The Pospiviroidae are a family of viroid

Viroid

Viroids are plant pathogens that consist of a short stretch of highly complementary, circular, single-stranded RNA without the protein coat that is typical for viruses. The smallest discovered is a 220 nucleobase scRNA associated with the rice yellow mottle sobemovirus...

s, 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 region sequence. The genome consists (in this order) of an LH terminal domain, a pathogenic domain, conserved central domain, variable domain, and an RH terminal domain. Pospiviroidae replication occurs in an asymmetric fashion via host cell RNA polymerase

RNA polymerase

RNA polymerase is an enzyme that produces RNA. In cells, RNAP is needed for constructing RNA chains from DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses...

, RNase, and RNA ligase.

Taxonomy

• Family Pospiviroidae
  • Genus Pospiviroid
    Pospiviroid
    Pospiviroid is a genus of viroid which most commonly infects tubers. It belongs to the family pospiviroidae.The first viroid discovered was a pospiviroid, the PSTVd species ....
    
    ; type species: Potato spindle tuber viroid
    Potato spindle tuber viroid
    The Potato spindle tuber viroid was the first viroid to be identified. PSTVd is a small, circular RNA molecule closely related to the Chrysanthemum stunt viroid. Present within the viroidal RNA is the Pospiviroid RY motif stem loop. The natural hosts are potatoes and tomatoes...
    
    
  • Genus Hostuviroid
    Hostuviroid
    Hostuviroid is a genus of viroids that includes the hop stunt viroids, a group of viroids that infects many different types of plants, including the common hop plant.Some hostuviroids:Citrus gummy bark viroidGrapevine viroid...
    
    ; type species: Hop stunt viroid
    Hop stunt viroid
    The hop stunt viroid is a viroid species that infects the common hop plant, citrus plants and grapevines, among others. It is a member of the Pospiviroidae family and the Hostuviroid genus....
    
    
  • Genus Cocadviroid; type species: Coconut cadang-cadang viroid
  • Genus Apscaviroid; type species: Apple scar skin viroid
  • Genus Coleviroid; type species: Coleus blumei viroid 1

External links

• http://www-micro.msb.le.ac.uk/3035/Viroids.html - extensive information on pospivirioidae and viroids.