Notes on Genus: Furovirus
rigid rods
Type member: Soil-borne wheat mosaic virus
Contents
General Description
Furoviruses (
fungally-transmitted
rod-shaped viruses) had originally been classified with tobamoviruses but are distinct in having multipartite genomes and in fungus transmission. The vectors (or putative vectors) of all members are root-infecting parasites, classified in the
Plasmodiophorales. One of these,
Polymyxa graminis, also transmits
Bymoviruses. Some viruses originally classified in the genus have now been moved to separate genera (
Benyvirus,
Pecluvirus,
Pomovirus) on the basis of differences in numbers of genome segments and in genome organisation.
Morphology
Virions rod-shaped, not enveloped. Usually straight with a distinct central canal. Generally of two modal lengths, 250-300 nm and 92-160 nm, (but difficult to estimate because they are fragile) and about 20 nm in diameter. Symmetry helical. Surface capsomere arrangement obvious. Pitch of helix 2.6 nm.
Genome
Linear, single-stranded, positive sense RNA in two segments. The 3'-terminus has a tRNA-like structure.
Genus Genomic Organization
There are three ORFs on each RNA. Product(s) for replication are encoded on RNA1. The coat protein, followed by a readthrough domain are at the 5'-end of RNA2.
Type Member Genomic Organization
RNA1 (c. 7100 nucleotides) produces: |
1 | 150 kDa | | Replication protein containing methyltransferase and helicase motifs |
2 | 209 kDa | | Polymerase readthrough of P1, incorporating RNA polymerase motif |
3 | 37 kDa | | Movement (cell-to-cell transport) protein |
RNA2 (c. 3600 nucleotides) produces: |
4 | 19 kDa | | Coat protein |
5 | 84 kDa | | Coat protein readthrough, probably involved in fungus transmission |
6 | 19 kDa | | Cysteine-rich protein |