Molecular characterization of plum pox potyvirus¹

Abstract

In recent years, our knowledge of the molecular biology of plum pox potyvirus (PPV) and of potyviruses in general has greatly increased. The genome of PPV consists of a unique single‐strand RNA molecule with messenger polarity. A terminal protein (VPg) and a poly‐(A) tail are present at the 5’and 3’ends, respectively, of the genomic RNA. Four complete and other partial nucleotide sequences of PPV isolates have been reported. According to the levels of homology three different PPV strains can be defined. PPV RNA is translated into a unique polyprotein starting at the second AUG codon of the large open‐reading frame that covers most of the genome. The polyprotein is proteolytically processed by three virus encoded proteases (P1Pro, HCPro and NIaPro). While P1Pro and HCPro cut at their own carboxyl termini, NIaPro recognizes seven cleavage sites characterized by conserved heptapeptides. These sites differ in their susceptibility to cis and trans processing and in their reaction profiles. Immunoelectron microscopy has shown NIa and NIb proteins to form nuclear inclusions, but also dense aggregates in the cytoplasm, and CI protein to make typical pinwheel cytoplasmic inclusions. On the basis of sequence comparisons, NIb protein has been proposed to be the viral RNA replicase. CI protein has been purified from infected leaves and from Escherichia coli harbouring a plasmid that encodes it. It has nucleic acid‐stimulated NTPase and RNA helicase activities. Virus infection has been achieved by inoculation with a PPV full‐length cDNA clone and with transcripts synthesized using another one as template. These clones can be used to apply genetic engineering techniques to the in vitro manipulation of the PPV genome.

Genetic diversity ofPlum pox virus: strains, disease and related challenges for control

“…1), and the full extent of this diversity has yet to be determined. PPV contains a positive-sense single-stranded RNA genome, approximately 9.8-10 kilobases (kb) in size, flanked by a virus-encoded protein (VPg) covalently linked to the 5 terminus, and a poly(A) tail at the 3 terminus (Laín et al, 1989;Maiss et al, 1989;Riechmann et al, 1989;García et al, 1994). The genome is bicistronic, encoding a major open reading frame (ORF) that encodes a polyprotein with a molecular mass of approximately 355 kDa.…”

“…The genome is bicistronic, encoding a major open reading frame (ORF) that encodes a polyprotein with a molecular mass of approximately 355 kDa. This polyprotein is cleaved post-translation by genome-encoded proteases into the functional proteins (García et al, 1994). The genome also encodes a small overlapping ORF (Pretty Interesting Potyviridae ORF, PIPO) that is located within the P3 cistron, and is expressed as a P3-PIPO fusion protein (Chung et al, 2008).…”

History and importance of plum pox in stone‐fruit production1

“…It has led to the numerous achievements in the molecular biology of plum pox of the last 10-15 years. These are treated more fully by Dunez et al (1994) and Garcia et al (1994).…”

Causal agent of sharka disease: Plum pox virus genome and function of gene products

“…However, information has also been gained on basic aspects of PPV biology, which together with data obtained for related potyviruses (Revers et al ., 1999; Riechmann et al ., 1992; Urcuqui‐Inchima et al ., 2001), have allowed a thorough molecular characterization of this virus. More than 10 years ago we published a review of this information (García et al ., 1994), and it is revised and updated in this paper.…”