K+ uptake and root-to-shoot allocation in Arabidopsis require coordination of nitrate transporter1/peptide transporter family member NPF6.3/NRT1.1

Abstract

K+ and NO3- are the major forms of potassium and nitrogen that are absorbed by the roots of most terrestrial plants. In this study, we observed that the close relationship between NO3- and K+ homeostasis was mediated by nitrate transporter1 (NRT1.1) in Arabidopsis. The nrt1.1 mutants lacking NRT1.1 function showed disturbed K+ uptake and root-to-shoot allocation, especially under K+-limited conditions, and had a yellow-shoot sensitive phenotype on K+-limited medium. The K+ uptake and root-to-shoot allocation of these mutants were partially rescued by expressing NRT1.1 in the root epidermis-cortex and central vasculature by using Sultr1;2 and PHO1 promoters, respectively. Furthermore, two-way analysis of variance based on the K+ content in nrt1.1-1/akt1, nrt1.1-1/hak5-3, nrt1.1-1/kup7, and nrt1.1-1/skor-2 double mutants and their corresponding single mutants and wild-type plants revealed physiological interactions between NRT1.1 and K+ channels located in the root epidermis-cortex and central vasculature. Taken together, these data suggest that the expression of NRT1.1 in the root epidermis-cortex coordinates with K+ uptake channels to improve K+ uptake, whereas its expression in the root central vasculature coordinates with the channels loading K+ into the xylem to facilitate K+ allocation from the roots to the shoot.