The Avsunviroidae are a family of viroids. At present three members are known of. They consist of RNA genomes between 246-375 nucleotides in length. They are single stranded covalent circles and have intramolecular base pairing. All members lack a central conserved region.

Replication

Replication occurs in the chloroplasts of plant cells. Key features of replication include no helper virus required and no proteins are encoded for. Unlike the other family of viroids, Pospiviroidae

Pospiviroidae

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 region sequence...

, Avsunviroidae are thought to replicate via a symmetrical rolling mechanism. It is thought the positive RNA strand acts as a template to form negative strands with the help of an enzyme thought to be RNA polymerase II. The negative RNA strands are then cleaved by ribozyme activity and circularises. A second rolling circle mechanism forms a positive strand which is also cleaved by ribozyme activity and then ligated to become circular.
The site of replication is unknown but it is thought to be in the chloroplast and in the presence of Mg²⁺ ions.

Structure

Predictions of structure have suggested that they exist either as rod-shaped molecules with regions of base pairing causing formation of some hair pin loops or have branched configurations.

• Family Avsunviroidae
  • Genus Avsunviroid; type species: Avocado sunblotch viroid
    Avocado sunblotch viroid
    Avocado sunblotch viroid is an important disease affecting avocado trees.Infections result in lower yields and poorer quality fruit. ASBV is the smallest known viroid that infects plants and is transmitted by pollen and infected seeds or budwood....
    
    
  • Genus Pelamoviroid; type species: Peach latent mosaic viroid
    Peach latent mosaic viroid
    Peach latent mosaic viroid is a type species from 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...
    
    
  • Genus Elaviroid; type species: Eggplant latent viroid