Nepovirus


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. Nepoviruses, unlike the genera Comovirus and Fabavirus in the subfamily Comovirinae, are transmitted by nematodes.

Taxonomy

The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species:Nepovirus aegaeum, Artichoke Aegean ringspot virusNepovirus aeonii, Aeonium ringspot virusNepovirus alphaparis, Paris nepovirus 1Nepovirus alphavitis, Grapevine nepovirus ANepovirus americaense, Cassava American latent virusNepovirus anatoliense, Grapevine Anatolian ringspot virusNepovirus anemones, Anemone nepovirus ANepovirus arabis, Arabis mosaic virusNepovirus armeniacae, Apricot latent ringspot virusNepovirus arracaciae, Arracacha virus ANepovirus australiaense, Lucerne Australian latent virusNepovirus avii, Cherry leaf roll virusNepovirus betae, Beet ringspot virusNepovirus betaparis, Paris polyphylla secovirus 1Nepovirus betasolani, Potato virus BNepovirus bulgariense, Grapevine Bulgarian latent virusNepovirus cari, Caraway yellows virusNepovirus carolinense, Horse nettle virusNepovirus cerasiferae, Myrobalan latent ringspot virusNepovirus chromusivum, Grapevine chrome mosaic virusNepovirus cichorii, Chicory yellow mottle virusNepovirus cucumis, Melon mild mottle virusNepovirus cycas, Cycas necrotic stunt virusNepovirus cynarae, Artichoke yellow ringspot virusNepovirus deformationis, Grapevine deformation virusNepovirus foliumflabelli, Grapevine fanleaf virusNepovirus fontinalis, Common water moss secovirusNepovirus glycinis, Soybean latent spherical virusNepovirus hibisci, Hibiscus latent ringspot virusNepovirus italiaense, Artichoke Italian latent virusNepovirus lonchitis, Tomato fern secovirusNepovirus lycopersici, Tomato ringspot virusNepovirus maculanulatum, Mulberry ringspot virusNepovirus manihotis, Cassava green mottle virusNepovirus mirae, Prunus mira virus ANepovirus mori, Mulberry mosaic leaf roll associated virusNepovirus myrtilli, Blueberry leaf mottle virusNepovirus nicotianae, Tobacco ringspot virusNepovirus nigranuli, Tomato black ring virusNepovirus oleae, Olive latent ringspot virusNepovirus persicae, Peach rosette mosaic virusNepovirus petuniae, Petunia chlorotic mottle virusNepovirus poaceae, Poaceae Liege nepovirus ANepovirus pratensis, Red clover nepovirus ANepovirus ribis, Blackcurrant reversion virusNepovirus rubi, Raspberry ringspot virusNepovirus sichuanense Green Sichuan pepper nepovirusNepovirus solani, Potato black ringspot virusNepovirus stenotaphri, Stenotaphrum nepovirusNepovirus theobromatis, Cocoa necrosis virusNepovirus trifolii, Crimson clover latent virusNepovirus tunisiaense, Grapevine Tunisian ringspot virusNepovirus usolani, Potato virus UNepovirus vaccinii, Blueberry latent spherical virusNepovirus 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.
GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
NepovirusIcosahedralPseudo T=3Non-envelopedLinearSegmented

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. Transmission routes are vector.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
NepovirusPlants-Viral movement; mechanical inoculationViral movementCytoplasmCytoplasmNematodes; 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 in order to produce a functional protein.

RNA1

The first segment 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.

RNA2

The second segment 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.