The K1 and NO32 interaction mediated by NITRATE TRANSPORTER1.1 Ensures better plant growth under K1-limiting conditions

Abstract

K1 and NO32 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 NO32 and K1 in Arabidopsis (Arabidopsis thaliana) is mediated by NITRATE TRANSPORTER1.1 (NRT1.1). The nrt1.1 knockout mutants showed disturbed K1 uptake and root-to-shoot allocation, and were characterized by growth arrest under K1-limiting conditions. The K1 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 K1 contents in nrt1.1-1/K1 transporter1, nrt1.1-1/high-affinity K1 transporter5-3, nrt1.1-1/K1 uptake permease7, and nrt1.1-1/stelar K1 outward rectifier-2 double mutants and the corresponding single mutants and wild-type plants revealed physiological interactions between NRT1.1 and K1 channels/transporters located in the root epidermis–cortex and central vasculature. Further study revealed that these K1 uptake-related interactions are dependent on an H1-consuming mechanism associated with the H1/NO32 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 K1 channels/transporters to improve K1 uptake and root-to-shoot allocation, respectively, which in turn ensures better growth under K1-limiting conditions.