Beet yellows virus: the importance of being different
Valerian V. Dolja
Department of Botany and Plant Pathology, Oregon State University,
Corvallis, OR 97331, USA
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| Taxonomic relationship: |
Type member of the genus Closterovirus,
family Closteroviridae. A member of the alphavirus-like supergroup
of positive-strand RNA viruses. |
| Physical Properties: |
Virions are flexuous filaments of
~1300 nm in length and ~12 nm in diameter that are made up of a ~15.5 kb
RNA and five proteins. The major capsid protein forms virion body of
helical symmetry that constitutes ~95% of the virion length. The short
virion tail is assembled by the minor capsid protein, Hsp70-homologue,
~64-kDa protein, and ~20-kDa protein. |
| Viral proteins: |
The 5'-most ORFs 1a and 1b encode
leader proteinase and RNA replicase. The remaining ORFs 2-8 are expressed
by subgenomic mRNAs that encode 6-kDa membrane protein, Hsp70 homologue,
~64-kDa protein, minor and major capsid proteins, ~20-kDa protein, and
~21-kDa protein, respectively. |
| Hosts: |
The principal crop plants affected
by Beet yellows virus (BYV) are sugar beet (Beta vulgaris)
and spinach (Spinacea oleracea). In addition, BYV was reported to
infect ~120 species in 15 families. Most suitable propagation species are Nicotiana
benthamiana, Tetragonia expansa, and Claytonia perfoliata. |
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Morphology of the BYV virions. (A) Electron micrograph of two BYV
virions. Virion tails marked by arrows were immunogold labelled using
anti-CPm serum (courtesy of Alberto J. Napuli). (B) Atomic force
microscopy image of a single BYV virion. The white appearance of the body
and the grey appearance of the tail are due to a larger depth of the body
compared to that of the tail. (C and D) 3D reconstruction of the virion
ends obtained using atomic force microscopy. Images B-D are courtesy of
Igor Andreev and Michael E. Taliansky.
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