Notes on Genus: Tospovirus
Type member: Tomato spotted wilt virus
This is the only plant virus genus in the large family Bunyaviridae
. Its name is derived from the type member, to
tted wilt virus.
Virions pleomorphic in shape and size, spheroidal and enveloped, 80-110 nm in diameter. 3 filamentous nucleocapsids per envelope, each 200-3000 nm long (depending on arrangement) and 2-2.5 nm in diameter. Symmetry helical.
Virions composed of 1-2 % nucleic acid, over 50 % protein and 20-30 % lipid.
Linear, tripartite ssRNA: L (c.
8900 nt), M (c.
4800 nt) and S (c.
2900 nt). Genomic nucleic acid is negative sense (RNA-L), or ambisense (RNA-M and RNA-S). Nucleotide sequences of 3'-termini are complementary to similar regions on the 5' end, thus forming a panhandle.
Genus Genomic Organization
Translation of the RNA is believed to produce a polymerase from RNA-L (complementary sense), while RNA-M and RNA-S each produces one product in the virus sense and one in the complementary sense. The coat protein is the complementary sense product of RNA-S.
Type Member Genomic Organization
Translation of the RNA is believed to produce the following products:
|ORF ||Segment ||complementary|| Size ||Putative function|
|1 ||RNA-L ||complementary || 331.5 kDa ||RNA polymerase|
|2||RNA-M ||viral ||33.6 kDa || NSM possibly involved in cell-to-cell movement|
|3||RNA-M ||complementary || 127.4 kDa ||precursor of glycoproteins G1 and G2|
|4||RNA-S ||viral || 52.4 kDa || NSS, unknown function|
|5||RNA-S ||complementary|| 28.8 kDa ||N, nucleoprotein (Coat protein)|