Family: Potyviridae
Genus: Roymovirus
Distinguishing features
The amino acid motifs KITC and PTK are not present in HC-Pro. Roymoviruses have low nucleotide and amino acid identities with other potyvirids. The nucleotide and deduced amino acid sequences of the polyprotein share greatest identities with other viruses in the family Potyviridae, but they are not clearly closer to members of any particular genera in the family. Comparison of the deduced amino acid sequence of the large ORF revealed identities with other viruses of the family to be low, ranging from 13% (some bymoviruses) to 23% (some potyviruses).
Virion
Morphology
Particles are 720 to 750 nm in size.
Nucleic acid
Rose yellow mosaic virus has a genome of 9,508 nt.
Proteins
The large polyprotein is probably processed in the same manner as potyviruses. PIPO is present.
Genome organization and replication
Genome organization (Figure 1.Roymovirus) resembles that of members of the genus Potyvirus (Figure 2.Potyviridae).
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| Figure 1. Roymovirus Schematic diagram of the rose yellow mosaic virus (RYMV) genome. The polyprotein ORF is indicated by the large open box divided into putative mature proteins. The pretty interesting Potyviridae protein (PIPO) is represented by a small box. The untranslated regions (UTR) are represented by lines on each end of the large ORF. Activities of mature proteins are postulated by analogy with genus Potyvirus. Conventions are as for the potyvirus genome organization map (Figure 2.Potyviridae). Not to scale. |
Biology
Isolates of the typical species, Rose yellow mosaic virus, were described in several rose cultivars in New York and Minnesota (Mollov et al., 2013).
The conserved amino acid motifs KITC and PTK are not present in the HC-Pro of rose yellow mosaic virus. Instead, a putative C-2x-C eriophyid mite transmission motif is located at amino acid residues 48–51 at the N-terminus of the protein. The CP acid motif DAG found in most aphid-transmitted potyvirids is also lacking. Together this information suggests that rose yellow mosaic virus may be transmitted by eriophyid mites, although this has not been proven experimentally.
Phylogenetic analysis of the coat protein and ORF places rose yellow mosaic virus basal to viruses belonging to the genera Tritimovirus, Poacevirus, and Ipomovirus (Figure 3.Potyviridae).
Species demarcation criteria
See discussion under family description.