• Phosphate (P_i) is a critical macronutrient for the biochemical and molecular functions of cells. Under phosphate limitation, plants manifest adaptative strategies to increase phosphate scavenging. However, how low phosphate sensing links to the transcriptional machinery remains unknown.
• The role of the MEDIATOR (MED) transcriptional co‐activator, through its MED16 subunit in Arabidopsis root system architecture remodeling in response to phosphate limitation was assessed. Its critical function acting over the SENSITIVE TO PROTON RHIZOTOXICITY1 (STOP1)‐ALUMINUM‐ACTIVATED MALATE TRANSPORT1 (ALMT1) signaling module was tested through a combination of genetic, biochemical, and genome‐wide transcriptomic approaches.
• Root system configuration in response to phosphate scarcity involved MED16 functioning, which modulates the expression of a large set of low‐phosphate‐induced genes that respond to local and systemic signals in the Arabidopsis root tip, including those directly activated by STOP1. Biomolecular fluorescence complementation analysis suggests that MED16 is required for the transcriptional activation of STOP1 targets, including the membrane permease ALMT1, to increase malate exudation in response to low phosphate.
• Our results unveil the function of a critical transcriptional component, MED16, in the root adaptive responses to a scarce plant macronutrient, which helps understanding how plant cells orchestrate root morphogenesis to gene expression with the STOP1‐ALMT1 module.

中文翻译：

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MEDIATOR16 协调对拟南芥根部磷酸盐缺乏的局部和全身反应

• 磷酸盐 (P _i ) 是细胞生化和分子功能的关键常量营养素。在磷酸盐限制下，植物表现出增加磷酸盐清除的适应性策略。然而，低磷酸盐传感与转录机制的联系程度仍然未知。
• 评估了 MEDIATOR (MED) 转录共激活因子通过其 MED16 亚基在响应磷酸盐限制的拟南芥根系结构重塑中的作用。通过遗传、生化和全基因组转录组学方法的组合，测试了其对质子根毒性敏感1（STOP1）-铝激活苹果酸转运1（ALMT1）信号模块的关键功能。
• 响应磷酸盐缺乏的根系统配置涉及 MED16 功能，它调节大量低磷酸盐诱导基因的表达，这些基因对拟南芥根尖中的局部和全身信号作出反应，包括那些直接被 STOP1 激活的基因。生物分子荧光互补分析表明 MED16 是 STOP1 靶标（包括膜通透酶 ALMT1）转录激活所必需的，以增加苹果酸渗出以响应低磷酸盐。
• 我们的研究结果揭示了关键转录成分 MED16 在根系对稀有植物常量营养素的适应性反应中的功能，这有助于了解植物细胞如何通过 STOP1-ALMT1 模块协调根部形态发生与基因表达。