Viroids are plant pathogens that consist of a short stretch (a few hundred nucleobases) of highly complementary, circular, single-stranded RNA without the protein coat that is typical for viruses. The smallest so far is a 220 nucleobase scRNA (small cytoplasmic RNA) associated with the rice yellow mottle sobemovirus (RYMV)^[1]. In comparison, the genome of the smallest known viruses capable of causing an infection by themselves are around 2 kilobases in size. For other uses, see Plant (disambiguation). ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ... Nucleobases are the parts of RNA and DNA that are involved in pairing up (see also base pairs). ... Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. ... The outer shell of a virus is called the capsid. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. ... Adenine Guanine Thymine Cytosine ... A unit of measurement in molecular biology denoting a length of 1000 nucleotides (bases) of DNA or RNA. Categories: | ...

Viroid RNA does not code for any known protein; some even lack the AUG initiation codon. The replication mechanism involves interaction with RNA polymerase II, an enzyme normally associated with synthesis of messenger RNA, and "rolling circle" synthesis of new RNA. Some viroids are ribozymes, having RNA enzyme properties which allow self-cleavage and ligation of unit-size genomes from larger replication intermediates. It has been proposed that viroids are "escaped introns". A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... ATG and AUG denote sequences of DNA and RNA respectively that are the start codon or initiation codon encoding the amino acid methionine (Met) in eukaryotes and a modified Met ( fMet) in prokaryotes. ... Rolling circle replication describes a process of DNA replication that can rapidly synthesize multiple copies of circular molecules of DNA, such as plasmids and the genomes of bacteriophages. ... A ribozyme, or RNA enzyme, is an RNA molecule that can catalyze a chemical reaction. ... Diagram of the location of introns and exons within a gene. ...

Viroids are usually transmitted by seed or pollen. Infected plants can show distorted growth. The first viroid to be identified was the Potato spindle tuber viroid (PSTVd). Some 33 species have been identified. A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), hollyhock (Sidalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Type species Potato spindle tuber viroid The Potato Spindle Tuber Viroid (PSTV) infects potatoes. ...

Primary and secondary structure of the PSTVd viroid:

 1 CGGAACUAAA CUCGUGGUUC CUGUGGUUCA CACCUGACCU CCUGAGCAGA AAAGAAAAAA 61 GAAGGCGGCU CGGAGGAGCG CUUCAGGGAU CCCCGGGGAA ACCUGGAGCG AACUGGCAAA 121 AAAGGACGGU GGGGAGUGCC CAGCGGCCGA CAGGAGUAAU UCCCGCCGAA ACAGGGUUUU 181 CACCCUUCCU UUCUUCGGGU GUCCUUCCUC GCGCCCGCAG GACCACCCCU CGCCCCCUUU 241 GCGCUGUCGC UUCGGCUACU ACCCGGUGGA AACAACUGAA GCUCCCGAGA ACCGCUUUUU 301 CUCUAUCUUA CUUGCUUCGG GGCGAGGGUG UUUAGCCCUU GGAACCGCAG UUGGUUCCU 

Putative secondary structure of the PSTVd viroid

Download high resolution version (1184x86, 6 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1184x86, 6 KB) Wikipedia does not have an article with this exact name. ...

Taxonomy

• Family Pospiviroidae
  • Genus Pospiviroid; type species: Potato spindle tuber viroid
  • Genus Hostuviroid; type species: Hop stunt viroid
  • Genus Cocadviroid; type species: Coconut cadang-cadang viroid
  • Genus Apscaviroid; type species: Apple scar skin viroid
  • Genus Coleviroid; type species: Coleus blumei viroid 1
• Family Avsunviroidae
  • Genus Avsunviroid; type species: Avocado sunblotch viroid
  • Genus Pelamoviroid; type species: Peach latent mosaic viroid

Genera Pospiviroid Hostuviroid Cocadviroid Apscaviroid Coleviroid The Pospiviroidae is a family of viroids. ... Species (PSTV) Potato spindle tuber viroid The Pospiviroid is a genus of viroid which most commonly infects tubers. ... Type species Potato spindle tuber viroid The Potato Spindle Tuber Viroid (PSTV) infects potatoes. ... Avocado Sunblotch Viroid (ASBV) is an important disease affecting avocado trees. ...

See also

Wikibooks has more about this subject:

General Biology/Classification of Living Things/Viruses, Prions, and Viroids

• Virus
• Virusoid
• Virus classification
• Satellite (biology)
• Prion

Image File history File links Wikibooks-logo-en. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. ... Virusoids are infectious agents that infect plants in conjunction with an assistant virus; the assistant virus is required for successful infection. ... Virus classification involves naming and placing viruses into a taxonomic system. ... Groups Satellite viruses Satellite nucleic acids Satellites are subviral agents composed of nucleic acids; they depend for their multiplication on coinfection of a host cell with a helper virus. ... A prion (IPA: [1]  ) — short for proteinaceous infectious particle — (by analogy to virion) is a type of infectious agent. ...

References

Further reading

• WikiSpecies:Virus
• Wikipedia:WikiProject Viruses