Distinct early transcriptional regulations by turgor and osmotic potential in the roots of Arabidopsis

In a context of climate change, deciphering signaling pathways driving plant adaptation to drought, changes in water availability, and salt is key. A crossing point of these plant stresses is their impact on plant water potential (Ψ), a composite physico-chemical variable reflecting the availability of water for biological processes such as plant growth and stomatal aperture. The Ψ of plant cells is mainly driven by their turgor and osmotic pressures. Here we investigated the effect of a variety of osmotic treatments on the roots of Arabidopsis plants grown in hydroponics. We used, among others, a permeating solute as a way to differentiate variations on turgor from variations in osmotic pressure. Measurement of cortical cell turgor pressure with a cell pressure probe allowed us to monitor the intensity of the treatments and thereby preserve the cortex from plasmolysis. Transcriptome analyses at an early time point (15 min) showed specific and quantitative transcriptomic responses to both osmotic and turgor pressure variations. Our results highlight how water-related biophysical parameters can shape the transcriptome of roots under stress and provide putative candidates to explore further the early perception of water stress in plants.