Beet yellows virus: the importance of being different

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 similar to 1300 nm in length and similar to 12 nm in diameter that are made up of a similar to 15.5 kb RNA and five proteins. The major capsid protein forms virion body of helical symmetry that constitutes similar to 95% of the virion length, The short virion tail is assembled by the minor capsid protein, Hsp70-homologue, similar to64-kDa protein, and similar to 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, similar to64-kDa protein, minor and major capsid proteins, similar to 20-kDa protein, and similar to 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 similar to 120 species in 15 families. Most suitable propagation species are Nicotiana benthamiana, Tetragonia expansa, and Claytonia perfoliata.