MED14/17招募对热诱导基因激活的差异需求
对植物热应激反应的机制进行了研究，主要集中在转录因子（TFs）的功能上。一般来说，TFs招募辅激活子，如中介体，需要组装转录机制。然而，尽管与TFs有着密切的关系，但在热应激条件下共激活子是如何参与转录调控的还不清楚。
我们发现MED14和MED17的拟南芥突变体具有严重的温度敏感性表型。转录组学分析显示，在这些突变体中，四分之一的热应激（HS）诱导基因普遍下调。此外，染色质免疫沉淀分析表明，HsfA1s作为热应激反应的主要调节因子，对HS诱导基因的表达起重要作用。
不同基因对中介体的需求存在差异，TF基因对介体的需求量较高，而热休克蛋白（HSPs）的需求量较低。
此外，人工激活HsfA1d以模拟蛋白质稳态的扰动诱导HSP基因表达，而不诱导MED14募集，而不诱导TF基因表达。考虑到共激活因子可能在其他细胞条件下发挥重要作用。
我们的研究结果强调了在植物中精确控制HS反应的介质的差异招募的重要性。
The mechanism of heat stress response in plants has been studied, focusing on the function of transcription factors (TFs). Generally, TFs recruit coactivators, such as Mediator, are needed to assemble the transcriptional machinery. However, despite the close relationship with TFs, how coactivators are involved in transcriptional regulation under heat stress conditions is largely unclear.
We found a severe thermosensitive phenotype of Arabidopsis mutants of MED14 and MED17. Transcriptomic analysis revealed that a quarter of the heat stress (HS)‐inducible genes were commonly downregulated in these mutants. Furthermore, chromatin immunoprecipitation assay showed that the recruitment of Mediator by HsfA1s, the master regulators of heat stress response, is an important step for the expression of HS‐inducible genes.
There was a differential requirement of Mediator among genes; TF genes have a high requirement whereas heat shock proteins (HSPs) have a low requirement. Furthermore, artificial activation of HsfA1d mimicking perturbation of protein homeostasis induced HSP gene expression without MED14 recruitment but not TF gene expression. Considering the essential role of MED14 in Mediator function, other coactivators may play major roles in HSP activation depending on the cellular conditions.
Our findings highlight the importance of differential recruitment of Mediator for the precise control of HS responses in plants.
下载链接：
https://sci-hub.st/10.1111/nph.17119
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