In vivo visualization of nitrate dynamics using a genetically encoded fluorescent biosensor.

Nitrate (NO₃^-) uptake and distribution are critical to plant life. Although the upstream regulation of NO₃^- uptake and downstream responses to NO₃^- in a variety of cells have been well studied, it is still not possible to directly visualize the spatial and temporal distribution of NO₃^- with high resolution at the cellular level. Here, we report a nuclear-localized, genetically encoded fluorescent biosensor, which we named NitraMeter3.0, for the quantitative visualization of NO₃^- distribution in <i>Arabidopsis thaliana</i>. This biosensor tracked the spatiotemporal distribution of NO₃^- along the primary root axis and disruptions by genetic mutation of transport (low NO₃^- uptake) and assimilation (high NO₃^- accumulation). The developed biosensor effectively monitors NO₃^- concentrations at the cellular level in real time and spatiotemporal changes during the plant life cycle.