Non-enveloped, spherical, icosahedral, about 28-34 nm in diameter, capsid with a T=3 icosahedral symmetry. 30 hexameric capsomers per nucleocapsid (virion composed of 180 protein subunits).
Monopartite, linear, ssRNA(+) genome of 3.9 kb.
The virion RNA is infectious and serves as both the genome and viral messenger RNA. Five ORFs are encoded: p27, its readthrough product p87 which encodes the RdRp, two small movement proteins MP1 and MP2, and the capsid protein (CP) which also acts as suppressor of RNA silencing. A single tricistronic subgenomic RNA is produced for expression of MP and CP genes. M2 movement protein initiates at a non-AUG start codon.
- 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.
- The RdRp recognizes internal subgenomic promoters on the negative-sense RNA to transcribe the 3'co-terminal subgenomic RNAs that will generate the capsid and movement protein.
- Virus assembly in the cytoplasm.
- Viral movement protein probably mediates virion cell-to-cell transfer.