Arabidopsis thaliana has the enzymatic machinery for replicating representative viroid species of the family Pospiviroidae
Arabidopsis thaliana has the enzymatic machinery for replicating representative viroid species of the family Pospiviroidae
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DOI：
10.1073/pnas.0401090101
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发表时间：
2004-04-27
影响因子：
11.1
通讯作者：
Flores, R
中科院分区：
文献类型：
--
作者：
Daròs, JA;Flores, R
类病毒、亚病毒非编码 RNA 在植物中复制、移动并引发疾病。类病毒通过滚环机制复制，其中一种或两种极性的寡聚RNA被切割并连接成环状单体。将类病毒传播到拟南芥的尝试因未知原因而失败。为了解决这个问题，用表达 Pospiviroidae 和 Avsunviroidae 代表物种的二聚体 (+) 转录物的 cDNA 转化拟南芥，它们分别在细胞核和叶绿体中复制。始终观察到对环状 (+) 单体的正确加工，这表明拟南芥具有适当的 RNase 和 RNA 连接酶。 Northern印迹杂交还揭示了柑橘外皮类病毒和啤酒花矮化类病毒(HSVd)的多聚体(-) RNA，但没有发现Avsunviroidae科的鳄梨日斑类病毒的多聚体(-) RNA，这表明滚环机制的第一个RNA-RNA转录发生在拟南芥中，对于这两种核类病毒，它们的多聚体(-) RNA与典型宿主一样保持未加工状态。此外，表达HSVd二聚体(-)转录物的转基因拟南芥积累了环状(+)单体，尽管水平较低，并且与用作第二RNA-RNA转录模板的未加工的初级转录物一起积累。用二聚体 (+) 柑橘外皮质类病毒、HSVd 和锦紫苏类病毒 1 cDNA 农杆菌接种拟南芥表明，这些类病毒不能移动到植物远端部分，这与在实验宿主中观察到的情况相反。因此，运动缺陷或低复制似乎是限制拟南芥中某些类病毒感染性的因素。
Viroids, subviral noncoding RNAs, replicate, move, and incite diseases in plants. Viroids replicate through a rolling-circle mechanism in which oligomeric RNAs of one or both polarities are cleaved and ligated into the circular monomers. Attempts to transmit viroids to Arabidopsis have failed for unknown reasons. To tackle this question, Arabidopsis was transformed with cDNAs expressing dimeric (+) transcripts of representative species of the families Pospiviroidae and Avsunviroidae, which replicate in the nucleus and the chloroplast, respectively. Correct processing to the circular (+) monomers was always observed, demonstrating that Arabidopsis has the appropriate RNase and RNA ligase. Northern blot hybridization also revealed the multimeric (-) RNAs of Citrus exocortis viroid and Hop stunt viroid (HSVd) of the family Pospiviroidae, but not of Avocado sunblotch viroid of the family Avsunviroidae, showing that the first RNA-RNA transcription of the rolling-circle mechanism occurs in Arabidopsis for the two nuclear viroids and that their multimeric (-) RNAs remain unprocessed as in typical hosts. Moreover, transgenic Arabidopsis expressing HSVd dimeric (-) transcripts accumulated the circular (+) monomers, although at low levels, together with the unprocessed primary transcript that served as the template for the second RNA-RNA transcription. Agroinoculation of Arabidopsis with the dimeric (+) Citrus exocortis viroid, HSVd, and Coleus blumei viroid 1 cDNAs showed that these viroids could not move to distal plant parts, in contrast with the situation observed in their experimental hosts. Therefore, deficiencies in movement or low replication appear to be the factors limiting infectivity of some viroids in Arabidopsis.