Notes on Genus: Topocuvirus
Type member: Tomato pseudo-curly top virus
This is one of 7 genera in the family Geminiviridae
. It differs from the genus Begomovirus
in having a monopartite genome and treehopper vectors. It differs from the other monopartite genera because the genome encodes 6 proteins and its members infect dicotyledonous plants. The genus Mastrevirus
has a slightly smaller genome, encoding 3 or 4 proteins and most members infect graminaceous plants, while the genus Curtovirus
is characterised by a genome encoding 7 proteins.
Virions are geminate (twinned) icosahedra, not enveloped, 38 nm long and 22 nm in diameter. 22 capsomeres per nucleocapsid.
Monopartite, closed circular, single stranded DNA, about 2850 nucleotides long.
Genus Genomic Organization
There are two open reading frames (ORFs) in the positive (virion) sense and four in the negative (complementary) sense.
Type Member Genomic Organization
|V1||+||27 kDa ||Coat protein|
|V2||+||11 kDa ||Movement protein|
|C1||-||40 kDa ||Replicase A|
|C2||-||18 kDa ||Replicase B|
|C3||-||16 kDa ||similar to the replication enhancer protein of begomoviruses|
|C4||-||9 kDa ||initiates cell division; symptom determinant|