Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress

Potassium transporters play crucial roles in K+ uptake and translocation in plants. However, so far little is known about the regulatory mechanism of potassium transporters. Here, we show that a Shaker-like potassium channel AtKC1, encoded by the AtLKT1 gene cloned from the Arabidopsis thaliana low-K+ (LK)-tolerant mutant Atlkt1, significantly regulates AKT1-mediated K+ uptake under LK conditions. Under LK conditions, the Atkc1 mutants maintained their root growth, whereas wild-type plants stopped their root growth. Lesion of AtKC1 significantly enhanced the tolerance of the Atkc1 mutants to LK stress and markedly increased K+ uptake and K+ accumulation in the Atkc1-mutant roots under LK conditions. Electrophysiological results showed that AtKC1 inhibited the AKT1-mediated inward K+ currents and negatively shifted the voltage dependence of AKT1 channels. These results demonstrate that the 'silent' K+ channel alpha-subunit AtKC1 negatively regulates the AKT1-mediated K+ uptake in Arabidopsis roots and consequently alters the ratio of root-to-shoot under LK stress conditions.