<正> Potassium is one of the major macro-nutrients essential for a number of cellular processes in plants. Low potassiumlevel in the soil represents a limiting factor for crop production. Recent studies have identified potassium transporters thatare involved in potassium acquisition, and some of them are critical for potassium nutrition under low potassium condi-tions. However, little is understood on the molecular components involved in low potassium signaling and responses. Wereport here the identification of a calcineurin B-like protein-interacting protein kinase （CIPK9） as a critical regulator oflow potassium response in Arabidopsis. The CIPK9 gene was responsive to abiotic stress conditions, and its transcriptwas inducible in both roots and shoots by potassium deprivation. Disruption of CIPK9 function rendered the mutantplants hypersensitive to low potassium media. Further analysis indicated that K+ uptake and content were not affected inthe mutant plants, implying CIPK9 in the regulation of potassium utilization or sensing processes.
