Abstract
In this study we have identified the first plant K+/H+ exchanger, LeNHX2 from tomato (Lycopersicon esculentum Mill. cv. Moneymaker), which is a member of the intracellular NHX exchanger protein family. The LeNHX2 protein, belonging to a subfamily of plant NHX proteins closely related to the yeast NHX1 protein, is abundant in roots and stems and is induced in leaves by short term salt or abscisic acid treatment. LeNHX2 complements the salt- and hygromycin-sensitive phenotype caused by NHX1 gene disruption in yeast, but affects accumulation of K+ and not Na+ in intracellular compartments. The LeNHX2 protein co-localizes with Prevacuolar and Golgi markers in a linear sucrose gradient in both yeast and plants. A histidine-tagged version of this protein could be purified and was shown to catalyze K+/H+ exchange but only minor Na+/H+ exchange in vitro. These data indicate that proper functioning of the endomembrane system relies on the regulation of K+ and H+ homeostasis by K+/H+ exchangers.
Highlights
With concentrations between 0.1 and 0.2 M, potassium is the most abundant cation in plant cells
Isolation and Molecular Description of LeNHX1 and LeNHX2—To clone antiporters of the NHX family from tomato we aimed at identifying homologues of the Arabidopsis thaliana vacuolar (Naϩ,Kϩ)/Hϩ antiporter AtNHX1
All NHX proteins described from other plant species fall within the same group as the AtNHX1 protein constituting a group of closely related plant NHX sequences
Summary
With concentrations between 0.1 and 0.2 M, potassium is the most abundant cation in plant cells. To test the involvement of the LeNHX2 protein in these processes we subjected tomato plants of 5-week-old grown in vermiculite to a shock of 130 mM NaCl. The LeNHX2 gene showed a rapid induction by salt stress or the stress hormone abscisic acid in leaves, but was constitutively expressed in stems and roots (Fig. 3), indicating a role of this protein in the salt or osmotic stress response.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call