Self-reporting Arabidopsis Thaliana expressing pH- and [CA2+] - Indicators unveil apoplastic ion dynamics

Abstract

The complex network of metabolic and signal transduction pathways in a living cell is ruled by a plethora of different compounds. In particular inorganic ions are of importance for cellular homeostasis and signal transduction and, therefore, tightly controlled. How ion flux and regulation is perturbed by abiotic stimuli has not yet been worked out in detail in whole intact plant systems. For non-invasive in vivo measurements of intra- and extracellular ion concentrations we Arabidopsis thaliana expressing fused pH- and calcium indicators in the cytoplasm and in the apoplast. The transgenic Arabidopsis lines provide new information how calcium and pH are regulated extracellularly and intracellularly in Arabidopsis under abiotic stress. By direct comparison of all four measurands (cytoplasmic free calcium concentration, [Ca2+]cyt; apoplastic free calcium concentration, [Ca2+]apo; cytoplasmic pH; pHcyt; and apoplastic pH, pHapo) taken under identical experimental conditions new general conclusions can be drawn on the impact of unfavourable situations on activity, flux, and crosstalk of second messenger ions like Ca2+ and H+