Nepovirus

Not to be confused with Nipah virus.

Nepovirus is a genus of viruses in the order Picornavirales, in the family Secoviridae, in the subfamily Comovirinae. Plants serve as natural hosts. There are 55 species in this genus.^[1][2] Nepoviruses, unlike the genera Comovirus and Fabavirus in the subfamily Comovirinae, are transmitted by nematodes.^[3]

Nepovirus
Crystal structure of Grapevine fanleaf virus
Virus classification
(unranked):	Virus
Realm:	Riboviria
Kingdom:	Orthornavirae
Phylum:	Pisuviricota
Class:	Pisoniviricetes
Order:	Picornavirales
Family:	Secoviridae
Subfamily:	Comovirinae
Genus:	Nepovirus
Species
see text

Taxonomy

The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species:^[2][4]

• Nepovirus aegaeum, Artichoke Aegean ringspot virus
• Nepovirus aeonii, Aeonium ringspot virus
• Nepovirus alphaparis, Paris nepovirus 1
• Nepovirus alphavitis, Grapevine nepovirus A
• Nepovirus americaense, Cassava American latent virus
• Nepovirus anatoliense, Grapevine Anatolian ringspot virus
• Nepovirus anemones, Anemone nepovirus A
• Nepovirus arabis, Arabis mosaic virus
• Nepovirus armeniacae, Apricot latent ringspot virus
• Nepovirus arracaciae, Arracacha virus A
• Nepovirus australiaense, Lucerne Australian latent virus
• Nepovirus avii, Cherry leaf roll virus
• Nepovirus betae, Beet ringspot virus
• Nepovirus betaparis, Paris polyphylla secovirus 1
• Nepovirus betasolani, Potato virus B
• Nepovirus bulgariense, Grapevine Bulgarian latent virus
• Nepovirus cari, Caraway yellows virus
• Nepovirus carolinense, Horse nettle virus
• Nepovirus cerasiferae, Myrobalan latent ringspot virus
• Nepovirus chromusivum, Grapevine chrome mosaic virus
• Nepovirus cichorii, Chicory yellow mottle virus
• Nepovirus cucumis, Melon mild mottle virus
• Nepovirus cycas, Cycas necrotic stunt virus
• Nepovirus cynarae, Artichoke yellow ringspot virus
• Nepovirus deformationis, Grapevine deformation virus
• Nepovirus foliumflabelli, Grapevine fanleaf virus
• Nepovirus fontinalis, Common water moss secovirus
• Nepovirus glycinis, Soybean latent spherical virus
• Nepovirus hibisci, Hibiscus latent ringspot virus
• Nepovirus italiaense, Artichoke Italian latent virus
• Nepovirus lonchitis, Tomato fern secovirus
• Nepovirus lycopersici, Tomato ringspot virus
• Nepovirus maculanulatum, Mulberry ringspot virus
• Nepovirus manihotis, Cassava green mottle virus
• Nepovirus mirae, Prunus mira virus A
• Nepovirus mori, Mulberry mosaic leaf roll associated virus
• Nepovirus myrtilli, Blueberry leaf mottle virus
• Nepovirus nicotianae, Tobacco ringspot virus
• Nepovirus nigranuli, Tomato black ring virus
• Nepovirus oleae, Olive latent ringspot virus
• Nepovirus persicae, Peach rosette mosaic virus
• Nepovirus petuniae, Petunia chlorotic mottle virus
• Nepovirus poaceae, Poaceae Liege nepovirus A
• Nepovirus pratensis, Red clover nepovirus A
• Nepovirus ribis, Blackcurrant reversion virus
• Nepovirus rubi, Raspberry ringspot virus
• Nepovirus sichuanense Green Sichuan pepper nepovirus
• Nepovirus solani, Potato black ringspot virus
• Nepovirus stenotaphri, Stenotaphrum nepovirus
• Nepovirus theobromatis, Cocoa necrosis virus
• Nepovirus trifolii, Crimson clover latent virus
• Nepovirus tunisiaense, Grapevine Tunisian ringspot virus
• Nepovirus usolani, Potato virus U
• Nepovirus vaccinii, Blueberry latent spherical virus
• Nepovirus vittariae, Shoestring fern secovirus

Structure

Viruses in Nepovirus are non-enveloped, with icosahedral geometries, and T=pseudo3 symmetry. The diameter is around 28-30 nm. Genomes are linear and segmented, bipartite, around 23.9kb in length.^[1]

Genus	Structure	Symmetry	Capsid	Genomic arrangement	Genomic segmentation
Nepovirus	Icosahedral	Pseudo T=3	Non-enveloped	Linear	Segmented

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. The virus is transmitted via a vector (nematodes, mite, and thrips). Transmission routes are vector.^[1]

Genus	Host details	Tissue tropism	Entry details	Release details	Replication site	Assembly site	Transmission
Nepovirus	Plants	None	Viral movement; mechanical inoculation	Viral movement	Cytoplasm	Cytoplasm	Nematodes; mites; thrips

Genome

Nepoviruses are classified as type IV viruses under the Baltimore classification system, and consequently contain bipartite, linear, single stranded positive sense RNA genomes. The two genome segments are encapsulated separately into two different icosahedral particles. Each of the genome segments produces a different polypeptide, which undergoes a series of steps (i.e. proteolysis, and other post-translational modifications) in order to produce a functional protein.^[3]

RNA1

The first segment (RNA1) is approximately 8,000 nucleotides in length and appears as a single copy in each B type virion. It encodes the proteins that are important in replication and is the first gene to be activated.^[3]

RNA2

The second segment (RNA2) is approximately 4,000–7,000 nucleotides in length and usually appears as a single copy in each M type virion. It encodes the proteins that are important in cell-cell transmission and evasion of cellular defenses.^[3]