Spatial and temporal control of transcription of the soybean β-conglycinin α subunit gene is conferred by its proximal promoter region and accounts for the unequal distribution of the protein during embryogenesis
Spatial and temporal control of transcription of the soybean β-conglycinin α subunit gene is conferred by its proximal promoter region and accounts for the unequal distribution of the protein during embryogenesis
复制标题
DOI：
10.1266/ggs.83.469
复制
发表时间：
2008-12-01
影响因子：
1.1
通讯作者：
Kanazawa, Akira
中科院分区：
文献类型：
--
作者：
Imoto, Yusuke;Yamada, Tetsuya;Kanazawa, Akira
分化成特定的胚细胞类型与导致植物中种子贮藏蛋白积累的过程相关。伴大豆球蛋白的α亚基是大豆种子贮藏蛋白的主要成分，在发育中的胚中，其在子叶中的积累水平高于在胚轴中的积累水平。为了理解这种现象的机制，我们的特点是在转录控制方面的a亚基基因的上游区域使用转基因拟南芥植物携带报告基因构建体，包括1357 bp的上游序列的a亚基基因和P-葡萄糖醛酸酶（GUS）基因。GUS基因表达的时程依赖模式的分析表明，表达首先局限于子叶和发生在整个胚胎在胚胎发生过程中。GUS基因在大豆胚中的表达量在整个表达过程中，子叶中的表达量高于胚轴中的表达量，这与α亚基蛋白在大豆胚中的分布一致。通过测试逐渐变短的启动子片段，子叶和胚轴中负责转录激活的顺式作用元件都定位于相对于转录起始位点跨越-245至-161的区域。它还得出结论，上游区域高达-245是足以控制转录的空间和时间模式，而进一步的上游区域影响转录速率而不影响转录模式。总体而言，这些结果表明，在胚胎内的亚基蛋白的不平等分布主要是建立作为一个短的近端启动子区的基因在不同的胚胎组织中控制的差异转录激活的结果。
Differentiation into specific embryo cell types correlates with the processes that lead to the accumulation of seed storage proteins in plants. The a subunit of beta-conglycinin, a major component of seed storage proteins in soybean, accumulates at a higher level in cotyledons than in the embryonic axis in developing embryos. To understand the mechanisms underlying this phenomenon, we characterized the upstream region of the a subunit gene in terms of transcriptional control using transgenic Arabidopsis thaliana plants carrying reporter gene constructs comprising the 1357-bp upstream sequence of the a subunit gene and the P-glucuronidase (GUS) gene. Analysis of the time-course-dependent pattern of GUS expression revealed that the expression was first confined to the cotyledons and occurred later in the entire embryo during embryogenesis. The level of GUS expression was higher in cotyledons than in the embryonic axis throughout the period of its expression, coincident with the distribution of the a subunit protein in soybean embryos. By testing progressively shorter promoter fragments, the cis-acting elements responsible for transcriptional activation in the cotyledons and the embryonic axis were both localized to the region spanning -245 to -161 relative to the transcription start site. It is also concluded that the upstream region up to -245 is sufficient to control the spatial and temporal pattern of transcription, while further upstream regions influence transcription rate without affecting the transcriptional pattern. Overall, these results indicate that the unequal distribution of a subunit protein within the embryos is established primarily as a consequence of differential transcriptional activation controlled by a short proximal promoter region of the gene in different embryonic tissues.