1a:I[76865,["/_next/static/chunks/d07a36b34c614bac.js","/_next/static/chunks/a439560253821848.js","/_next/static/chunks/992d80515d7f780d.js","/_next/static/chunks/3adfb55b15c8d19c.js","/_next/static/chunks/b642b3e65e2c6231.js","/_next/static/chunks/fc50eca1ad01dc11.js","/_next/static/chunks/afc6bdd59b458409.js","/_next/static/chunks/6448cccc5d968256.js"],"Grid"] 1b:I[17291,["/_next/static/chunks/d07a36b34c614bac.js","/_next/static/chunks/a439560253821848.js","/_next/static/chunks/992d80515d7f780d.js","/_next/static/chunks/3adfb55b15c8d19c.js","/_next/static/chunks/b642b3e65e2c6231.js","/_next/static/chunks/fc50eca1ad01dc11.js","/_next/static/chunks/afc6bdd59b458409.js","/_next/static/chunks/6448cccc5d968256.js"],"GridCol"] 1c:I[34616,["/_next/static/chunks/d07a36b34c614bac.js","/_next/static/chunks/a439560253821848.js","/_next/static/chunks/992d80515d7f780d.js","/_next/static/chunks/3adfb55b15c8d19c.js","/_next/static/chunks/b642b3e65e2c6231.js","/_next/static/chunks/fc50eca1ad01dc11.js","/_next/static/chunks/afc6bdd59b458409.js","/_next/static/chunks/6448cccc5d968256.js"],"Avatar"] 1d:I[32972,["/_next/static/chunks/d07a36b34c614bac.js","/_next/static/chunks/a439560253821848.js","/_next/static/chunks/992d80515d7f780d.js","/_next/static/chunks/3adfb55b15c8d19c.js","/_next/static/chunks/b642b3e65e2c6231.js","/_next/static/chunks/fc50eca1ad01dc11.js","/_next/static/chunks/afc6bdd59b458409.js","/_next/static/chunks/6448cccc5d968256.js"],"default"] 1e:T4c7,Excessive Na⁺ in soils inhibits plant growth. Here, we report that Na⁺ stress triggers primary calcium signals specifically in a cell group within the root differentiation zone, thus forming a "sodium-sensing niche" in Arabidopsis. The amplitude of this primary calcium signal and the speed of the resulting Ca²⁺ wave dose-dependently increase with rising Na⁺ concentrations, thus providing quantitative information about the stress intensity encountered. We also delineate a Ca²⁺-sensing mechanism that measures the stress intensity in order to mount appropriate salt detoxification responses. This is mediated by a Ca²⁺-sensor-switch mechanism, in which the sensors SOS3/CBL4 and CBL8 are activated by distinct Ca²⁺-signal amplitudes. Although the SOS3/CBL4-SOS2/CIPK24-SOS1 axis confers basal salt tolerance, the CBL8-SOS2/CIPK24-SOS1 module becomes additionally activated only in response to severe salt stress. Thus, Ca²⁺-mediated translation of Na⁺ stress intensity into SOS1 Na⁺/H⁺ antiporter activity facilitates fine tuning of the sodium extrusion capacity for optimized salt-stress tolerance.

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