1. Viroids Lyndsay Murrow BMS 265

2. Nomenclature Viroid = “virus- like” Adapted from Flores R et al (1998) Arch Virol 143, 623-629.

3. 1974: Confirmation that viroids are non- coding 1973: Electron micrograph shows viroid’s hairpin structure Discovery Early 1960s: Raymer and O’Brien develop a bioassay for the agent causing potato spindle tuber disease 1965: Raymer teams up with Diener; they show that agent is not a typical virion 1971: Diener demonstrates that the agent is a free non-coding RNA, coins the term viroid 1968: Characterization of chrysanthemum stunt and citrus exocortis as non- typical viruses 1978: PSTVd is sequenced 1976: EM shows that viroids form closed circular RNAs

4. Example Members Genus Pospiviroids: PSTVd (potato spindle tuber) Genus Hostuviroids: HSVd (hop stunt) Genus Cocadviroids: CCCVd (coconut cadang-cadang) Genus Apscaviroids: ASSVd (apple scar skin) Genus Coleviroids: CbVd 1 (coleus blumei 1) Genus Avsunviroids: ASBVd (avocado sunblotch) Genus Pelamoviroids: PLMVd (peach latent mosaic) Pospiviroidae: Nuclear, CCR, no hammerhead self-cleavage Avsunviroidae: Chloroplastic, no CCR, hammerhead self-cleavage

5. Evolution and Conservation Diener TO (1996) Virus Genes 11, 119-131.William G. Scott

6. Biogenesis Adapted from Daròs J et al (2006) EMBO Reports 7, 593-598.

7. Cellular Functions (Pathogenicity) Pray LA (2004) The Scientist 18, 23.

8. Mechanism of Action Martick M and Scott WG (2006) SSRL Research Highlight 11, 119-131. http://ssrl.slac.stanford.edu/research/highlights_archive/ribozyme.html http://rnaworld.bio.ku.edu

9. Potential as a Tool Citti L and Rainaldi G (2005) Curr Gene Ther 5, 11-24.