Molecular Mechanisms and Regulation of K⁺ Transport in Higher Plants

Potassium (K⁺) plays a number of important roles in plant growth and development. Over the past few years, molecular approaches associated with electrophysiological analyses have greatly advanced our understanding of K⁺ transport in plants. A large number of genes encoding K⁺ transport systems have been identified, revealing a high level of complexity. Characterization of some transport systems is providing exciting information at the molecular level on functions such as root K⁺ uptake and secretion into the xylem sap, K⁺ transport in guard cells, or K⁺ influx into growing pollen tubes. In this review, we take stock of this recent molecular information. The main families of plant K⁺ transport systems (Shaker and KCO channels, KUP/HAK/KT and HKT transporters) are described, along with molecular data on how these systems are regulated. Finally, we discuss a few physiological questions on which molecular studies have shed new light.