Project name: Bromoviridae

Description: Description of Bromoviridae adapted from ICTVdb Virion Properties Morphology Virions consist of a capsid. Virus capsid is not enveloped. Capsid is round to elongated with icosahedral symmetry (T=3 or T=1 in Alfamovirus Ta particles). The capsid is isometric to bacilliform and has a diameter of 26-35 nm. The capsid shells of virions are composed of a single layer. The capsid surface structure does not reveal a regular pattern with distinctive features. Virus preparations contain more than one particle component. Virions consist of several nucleocapsids, capsids and segments have different lengths, but constant diameter. The nucleocapsid is segmented, but only one species is recovered in preparations. Nucleic Acid The Mr of the genome constitutes 14-25% of the virion by weight. The genome is monomeric; segmented; tripartite, segements are distribute among 3 particle types of different size; consists of four segments of linear positive-sense, single-stranded RNA. Minor species of non-genomic nucleic acid are also found in virions. The encapsidated nucleic acid is mainly of genomic origin, but virions may also contain subgenomic RNA, that is mRNA derived from genomic RNA-3. The complete genome is 7900-8910 nucleotides long. The RNA-1 is fully sequenced, complete sequence is 3200-3644 nucleotides long. RNA-2 is sequenced, but only an estimate is available, complete sequence is 2600-3050 nucleotides long. RNA-3 is sequenced, but only an estimate is given, complete sequence is 2100-2216 nucleotides long. RNA-4 is the encapsidated mRNA has been fully sequenced, complete sequence is 800-1000 nucleotides long. Subgenomic RNA-4 is an mRNA derived from RNA-3 negative strand template. Nucleotide sequences at the 3'-terminus are similar. The 5'-end of the genome has a methylated nucleotide cap; cap sequence type is m7G5'ppp5 ('Gp..). The 3'-terminus has conserved nucleotide sequences; sequence has of most viruses 150-200 nucleotides in length; in all RNA species. The 3'-terminus has no poly (A) tract. The 3'-terminus has a tRNA-like structure that cannot be aminoacylated, or can be aminoacylated (in the genera Cucumovirus and Bromovirus). The multipartite genome is divided among more than one type of particle and the segments are distributed between 3-7 different types of particles. Proteins The viral genome encodes structural proteins and non-structural proteins located in the capsid. Structural Proteins: Capsid protein (CP) encoded by sgRNA-4 is encapsidated in all but the genus Oleavirus. Capsid protein has a molecular mass of 19800-26200 Da; is involved in viral encapsidation and involved in protein movement. Lipids Lipids are absent. Genome Organization and Replication By itself, genomic nucleic acid is not infectious. Transcription: Sub-genomic RNA is present in infected cells; encoding the coat

Last updated: 2006-10-10