Straining the root on and off triggers local calcium signaling

Throughout their life, plant root are submitted to mechanical stresses due to pressure exerted by the soil. So far, few studies addressed root cell deformation and calcium signaling elicited by soil compression. In this study, we designed a microchip inspired by pneumatic microvalve concept in order to deliver a lateral pressure to the root of a plant expressing the RGECO1-mTurquoise calcium reporter. Lateral pressure applied on the root induced a moderate elastic deformation of root cortical cells and elicited a multicomponent calcium signal at the onset of the pressure pulse, followed by a second one at the release of the pressure. This indicates that straining rather than stressing of tissues is relevant to trigger the calcium signal. The calcium elevation was restricted to the tissue under pressure and did not propagate. Additionally, the calcium signals exhibited a remarkable attenuation upon repetitive stimulations. Highlights - A microvalve concept mimicking lateral soil pressure was developed. - Non-damaging lateral compression of the root induces an elastic deformation of cortical cells. - A multicomponent calcium signal is elicited at the onset of a pressure pulse and upon release of the pressure. - Straining rather than stressing of tissues is relevant to trigger the calcium signal. - The calcium signal is localized at the tissue under pressure and does not propagate. - Calcium signals exhibit a remarkable attenuation upon repetitive stimulations.