The Pospiviroidae are a family of

viroid 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 (flowering plants), and most cause diseases, whose respective econo ...

s, including the first viroid to be discovered,

PSTVd The potato spindle tuber viroid (PSTVd) was the first viroid to be identified.Disco ...

. Their secondary structure is key to their

biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...

. The classification of this family is based on differences in the conserved central region sequence. The genome consists (in this order) of an LH terminal domain, a pathogenic domain, conserved central region (

pospiviroid RY motif stem loop The Pospiviroid RY motif stem loop is an RNA element found in Pospiviroids such as potato spindle tuber viroid (PSTVd). The RY nucleotide sequence motif (5'-ACAGG and CUCUUCC-5') in PSTVd, is thought to bind with the tomato protein Virp1. The ...

), variable domain, and an RH terminal domain. ''Pospiviroidae'' replication occurs in an asymmetric fashion via host cell

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

RNase Ribonuclease (commonly abbreviated RNase) is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within th ...

, and

RNA ligase In enzymology, an RNA ligase (ATP) () is an enzyme that catalyzes the chemical reaction :ATP + (ribonucleotide)n + (ribonucleotide)m \rightleftharpoons AMP + diphosphate + (ribonucleotide)n+m The 3 substrates of this enzyme are ATP, (ribonucl ...

Taxonomy

The family contains the following genera: * ''

Apscaviroid The Pospiviroidae are a family of viroids, including the first viroid to be discovered, PSTVd. Their secondary structure is key to their biological activity. The classification of this family is based on differences in the conserved central reg ...

'' * ''

Cocadviroid The Pospiviroidae are a family of viroids, including the first viroid to be discovered, PSTVd. Their secondary structure is key to their biological activity. The classification of this family is based on differences in the conserved central reg ...

'' * ''

Coleviroid The Pospiviroidae are a family of viroids, including the first viroid to be discovered, PSTVd. Their secondary structure is key to their biological activity. The classification of this family is based on differences in the conserved central reg ...

'' * ''

Hostuviroid Hostuviroid is a genus of viroids that includes ''Hop stunt viroid The hop stunt viroid (abbreviated HSVd) is a viroid species that infects the common hop plant, citrus plants and grapevines, among others. It is a member of the Pospiviroidae ...

'' * ''

Pospiviroid ''Pospiviroid'' is a genus of viroids that most commonly infects tubers. It belongs to the family ''Pospiviroidae The Pospiviroidae are a family of viroids, including the first viroid to be discovered, PSTVd. Their secondary structure is ke ...

References

External links

ICTV Report: ''Pospiviroidae''
– extensive information on pospivirioidae and viroids. Viroids {{virus-stub