Live measurement of organelle pH by plant pHluorins.

The regulation of intracellular pH homeostasis is essential for the survival of cells, but assessing the organellar pH in plants has remained challenging. The plant-compatible genetically encoded pH sensors, developed from pH-sensitive GFP variants pHluorins, are irreplaceable tools for noninvasive real-time tracking of pH in particular organelles. Plant ecliptic pHluorin (PEpHluorin) shows acidification-dependent fluorescence intensity changes, whereas the plant ratiometric pHluorin (PRpHluorin or RaVC) allows precise pH measurements in vivo.