Deciphering the Molecular Mechanisms Underpinning the Transcriptional Control of Gene Expression by Master Transcriptional Regulators in Arabidopsis Seed
Deciphering the Molecular Mechanisms Underpinning the Transcriptional Control of Gene Expression by Master Transcriptional Regulators in Arabidopsis Seed
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DOI：
10.1104/pp.16.00034
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发表时间：
2016-06-01
期刊：
影响因子：
7.4
通讯作者：
Dubreucq, Bertrand
中科院分区：
文献类型：
--
作者：
Baud, Sebastien;Kelemen, Zsolt;Dubreucq, Bertrand
在拟南芥（Arabidopsis thaliana）中，种子成熟的转录控制涉及具有B3结构域的三个相关调节子，即叶子叶2（LEC 2）、脱落酸不敏感3（ABI 3）和FUSCA 3（ABI 3/FUS 3/LEC 2 [AFL]）。虽然遗传分析已经证明这些调节器的部分重叠功能，潜在的分子机制仍然难以捉摸。这里呈现的结果证实了三种蛋白质结合RY DNA元件（具有5 '-CATG-3'核心序列），但对侧翼核苷酸具有不同的特异性。在植物中，如在藓类立碗藓原生质体中，RY样（RYL）元件的存在对于B3 AFL调节OLEOSIN 1（OLE 1）启动子是必要的，但不是充分的。位于RYL元件附近的G盒样结构域也是启动子正确激活所需的，这表明涉及几种蛋白质。与这一想法一致，LEC 2和ABI 3对OLE 1启动子的激活显示出协同效应。此外，LEC 1（CCAAT结合复合物的NF-YB亚基的同源物）在LEC 2和ABI 3存在下进一步增强了该靶启动子的激活。最后，在拟南芥原生质体中产生的重组LEC 1和LEC 2蛋白可以在体外与NF-YC 2形成三元复合物，为它们的功能相互作用提供了分子解释。两者合计，这些结果使我们能够提出一个分子模型的转录调控种子基因的L-AFL蛋白，基于形成的调节多蛋白复合物之间的NF-YBs，其中携带一个特定的天冬氨酸-55残基，和B3转录因子。
In Arabidopsis (Arabidopsis thaliana), transcriptional control of seed maturation involves three related regulators with a B3 domain, namely LEAFY COTYLEDON2 (LEC2), ABSCISIC ACID INSENSITIVE3 (ABI3), and FUSCA3 (ABI3/FUS3/LEC2 [AFLs]). Although genetic analyses have demonstrated partially overlapping functions of these regulators, the underlying molecular mechanisms remained elusive. The results presented here confirmed that the three proteins bind RY DNA elements (with a 5'-CATG-3' core sequence) but with different specificities for flanking nucleotides. In planta as in the moss Physcomitrella patens protoplasts, the presence of RY-like (RYL) elements is necessary but not sufficient for the regulation of the OLEOSIN1 (OLE1) promoter by the B3 AFLs. G box-like domains, located in the vicinity of the RYL elements, also are required for proper activation of the promoter, suggesting that several proteins are involved. Consistent with this idea, LEC2 and ABI3 showed synergistic effects on the activation of the OLE1 promoter. What is more, LEC1 (a homolog of the NF-YB subunit of the CCAAT-binding complex) further enhanced the activation of this target promoter in the presence of LEC2 and ABI3. Finally, recombinant LEC1 and LEC2 proteins produced in Arabidopsis protoplasts could form a ternary complex with NF-YC2 in vitro, providing a molecular explanation for their functional interactions. Taken together, these results allow us to propose a molecular model for the transcriptional regulation of seed genes by the L-AFL proteins, based on the formation of regulatory multiprotein complexes between NF-YBs, which carry a specific aspartate-55 residue, and B3 transcription factors.