Molecular biology
VIRION
Non-enveloped, flexuous, filamentous, of two lengths (500-600 and 200-300 nm) x 12-15 nm in diameter. Symmetry helical. Presence of characteristic inclusion bodies within infected plant cells.
GENOME
Bipartite, linear, ssRNA(+) genome, composed of RNA1=7.6-7.8 kb and RNA2=3.5-3.8 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 segments are translated into polyproteins which are subsequently processed by virus-encoded proteases into functional products.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNAs are translated to produce two polyproteins which are processed by viral proteases.
- A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
- New genomic RNA is synthesized using the negative-sense RNA as a template.
- Formation of new virus particles.