Chimeric Activators and Repressors Define HY5 Activity and Reveal a Light-Regulated Feedback Mechanism[OPEN]
Chimeric Activators and Repressors Define HY5 Activity and Reveal a Light-Regulated Feedback Mechanism[OPEN]
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DOI：
10.1105/tpc.19.00772
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发表时间：
2020-04-01
期刊：
影响因子：
11.6
通讯作者：
Chory, Joanne
中科院分区：
文献类型：
--
作者：
Burko, Yogev;Seluzicki, Adam;Chory, Joanne
第一次暴露在阳光下标志着植物发育的一个关键转变。这种转变依赖于转录因子HY 5控制复杂的下游生长程序。尽管其重要性，其在转录中的功能仍然不清楚。先前的研究已经产生了数千个潜在的靶基因和HY 5转录调控的竞争模型。在这项工作中，我们进行了详细的表型和组成型激活和阻遏HY 5融合蛋白的分子分析。使用这种策略，我们能够过滤掉大量不太可能成为直接靶点的基因，从而消除了HY 5作用机制的几种拟议模型。我们证明HY 5的主要活性是促进转录，并且这种功能依赖于其他可能的光调节因子。此外，这种方法揭示了通过COP 1/SPA E3泛素连接酶复合物的分子反馈回路，表明在黑暗中保持低HY 5的机制，在光照下快速积累以重新编程生长。我们的策略广泛适用于转录因子活性的研究。最后，我们发现，调节这个反馈回路可以在拟南芥（Arabidopsis thaliana）和番茄（Solanum lycopersicum）中产生显着的表型多样性。HY 5促进激活而不是抑制其直接靶点，包括SPA 1，揭示了光调节反馈机制。
The first exposure to light marks a crucial transition in plant development. This transition relies on the transcription factor HY5 controlling a complex downstream growth program. Despite its importance, its function in transcription remains unclear. Previous studies have generated lists of thousands of potential target genes and competing models of HY5 transcription regulation. In this work, we carry out detailed phenotypic and molecular analysis of constitutive activator and repressor HY5 fusion proteins. Using this strategy, we were able to filter out large numbers of genes that are unlikely to be direct targets, allowing us to eliminate several proposed models of HY5's mechanism of action. We demonstrate that the primary activity of HY5 is promoting transcription and that this function relies on other, likely light-regulated, factors. In addition, this approach reveals a molecular feedback loop via the COP1/SPA E3 ubiquitin ligase complex, suggesting a mechanism that maintains low HY5 in the dark, primed for rapid accumulation to reprogram growth upon light exposure. Our strategy is broadly adaptable to the study of transcription factor activity. Lastly, we show that modulating this feedback loop can generate significant phenotypic diversity in both Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum).HY5 promotes activation rather than repression of its direct targets, including SPA1, revealing a light-regulated feedback mechanism.