''Hypovirus'' is a genus of

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

, in the family ''Hypoviridae''. Fungi serve as natural hosts. There are four species in this genus. Infection reduces the

virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ...

of its parasitic host, making it a

hyperparasite A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two oth ...

useful for

blight Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral org ...

control.

Species

The following species are recognized by the ICTV, all of which were found with ''

Cryphonectria parasitica The pathogenic fungus ''Cryphonectria parasitica'' (formerly ''Endothia parasitica'') is a member of the Ascomycota (sac fungi). This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America ...

'': *'' Cryphonectria hypovirus 1'' *'' Cryphonectria hypovirus 2'' *'' Cryphonectria hypovirus 3'' *'' Cryphonectria hypovirus 4'' There are numerous family members affecting other plant-pathogenic fungi not yet accepted into the ICTV nomenclature. A proposal reorganizes the family into three genera. The informal family '' Fusariviridae'' is the sister group.

Structure

The diameter is around 50–80 nm. Genomes are linear, around 9–13kb in length. The genome has 1 or 2 open reading frames, named OrfA (not always present) and OrfB. The genome contains no structural proteins. The virus accordingly does not bud out of the cell (see "life cycle" below). Both ORFs of CHV1 contain a papain-like protease to the N-terminal that is autocatalyticly cleaved. OrfA (p69, ) cleaves into the p29 C7 protease and a nonessential p40 protein. OrfB () cleaves into a p48 C8 protease and the

RNA replicase RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to ...

–

helicase Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separatin ...

Life cycle

Viral replication is cytoplasmic. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The virus exits the host cell by cell to cell movement. Fungi serve as the natural host.

CHV1 – Chestnut blight hypovirulence

Hypovirus CHV1 is the only hypovirus found in Europe up to 2000. It is known for reducing the virulence of the fungus that causes chestnut blight (i.e. hypovirulence). ''Cryphonectria parasitica'', the ascomycete fungus, originated in Asia and causes the disease chestnut blight in several chestnut species (''Castanea'' spp.). Although symptoms are mild in Asian chestnut species that have co-evolved with the fungus, they are very severe in the North American chestnut species ''C. dentata'' and also in the European sweet chestnut, ''C. sativa''. Hypovirus has been used for protection against chestnut blight in Europe since the 1970s.

References

External links

ICTV Report ''Hypoviridae''

*

MEROPS MEROPS is an online database for peptidases (also known as proteases, proteinases and proteolytic enzymes) and their inhibitors. The classification scheme for peptidases was published by Rawlings & Barrett in 1993, and that for protein inhibit ...

protease families
C7C8
{{Taxonbar, from1=Q3775807, from2=Q10885843 Hypoviridae Virus genera