Identification of epigenetic regulators of a transcriptionally silenced transgene in maize.
Identification of epigenetic regulators of a transcriptionally silenced transgene in maize.
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DOI：
10.1534/g3.111.000232
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发表时间：
2011-06
期刊：
影响因子：
--
通讯作者：
McGinnis KM
中科院分区：
文献类型：
--
作者：
Madzima TF;Mills ES;Gardiner JM;McGinnis KM
转录基因沉默是一种对所有生物都至关重要的基因调控机制。许多转录调控机制与表观遗传修饰有关，如染色质结构的变化，核心组蛋白的乙酰化和甲基化，以及内源基因和转基因调节区内的DNA甲基化。虽然已经从之前的表观遗传转录沉默的正向遗传筛选中鉴定出几个玉米突变体，但这些筛选远未达到饱和。在这里，转录沉默的b1基因组转基因(BTG-Silent)是玉米(Zea Mays)中一个稳定的、表观遗传沉默的转基因基因，被证明是一种有效的正向遗传筛选的表型。当转基因被重新激活时，暗紫色的植物表型明显，因为B1转录因子激活了花青素的生物合成，使得沉默突变体的丢失很容易识别。利用BTG-Silent，鉴定出10个新的可能的突变体，命名为转基因再激活1-11(tgr1-6和tgr8-11)。对其中三个突变体进行了更详细的研究，分子和遗传分析表明，这些突变体与先前发现的缓解表观遗传转录沉默的玉米突变体具有不同的和重叠的表型。连锁分析表明，tgr2和tgr3不对应于其他正向遗传筛选所导致的玉米基因座上的突变，而tgr1显示与一个特征基因连锁。这些结果表明，这些突变体对未来的研究是一个有价值的资源，因为其中一些突变体可能揭示了编码玉米表观遗传基因调控所需产物的基因，但目前还没有测序的突变。
Transcriptional gene silencing is a gene regulatory mechanism essential to all organisms. Many transcriptional regulatory mechanisms are associated with epigenetic modifications such as changes in chromatin structure, acetylation and methylation of core histone proteins, and DNA methylation within regulatory regions of endogenous genes and transgenes. Although several maize mutants have been identified from prior forward genetic screens for epigenetic transcriptional silencing, these screens have been far from saturated. Herein, the transcriptionally silent b1 genomic transgene (BTG-silent), a stable, epigenetically silenced transgene in Zea mays (maize), is demonstrated to be an effective phenotype for a forward genetic screen. When the transgene is reactivated, a dark purple plant phenotype is evident because the B1 transcription factor activates anthocyanin biosynthesis, making loss of silencing mutants easy to identify. Using BTG-silent, ten new putative mutants were identified and named transgene reactivated1 through 11 (tgr1-6 and tgr8-11). Three of these mutants have been examined in more detail, and molecular and genetic assays demonstrated that these mutants have both distinct and overlapping phenotypes with previously identified maize mutants that relieve epigenetic transcriptional silencing. Linkage analysis suggests that tgr2 and tgr3 do not correspond to a mutation at previously identified maize loci resulting from other forward genetic screens, while tgr1 shows linkage to a characterized gene. These results suggest that the mutants are a valuable resource for future studies because some of the mutants are likely to reveal genes that encode products required for epigenetic gene regulation in maize but are not currently represented by sequenced mutations.
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