MULTIPLE OCS-LIKE ELEMENTS REQUIRED FOR EFFICIENT TRANSCRIPTION OF THE MANNOPINE SYNTHASE GENE OF T-DNA IN MAIZE PROTOPLASTS
MULTIPLE OCS-LIKE ELEMENTS REQUIRED FOR EFFICIENT TRANSCRIPTION OF THE MANNOPINE SYNTHASE GENE OF T-DNA IN MAIZE PROTOPLASTS
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DOI：
10.1007/bf00014490
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发表时间：
1992-10-01
影响因子：
5.1
通讯作者：
GURLEY, WB
中科院分区：
文献类型：
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作者：
FOX, PC;VASIL, V;GURLEY, WB
通过对玉米原生质体瞬时表达实验中缺失突变的分析，确定了甘露醇合成酶2‘启动子转录活性的调控元件。与野生型相比，含有与章鱼合成酶(OCS)启动子元件序列相似的-305至-290区域的缺失使活性降低67%。只有不到1%的活性保留在-153下游的5‘端缺失。在位置-325的上游包含各种异源增强子样序列，可将活性提高7.5倍。单独插入-325至-275序列，或与异源增强子类似元件结合，恢复了一些5‘-缺失突变体的活性。通过位置-127删除的突变体没有获得活性的恢复。我们的结果表明，来自玉米的一类核蛋白与OCS启动子的20bp元件以及与之高亲和力的元件相互作用，这些元件分别命名为masb(-306到-275，mas1‘元件)、d(-127到-108)和e(-82到-39；mas2’元件)。尽管Mas D处的结合位点似乎只容纳一个蛋白质，但该元件有可能对Mas 2‘启动子的活性做出微弱但积极的贡献。在mA和c处不能证明核蛋白的结合，两者与OCS元件的同源性有限。突变证据表明，mas a和mas c也可能对mas 2‘转录起作用。
Regulatory elements controlling transcriptional activity of the mannopine synthase 2' promoter (mas 2') were defined by analysis of deletion mutants in transient expression assays in maize protoplasts. Deletion of the region between -305 and -290 containing sequence similarity to the octopine synthase (ocs) promoter element reduced activity by 67% compared to wild type activity. Less than 1% of the activity remained in 5' deletions downstream of -153. Inclusion of various heterologous enhancer-like sequences immediately upstream of position -325 increased activity by up to 7.5-fold. Insertion of the -325 to -275 sequence alone, or in combination with heterologous enhancer-like elements, restored activity of some of the 5'-deletion mutants. Restoration of activity was not obtained with mutants deleted past position -127. Our results suggest that a single class of nuclear proteins from maize interact with high affinity at elements designated mas b (-306 to -275, mas 1' element), d (-127 to -108), and e (-82 to -39; mas 2' element) as well as the 20 bp element from the ocs promoter. Although the binding site at mas d only appears to accommodate a single protein, this element has the potential to make a weak, but positive, contribution to the activity of the mas 2' promoter. The binding of nuclear proteins could not be demonstrated at mas a and c, both of which showed limited homology to the ocs element. Mutational evidence suggested that mas a and c may also contribute to mas 2' transcription.