VIRION
Capsidless virus: These viruses don't produce virions, and cannot be assigned to the Baltimore classification in the strict sense. The polymerase shows homologies to dsRNA Durnavirales, but experimental data suggest that they can be considered ssRNA viruses "with dsRNA lifestyle".
GENOME
Linear dsRNA genome of 9-13kb, encodes one or two ORFs (ORFB, and eventually ORFA). The 3'end is polyadenylated. The genome only encodes non-structural proteins.
May also contain additional satellite dsRNAs.
GENE EXPRESSION
ORFB (and if present, ORFA) encodes a polyprotein that is proteolytically processed.
Translation is initiated on a unique internal ribosome entry site internal ribosome entry site (IRES) element situated at the 5'-UTR.
ENZYMES
- RNA-directed RNA polymerase [RdRp]
- Self cleavage N-ter (Peptidase C7) [p69]
- Self cleavage N-ter (Peptidase C8) [p48]
- No capping activity [IRES]
REPLICATION
CYTOPLASMIC
Poorly understood. The virus never buds out of its host and probably replicates in lipid pleomorphic vesicles like positive ssRNA virus replication viral manner. Transmission depends on cell-to-cell cytoplasmic exchange and hyphal anastomosis.