title: AtCHX13 is a plasma membrane K+ transporter.
abstract: Potassium (K+) homeostasis is essential for diverse cellular processes, although how various cation transporters collaborate to maintain a suitable K+ required for growth and development is poorly understood. The Arabidopsis (Arabidopsis thaliana) genome contains numerous cation:proton antiporters (CHX), which may mediate K+ transport; however, the vast majority of these transporters remain uncharacterized. Here, we show that AtCHX13 (At2g30240) has a role in K+ acquisition. AtCHX13 suppressed the sensitivity of yeast (Saccharomyces cerevisiae) mutant cells defective in K+ uptake. Uptake experiments using (86)Rb+ as a tracer for K+ demonstrated that AtCHX13 mediated high-affinity K+ uptake in yeast and in plant cells with a K(m) of 136 and 196 microm, respectively. Functional green fluorescent protein-tagged versions localized to the plasma membrane of both yeast and plant. Seedlings of null chx13 mutants were sensitive to K+ deficiency conditions, whereas overexpression of AtCHX13 reduced the sensitivity to K+ deficiency. Collectively, these results suggest that AtCHX13 mediates relatively high-affinity K+ uptake, although the mode of transport is unclear at present. AtCHX13 expression is induced in roots during K+-deficient conditions. These results indicate that one role of AtCHX13 is to promote K+ uptake into plants when K+ is limiting in the environment.
authors.affiliation: United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Ning-Hui
authors.initials: NH
authors.lastname: Cheng
authors.forename: Christy M
authors.initials: CM
authors.lastname: Motes
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
authors.forename: Miranda
authors.initials: M
authors.lastname: Moore
authors.forename: Naomi
authors.initials: N
authors.lastname: Gonzales
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Padmanaban
authors.forename: Heven
authors.initials: H
authors.lastname: Sze
authors.forename: John M
authors.initials: JM
authors.lastname: Ward
authors.forename: Kendal D
authors.initials: KD
authors.lastname: Hirschi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010641:Phenotype; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D011188:Potassium / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D018749:RNA, Plant; D011188:Potassium