VIRION
Non-enveloped, flexuous, filamentous, about 800 nm long and 12-15 nm in diameter. Symmetry helical. Presence of characteristic inclusion bodies within infected plant cells.
GENOME
Monopartite, linear, ssRNA(+) genome of about 11 kb. 3' terminus has a poly (A) tract. 5' terminus has a genome-linked protein (VPg).
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. The genome is translated into a polyprotein which is subsequently processed by virus-encoded protease)s) into functional products.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated to produce a polyprotein which is processed by viral proteases into the RdRp protein and structural proteins.
- 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.
- Virus assembly in the cytoplasm.