VIRION
Non-enveloped, rod shaped with helical symmetry. The virion is composed of two segments about 140-160 nm and 260-300nm in length and 20 nm in diameter.
GENOME
Segmented, linear, ssRNA(+) genome. The two segments are 6-7 kb and 3.5-3.6 kb in size respectively. The genomic RNAs are capped, and display a tRNA-like structure in 3'.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. The virion RNA is infectious and serves as both the genome and viral messenger RNA. The RNA-1 5'-proximal ORFs are directly translated to produce the viral constituents of the replicase complex. RdRp is translated through suppression of termination at the end of ORF1. The downstream gene encoding the movement protein (MP) is probably translated from a subgenomic RNA. Suppression of termination on RNA-2 produces the extended capsid protein. The 19k protein is a viral suppressor of RNA silencing.
ENZYMES
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated to produce the two proteins necessary for RNA synthesis (replication and transcription).
- Replication takes place in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Expression of the movement protein, viral suppressor of RNA silencing (VSR) and capsid protein.
- Virus assembly in the cytoplasm. Each segment (if multipartite) is encapsidated.
- Viral movement protein probably mediate virion cell-to-cell transfer.
