Plants are constantly adapting to ambient fluctuations through spatial and temporal transcriptional responses. Here, we implemented the latest-generation RNA imaging system and combined it with microfluidics to visualize transcriptional regulation in living Arabidopsis plants. This enabled quantitative measurements of the transcriptional activity of single loci in single cells, in real time and under changing environmental conditions. Using phosphate-responsive genes as a model, we found that active genes displayed high transcription initiation rates (one initiation event every ~3 s) and frequently clustered together in endoreplicated cells. We observed gene bursting and large allelic differences in single cells, revealing that at steady state, intrinsic noise dominated extrinsic variations. Moreover, we established that transcriptional repression triggered in roots by phosphate, a crucial macronutrient limiting plant development, occurred with unexpectedly fast kinetics (on the order of minutes) and striking heterogeneity between neighbouring cells. Access to single-cell RNA polymerase II dynamics in live plants will benefit future studies of signalling processes.

植物通过时空转录反应不断适应环境波动。在这里，我们实施了最新一代的 RNA 成像系统，并将其与微流体技术相结合，以可视化拟南芥中的转录调控植物。这使得能够在不断变化的环境条件下实时定量测量单个细胞中单个位点的转录活性。使用磷酸盐反应基因作为模型，我们发现活性基因显示出高转录起始率（每约 3 秒一个起始事件）并且经常在核内复制细胞中聚集在一起。我们观察到单个细胞中的基因爆发和大的等位基因差异，表明在稳定状态下，内在噪声主导外在变异。此外，我们确定由磷酸盐（一种限制植物发育的重要常量营养素）在根部引发的转录抑制以出乎意料的快速动力学（大约几分钟）和相邻细胞之间显着的异质性发生。