Evolution and control of imprinted FWA genes in the genus Arabidopsis.
Evolution and control of imprinted FWA genes in the genus Arabidopsis.
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DOI：
10.1371/journal.pgen.1000048
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发表时间：
2008-04-04
期刊：
影响因子：
4.5
通讯作者：
Kakutani T
中科院分区：
文献类型：
--
作者：
Fujimoto R;Kinoshita Y;Kawabe A;Kinoshita T;Takashima K;Nordborg M;Nasrallah ME;Shimizu KK;Kudoh H;Kakutani T
基因组印记的一个中心问题是如何将特定序列识别为表观遗传标记的靶标。在哺乳动物和植物中，印迹基因通常与串联重复序列和转座子相关序列相关，但这些元件在表观遗传基因沉默中的作用仍然难以捉摸。FWA是拟南芥中的一个印记基因，在雌配子体和胚乳中特异表达。FWA的组织特异性和印迹表达依赖于FWA启动子中的DNA甲基化，FWA启动子由两个含有与SINE逆转录元件相关的序列的正向重复序列组成。该元件的甲基化导致表观遗传沉默，但尚不清楚甲基化是否靶向SINE相关序列本身或直接重复结构也是必需的。在这里，我们表明，在FWA启动子的重复结构是高度多样化的物种内属拟南芥。四个独立的串联重复序列形成事件中发现的三个密切相关的物种。另一个相关物种，A。halleri，在FWA启动子中没有串联重复序列。出乎意料的是，即使在该物种中，FWA表达也是印记的，并且FWA启动子被甲基化。此外，我们的FWA基因在营养组织中的表达分析揭示了高频率的表达水平的种内变异。总之，我们表明，串联重复序列结构是不稳定的表观遗传沉默的FWA基因。相反，SINE相关序列足以用于印记、营养沉默和靶向DNA甲基化。在FWA启动子中频繁的独立串联重复序列形成事件使我们提出它们可能是表观遗传控制的后果，而不是原因。表观遗传变异在进化过程中的生殖策略的可能意义进行了讨论。基因组印记是哺乳动物和开花植物中已知的一种表观遗传过程，是依赖于亲本的单等位基因表达。基因组印记的一个中心问题是如何将特定序列识别为表观遗传标记的靶标。在哺乳动物和植物中，印迹基因通常与串联重复序列和转座子相关序列相关，但这些元件在表观遗传基因沉默中的作用仍然难以捉摸。FWA是拟南芥中的一个印记基因，在雌配子体和胚乳中特异表达。FWA启动子由两个含有与SINE逆转录元件相关的序列的同向重复序列组成。该元件的甲基化导致表观遗传沉默，但尚不清楚甲基化是否靶向SINE相关序列本身或直接重复结构是必需的。在这里，我们表明，直接重复结构是高度多样性的物种内属拟南芥。出乎意料的是，我们发现，直接重复结构是无关的表观遗传沉默和甲基化的FWA启动子。相反，SINE相关的启动子序列对于这些特征是足够的。频繁的独立形成的串联重复序列表明，它们可能是表观遗传控制系统的结果。
A central question in genomic imprinting is how a specific sequence is recognized as the target for epigenetic marking. In both mammals and plants, imprinted genes are often associated with tandem repeats and transposon-related sequences, but the role of these elements in epigenetic gene silencing remains elusive. FWA is an imprinted gene in Arabidopsis thaliana expressed specifically in the female gametophyte and endosperm. Tissue-specific and imprinted expression of FWA depends on DNA methylation in the FWA promoter, which is comprised of two direct repeats containing a sequence related to a SINE retroelement. Methylation of this element causes epigenetic silencing, but it is not known whether the methylation is targeted to the SINE-related sequence itself or the direct repeat structure is also necessary. Here we show that the repeat structure in the FWA promoter is highly diverse in species within the genus Arabidopsis. Four independent tandem repeat formation events were found in three closely related species. Another related species, A. halleri, did not have a tandem repeat in the FWA promoter. Unexpectedly, even in this species, FWA expression was imprinted and the FWA promoter was methylated. In addition, our expression analysis of FWA gene in vegetative tissues revealed high frequency of intra-specific variation in the expression level. In conclusion, we show that the tandem repeat structure is dispensable for the epigenetic silencing of the FWA gene. Rather, SINE-related sequence is sufficient for imprinting, vegetative silencing, and targeting of DNA methylation. Frequent independent tandem repeat formation events in the FWA promoter led us to propose that they may be a consequence, rather than cause, of the epigenetic control. The possible significance of epigenetic variation in reproductive strategies during evolution is also discussed. Genomic imprinting, mono-allelic gene expression depending on the parent-of-origin, is an epigenetic process known in mammals and flowering plants. A central question in genomic imprinting is how a specific sequence is recognized as the target for epigenetic marking. In both mammals and plants, imprinted genes are often associated with tandem repeats and transposon-related sequences, but the role of these elements in epigenetic gene silencing remains elusive. FWA is an imprinted gene in Arabidopsis thaliana expressed specifically in the female gametophyte and endosperm. The FWA promoter is comprised of two direct repeats containing a sequence related to a SINE retroelement. Methylation of this element causes epigenetic silencing, but it is not known whether the methylation is targeted to the SINE-related sequence itself or the direct repeat structure is necessary. Here we show that the direct repeat structure is highly diverse in species within the genus Arabidopsis. Unexpectedly, we found that the direct repeat structure is dispensable for the epigenetic silencing and methylation of the FWA promoter. Rather, the SINE-related promoter sequence is sufficient for these features. Frequent independent formation of the tandem repeats suggests that they may be a consequence of the epigenetically controlled system.
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影响因子：
30.8
作者：
Martienssen, RA
通讯作者：
Martienssen, RA
影响因子：
5.3
作者：
Lewis, A;Mitsuyaj, K;Reik, W
通讯作者：
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将RNA定向DNA甲基化的两步募集到串联重复序列。
影响因子：
9.8
作者：
Chan, Simon W-L;Zhang, Xiaoyu;Bernatavichute, Yana V;Jacobsen, Steven E
通讯作者：
Jacobsen, Steven E
影响因子：
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作者：
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通讯作者：
Kakutani, T
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作者：
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