Exquisitely regulated plastid-to-nucleus communication by retrograde signaling pathways is essential for fine-tuning of responses to the prevailing environmental conditions. The plastidial retrograde signaling metabolite methylerythritol cyclodiphosphate (MEcPP) has emerged as a stress signal transduced into a diverse ensemble of response outputs. Here, we demonstrate enhanced phytochrome B protein abundance in red light-grown MEcPP-accumulating ceh1 mutant Arabidopsis (Arabidopsis thaliana) plants relative to wild-type seedlings. We further establish MEcPP-mediated coordination of phytochrome B with auxin and ethylene signaling pathways and uncover differential hypocotyl growth of red light-grown seedlings in response to these phytohormones. Genetic and pharmacological interference with ethylene and auxin pathways outlines the hierarchy of responses, placing ethylene epistatic to the auxin signaling pathway. Collectively, our findings establish a key role of a plastidial retrograde metabolite in orchestrating the transduction of a repertoire of signaling cascades. This work positions plastids at the zenith of relaying information coordinating external signals and internal regulatory circuitry to secure organismal integrity.

逆行信号通路对质体与核之间的通讯进行精确调节，对于微调对主要环境条件的响应至关重要。质体逆行信号代谢物甲基赤藓糖醇环二磷酸酯（MEcPP）已作为压力信号转导到各种响应输出集合中。在这里，我们证明了在红光生长的累积MEcPP的ceh1突变拟南芥（拟南芥（Arabidopsis thaliana）中增强了植物色素B蛋白的丰度）相对于野生型幼苗的植物。我们进一步建立了MEcPP介导的植物色素B与植物生长素和乙烯信号通路的协调，并揭示了响应这些植物激素的红光生长幼苗的下胚轴生长差异。对乙烯和植物生长素途径的遗传和药理学干扰概述了反应的层次，将乙烯上位性置于植物生长素信号传导途径上。总的来说，我们的发现确立了质体逆行代谢产物在协调信号级联反应全集的转导中的关键作用。这项工作将质体定位在传递信息的顶点，以协调外部信号和内部调节电路，以确保机体完整性。