An infectious pathogen with a very simple structure that was discovered in 1971 as potato wilt disease. Viruses generally have nucleic acid (DNA or RNA) as genes covered with a protein coat, but viroids are made of naked RNA (→ ribonucleic acid) without a protein coat. In Japan, they have sometimes been called "virus-like." Fifteen types of plant viroid diseases have been discovered, including hop stunt disease, apple rust, and plum variegation. Viroid RNA is less than one-tenth the size of the smallest viral RNA, but its infectious power is far stronger than that of any plant virus. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
1971年にジャガイモヤセ病で発見された,きわめて単純な構造の感染性病原体。ウイルスは一般に遺伝子としての核酸 (DNAまたは RNA) が蛋白質の殻をかぶっているが,ウイロイドは蛋白質の殻をもたない裸の RNA (→リボ核酸 ) から成る。日本では「ウイルスもどき」と呼ばれていたこともある。ホップ矮化病,リンゴ銹病,スモモ斑入り果病など 15種の植物ウイロイド病が発見されている。ウイロイドの RNAは,最も小さいウイルス RNAの 10分の1以下の大きさしかないが,その感染力はどの植物ウイルスよりもはるかに強い。
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