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Plant Cell Environ. 2015 Nov;38(11):2223-38. doi: 10.1111/pce.12524. Epub 2015 Apr 25.

CHX14 is a plasma membrane K-efflux transporter that regulates K(+) redistribution in Arabidopsis thaliana.

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National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Agricultural Research Service Children's Nutrition Research Center, United States Department of Agriculture, Baylor College of Medicine, 1100 Bates Street, Houston, TX, 77030, USA.
Plant Biology Division, Samuel Roberts Noble Foundation Inc, 2510 Sam Noble Parkway, Ardmore, OK, 73401, USA.
Department of Horticulture, Forestry and Recreation Resources, Kansas State University, Manhattan, KS, 66506, USA.
Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX, 77845, USA.


Potassium (K(+) ) is essential for plant growth and development, yet the molecular identity of many K(+) transporters remains elusive. Here we characterized cation/H(+) exchanger (CHX) 14 as a plasma membrane K(+) transporter. CHX14 expression was induced by elevated K(+) and histochemical analysis of CHX14 promoter::GUS transgenic plants indicated that CHX14 was expressed in xylem parenchyma of root and shoot vascular tissues of seedlings. CHX14 knockout (chx14) and CHX14 overexpression seedlings displayed different growth phenotypes during K(+) stress as compared with wild-type seedlings. Roots of mutant seedlings displayed higher K(+) uptake rates than wild-type roots. CHX14 expression in yeast cells deficient in K(+) uptake renders the mutant cells more sensitive to deficiencies of K(+) in the medium. CHX14 mediates K(+) efflux in yeast cells loaded with high K(+) . Uptake experiments using (86) Rb(+) as a tracer for K(+) with both yeast and plant mutants demonstrated that CHX14 expression in yeast and in planta mediated low-affinity K(+) efflux. Functional green fluorescent protein (GFP)-tagged versions of CHX14 were localized to both the yeast and plant plasma membranes. Taken together, we suggest that CHX14 is a plasma membrane K(+) efflux transporter involved in K(+) homeostasis and K(+) recirculation.


Arabidopsis; CHX; nutrition; potassium

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