Viroid

Pospiviroidae

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Avsunviroidae

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Viroids are infectious agents that consist of single-stranded RNA. They are much smaller and simpler than viruses and lack the protein cover that is typical for viruses. Viroids use higher plants (such as potatoes, tomatoes and cucumbers) to reproduce, inserting themselves into the nucleus of a plant cell to be replicated there. 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 (PSTV). Some 33 species have been identified.

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Primary and secondary structure of the PSTV viroid:

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1 CGGAACUAAA CUCGUGGUUC CUGUGGUUCA CACCUGACCU CCUGAGCAGA AAAGAAAAAA

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61 GAAGGCGGCU CGGAGGAGCG CUUCAGGGAU CCCCGGGGAA ACCUGGAGCG AACUGGCAAA

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121 AAAGGACGGU GGGGAGUGCC CAGCGGCCGA CAGGAGUAAU UCCCGCCGAA ACAGGGUUUU

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181 CACCCUUCCU UUCUUCGGGU GUCCUUCCUC GCGCCCGCAG GACCACCCCU CGCCCCCUUU

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241 GCGCUGUCGC UUCGGCUACU ACCCGGUGGA AACAACUGAA GCUCCCGAGA ACCGCUUUUU

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301 CUCUAUCUUA CUUGCUUCGG GGCGAGGGUG UUUAGCCCUU GGAACCGCAG UUGGUUCCU

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RNA: Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. It is biochemically distinguished from DNA by the presence of an additional hydroxyl group, attached to each pentose ring. While RNA usually contains uracil instead of thymine, this is not always true, f...

Virus: :This article is concerned with virus as a biological infectious particle; for other uses of the term see virus (disambiguation). An extensive treatment of the pluralization of the word "virus" in English is found in the article Plural of virus. A list of biological viruses has also been prepared. ...

Protein: A protein (in Greek πρωτεϊνη = first thread) is a complex, high-molecular-weight organic compound that consists of amino acids joined by peptide bonds. Proteins are essential to the structure and function of all living cells and viruses....