Robigovirus

VIRION

Non-enveloped, flexuous, filamentous,800 nm or more long and 12-13 nm in diameter.

GENOME

Linear ssRNA(+) genome of 8-8.5 kb in size. The 3' terminus is polyadenylated and 5’end is capped. Encodes for 5 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

  1. Virus penetrates into the host cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. The viral RNA is translated as a monocistronic mRNA to produce the RdRp (encoded by the 5'-proximal ORF).
  4. Replication occurs in viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. Internal subgenomic promoters are used to transcribe the sgRNAs. Traduction of these sgRNAs yields the capsid and movement proteins.
  7. Assembly of new virus particles.
  8. Triple gene block proteins (TGBp) allow cell-to-cell and long-distance movement.