Non-enveloped, rigid helical rods with a helical symmetry, about 20 nm in diameter with a central “canal”. There are two segments.
Segmented, linear, ssRNA(+) genome, segments of about 4kb and 6kb. Genomic RNA displays a tRNA-like structure in 3', but no poly-A tail.
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. RNA-2 encodes the capsid protein, triple gene block proteins acting as movement proteins and a viral suppressor of RNA silencing (VSR).
- 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 protein, movement protein(s) and viral suppressor of RNA silencing (VSR).
- Virus assembly in the cytoplasm. Each segment is encapsidated.
- Viral movement protein(s) probably mediate virion cell-to-cell transfer.