Yang Wei, Jefferson Richard A, Huttner Eric, Moore James M, Gagliano Wendy B, Grossniklaus Ueli
CAMBIA, Canberra, Australian Capital Territory 2601, Australia.
Plant Physiol. 2005 Nov;139(3):1421-32. doi: 10.1104/pp.105.068262. Epub 2005 Oct 28.
Despite a central role in angiosperm reproduction, few gametophyte-specific genes and promoters have been isolated, particularly for the inaccessible female gametophyte (embryo sac). Using the Ds-based enhancer-detector line ET253, we have cloned an egg apparatus-specific enhancer (EASE) from Arabidopsis (Arabidopsis thaliana). The genomic region flanking the Ds insertion site was further analyzed by examining its capability to control gusA and GFP reporter gene expression in the embryo sac in a transgenic context. Through analysis of a 5' and 3' deletion series in transgenic Arabidopsis, the sequence responsible for egg apparatus-specific expression was delineated to 77 bp. Our data showed that this enhancer is unique in the Arabidopsis genome, is conserved among different accessions, and shows an unusual pattern of sequence variation. This EASE works independently of position and orientation in Arabidopsis but is probably not associated with any nearby gene, suggesting either that it acts over a large distance or that a cryptic element was detected. Embryo-specific ablation in Arabidopsis was achieved by transactivation of a diphtheria toxin gene under the control of the EASE. The potential application of the EASE element and similar control elements as part of an open-source biotechnology toolkit for apomixis is discussed.
尽管在被子植物繁殖中起着核心作用，但很少有配子体特异性基因和启动子被分离出来，尤其是针对难以获取的雌配子体（胚囊）。利用基于Ds的增强子捕获系ET253，我们从拟南芥（Arabidopsis thaliana）中克隆了一个卵器特异性增强子（EASE）。通过检测其在转基因背景下控制胚囊中gusA和GFP报告基因表达的能力，对Ds插入位点侧翼的基因组区域进行了进一步分析。通过对转基因拟南芥中5'和3'缺失系列的分析，将负责卵器特异性表达的序列划定为77 bp。我们的数据表明，该增强子在拟南芥基因组中是独特的，在不同的种质中是保守的，并且呈现出不寻常的序列变异模式。这个EASE在拟南芥中独立于位置和方向起作用，但可能与任何附近的基因无关，这表明它要么在远距离起作用，要么检测到了一个隐蔽元件。通过在EASE控制下激活白喉毒素基因，实现了拟南芥中的胚胎特异性消融。本文还讨论了EASE元件和类似控制元件作为无融合生殖开源生物技术工具包一部分的潜在应用。
