Abstract
K(+) and NO(3) (-) are the major forms of potassium and nitrogen that are absorbed by the roots of most terrestrial plants. In this study, we observed that a close relationship between NO(3) (-) and K(+) in Arabidopsis (Arabidopsis thaliana) is mediated by NITRATE TRANSPORTER1.1 (NRT1.1). The nrt1.1 knockout mutants showed disturbed K(+) uptake and root-to-shoot allocation, and were characterized by growth arrest under K(+)-limiting conditions. The K(+) uptake and root-to-shoot allocation of these mutants were partially recovered by expressing NRT1.1 in the root epidermis-cortex and central vasculature using SULFATE TRANSPORTER1;2 and PHOSPHATE1 promoters, respectively. Two-way analysis of variance based on the K(+) contents in nrt1.1-1/K (+) transporter1, nrt1.1-1/high-affinity K (+) transporter5-3, nrt1.1-1/K (+) uptake permease7, and nrt1.1-1/stelar K (+) outward rectifier-2 double mutants and the corresponding single mutants and wild-type plants revealed physiological interactions between NRT1.1 and K(+) channels/transporters located in the root epidermis-cortex and central vasculature. Further study revealed that these K(+) uptake-related interactions are dependent on an H(+)-consuming mechanism associated with the H(+)/NO(3) (-) symport mediated by NRT1.1. Collectively, these data indicate that patterns of NRT1.1 expression in the root epidermis-cortex and central vasculature are coordinated with K(+) channels/transporters to improve K(+) uptake and root-to-shoot allocation, respectively, which in turn ensures better growth under K(+)-limiting conditions.