Notes on Genus: Topocuvirus

twinned icosahedra

Type member: Tomato pseudo-curly top virus

Contents

• Members of this Genus
• General Description
• Morphology
• Electron Micrograph
• Genome
• Genus Genomic Organization
• Genome Map
• Type Member Genomic Organization
• All Known Sequences
• Curated Sequences

General Description

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.

Morphology

Virions are geminate (twinned) icosahedra, not enveloped, 38 nm long and 22 nm in diameter. 22 capsomeres per nucleocapsid.

Genome

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

ORF	sense	product
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