title: Thellungiella halophila, a salt-tolerant relative of Arabidopsis thaliana, has specific root ion-channel features supporting K+/Na+ homeostasis under salinity stress.
abstract: Thellungiella halophila is a salt-tolerant relative of Arabidopsis thaliana with high genetic and morphological similarity. In a saline environment, T. halophila accumulates less sodium and retains more potassium than A. thaliana. Detailed electrophysiological comparison of ion currents in roots of both species showed that, unlike A. thaliana, T. halophila exhibits high potassium/sodium selectivity of the instantaneous current. This current differs in its pharmacological profile from the current through inward- and outward-rectifying K(+) channels insofar as it is insensitive to Cs(+) and TEA(+), but resembles voltage-independent channels of glycophytes as it is inhibited by external Ca(2+). Addition of Cs(+) and TEA(+) to the growth medium confirmed the key role of the instantaneous current in whole-plant sodium accumulation. A negative shift in the reversal potential of the instantaneous current under high-salt conditions was essential for decreasing sodium influx to twofold lower than the corresponding value in A. thaliana. The lower overall sodium permeability of the T. halophila root plasma membrane resulted in a smaller membrane depolarization during salt exposure, thus allowing the cells to maintain their driving force for potassium uptake. Our data provide quantitative evidence that specific features of ion channels lead to superior sodium/potassium homeostasis in a halophyte compared with a closely related glycophyte.
authors.affiliation: Plant Science Group, IBLS, University of Glasgow, Glasgow G12 8QQ, UK. v.volkov@bio.gla.ac.uk
authors.forename: Vadim
authors.initials: V
authors.lastname: Volkov
authors.forename: Anna
authors.initials: A
authors.lastname: Amtmann
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D017136:Ion Transport; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D018517:Plant Roots / Q000502:physiology*; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D013045:Species Specificity
chemical_list: D007473:Ion Channels; D012964:Sodium; D011188:Potassium