Viroids Lyndsay Murrow BMS 265 Nomenclature Viroid = “virus- like” Adapted from Flores R et al (1998) Arch Virol 143, 623-629. Discovery Early 1960s: 1968: 1973: Electron 1976: EM Raymer and O’Brien develop a bioassay for the agent causing potato spindle tuber disease Characterization of chrysanthemum stunt and citrus exocortis as nontypical viruses micrograph shows viroid’s hairpin structure shows that viroids form closed circular RNAs 1965: Raymer 1971: Diener 1974: 1978: PSTVd is teams up with Diener; they show that agent is not a typical virion demonstrates that the agent is a free non-coding RNA, coins the term viroid Confirmation that viroids are noncoding sequenced Example Members Genus Pospiviroids: Genus Coleviroids: PSTVd (potato spindle tuber) CbVd 1 (coleus blumei 1) Genus Hostuviroids: Genus Avsunviroids: HSVd (hop stunt) ASBVd (avocado sunblotch) Genus Cocadviroids: Genus Pelamoviroids: CCCVd (coconut cadang-cadang) PLMVd (peach latent mosaic) Genus Apscaviroids: ASSVd (apple scar skin) Pospiviroidae: Nuclear, CCR, no hammerhead self-cleavage Avsunviroidae: Chloroplastic, no CCR, hammerhead self-cleavage Evolution and Conservation William G. Scott Diener TO (1996) Virus Genes 11, 119-131. Biogenesis Adapted from Daròs J et al (2006) EMBO Reports 7, 593-598. Cellular Functions (Pathogenicity) Pray LA (2004) The Scientist 18, 23. 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 Potential as a Tool Citti L and Rainaldi G (2005) Curr Gene Ther 5, 11-24.