Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA.
Plant Physiol. 2011 Jul;156(3):1556-64. doi: 10.1104/pp.111.178012. Epub 2011 May 16.
RNA-silencing mechanisms control many aspects of gene regulation including the detection and degradation of viral RNA through the action of, among others, Dicer-like and Argonaute (AGO) proteins. However, the extent to which RNA silencing restricts virus host range has been difficult to separate from other factors that can affect virus-plant compatibility. Here we show that Potato virus X (PVX) can infect Arabidopsis (Arabidopsis thaliana), which is normally a nonhost for PVX, if coinfected with a second virus, Pepper ringspot virus. Here we show that the pepper ringspot virus 12K protein functions as a suppressor of silencing that appears to enable PVX to infect Arabidopsis. We also show that PVX is able to infect Arabidopsis Dicer-like mutants, indicating that RNA silencing is responsible for Arabidopsis nonhost resistance to PVX. Furthermore, we find that restriction of PVX on Arabidopsis also depends on AGO2, suggesting that this AGO protein has evolved to specialize in antiviral defenses.
RNA 沉默机制控制着基因调控的许多方面，包括通过 Dicer-like 和 Argonaute (AGO) 蛋白等的作用检测和降解病毒 RNA。然而，RNA 沉默在多大程度上限制了病毒的宿主范围，这一直难以与其他可能影响病毒-植物相容性的因素区分开来。在这里，我们表明，如果与第二种病毒——胡椒环斑病毒共感染，马铃薯病毒 X (PVX) 可以感染拟南芥（Arabidopsis thaliana），而拟南芥通常是 PVX 的非宿主。在这里，我们表明，胡椒环斑病毒 12K 蛋白作为一种沉默抑制因子发挥作用，似乎使 PVX 能够感染拟南芥。我们还表明，PVX 能够感染拟南芥 Dicer-like 突变体，表明 RNA 沉默是拟南芥对 PVX 的非宿主抗性的原因。此外，我们发现 PVX 在拟南芥上的限制也依赖于 AGO2，这表明这种 AGO 蛋白已经进化为专门用于抗病毒防御。
