Avsunviroidae (lat.) - a family of viroids . To date, three representatives are known. They consist of an RNA molecule that makes up the viroid genome , 246-375 nucleotides long . They are represented by a single-stranded ring RNA molecule and have intramolecular paired bases. All representatives lack an unchanged central site.
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Content
- 1 Replication
- 2 Structure
- 3 Classification
- 4 notes
- 5 Links
Replication
Replication occurs in plant cell chloroplasts . The key features of replication in representatives of this family are the absence of the need for a helper virus , as well as the lack of protein coding. Unlike another family of viroids, Pospiviroidae , replication in Avsunviroidae follows a symmetrical repetitive mechanism. It is believed that positive RNA chains act as a template for the formation of negative strands using an enzyme similar to RNA polymerase II. The negative RNA strand is then cleaved with a ribozyme . In the second repetition of the mechanism, a positive thread is formed, which is also cleaved by the ribozyme, and then fastened and becomes annular. The exact location where replication takes place is unknown, but it is believed that this occurs in chloroplasts in the presence of magnesium ions .
Structure
It is believed that the viroids of this family exist as rod-shaped molecules with regions of paired bases, where they form pin-like structures or have branched configurations.
Classification
According to the International Committee on Taxonomy of Viruses (ICTV) , as of May 2016, 3 genera are included in the Avsunviroidae family [3] :
- Genus Avsunviroid - Type Species: ASBV (Avocado Disease Species)
- Pelamoviroid genus - type species: viroid causing peach mosaic
- Genus Elaviroid - type view: viroid affecting eggplant
Notes
- ↑ Virus taxonomy (English) on the website of the International Committee on Taxonomy of Viruses (ICTV) .
- ↑ Since 1998, Viroids has not been a valid ICTV taxon, but has been used by it for the generic name of a group of subviral particles [paragraphs 3.26 and 3.27 of the International Code for the Classification and Nomenclature of Viruses ].
- ↑ Virus taxonomy (English) on the website of the International Committee on Taxonomy of Viruses (ICTV) . (Retrieved July 15, 2016) .
Links
- MicrobiologyBytes: Viroids , < http://www.microbiologybytes.com/virology/Viroids.html > . Retrieved March 16, 2007. Archived February 24, 2007 on the Wayback Machine
- Description of Plant Viruses- Avsunviroidae , < http://www.dpvweb.net/notes/showfamily.php?family=Avsunviroidae > . Retrieved March 16, 2007.
- STUDIES ON CATALYTIC RNA MOLECULES RELEVANT TO THE RNA WORLD HYPOTHESIS , < http://www.scuoladottoratomontelatici.unifi.it/upload/sub/Talini.pdf > . Retrieved March 17, 2012. Archived July 22, 2011 on Wayback Machine