Figure 1 (Left) Schematic diagram of a potyvirus particle. The N-terminal ~ 30 amino acids (large rectangle) and C-terminal ~ 19 amino acids (small rectangle) of the capsid protein molecules are exposed on the surface of the intact virus particle (from Shukla and Ward, 1989). (Right) Negative contrast electron micrograph of particles of Plum pox virus (PPV) stained with 1% PTA, pH 6.0. The bar represents 200 nm (from Scottish Crop Research Institute).
Figure 2 Generic genomic map of a member of the genus Potyvirus. The RNA genome is represented by thin lines and an open box which represent untranslated and translated segments of the ssRNA, respectively. Activities associated with these products are shown. VPg, genome-linked viral protein covalently attached to the 5 terminal nucleotide (represented by the filled oval at the 5-end); P1, a protein with a proteolytic activity responsible for cleavage at Phe-Ser (O); HC-Pro, a protein with aphid transmission helper component activity and proteolytic activity responsible for cleavage at a Gly-Gly (); Pro, serine-like proteolytic activity responsible for cleavage at Gln-(Ser/Gly) (). Some of these proteins of particular member viruses of the family Potyviridae aggregate to form inclusion bodies during infection. The protein involved and the particular type of inclusion body is shown above the genetic map; AI, amorphous inclusion; CI, cylindrical-shaped inclusion body found in the cytoplasm; NIa and NIb, small and large nuclear inclusion proteins, respectively, which aggregate in the nucleus to form a nuclear inclusion body.
Figure 3 Virions of Barley yellow mosaic virus (BaYMV) stained with 1% PTA, pH 7.0. The bar represents 200 nm (from D. Lesemann,).
Figure 4 Genomic map of the Bymovirus bipartite genome, using Barley yellow mosaic virus (BaYMV) as an example. The same conventions as for Potyvirus genome organization map (Fig. 2) are employed. The boundaries of possible gene products are represented by vertical lines. Activities of most gene products are postulated by analogy with genus Potyvirus. P1 corresponds to the C-terminal protease of HC-Pro.
Figure 5 Phylogenetic tree of the family Potyviridae using amino acid sequence relationships of the coat protein. Inference based on the Fitch-Margoliash (1967) least squares method. The sequences were aligned using PILEUP (Devereux et al., 1984). Branch lengths are proportional to sequence distances. The dendrogram was bootstrapped 100 times (percent scores shown at nodes), and are not rooted. Many branches are condensed and may contain multiple viruses. BCMV+, for example, includes BCMNV, CABMV, DMV, PWV, SAPV, SMV, WMV and ZYMV, as well as all the viruses contained in the BCMV subgroup (AzMV, BlCMV, DeMV, and PStV). Similarly, the branch labeled BYMV+ included CYVV, PMV, PSbMV and PeMotV.
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