背景回顾：One of the most important regulatory small molecules in plants is indole-3-acetic acid, also known as auxin. Its dynamic redistribution has an essential role in almost every aspect of plant life, ranging from cell shape and division to organogenesis and responses to light and gravity. 

提出问题：So far, it has not been possible to directly determine the spatial and temporal distribution of auxin at a cellular resolution. Instead it is inferred from the visualization of irreversible processes that involve the endogenous auxin-response machinery; however, such a system cannot detect transient changes. 

主要研究biosensor

结果1-构建：The sensor is based on the Escherichia coli tryptophan repressor, the binding pocket of which is engineered to be specific to auxin. Coupling of the auxin-binding moiety with selected fluorescent proteins enables the use of a fluorescence resonance energy transfer signal as a readout. 

结果2-作用：Unlike previous systems, this sensor enables direct monitoring of the rapid uptake and clearance of auxin by individual cells and within cell compartments in planta. 

结果3-应用sensorenables real-time monitoring of auxin concentrations at a (sub)cellular resolution.

 摘 要 

植物中最重要的一个小分子调节物质就是吲哚-3-乙酸，也就是众所周知的生长素。其动态分布几乎参与了植物生长和发育的方方面面，从细胞形状和分裂，到器官发生和对光照、重力的响应等。目前为止，还没有能够从细胞水平上直接监测生长素的时空分布模式的技术。相反，目前对于生长素时空分布的推断是基于内源性生长素响应机制的不可逆过程的可视化；然而，这种系统不能检测生长素的瞬时变化。本文中，作者报道了一种用于植物体内定量可视化生长素分布的基因编码生物感应器。该生物传感器的设计基于的是大肠杆菌的色氨酸抑制子，其结合囊被设计为对生长素具有特异性。将生长素结合部分与所选择的荧光蛋白偶联，从而通过荧光共振能量转移信号作为监测读数。与以前的系统不同，这种生物传感器能够直接监测单个细胞以及细胞内区室中的生长素快速吸取和清除。通过对生长素沿根轴的分级空间分布和转运抑制剂的干扰，以及内源生长素在重力矢量变化下的快速可逆再分布的测试结果表明，作者设计的生物传感器能够实时监测植物生命周期中，（亚）细胞层面的生长素浓度及其时空分布。