''Potyviridae'' is a family of

positive-strand RNA virus Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have Sense (molecular biology), positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can ...

es that encompasses more than 30% of known

plant virus Plant viruses are viruses that have the potential to affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathoge ...

es, many of which are of great agricultural significance. The family contains 13 genera that contain 259 species.

Structure

Potyvirid virions are nonenveloped, flexuous filamentous, rod-shaped particles. The diameter is around 11–20 nm, with a length of 650–950 nm.

Genome

Genomes are linear and usually nonsegmented, around 8–12kb in length, consisting of positive-sense RNA, which is surrounded by a protein coat made up of a single viral encoded protein called a

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or m ...

. All induce the formation of virus

inclusion bodies Inclusion bodies are aggregates of specific types of protein found in neurons, and a number of tissue (biology), tissue cells including red blood cells, bacteria, viruses, and plants. Inclusion bodies of aggregations of multiple proteins are also ...

called cylindrical inclusions (‘pinwheels’) in their hosts. These consist of a single protein (about 70 kDa) made in their hosts from a single viral genome product. Member viruses encode large polypeptides that are cleaved into mature

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s. In 5'–3' order these proteins are * P1 (a

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

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 ...

): 83 kDa * HC (a protease): 51 kDa * P3: 34 kDa * 6K1: 5 kDa * Cl (

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 ...

): 71 kDa * 6K2: 6 kDa * VPg (the 5' binding protein): 20 kDa * NIa-Pro (a protease): 27 kDa * NIb ( RNA dependent RNA polymerase): 57 kDa * Capsid protein: 34 kDa There may be some variation in the number of the proteins depending on the genera and species. For instance some genera lack P1, some virus of the genus '' Ipomovirus'' lack HC and have a P1 tandem. Pretty interesting sweet potato potyviral ORF (PISPO), alkylation B (AlkB), and inosine triphosphate pyrophosphatase (known as ITPase or HAM1) are protein domains identified in atypical members.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration. Replication follows the positive-stranded RNA virus replication model. Positive-stranded RNA virus transcription is the method of transcription. Translation takes place by −1 ribosomal frameshifting. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. The virus is transmitted via a vector (often an insect or mite). Transmission routes are vector and mechanical.

Transmission

''Potyvirus'' is the largest genus in the family, with 183 known species. These viruses are 720–850 nm in length and are transmitted by

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

s. They can also be easily transmitted by mechanical means. These viruses shared a common ancestry 6,600 years agoNigam D, LaTourrette K, Souza PFN, Garcia-Ruiz H (2019) Genome-wide variation in Potyviruses. Front Plant Sci 10:1439 and are transmitted by over 200 species of aphids. The species in the genus ''Macluravirus'' are 650–675 nm in length and are also transmitted by aphids. The plant viruses in the genus ''Ipomovirus'' are transmitted by

whiteflies Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described. Description and taxonomy The A ...

and they are 750–950 nm long. ''Tritimovirus'' and the ''Rymovirus'' viruses are 680–750 nm long and are transmitted b
eriophydid mites
(The rymoviruses are closely related to the potyviruses and may eventually be merged with the potyviruses.Description of Plant Viruses
Family ''Potyviridae'' figure
/ref>) The ''Bymovirus'' genome consists of two particles instead of one (275 and 550 nm) and these viruses are transmitted by the chytrid fungus, '' Polymyxa graminis''.

Taxonomy

The family contains the following genera: * '' Arepavirus'' * '' Bevemovirus'' * '' Brambyvirus'' * '' Bymovirus'' * '' Celavirus'' * '' Ipomovirus'' * '' Macluravirus'' * '' Phragmivirus'' * '' Poacevirus'' * '' Potyvirus'' * '' Roymovirus'' * '' Rymovirus'' * '' Tritimovirus''

References

External links

ICTV Online (10th) Report: ''Potyviridae''

{{Authority control Viral plant pathogens and diseases Virus families Riboviria