Qin Huaxia, von Arnim Albrecht G
Department of Botany, The University of Tennessee, Knoxville, TN 37996-1100, USA.
BMC Plant Biol. 2002 Dec 11;2:11. doi: 10.1186/1471-2229-2-11.
Meiotically heritable epimutations affecting transgene expression are not well understood, even and in particular in the plant model species, Arabidopsis thaliana. The Arabidopsis trans-silencer locus, C73, which encodes a fusion protein between the repressor of photomorphogenesis, COP1, and green fluorescent protein (GFP-COP1), heritably modifies the expression pattern and cop1-like cosuppression phenotypes of multiple GFP-COP1 target loci by transcriptional gene silencing.
Here we describe three additional features of trans-silencing by the C73 locus. First, the silencing phenotype of C73 and of similar complex loci was acquired epigenetically over the course of no more than two plant generations via a stage resembling posttranscriptional silencing. Second, imprints imposed by the C73 locus were maintained heritably for at least five generations in the absence of the silencer with only sporadic spontaneous reversion. Third, the pairing of two other GFP-COP1 transgene loci, L91 and E82, showed an increased tendency for epigenetic modification when L91 carried an epigenetic imprint from C73, but not when E82 bore the imprint.
The latter data suggest a transfer of trans-silencing activity from one transgene locus, C73, to another, namely L91. These results extend our operational understanding of interactions among transgenes in Arabidopsis.
影响转基因表达的减数分裂可遗传表观突变尚未得到充分理解，尤其是在植物模式物种拟南芥中。拟南芥反式沉默位点C73编码一种光形态建成抑制因子COP1与绿色荧光蛋白的融合蛋白（GFP-COP1），通过转录基因沉默可遗传地改变多个GFP-COP1靶位点的表达模式和类cop1共抑制表型。
在此，我们描述了C73位点反式沉默的另外三个特征。首先，C73和类似复杂位点的沉默表型在不超过两代植物的过程中通过类似于转录后沉默的阶段表观遗传获得。其次，在没有沉默因子的情况下，C73位点施加的印记可遗传地维持至少五代，只有零星的自发回复。第三，当L91带有来自C73的表观遗传印记时，另外两个GFP-COP1转基因位点L91和E82的配对显示出表观遗传修饰的趋势增加，但当E82带有该印记时则不然。
后一组数据表明反式沉默活性从一个转基因位点C73转移到另一个位点，即L91。这些结果扩展了我们对拟南芥中转基因之间相互作用的实际理解。
