Notes on Genus: Ampelovirus

flexuous filaments

Type member: Grapevine leafroll-associated virus 3

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 three genera in the family Closteroviridae, which are characterised by their very long (950-2000 nm) and very flexuous particles. Viruses in this genus were previously classified in the genus Closterovirus, but have been separated because of their mealybug transmission and different genome organisation. The name is from the Greek ampelos meaning grapevine, the plant host of the type member.

Morphology

Virions filamentous, not enveloped, very flexuous, 950-2000 nm long and 10-13 nm in diameter. There is a distinct virion tail. Symmetry helical, with pitch of 3.4-3.7 nm.

Virions composed of 5% nucleic acid.

Genome

Monopartite, linear, single-stranded, positive sense RNA 15,000 to 20,000 nucleotides long. There are sequences with potential hairpin structure near the 3'-end. 3' terminus has no poly(A) tract and the 5' terminus probably has a methylated nucleotide cap.

Genus Genomic Organization

The RNA is translated from up to 12 reading frames. There is a large replicase near the 5'-end and the coat proteins are towards (but not at) the 3'-end.

Type Member Genomic Organization

The RNA is believed to be translated from twelve open reading frames:

1a	245 kDa	replication protein
1b	61 kDa	polymerase, expressed as a 1a/1b fusion protein
2	6 kDa	unknown protein
3	5 kDa	unknown protein
4	59 kDa	similar to the HSP70 heat-shock proteins which are molecular chaperones
5	55 kDa	probably involved in cell-to-cell movement
6	35 kDa	Coat protein; assembled into particles as the major virion protein
7	53 kDa	Minor coat protein incorporated into the virion tail
8	21 kDa	unknown protein
9	20 kDa	unknown protein
10	20 kDa	unknown protein
11	4 kDa	unknown protein
12	7 kDa	unknown protein

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