Functional interactions between a glutamine synthetase promoter and MYB proteins
Functional interactions between a glutamine synthetase promoter and MYB proteins
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DOI：
10.1111/j.1365-313x.2004.02153.x
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发表时间：
2004-08-01
期刊：
影响因子：
7.2
通讯作者：
Campbell, MM
中科院分区：
文献类型：
--
作者：
Gómez-Maldonado, J;Avila, C;Campbell, MM
樟子松的氨同化是由PsGS1a和PsGS1b两个基因编码的谷氨酰胺合成酶(GS)[EC 6.3.1.2]催化的。PsGS1b在整个植物体内的维管组织中都有表达，被认为在代谢的各个方面释放的铵的循环中发挥作用。探讨了可能支持PsGS1b转录调控的机制。PsGS1b启动子包含一个富含先前特征的顺式作用元件的区域，称为AC元件。松树核蛋白以组织特异性的方式结合这些AC元素丰富的区域。由于以前的实验表明R2R3-MYB转录因子可以与AC元件相互作用，因此我们检测了PsGS1b启动子中的AC元件与MYB蛋白相互作用的能力。火炬松(Pinus Taeda)的两个MYB蛋白PtMYB1和PtMYB4与PsGS1b启动子结合后，能够激活该启动子在酵母、拟南芥和松树细胞中的转录。免疫定位实验表明，这两种MYB蛋白在先前显示积累PsGS1b转录本的细胞中含量最高。免疫沉淀分析和超转移电泳迁移率改变分析表明，这两个相同的蛋白质参与了松核提取物和PsGS1b启动子之间的复合体的形成。鉴于这些MYB蛋白具有激活与木质素生物合成相关的基因表达的能力，我们推测它们可能具有共同调节木质化和GS的功能，木质化是氮循环的重要要求，GS是参与氮循环途径的主要酶。
In Scots pine (Pinus sylvestris), ammonium assimilation is catalysed by glutamine synthetase (GS) [EC 6.3.1.2], which is encoded by two genes, PsGS1a and PsGS1b. PsGS1b is expressed in the vascular tissue throughout the plant body, where it is believed to play a role in recycling ammonium released by various facets of metabolism. The mechanisms that may underpin the transcriptional regulation of PsGS1b were explored. The PsGS1b promoter contains a region that is enriched in previously characterized cis-acting elements, known as AC elements. Pine nuclear proteins bound these AC element-rich regions in a tissue-specific manner. As previous experiments had shown that R2R3-MYB transcription factors could interact with AC elements, the capacity of the AC elements in the PsGS1b promoter to interact with MYB proteins was examined. Two MYB proteins from loblolly pine (Pinus taeda), PtMYB1 and PtMYB4, bound to the PsGS1b promoter were able to activate transcription from this promoter in yeast, arabidopsis and pine cells. Immunolocalization experiments revealed that the two MYB proteins were most abundant in cells previously shown to accumulate PsGS1b transcripts. Immunoprecipitation analysis and supershift electrophoretic mobility shift assays implicated these same two proteins in the formation of complexes between pine nuclear extracts and the PsGS1b promoter. Given that these MYB proteins were previously shown to have the capacity to activate gene expression related to lignin biosynthesis, we hypothesize that they may function to co-regulate lignification, a process that places significant demands on nitrogen recycling, and GS, the major enzyme involved in the nitrogen recycling pathway.