viroid


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viroid,

microscopic infectious agent, much smaller than a virusvirus,
parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
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, that infects higher plants such as potatoes, tomatoes, chrysanthemums, and cucumbers, causing stunted or distorted growth and sometimes death. It can be transmitted by pollen, seed, or farm implements. Viroids are single strands of RNA and lack the protein coat of viruses. They do not code for any specific protein but are able to replicate themselves in the nuclei of infected cells. Some scientists believe viroids are parts of normal RNA that have gone awry. Potato spindle tuber viroid was the first to be identified.

viroid

[′vī‚rȯid]
(microbiology)
The smallest known agents of infectious disease, characterized by the absence of encapsidated proteins.
References in periodicals archive ?
An actinide dependent shadow biosphere of archaea and viroids in the above mentioned disease states are described.
That helped us decide to look at all of the loops of a viroid RNA and see how each one functions," Ding explains.
The induction and accumulation of the pathogenesis-related P69 proteinase in tomato during citrus exocortis viroid infection and in response to chemical treatments.
Viroid life: Perspectives on Nietszche and the transhuman condition.
In fact, Viroid Life consists of six essays, of which five (in modified form) have already appeared or are due to appear elsewhere.
However, despite the impressive studies, Bigornia (1977) was of the opinion that "until in-effectivity of the RNAs is conclusively demonstrated through experimental transmission, the characterization of the ccRNA-1 and ccRNA-2 and their more or less constant association with diseased condition can only be regarded as indirect supporting evidence for the viroid hypothesis of cadang-cadang."
Because researchers are unsure about how to classify them, various names have been ascribed for them, such as slow virus, virino, viroid, virion and prion, or proteinaceous infectious particle.
Another USDA scientist found the first viroid ever identified by scientists when studying potato spindle tuber disease, which is transmitted in tubers and seed.
This viroid is transmissible via seeds, but with low rate, around one to 300 (HANOLD; RANDLES, 1991b; PACUMBABA et al., 1994) and more rarely by the pollen (PACUMBABA et al., 1994).