The Rice Protein Kinase OsCIPK7 Enhances Salt Tolerance by Regulating Potassium Homeostasis

Salt stress disrupts ion homeostasis, leading to toxic sodium accumulation and reduced potassium uptake. The Calcineurin B-like protein (CBL) and CBL-interacting protein kinase (CIPK) network plays pivotal roles in response to abiotic stresses. Here, the root preferentially expressed OsCIPK7 with significantly salt-induced transcription was identified and functional characterized. Knockout of OsCIPK7 increased sensitivity to salt stress and a pronounced reduction of potassium content in their tissues under salt stress was observed compared to wild type. Decreased allocation of potassium was observed in the root and the youngest leaf of the knockout seedlings, accompanied by an increased distribution in older leaves relative to the wild type. However, the disruption of OsCIPK7 hardly affected the accumulation and the distribution of sodium across different organs. Notably, these phenotypic differences were completely mitigated by the addition of tetraethylammonium chloride, a non-specific inhibitor of potassium channels. Transcriptomic profiling revealed that OsCIPK7 modulates differentially expressed genes involved in ion transport, redox homeostasis, cell wall integrity and hormonal signaling. Collectively, we propose that OsCIPK7 function as a potentially salt-induced calcium-signaling component essential for maintaining sodium/potassium homeostasis and supporting certain physiological response. These findings underscore the potential for enhancing salt tolerance through precise manipulation of OsCIPK7 in plants.