3. Further proof of the satellite nature of RNA3 is that it depends on RNA1 and RNA2 for its multiplication in C. quinoa. RNA3 acts as mRNA in wheatgerm extract and directs the synthesis of a Mr 39000 protein.

Immunodetection of grapevine fanleaf virus satellite RNA-encoded protein in infected Chenopodium quinoa

“…RNA 3 contains one open reading frame encoding a highly hydrophilic, basic polypeptide of 341 residues and Mr 37275 (Fuchs et al, 1989). In a wheatgerm translation system, RNA 3 directs the synthesis of a protein (P3) with an apparent Mr of 39K (Pinck et al, 1988). However such a polypeptide has never been observed in infected plants.…”

Replication of Grapevine Fanleaf Virus Satellite RNA Transcripts in Chenopodium quinoa Protoplasts

“…The proteins translated from all transcripts comigrated with the P3 protein synthetised from the natural RNA3 (data not shown) (Pinck et al, 1988). This indicated that the full-length clones of RNA3 were not altered during the cloning and mutagenesis steps.…”

“…RNA3 belongs to the class of large satellites (Fritsch & Mayo, 1989). It has coding capacity for a protein, P3, of M~ 37K and is translated in wheat germ extracts to produce a species of apparent Mr 39K (Pinck et al, 1988).…”

“…Its genome comprises two single-stranded polyadenylated RNAs which carry a genome-linked protein at their 5' ends (Pinck et al, 1988). RNA1 (7342 nucleotides) encodes polyprotein P1 (Mr 253K;Ritzenthaler et al, 1991) and RNA2 (3774 nucleotides) encodes polyprotein P2 (Mr 122K ;Serghini et al, 1990) (Fig.…”

Molecular Characterization of Phylogenetically Distinct Isolates of Grapevine fanleaf virus from Iran Based on 2AHP Gene

“…The viral genome is composed of two single-stranded positive polarity linear RNA (?ssRNA) segments with a small virus-genome linked protein (VPg) and poly (A) tail at their 5 0 and 3 0 end, respectively. Both RNA segments contain only one open reading frame (ORF) and codes for a polyprotein, which are processed proteolytically at defined dipeptide cleavage sites by the RNA1-encoded proteinase into functional proteins [23]. RNA1 codes for the proteins involved in virus replication [26] and for the viral proteinase [18].…”