A viral suppressor of gene silencing in plants
A viral suppressor of gene silencing in plants
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DOI：
10.1073/pnas.95.22.13079
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发表时间：
1998-10-27
影响因子：
11.1
通讯作者：
Vance, VB
中科院分区：
文献类型：
--
作者：
Anandalakshmi, R;Pruss, GJ;Vance, VB
基因沉默是植物中一种重要但鲜为人知的调控机制。在这里，我们报道了一种病毒序列，最初被鉴定为协同病毒疾病的介质，可抑制转基因诱导和病毒诱导的转录后基因沉默的建立。病毒沉默抑制子包含编码P1、辅助成分蛋白酶(HC-Pro)和一小部分P3的烟草蚀刻病毒基因组RNA的5'-近端区域，并且被称为P1/HC-Pro序列。使用逆转沉默测定来评估 P1/HC-Pro 序列对 uidA 报告基因转录后沉默的转基因烟草植物（T4 系）的影响。在 T4 与表达 P1/HC-Pro 的四个独立转基因系杂交的后代中，沉默被解除，但在对照杂交的后代中则没有。使用病毒载体评估P1/HC-Pro表达对病毒诱导的基因沉默(VIGS)的影响。当P1/HC-Pro从同一载体或共感染的马铃薯病毒X载体表达时，表达绿色荧光蛋白的马铃薯病毒X载体诱导绿色荧光蛋白转基因沉默的能力被消除或大大降低。 HC-Pro编码序列的单独表达足以抑制病毒诱导的基因沉默，并且HC-Pro蛋白产物是抑制所必需的。这一发现指出了基因沉默作为植物天然抗病毒防御系统的作用，并提供了不同的方法来阐明基因沉默的分子基础。
Gene silencing is an important but little understood regulatory mechanism in plants. Here we report that a viral sequence, initially identified as a mediator of synergistic viral disease, acts to suppress the establishment of both transgene-induced and virus-induced posttranscriptional gene silencing. The viral suppressor of silencing comprises the 5'-proximal region of the tobacco etch potyviral genomic RNA encoding P1, helper component-proteinase (HC-Pro) and a small part of P3, and is termed the P1/HC-Pro sequence. A reversal of silencing assay was used to assess the effect of the P1/HC-Pro sequence on transgenic tobacco plants (line T4) that are posttranscriptionally silenced for the uidA reporter gene. Silencing was lifted in offspring of T4 crosses with four independent transgenic lines expressing P1/HC-Pro, but not in offspring of control crosses. Viral vectors were used to assess the effect of P1/HC-Pro expression on virus-induced gene silencing (VIGS), The ability of a potato virus X vector expressing green fluorescent protein to induce silencing of a green fluorescent protein transgene was eliminated or greatly reduced when P1/HC-Pro was expressed from the same vector or from coinfecting potato virus X vectors. Expression of the HC-Pro coding sequence alone was sufficient to suppress virus-induced gene silencing, and the HC-Pro protein product was required for the suppression. This discovery points to the role of gene silencing as a natural antiviral defense system in plants and offers different approaches to elucidate the molecular basis of gene silencing.