Expression of granule-bound starch synthase 1 (GBSS1) in wheat is restricted to the grain filling process. In order to identify promoter regions which are involved in transcriptional control of the observed expression pattern, we isolated about 8 kb of a wheat gbss1-upstream region. Within this sequence several putative cis-acting elements were identified. In addition, an untranslated leader region is located in the 5' region of the gbss1 gene. To investigate promoter activity of the isolated region, the proximal 4.0 kb and progressively 5'-deleted fragments were transcriptionally fused to a beta-glucuronidase reporter gene. The function of the promoter constructs was tested by transient expression assays in various wheat tissues and in transgenic wheat plants, which were selected for low number and integrity of transgene copies. Analysis of stable transformants revealed that the -4.0 kb promoter region mediates reporter gene expression that is in accordance with the endogenous gbss1 expression. Promoter deletion to -1.9 kb or to -1.0 kb did not change the expression profile with regard to grain and pollen specificity. However, the profile of beta-glucuronidase expression during the grain filling process is altered in such a way that the level of beta-glucuronidase activity declines due to the decreasing promoter length. It is proposed that enhancer elements and cis-acting elements, which are involved in gbss1 transcription during the grain filling process, are located -1.9 kb upstream of the promoter. In addition, participation of the untranslated leader region in tissue-specific gene expression is discussed.

中文翻译：

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小麦中gbss1启动子区域的5'缺失导致组织和发育特异性的改变。

颗粒结合的淀粉合酶1（GBSS1）在小麦中的表达仅限于籽粒填充过程。为了鉴定与观察到的表达模式的转录控制有关的启动子区域，我们分离了约8 kb的小麦gbss1上游区域。在该序列内，鉴定了几种推定的顺式作用元件。此外，未翻译的前导区位于gbss1基因的5'区域。为了研究分离区的启动子活性，将近端4.0 kb和5'逐渐缺失的片段转录融合至β-葡萄糖醛酸苷酶报道基因。通过瞬时表达测定法在各种小麦组织和转基因小麦植物中测试了启动子构建体的功能，选择这些基因是为了减少转基因拷贝的数量和完整性。稳定转化体的分析表明，-4.0 kb启动子区域介导的报告基因表达与内源性gbss1表达一致。启动子缺失至-1.9kb或至-1.0kb并没有改变关于谷物和花粉特异性的表达谱。然而，在谷粒填充过程中β-葡糖醛酸苷酶表达的分布以这样的方式改变，即β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。0 kb启动子区域介导的报告基因表达符合内源性gbss1表达。启动子缺失至-1.9kb或至-1.0kb并没有改变关于谷物和花粉特异性的表达谱。然而，在谷粒填充过程中β-葡糖醛酸苷酶表达的概况以这样的方式改变，使得β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。0 kb启动子区域介导的报告基因表达符合内源性gbss1表达。启动子缺失至-1.9kb或至-1.0kb并没有改变关于谷物和花粉特异性的表达谱。然而，在谷粒填充过程中β-葡糖醛酸苷酶表达的分布以这样的方式改变，即β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。9 kb或-1.0 kb不会改变谷物和花粉特异性的表达谱。然而，在谷粒填充过程中β-葡糖醛酸苷酶表达的概况以这样的方式改变，使得β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。9 kb或-1.0 kb不会改变谷物和花粉特异性的表达谱。然而，在谷粒填充过程中β-葡糖醛酸苷酶表达的概况以这样的方式改变，使得β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。谷粒填充过程中β-葡糖醛酸苷酶表达的分布以如下方式改变：β-葡糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。谷粒填充过程中β-葡萄糖醛酸苷酶表达的分布以如下方式改变：β-葡萄糖醛酸苷酶活性的水平由于启动子长度的减少而降低。建议在籽粒充实过程中参与gbss1转录的增强子元件和顺式作用元件位于启动子上游-1.9 kb处。另外，讨论了非翻译的前导区参与组织特异性基因表达。