The Arabidopsis nitrate transporter NPF7.3/NRT1.5 is involved in lateral root development under potassium deprivation

Plants have evolved a large array of transporters and channels that are responsible for uptake, source-to-sink distribution, homeostasis and signaling of nitrate (NO3-), which is for most plants the primary nitrogen source and a growth-limiting macronutrient. To optimize NO3- uptake in response to changing NO3- concentrations in the soil, plants are able to modify their root architecture. Potassium is another macronutrient that influences the root architecture. We recently demonstrated that the Arabidopsis NO3- transporter NPF7.3/NRT1.5, which drives root-to-shoot transport of NO3-, is also involved in root-to-shoot translocation of K+ under low NO3- nutrition. Here, we show that K+ shortage, but not limiting NO3- supply, causes in nrt1.5 mutant plants an altered root architecture with conspicuously reduced lateral root density. Since lateral root development is influenced by auxin, we discuss a possible involvement of NPF7.3/NRT1.5 in auxin homeostasis in roots under K+ deprivation.