Sequence Analysis and Genome Organisation of Poinsettia Mosaic Virus (PnMV) Reveal Closer Relationship to Marafiviruses Than to Tymoviruses

Abstract

Sequence comparison and genome organisation of poinsettia mosaic virus (PnMV), a putative member of the tymoviruses, revealed a closer relationship to marafiviruses. The complete nucleotide sequence of PnMV was determined. The 6099-nt RNA genome encodes a putative 221-kDa polyprotein that lacks a stop codon between the replicase and the coat protein genes, as in most tymovirus RNAs. The genomic RNA has a poly(A) tail at its 3Ј-terminus in contrast to the tRNA-like structure found in the RNA of most tymoviruses, and no homology was observed to the conserved noncoding region of the tymoviral 3Ј-termini. The tymobox of PnMV, a 16-nt region of the subgenomic RNA (sgRNA) promoter shared by most tymoviruses, differs in 3 nt from the RNA sequence of tymoviruses but is identical to the sequence of marafiviruses. At least three sgRNAs were found in PnMV-infected Euphorbia pulcherrima and in isolated PnMV particles; one that is 650 nt long encodes the 21.4-kDa coat protein, and the others are about 3.5 and 1.7 kb and contain the 5Ј-and the 3Ј-terminal parts of genomic RNA, respectively. Like tymoviruses, PnMV particles sediment as top and bottom components. The particles of the top component contain the sgRNA (650 nt) encoding the coat protein, and those of bottom component contain both genomic and sgRNAs.

Molecular Characterization of the Genome of Maize Rayado Fino Virus, the Type Member of the Genus Marafivirus

“…The complete sequence of OBDV has been reported (Edwards et al, 1997) and recently, the nucleotide sequence of Poinsettia mosaic virus (PnMV) was shown to have a close relationship to marafiviruses (Bradel et al, 2000). In this paper, we report the complete nucleotide sequence of the MRFV genome and propose a putative genome expression strategy that differs from that reported for OBDV and PnMV.…”

“…Although the 3Ј terminal noncoding region can be folded into a stem-loop structure, it lacks the tRNA-like secondary structure possessed by most tymoviruses and other plant viral RNAs (data not shown) (Rietveld et al, 1983). In that respect, MRFV resembles Erysimum latent tymovirus (ELV) (Srifah et al, 1992), OBDV (Edwards et al, 1997), and PnMV (Bradel et al, 2000). However, unlike OBDV and PnMV, MRFV appears to lack a poly(A) tail.…”

Agrobacterium tumefaciens-mediated transformation of poinsettia, Euphorbia pulcherrima, with virus-derived hairpin RNA constructs confers resistance to Poinsettia mosaic virus

“…Poinsettia mosaic virus (PnMV) is a single-stranded, positive-sense RNA virus (Bradel et al 2000 ) that belongs to the family Tymoviridae (Dreher et al 2005 ). Infection of poinsettia plants with PnMV results in mosaic symptoms during parts of the growing season (Fulton and Fulton 1980 ), which in turn decreases the commercial value of this ornamental plant.…”

Diseases of Poinsettia

“…Particles of PnMV are icosahedrons 26-29 nm in diameter. Although when initially characterized PnMV was thought to be a tymovirus (Fulton and Fulton 1980), studies on PnMV recently provided good evidence that the virus is instead a Marafivirus, and it has now been designated a species of the genus Marafivirus (Bradel et al 2000b;Koenig et al 1986). PnMV was transmitted by grafting to two other euphorbias: E. cornastra (Dressler) A. Radcliffe-Smith, which was symptomless, and E. bubalina Boiss., which showed a mild mosaic (Fløistad and Blystad 1999).…”