Production and Processing of siRNA Precursor Transcripts from the Highly Repetitive Maize Genome
Production and Processing of siRNA Precursor Transcripts from the Highly Repetitive Maize Genome
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DOI：
10.1371/journal.pgen.1000598
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发表时间：
2009-08-01
期刊：
影响因子：
4.5
通讯作者：
Hollick, Jay B.
中科院分区：
文献类型：
--
作者：
Hale, Christopher J.;Erhard, Karl F., Jr.;Hollick, Jay B.
影响玉米可遗传表观遗传状态维持的突变确定了多个RNA指导的DNA甲基化(RdDM)因子，包括RMR1，一个植物特有的Snf2相关蛋白分支的新成员。在这里，我们证明了RMR1是积累大多数24个核苷酸小RNA所必需的，包括那些来自玉米基因组中最常见的重复特征--长末端重复(LTR)反转录转座子的RNA。对DNA转座子抑制的遗传分析表明，RMR1作用于RNA依赖的RNA聚合酶RDR2(MOP1)的上游。令人惊讶的是，我们发现来自LTR反转录转座子样本的非多聚腺苷转录本在rmr1和RDR2突变体中都丢失了。相反，RNA聚合酶IV(POL IV)功能缺陷的植物表现出多腺化LTRRNA转录本的增加。这些发现支持一个模型，在该模型中，Pol IV的功能独立于RMR1和RDR2促进的小RNA积累，并支持Pol IV的丢失导致基于RNA聚合酶II的转录。此外，尽管全球范围内丢失了24个核苷酸小RNA，但rmr1突变体的基因组总体动态平衡缺乏变化，这挑战了siRNAs在维持异交草种基因组中功能异染色质方面的作用。
Mutations affecting the maintenance of heritable epigenetic states in maize identify multiple RNA-directed DNA methylation (RdDM) factors including RMR1, a novel member of a plant-specific clade of Snf2-related proteins. Here we show that RMR1 is necessary for the accumulation of a majority of 24 nt small RNAs, including those derived from Long-Terminal Repeat (LTR) retrotransposons, the most common repetitive feature in the maize genome. A genetic analysis of DNA transposon repression indicates that RMR1 acts upstream of the RNA-dependent RNA polymerase, RDR2 (MOP1). Surprisingly, we show that non-polyadenylated transcripts from a sampling of LTR retrotransposons are lost in both rmr1 and rdr2 mutants. In contrast, plants deficient for RNA Polymerase IV (Pol IV) function show an increase in polyadenylated LTR RNA transcripts. These findings support a model in which Pol IV functions independently of the small RNA accumulation facilitated by RMR1 and RDR2 and support that a loss of Pol IV leads to RNA Polymerase II-based transcription. Additionally, the lack of changes in general genome homeostasis in rmr1 mutants, despite the global loss of 24 nt small RNAs, challenges the perceived roles of siRNAs in maintaining functional heterochromatin in the genomes of outcrossing grass species.