Eggplant latent viroid: a friendly experimental system in the family Avsunviroidae.

TAXONOMY: Eggplant latent viroid (ELVd) is the only species of the genus Elaviroid (family Avsunviroidae). All the viroids in the family Avsunviroidae contain hammerhead ribozymes in the strands of both polarities, and are considered to replicate in the chloroplasts of infected cells. This family includes two other genera: Avsunviroid and Pelamoviroid. PHYSICAL PROPERTIES: ELVd consists of a single-stranded, circular, non-coding RNA of 332-335 nucleotides that folds in a branched quasi-rod-like minimum free-energy conformation. RNAs of complementary polarity exist in infected cells and are considered to be replication intermediates. Plus (+) polarity is assigned arbitrarily to the strand that accumulates at a higher concentration in infected tissues. HOST: To date, ELVd has only been shown to infect eggplant (Solanum melongena L.), the species in which it was discovered. A very narrow host range seems to be a common property in members of the family Avsunviroidae. SYMPTOMS: ELVd infections of eggplants are apparently symptomless. TRANSMISSION: ELVd is transmitted mechanically and by seed. USEFUL WEBSITE: http://subviral.med.uottawa.ca.