Molecular biology
VIRION
Enveloped, spherical. Diameter from 80 to 120nm.
GENOME
Segmented Negative-stranded RNA linear genome, L segment is between 6.8 and 12 kb, M segment between 3.2 and 4.9 kb and S segment between 1 and 3 kb.
Encodes for four to six proteins.
GENE EXPRESSION
The viral RNA dependent RNA polymerase (L) bind to a promoter on each encapsidated segment, and transcribe a messager RNA. Transcription is terminated by a strong hairpin sequence at the end of each gene. mRNAs are capped L protein during synthesis. Phlebovirus and Tospovirus have ambisense segment(s).
REPLICATION
CYTOPLASMIC
- Virus attaches to host receptors though Gn-Gc glycoprotein dimer and is endocytosed into vesicles in the host cell.
- Fusion of virus membrane with the vesicle membrane; ribonucleocapsid segments are released in the cytoplasm.
- Transcription, viral mRNAs are capped in the cytoplasm.
- Replication presumably starts when enough nucleoprotein is present to encapsidate neo-synthetized antigenomes and genomes.
- The ribonucleocapsids migrate under the plasma membrane and buds, releasing the virion.