Suppression of antiviral silencing by cucumber mosaic virus 2b protein in Arabidopsis is associated with drastically reduced accumulation of three classes of viral small interfering RNAs
Suppression of antiviral silencing by cucumber mosaic virus 2b protein in Arabidopsis is associated with drastically reduced accumulation of three classes of viral small interfering RNAs
复制标题
DOI：
10.1105/tpc.106.047449
复制
发表时间：
2007-06-01
期刊：
影响因子：
11.6
通讯作者：
Ding, Shou-Wei
中科院分区：
文献类型：
--
作者：
Diaz-Pendon, Juan A.;Li, Feng;Ding, Shou-Wei
我们研究了黄瓜花叶病毒（CMV）2b蛋白在感染拟南芥过程中所针对的遗传途径，已知该蛋白可抑制非细胞自主转基因沉默以及水杨酸（SA）介导的病毒抗性。我们发现，由CMV基因组表达的2b极大地减少了分别由Dicer - like4（DCL4）、DCL2和DCL3产生的21 -、22 - 和24 - 核苷酸类病毒小干扰RNA（siRNAs）的积累。在既不产生21 - 也不产生22 - 核苷酸病毒siRNAs的拟南芥突变体中，CMV 2b缺失突变体（CMV - D2b）在植物感染方面的缺陷得到了有效修复。由于遗传分析进一步确定了DCL3在DCL4上游具有独特的抗病毒作用，我们的数据表明，抑制不同病毒siRNAs的积累在2b对 antiviral silencing的抑制中起关键作用。引人注目的是，在抗病毒沉默缺陷的拟南芥突变体中，CMV - D2b引起的疾病症状与CMV引起的一样严重，这表明沉默抑制活性在病毒毒力中具有间接作用。我们发现，在没有2b干扰的情况下，CMV siRNAs的产生在很大程度上依赖于可由SA诱导的RNA依赖的RNA聚合酶1（RDR1）。鉴于已知RDR6依赖的转基因siRNAs在非细胞自主沉默中的作用，我们的结果提出了一个模型，即2b通过引导非细胞自主抗病毒沉默，抑制了赋予SA依赖的病毒抗性的RDR1依赖的病毒siRNAs的产生。
We investigated the genetic pathway in Arabidopsis thaliana targeted during infection by cucumber mosaic virus (CMV) 2b protein, known to suppress non-cell-autonomous transgene silencing and salicylic acid ( SA)-mediated virus resistance. We show that 2b expressed from the CMV genome drastically reduced the accumulation of 21-, 22-, and 24-nucleotide classes of viral small interfering RNAs (siRNAs) produced by Dicer-like4 (DCL4), DCL2, and DCL3, respectively. The defect of a CMV 2b-deletion mutant (CMV-D2b) in plant infection was efficiently rescued in Arabidopsis mutants producing neither 21- nor 22- nucleotide viral siRNAs. Since genetic analysis further identifies a unique antiviral role for DCL3 upstream of DCL4, our data indicate that inhibition of the accumulation of distinct viral siRNAs plays a key role in 2b suppression of antiviral silencing. Strikingly, disease symptoms caused by CMV-D2b in Arabidopsis mutants defective in antiviral silencing were as severe as those caused by CMV, demonstrating an indirect role for the silencing suppressor activity in virus virulence. We found that production of CMV siRNAs without 2b interference depended largely on RNA-dependent RNA polymerase 1 (RDR1) inducible by SA. Given the known role of RDR6-dependent transgene siRNAs in non-cell-autonomous silencing, our results suggest a model in which 2b inhibits the production of RDR1-dependent viral siRNAs that confer SA-dependent virus resistance by directing non-cell-autonomous antiviral silencing.