title: AtNHX3 is a vacuolar K+/H+ antiporter required for low-potassium tolerance in Arabidopsis thaliana.
abstract: Three vacuolar cation/H+ antiporters, AtNHX1 (At5g27150), 2 (At3g05030) and 5 (At1g54370), have been characterized as functional Na+/H+ antiporters in Arabidopsis. However, the physiological functions of AtNHX3 (At5g55470) still remain unclear. In this study, the physiological functions of AtNHX3 were studied using T-DNA insertion mutant and 35S-driven AtNHX3 over-expression Arabidopsis plants. RT-PCR analyses revealed that AtNHX3 is highly expressed in germinating seeds, flowers and siliques. Experiments with AtNHX3::YFP fusion protein in tobacco protoplasts indicated that AtNHX3 is mainly localized to vacuolar membrane, with a minor localization to pre-vacuolar compartments (PVCs) and endoplasmic reticulum (ER). Seedlings of null nhx3 mutants were hypersensitive to K+-deficient conditions. Expression of AtNHX3 complemented the sensitivity to K+ deficiency in nhx3 seedlings. Tonoplast vesicles isolated from transgenic plants over-expressing AtNHX3 displayed significantly higher K+/H+ exchange rates than those isolated from wild-type plants. Furthermore, nhx3 seeds accumulated less K+ and more Na+ when both wild-type and nhx3 were grown under normal growth condition. The overall results indicate that AtNHX3 encodes a K+/H+ antiporter required for low-potassium tolerance during germination and early seedling development, and may function in K+ utilization and ion homeostasis in Arabidopsis.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.forename: Renjie
authors.initials: R
authors.lastname: Tang
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Cuiting
authors.initials: C
authors.lastname: Wang
authors.forename: Qundan
authors.initials: Q
authors.lastname: Lv
authors.forename: Xiaoshu
authors.initials: X
authors.lastname: Gao
authors.forename: Wenbin
authors.initials: W
authors.lastname: Li
authors.forename: Hongxia
authors.initials: H
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018525:Germination; D016254:Mutagenesis, Insertional; D009154:Mutation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000254:growth & development; D014026:Nicotiana / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D027961:Potassium-Hydrogen Antiporters; D018749:RNA, Plant; C036483:T-DNA; D011188:Potassium