Characterization of AtCHX17, a member of the cation/H+ exchangers, CHX family, from Arabidopsis thaliana suggests a role in K+ homeostasis

• Published in: The Plant journal : for cell and molecular biology Vol. 39; no. 6; pp. 834 - 846
• Main Authors: Cellier, F, Conejero, G, Ricaud, L, Luu, D.T, Lepetit, M, Gosti, F, Casse, F
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-09-2004; Blackwell Science; Wiley
• Subjects: abscisic acid; alleles; Amino Acid Sequence; amino acid sequences; antiporters; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; AtCHX17 gene; Base Sequence; beta-glucuronidase; Biological and medical sciences; Cell physiology; CHX transporters; Conserved Sequence; cortex; DNA Primers; epidermis (plant); Fundamental and applied biological sciences. Psychology; gene expression regulation; genetic complementation; Genetics; Glucuronidase - genetics; Homeostasis; hydroponics; K+ transport; K+‐starvation; knockout mutants; Life Sciences; Molecular Sequence Data; Na+,K+/H+ antiporters; nucleotide sequences; phenotypic variation; plant morphology; Plant physiology and development; plant proteins; Plants genetics; Plants, Genetically Modified - metabolism; Plasma membrane and permeation; potassium; Potassium - metabolism; reporter genes; roots; Saccharomyces cerevisiae; salt stress; Sequence Alignment; Sequence Homology, Amino Acid; signal transduction; sodium, potassium-hydrogen antiporters; Sodium-Hydrogen Exchangers - chemistry; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; tissue distribution; transgenic plants; Calcium; Arabidopsis; Homeostasis; Ion transport; salt stress; Inorganic element; Stress; Salinity; K+ transport; Arabidopsis thaliana; CHX transporters; K+-starvation; Cruciferae; Dicotyledones; Na+,K+/H+ antiporters; Angiospermae; Spermatophyta; Mutation; Biological accumulation; Potassium; Carrier protein; Proton transport
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2004.02177.x

The Arabidopsis genome contains many sequences annotated as encoding H+-coupled cotransporters. Among those are the members of the cation:proton antiporter-2 (CPA2) family (or CHX family), predicted to encode Na+,K+/H+ antiporters. AtCHX17, a member of the CPA2 family, was selected for expression studies, and phenotypic analysis of knockout mutants was performed. AtCHX17 expression was only detected in roots. The gene was strongly induced by salt stress, potassium starvation, abscisic acid (ABA) and external acidic pH. Using the β-glucuronidase reporter gene strategy and in situ RT-PCR experiments, we have found that AtCHX17 was expressed preferentially in epidermal and cortical cells of the mature root zones. Knockout mutants accumulated less K+ in roots in response to salt stress and potassium starvation compared with the wild type. These data support the hypothesis that AtCHX17 is involved in K+ acquisition and homeostasis.