Control of FWA gene silencing in Arabidopsis thaliana by SINE-related direct repeats
Control of FWA gene silencing in Arabidopsis thaliana by SINE-related direct repeats
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DOI：
10.1111/j.1365-313x.2006.02936.x
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发表时间：
2007-01-01
期刊：
影响因子：
7.2
通讯作者：
Kakutani, Tetsuji
中科院分区：
文献类型：
--
作者：
Kinoshita, Yuki;Saze, Hidetoshi;Kakutani, Tetsuji
晚花FWA表观遗传突变的一个独特特征是表型是由同源异型盒基因FWA的异位表达引起的。在正常发育过程中，FWA基因以印记方式在胚乳中特异性表达。CG甲基转移酶MET 1（甲基转移酶1）或染色质重塑基因DDM 1（DNA甲基化减少1）的突变体可以诱导异位FWA表达和印记破坏，这表明正确的FWA表达取决于胞嘧啶甲基化。然而，控制FWA沉默的关键甲基化残基没有被精确定位。也不知道FWA基因最初是如何在野生型植物中甲基化和沉默的。在这里，我们映射序列的关键FWA沉默的应用RdDM（RNA指导的DNA甲基化）的ddm1诱导的稳定的fwa表观等位基因。FWA转录起始位点周围的串联直接重复序列对应的双链RNA的转录诱导了DNA从头甲基化、转录抑制和表型逆转。即使没有转基因，诱导的变化也是可遗传的，这与直接重复序列中CG甲基化的遗传相关。新沉默的FWA等位基因转录胚乳特异性和印记的方式，是野生型FWA基因的情况下。结果表明，甲基化的同向重复，这可能是起源于一个短的散在核元件（SINE），足以诱导适当的表观遗传控制的FWA基因。
A unique feature of late-flowering fwa epigenetic mutations is that the phenotype is caused by ectopic expression of the homeobox gene FWA. During normal development the FWA gene is expressed specifically in the endosperm in an imprinted manner. Ectopic FWA expression and disruption of imprinting can be induced in mutants of a CG methyltransferase MET1 (methyltransferase 1) or a chromatin-remodeling gene DDM1 (decrease in DNA methylation 1), suggesting that the proper FWA expression depends on cytosine methylation. However, critical methylated residues controlling FWA silencing are not pinpointed. Nor is it understood how the FWA gene is initially methylated and silenced in wild-type plants. Here we mapped sequences critical for FWA silencing by application of RdDM (RNA-directed DNA methylation) to a ddm1-induced stable fwa epiallele. Transcription of double-stranded RNA corresponding to the tandem direct repeats around the FWA transcription start site induced de novo DNA methylation, transcriptional suppression and phenotypic reversion. The induced changes were heritable even without the transgene, which correlates with inheritance of CG methylation in the direct repeats. The newly silenced FWA allele was transcribed in an endosperm-specific and imprinted manner, as is the case for the wild-type FWA gene. The results indicate that methylation of the direct repeats, which presumably originated from a short interspersed nuclear element (SINE), is sufficient to induce proper epigenetic control of the FWA gene.