VIRION
Non-enveloped, flexuous, filamentous, 650 nm or more long and 13 nm in diameter.
GENOME
Linear ssRNA(+) genome of 7.5 kb in size. The 3' terminus is polyadenylated. Encodes for 6 proteins.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. RNA-dependent RNA polymerase (RdRp) is translated directly from the genomic RNA. The other ORFS are transcribed presumably as subgenomic mRNAs (sgRNAs).
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated as a monocistronic mRNA to produce the RdRp (encoded by the 5'-proximal ORF).
- Replication occurs in viral factories recruited by TGB1. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Internal subgenomic promoters are used to transcribe the sgRNAs. Traduction of these sgRNAs yields the capsid and movement proteins.
- Assembly of new virus particles.
- Triple gene block proteins (TGBp) allow cell-to-cell and long-distance movement.