Molecular biology
VIRION
Non-enveloped, rigid helical rods with a helical symetry. Virion is about 18 nm in diameter, and 300-310 nm in lenght.
GENOME
Monopartite, linear, ssRNA(+) genome of 6.3-6.5 kb. The 3’-terminus has a tRNA-like structure. The 5’ terminus has a methylated nucleotide cap (m7G5’pppG).
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. The genome encodes at least four proteins. The methyltransferase/helicase (mt/hel) and RNA-dependent RNA polymerase (RdRp) involved in virus replication are in the 5’ half of the genome. The first one is directly translated from genomic RNA, and the second one is produced by readthrough of the termination codon of the first gene. The other two, a movement protein and the capsid protein are expressed from separate subgenomic mRNAs.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- Genomic RNA is translated to produce the two proteins necessary for Rreplication.
- 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, as well as subgenomic RNA encoding for MP and CP proteins.
- Assembly of new virus particles.