| Pospiviroid | |
|---|---|
Virus classification  | |
| (unranked): | Viroid |
| Family: | Pospiviroidae |
| Genus: | Pospiviroid |
| Species | |
Pospiviroid is a genus of ssRNA viroids that infects plants, most commonly tubers. It belongs to the family Pospiviroidae . [1] The first viroid discovered was a pospiviroid, the PSTVd species (potato spindle tuber viroid).[ citation needed ]
Pospiviroid has 10 virus species [1]
| Name | Abbr | GenBank | REFSEQ |
|---|---|---|---|
| Chrysanthemum stunt viroid | CSVd | V01107 | NC_002015 |
| Citrus exocortis viroid | CEVd | J02053 | NC_001464 |
| Columnea latent viroid | CLVd | X15663 | NC_003538 |
| Iresine viroid 1 | IrVd1 | X95734 | NC_003613 |
| Pepper chat fruit viroid | PCFVd | FJ409044 | NC_011590 |
| Pospiviroid plvd | PLVd | KR677387 | NC_027432 |
| Potato spindle tuber viroid | PSTVd | V01465 | NC_002030 |
| Tomato apical stunt viroid | TASVd | K00818 | NC_001553 |
| Tomato chlorotic dwarf viroid | TCDVd | AF162131 | NC_000885 |
| Tomato planta macho viroid | TPMVd | K00817 | NC_001558 |
An RNA virus is a virus—other than a retrovirus—that has ribonucleic acid (RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, COVID-19, Dengue virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio, mumps, and measles.
Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms, and most cause diseases, whose respective economic importance to humans varies widely. A recent metatranscriptomics study suggests that the host diversity of viroids and other viroid-like elements is broader than previously thought and that it would not be limited to plants, encompassing even the prokaryotes.
Order is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.
Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms.
Virusoids are circular single-stranded RNA(s) dependent on viruses for replication and encapsidation. The genome of virusoids consists of several hundred (200–400) nucleotides and does not code for any proteins.
Theodor Otto Diener was a Swiss-American plant pathologist. In 1971, he discovered that the causative agent of the potato spindle tuber disease is not a virus, but a novel agent, which consists solely of a short strand of single-stranded RNA without a protein capsid, eighty times smaller than the smallest viruses. He proposed to name it, and similar agents yet to be discovered, viroids. Viroids displaced viruses as the smallest known infectious agents.
The potato spindle tuber viroid (PSTVd) was the first viroid to be identified. PSTVd is a small, single stranded circular RNA molecule closely related to the chrysanthemum stunt viroid. Present within the viroidal RNA is the Pospiviroid RY motif stem loop common to its genus. The natural hosts are potatoes and tomatoes. All potatoes and tomatoes are susceptible to PSTVd and there is no form of natural resistance. Natural infections have also been seen in avocados and infections in other solanaceous crops have been induced in the laboratory. Until 2017 PSTVd was thought to be unable to infect Solanum sisymbriifolium. Then in May seeds exported by a Dutch company were noticed to be infected. These seeds were shipped from the company, but had been originally bred to their specifications in two Asian countries. Pstv also causes Tomato bunchy top and is seed transmitted in tomato.
The Pospiviroidae are a incertae sedis family of ssRNA viroids with 5 genera and 39 species, including the first viroid to be discovered, PSTVd, which is part of genus Pospiviroid. Their secondary structure is key to their biological activity. The classification of this family is based on differences in the conserved central region sequence. Pospiviroidae replication occurs in an asymmetric fashion via host cell RNA polymerase, RNase, and RNA ligase. Its hosts are plants, specifically dicotyledons and some monocotyledons.
The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic classification of and the nomenclature for viruses. The ICTV develops a universal taxonomic scheme for viruses, and thus has the means to appropriately describe, name, and classify every virus taxon. The members of the International Committee on Taxonomy of Viruses are considered expert virologists. The ICTV was formed from and is governed by the Virology Division of the International Union of Microbiological Societies. Detailed work, such as identifying new taxa and delimiting the boundaries of species, genera, families, etc. typically is performed by study groups of experts in the families.
Totivirus is a genus of double-stranded RNA viruses in the family Totiviridae. Fungi serve as natural hosts. The name of the group derives from Latin toti which means undivided or whole. There are seven species in this genus.
Peach latent mosaic viroid is a species of the genus Pelamoviroid, which belongs to the family Avsunviroidae. This family is characterized as having chloroplastic viroids with hammerhead ribozymes. Peach latent mosaic viroid is a 336-351nt circular RNA which has a branched formation. This branched formation is stabilised by a pseudoknot between two kissing loops. Peach latent mosaic viroid was first described in the 1980s in Spain by a group of scientists.
The Avsunviroidae are a family of viroids. There are four species in three genera. They consist of RNA genomes between 246 and 375 nucleotides in length. They are single-stranded covalent circles and have intramolecular base pairing. All members lack a central conserved region.
The hop stunt viroid is a viroid species that infects the common hop plant, citrus plants, grapevines, cucumber, and several Prunus species such as almond, apricot, plum, and peach. It is asymptomatic or latent in most host plants, but in some hosts it can cause stunting and other symphtoms. A study of HSVd-infected hops in the USA showed that the severity of yield reduction was highly dependent on the infected hop cultivar.
Hostuviroid is a genus of ssRNA viroids that includes Hop stunt viroid, a species of viroids that infects many different types of plants, including the common hop plant. It belongs to the family Pospiviroidae.
Bottigliavirus is the only genus in the family Ampullaviridae and contains 3 species. Ampullaviridae infect archaea of the genus Acidianus. The name of the family and genus is derived from the Latin word for bottle, ampulla, due to the virions having the shape of a bottle. The family was first described during an investigation of the microbial flora of hot springs in Italy.
Tepovirus is a genus of viruses in the order Tymovirales, in the family Betaflexiviridae. Plants as well as some other root and tuber crops in the andes serve as natural hosts. There are two species in this genus.
Apscaviroid is a genus of ssRNA viroids that belongs to the family Pospiviroidae.
In virology, realm is the highest taxonomic rank established for viruses by the International Committee on Taxonomy of Viruses (ICTV), which oversees virus taxonomy. Six virus realms are recognized and united by specific highly conserved traits:
Ribozyviria is a realm of satellite nucleic acids — infectious agents that resemble viruses, but cannot replicate without a helper virus. Established in ICTV TaxoProp 2020.012D, the realm is named after the presence of genomic and antigenomic ribozymes of the Deltavirus type. The agents in Ribozyviria are satellite nucleic acids, which are distinct from satellite viruses in that they do not encode all of their own structural proteins but require proteins from their helper viruses in order to assemble. Additional common features include a rod-like structure, an RNA-binding "delta antigen" encoded in the genome, and animal hosts. Furthermore, the size range of the genomes of these viruses is between around 1547–1735nt, they encode a hammerhead ribozyme or a hepatitis delta virus ribozyme, and their coding capacity only involves one conserved protein. Most lineages of this realm are poorly understood, the notable exception being the genus Deltavirus, comprising the causal agents of hepatitis D in humans.
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