Mobile 24 nt Small RNAs Direct Transcriptional Gene Silencing in the Root Meristems of Arabidopsis thaliana
Mobile 24 nt Small RNAs Direct Transcriptional Gene Silencing in the Root Meristems of Arabidopsis thaliana
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DOI：
10.1016/j.cub.2011.08.065
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发表时间：
2011-10-11
期刊：
影响因子：
9.2
通讯作者：
Baulcombe, David C.
中科院分区：
文献类型：
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作者：
Melnyk, Charles W.;Molnar, Attila;Baulcombe, David C.
开花植物中的RNA沉默产生在细胞之间移动并通过韧皮部的信号[1，2]。信号的核苷酸序列特异性由Dicer样（DCL）蛋白产生的21、22和24个核苷酸（nt）sRNA赋予[3]。在受体细胞中，这些sRNA与Argonaute（AGO）沉默效应物结合，21 nt sRNA通过mRNA切割介导转录后调节（PTGS）[4]，而24 nt sRNA与RNA依赖性DNA甲基化（RdDM）[5]相关，这可能是转录基因沉默（TGS）的基础。有趣的是，参与TGS的基因是与PTGS相关的移植物可传递基因沉默所必需的[6]。然而，PTGS沉默信号从拟南芥属的脉中传播出来也需要一些相同的基因[7]，并且嫁接试验未能证明TGS信号的直接传递[8-10]。因此，移动的沉默似乎只与PTGS相关。为了解决这种可能性，我们嫁接的TGS-inducing野生型拟南芥和突变体，这是妥协的24 nt的sRNA生产到野生型报告线。来自TGS构建体的21-24 nt sRNA被传递穿过嫁接联合，但只有24 nt sRNA指导分生组织细胞中转基因启动子的RdDM和TGS。这些数据扩展了RNA沉默信号的意义，以涵盖表观遗传学和转录基因沉默，并支持这些信号将信息传递到分生组织细胞的假设，在那里它们启动可能影响生长，发育和遗传表型的持续表观遗传变化。
RNA silencing in flowering plants generates a signal that moves between cells and through the phloem [1, 2]. Nucleotide sequence specificity of the signal is conferred by 21, 22, and 24 nucleotide (nt) sRNAs that are generated by Dicer-like (DCL) proteins [3]. In the recipient cells these sRNAs bind to Argonaute (AGO) effectors of silencing and the 21 nt sRNAs mediate posttranscriptional regulation (PTGS) via mRNA cleavage [4] whereas the 24 nt sRNAs are associated with RNA-dependent DNA methylation (RdDM) [5] that may underlie transcriptional gene silencing (TGS). Intriguingly, genes involved in TGS are required for graft-transmissible gene silencing associated with PTGS [6]. However, some of the same genes were also required for spread of a PTGS silencing signal out of the veins of Arabidopsis [7], and grafting tests failed to demonstrate direct transmission of TGS signals [8-10]. It seemed likely, therefore, that mobile silencing is associated only with PTGS. To address this possibility, we grafted TGS-inducing wild-type Arabidopsis and a mutant that is compromised in 24 nt sRNA production onto a wild-type reporter line. The 21-24 nt sRNAs from the TGS construct were transmitted across a graft union but only the 24 nt sRNAs directed RdDM and TGS of a transgene promoter in meristematic cells. These data extend the significance of an RNA silencing signal to embrace epigenetics and transcriptional gene silencing and support the hypothesis that these signals transmit information to meristematic cells where they initiate persistent epigenetic changes that may influence growth, development, and heritable phenotypes.