Regulation of potassium uptake and storage

Abstract

Potassium (K) is an essential nutrient for every living organism, but in plants K reaches organismal contents of up to 10% of dry weight. The avidity that plants have for K is a key issue in agriculture. While cytosolic K is kept at homeostatic concentrations close to 100 mM, surplus K is stored in cell vacuoles in large quantities. An array of K transporters and direct regulators (protein kinases and phosphatases, interacting proteins, diffusive chemical messengers) have been identified as the basic elements underpinning K fluxes, but the regulatory networks involved in controlling K homeostasis in individual cells and whole organisms remain largely unknown. Current evidence indicates that active K uptake (i.e., against the electrochemical K gradient) involves K-H symporters at the plasma membrane (HAK, High-Affinity K transporters) and K/H antiporters (NHX) at the tonoplast [1-3]. These transporters, together with K-selective channels that fine-tune the membrane electrical potential by K uptake and release, share common regulators that are focal effectors of K nutrition [4-6].

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