Nodaviridae. Nodaviridae

Description of Nodaviridae adapted from ICTVdb Virion Properties Morphology Virions consist of a capsid. Virus capsid is not enveloped, round with icosahedral symmetry (T=3). The isometric capsid has a diameter of 30 nm. The capsid consists of 32 capsomers. Physicochemical and Physical Properties The molecular mass (Mr) of virions is 9 x 106. Virions have a buoyant density in CsCl of 1.3-1.37 g cm-3. The sedimentation coefficient is 134-140 S20w. Under in vitro conditions virions are stable when stored at 20°C (Nodamura virus, black beetle virus and flock house virus, not stable when stored at 20°C (Boolarra virus, stable in acid environment of pH 5; stable. Virions are not sensitive to treatment with chloroform (extraction in aqueous suspensions). Nucleic Acid The Mr of the genome constitutes 20% of the virion by weight. The genome is segmented and consists of two segments of to three segments of linear positive-sense, single-stranded RNA. The complete genome is 4500 nucleotides long. The RNA-1 is fully sequenced. Complete sequence is 3100 nucleotides long. RNA-2 is sequenced, but only an estimate is available, complete sequence is 1400 nucleotides long. Subgenomic RNA-3 is sequenced, complete sequence is 389 nucleotides long. The 5'-end of the genome has a methylated nucleotide cap (on each segment). The 3'-terminus has no poly (A) tract (the 3'ends cannot be chemically derivatised even after treatment with denaturing solvents suggesting they are blocked, possibly with a protein). The multipartite genome is found in one type of particle only. Each virion contains a single copy of the genome; a full length copy, or defective interfering copies (that are readily formed if the virus is not passaged at low multiplicity of infection). Proteins The viral genome encodes structural proteins. Virions consist of of provirion 1 structural protein(s), or 2 structural protein(s) (in mature infective virion). Lipids Lipids are undetermined (, however the amino terminus of the coat protein precursor, alpha, is blocked by an unidentified entity). Genome Organization and Replication By itself, genomic nucleic acid is infectious (both segments are required). Transcription: Sub-genomic RNA is present in infected cells; a transcription of RNA3 encodes protein B which may play a role in synthesis of positive-strand RNA.