Mature monomeric forms of Hop stunt viroid resist RNA silencing in transgenic plants
Mature monomeric forms of Hop stunt viroid resist RNA silencing in transgenic plants
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DOI：
10.1111/j.1365-313x.2007.03203.x
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发表时间：
2007-09-01
期刊：
影响因子：
7.2
通讯作者：
Pallas, V.
中科院分区：
文献类型：
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作者：
Gomez, G.;Pallas, V.
类病毒，小的非编码致病性RNA，能够诱导RNA沉默，这一现象与这些小RNA的发病和进化有关。最近有人提出，类病毒可能会抵抗植物的这种防御机制。然而，非复制全长类病毒RNA的同时降解，以及成熟形式的类病毒对RNA沉默的抗性，尚未得到实验证明。本拟烟草转基因植物表达二聚体形式的啤酒花病毒（HSVd），具有切割和循环这种类病毒RNA的能力来解决这个问题。一个由全长HSVd RNA与GFP-mRNA融合组成的报告基因在这些植物中被混染，其表达被抑制。有趣的是，在这些限制性条件下，圆形和线性HSVd分子都是稳定的，并且能够通过移植物运输，这表明成熟形式的HSVd能够以某种方式抵抗rna沉默机制。观察到全长HSVd RNA与GFP-mRNA融合，但不是圆形和/或线性类病毒形式，完全容易受到RNA降解的影响，这强烈表明，自由成熟单体采用的结构保护了与发病相关的类病毒形式免受RNA沉默。
Viroids, small non-coding pathogenic RNAs, are able to induce RNA silencing, a phenomenon that has been associated with the pathogenesis and evolution of these small RNAs. It has been recently suggested that viroids may resist this plant defense mechanism. However, the simultaneous degradation of non-replicating full-length viroid RNA, and the resistance of mature forms of viroids to RNA silencing, have not been experimentally demonstrated. Transgenic Nicotiana benthamiana plants expressing a dimeric form of Hop stunt viroid (HSVd) that have the capability to cleave and circularize this viroid RNA were used to address this question. A reporter construct, consisting of a full-length HSVd RNA fused to GFP-mRNA, was agroinfiltrated in these plants and its expression was suppressed. Interestingly, both circular and linear HSVd molecules were stable and able to traffic through grafts in these restrictive conditions, indicating that the mature forms of HSVd are able, in some way, to resist the RNA-silencing mechanism. The observation that a full-length HSVd RNA fused to GFP-mRNA, but not circular and/or linear viroid forms, was fully susceptible to RNA degradation strongly suggests that structures adopted by the free mature monomer protect the pathogenesis-associated forms of the viroid from RNA silencing.