NPF (NRT1) Family Nitrate Transporter EhNPF6.3, an Ortholog of AtNPF6.3, from the Halophyte Eutrema halophilum (C.A.Mey.) O.E.Schulz: Cloning and Functional Analysis

Abstract

The coding sequence of EhNPF6.3, a homolog of the Arabidopsis thaliana dual-affinity nitrate transporter gene AtNPF6.3 (NRT1.1/CHL1), was cloned from the halophyte Eutrema halophilum (C.A.Mey.) O.E.Schulz / Thellungiella halophila. Expression of EhNPF6.3 in cells of a yeast Ogataea (Hansenula) polymorpha mutant strain for YNT1, the gene of the only nitrate transporter in this organism, restored nitrate uptake by the mutant cells and their ability to growth in selective media containing nitrate as the sole nitrogen source. Examination of nitrate ion uptake from the culture media by cells of O. polymorpha (Morais & M.H. Maia) Y. Yamada, K. Maeda and Mikata strains of wild-type, the Δynt1 knockout mutant, and the knockout mutant expressing EhNPF6.3, using a nitrate-selective electrode, showed that the rate of nitrate uptake by the halophyte transporter, EhNPF6.3, was comparable to that by the endogenous yeast nitrate transporter, YNT1. The results obtained indicate that the protein cloned from the halophyte E. halophilum, EhNPF6.3, is an ortholog of the dual-affinity nitrate transporter and, most likely, plays an important role in nitrate uptake and nitrate distribution among organs and tissues in E. halophilum plants.