Vitivirus (taxid:184751)

VIRION

Non-enveloped, flexuous, filamentous, 725-825 nm or more long and 12 nm in diameter.

GENOME

Linear ssRNA(+) genome of 7.6 kb in size. The 5' end is capped and 3' terminus is polyadenylated. 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). RBP is a RNA-binding protein.

ENZYMES

• RNA-dependent RNA polymerase [Polyprotein]
• Alpha-type capping [Polyprotein]
• Polyprotein major protease (Peptidase C23) [Polyprotein]
• Fe2OG dioxygenase [Polyprotein]

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.

Host-virus interaction

Suppression of RNA silencing

Grapevine virus A ORF5 p10 suppresses local and systemic RNA silencing .