Hypoviruses are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

es that constitute the family ''Hypoviridae''.

Fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

serve as natural hosts. There are eight genera in the family. Infection reduces the

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

of its parasitic host, making it a hyperparasite useful for

blight Blight is 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 organs. A ...

control.

Taxonomy

The family contains the following genera: * '' Alphahypovirus'' * '' Betahypovirus'' * '' Deltahypovirus'' * '' Epsilonhypovirus'' * '' Etahypovirus'' * '' Gammahypovirus'' * '' Thetahypovirus'' * '' Zetahypovirus''

Structure

The diameter is around 50–80 nm. Genomes are linear, around 9–13kb in length. The genome has 1 or 2

open reading frame In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames ...

s, named OrfA (not always present) and OrfB. The genome contains no structural proteins. The virus accordingly does not bud out of the cell. Both

s of CHV1 contain a

papain Papain, also known as papaya proteinase I, is a cysteine protease () enzyme present in papaya (''Carica papaya'') and mountain papaya (''Vasconcellea cundinamarcensis''). It is the namesake member of the papain-like protease family. It has wi ...

-like

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

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–

helicase Helicases are a class of enzymes that are 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 double helix, separating the two hybridized ...

Life cycle

Viral replication is

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

ic. 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

Up to 2000, Hypovirus CHV1 was the only hypovirus found in Europe. It is known for reducing the virulence of the fungus that causes

chestnut blight 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 ...

(i.e. hypovirulence). ''Cryphonectria parasitica'', the ascomycete fungus, originated in Asia and causes the disease

in several

chestnut The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. The name also refers to the edible nuts they produce. They are native to temperate regions of the Northern Hemisphere. Description ...

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 The American chestnut (''Castanea dentata'') is a large, fast-growing deciduous tree of the Fagaceae, beech family native to eastern North America. As is true of all species in the genus ''Chestnut, Castanea'', the American chestnut produces Bur ...

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''

Viralzone: Hypoviridae
* MEROPS protease families
C7C8
{{Taxonbar, from1=Q3775807, from2=Q10885843 Hypoviridae Virus families