Potassium channel function is fundamental to many physiological processes in plants. In this issue of Cell, identify a protein complex in Arabidopsis consisting of a potassium channel, a protein kinase, and a calcium sensor. This study reveals that plants cope with limited soil potassium by coupling potassium channel activation to a cellular calcium signaling network.

Primary cultures of rat brain astrocytes were used to examine the uptake of the glucose analogue, 2-deoxy-d-glucose (2-DOG). 2-DOG competes with glucose for uptake, indicating that both are transported by the same carrier system. Extracellular K + at 1 1 . 9 m ~ increased the uptake of 2-DOG at 2-DOG concentrations greater than 100 p ~ . Uptake appears Na+-dependent only at high concentrations ...

Kinetics of K exchange in the steady state and of net K uptake after osmotic upshock are reported for the four K transport systems of Escherichia coli: Kdp, TrkA, TrkD, and TrkF. Energy requirements for K exchange are reported for the Kdp and TrkA systems. For each system, kinetics of these two modes of K transport differ from those for net K uptake by K-depleted cells (Rhoads, D. B. F.B. Walt...

Analysis of K transport mutants indicates the existence of four separate K uptake systems in Escherichia coli K-12. A high affinity system called Kdp has a Km of 2 muM, and Vmax at 37 degrees C of 150 mumol/g min. This system is repressed by growth in high concentrations of K. Two constitutive systems, TrkA and TrkD, have Km's of 1.5 and 0.5 mM and Vmax's of 550 and 40 at 37 and 30 degrees C, r...

This study investigated the uptake of three macronutrients, including nitrogen (N), phosphorus (P), and potassium (K), by rice roots in response to different infestation levels of Nilaparvata lugens (Stål) (Homoptera: Delphacidae). Hydroponics experiments were conducted on the rice variety 'Zhendao 2' (moderately resistant to Tryporyza incertulas, Lepidoptera: Pyralidae) and the variety 'Xiushu...

K+ released from exercising muscle via K+ channels needs to be removed from the interstitium into the blood to maintain high muscle cell membrane potential and allow normal muscle contractility. Uptake by red blood cells has been discussed as one mechanism that would also serve to regulate red blood cell volume, which was found to be constant despite increased plasma osmolality and K+ concentra...

Potassium (K(+)) is one of the essential nutrient elements for plant growth and development. Plants absorb K(+) ions from the environment via root cell K(+) channels and/or transporters. In this study, the Shaker K(+) channel Os-AKT1 was characterized for its function in K(+) uptake in rice (Oryza sativa) roots, and its regulation by Os-CBL1 (Calcineurin B-Like protein1) and Os-CIPK23 (CBL-Inte...

The function of HKT1 in roots is controversial. We tackled this controversy by studying Na+ uptake in barley (Hordeum vulgare) roots, cloning the HvHKT1 gene, and expressing the HvHKT1 cDNA in yeast (Saccharomyces cerevisiae) cells. High-affinity Na+ uptake was not detected in plants growing at high K+ but appeared soon after exposing the plants to a K(+)-free medium. It was a uniport, insensit...

Potassium (K+) is one of the essential nutrient elements for plant growth and development. Plants absorb K+ ions from the environment via root cell K+ channels and/or transporters. In this study, the Shaker K+ channel Os-AKT1 was characterized for its function in K+ uptake in rice (Oryza sativa) roots, and its regulation by Os-CBL1 (Calcineurin B-Like protein1) and OsCIPK23 (CBL-Interacting Pro...