Figure 1 (A) Section of palisade mesophyll cell from a leaf of Nicotiana clevelandii systemically infected with carrot mottle virus (CMoV), showing enveloped structures (E) about 52 nm in diameter in the cell vacuole (V) in association with the tonoplast (T). The bar represents 250 nm. (B) Enveloped structures about 52 nm in diameter in a partially purified preparation from CMoV-infected N. clevelandii, stained with 2% uranyl acetate. The bar represents 100 nm. (C) Section of a Nicotiana benthamiana cell expressing the GRV ORF3 protein. The section shows filamentous ribonucleoprotein particles embedded in an electron-dense matrix. The section was labeled by in situ hybridization with a GRV-specific RNA probe. The bar represents 100 nm.
Figure 2 Diagram showing the genomic organization of groundnut rosette virus (GRV). The continuous horizontal line represents the genome RNA, and the numbered blocks the correspondingly numbered ORFs. The lower part of the diagram shows the predicted translation products, with their size. The potential product of ORF1 has not been shown to exist. The single product produced from ORFs 1 and 2, probably as a result of a −1 frameshift event (FS), is thought to be a polymerase because it contains, in the ORF2 region, sequences characteristic of viral RdRp. The ORF3 product functions to protect viral RNA and enable its transport through the phloem. The ORF4 product, marked MP, has a cell-to-cell movement function.
Figure 3 Phylogenetic relationships of the RdRps of umbraviruses and some other plant viruses. Amino acid sequences were aligned using the ClustalX2 program. The neighbour-joining trees were produced and bootstrapped using the PHYLIP package programs. Numbers at the nodes represent bootstrap values as percentages obtained from 2000 replications, shown only for branches supported by more than 40%. Length of branches is proportional to number of changes.