The K(+) transporter NPF7.3/NRT1.5 and the proton pump AHA2 contribute to K(+) transport in Arabidopsis thaliana under K(+) and NO(3) (-) deficiency

Nitrate (NO(3) (-)) and potassium (K(+)) are distributed in plants via short and long-distance transport. These two pathways jointly regulate NO(3) (-) and K(+) levels in all higher plants. The Arabidopsis thaliana transporter NPF7.3/NRT1.5 is responsible for loading NO(3) (-) and K(+) from root pericycle cells into the xylem vessels, facilitating the long-distance transport of NO(3) (-) and K(+) to shoots. In this study, we demonstrate a protein-protein interaction of NPF7.3/NRT1.5 with the proton pump AHA2 in the plasma membrane by split ubiquitin and bimolecular complementation assays, and we show that a conserved glycine residue in a transmembrane domain of NPF7.3/NRT1.5 is crucial for the interaction. We demonstrate that AHA2 together with NRT1.5 affects the K(+) level in shoots, modulates the root architecture, and alters extracellular pH and the plasma membrane potential. We hypothesize that NRT1.5 and AHA2 interaction plays a role in maintaining the pH gradient and membrane potential across the root pericycle cell plasma membrane during K(+) and/or NO(3) (-) transport.