AtCHX13 Is a Plasma Membrane K+ Transporter

Zhao, Jian; Cheng, Ning; Motes, Christy M.; Blancaflor, Elison B.; Moore, Miranda; Gonzales, Naomi; Padmanaban, Senthilkumar; Sze, Heven; Ward, John M.; Hirschi, Kendal D.

doi:10.1104/pp.108.124248

Cited by 96 publications

(111 citation statements)

References 41 publications

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“…Two related members, CHX20 and CHX17, restored growth of KTA40-2 yeast mutants on alkaline medium containing a low concentration of K + (Maresova and Sychrova, 2006;Padmanaban et al, 2007). By contrast, a PMlocalized CHX13 facilitated both yeast and plant growth under low K + and acidic conditions and mediated high-affinity K + uptake in yeast at pH 4.3 (Zhao et al, 2008). Thus, different CHXs appear to have a role in K + acquisition at various pH levels.…”

Section: Cellular Role Of Chx23mentioning

confidence: 95%

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

et al. 2011

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Flowering plant reproduction requires precise delivery of the sperm cells to the ovule by a pollen tube. Guidance signals from female cells are being identified; however, how pollen responds to those cues is largely unknown. Here, we show that two predicted cation/proton exchangers (CHX) in Arabidopsis thaliana, CHX21 and CHX23, are essential for pollen tube guidance. Male fertility was unchanged in single chx21 or chx23 mutants. However, fertility was impaired in chx21 chx23 double mutant pollen. Wild-type pistils pollinated with a limited number of single and double mutant pollen producing 62% fewer seeds than those pollinated with chx23 single mutant pollen, indicating that chx21 chx23 pollen is severely compromised. Double mutant pollen grains germinated and grew tubes down the transmitting tract, but the tubes failed to turn toward ovules. Furthermore, chx21 chx23 pollen tubes failed to enter the micropyle of excised ovules. Green fluorescent protein-tagged CHX23 driven by its native promoter was localized to the endoplasmic reticulum of pollen tubes. CHX23 mediated K + transport, as CHX23 expression in Escherichia coli increased K + uptake and growth in a pH-dependent manner. We propose that by modifying localized cation balance and pH, these transporters could affect steps in signal reception and/or transduction that are critical to shifting the axis of polarity and directing pollen growth toward the ovule.

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Section: Cellular Role Of Chx23mentioning

confidence: 95%

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

et al. 2011

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“…This possibility is supported by a recent study of one of the K 1 transporters in Arabidopsis. Overexpression of a cation:proton antiporter, CHX13, slightly improved growth at low pH (pH 4.3 and 5.6;Zhao et al, 2008) in K 1 -limited conditions, suggesting that K 1 homeostasis in Arabidopsis is linked to H 1 sensitivity. Dysfunction of STOP1 affected other mechanisms, which were predicted to be members of the pH homeostasis process in plant cells, namely pH-regulating metabolic pathways.…”

Section: Discussionmentioning

confidence: 99%

STOP1 Regulates Multiple Genes That Protect Arabidopsis from Proton and Aluminum Toxicities

et al. 2009

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The Arabidopsis (Arabidopsis thaliana) mutant stop1 (for sensitive to proton rhizotoxicity1) carries a missense mutation at an essential domain of the histidine-2-cysteine-2 zinc finger protein STOP1. Transcriptome analyses revealed that various genes were down-regulated in the mutant, indicating that STOP1 is involved in signal transduction pathways regulating aluminum (Al)- and H+-responsive gene expression. The Al hypersensitivity of the mutant could be caused by down-regulation of AtALMT1 (for Arabidopsis ALUMINUM-ACTIVATED MALATE TRANSPORTER1) and ALS3 (ALUMINUM-SENSITIVE3). This hypothesis was supported by comparison of Al tolerance among T-DNA insertion lines and a transgenic stop mutant carrying cauliflower mosaic virus 35S∷AtALMT1. All T-DNA insertion lines of STOP1, AtALMT1, and ALS3 were sensitive to Al, but introduction of cauliflower mosaic virus 35S∷AtALMT1 did not completely restore the Al tolerance of the stop1 mutant. Down-regulation of various genes involved in ion homeostasis and pH-regulating metabolism in the mutant was also identified by microarray analyses. CBL-INTERACTING PROTEIN KINASE23, regulating a major K+ transporter, and a sulfate transporter, SULT3;5, were down-regulated in the mutant. In addition, integral profiling of the metabolites and transcripts revealed that pH-regulating metabolic pathways, such as the γ-aminobutyric acid shunt and biochemical pH stat pathways, are down-regulated in the mutant. These changes could explain the H+ hypersensitivity of the mutant and would make the mutant more susceptible in acid soil stress than other Al-hypersensitive T-DNA insertion lines. Finally, we showed that STOP1 is localized to the nucleus, suggesting that the protein regulates the expression of multiple genes that protect Arabidopsis from Al and H+ toxicities, possibly as a transcription factor.

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“…In addition, we discover an unexpected high Na + restoration of photosynthetic activity in the mutants. (17)(18)(19). The significance of this transporter class was shown in chx20 loss-of-function mutants, in which endomembrane dynamics and osmoregulation needed for stomatal opening is affected (20).…”

Section: Significancementioning

confidence: 99%

Plastidial transporters KEA1, -2, and -3 are essential for chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis

Kunz

Gierth

Herdean

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Multiple K+ transporters and channels and the corresponding mutants have been described and studied in the plasma membrane and organelle membranes of plant cells. However, knowledge about the molecular identity of chloroplast K + transporters is limited. Potassium transport and a well-balanced K + homeostasis were suggested to play important roles in chloroplast function. Because no loss-of-function mutants have been identified, the importance of K + transporters for chloroplast function and photosynthesis remains to be determined. Here, we report single and higherorder loss-of-function mutants in members of the cation/proton antiporters-2 antiporter superfamily KEA1, KEA2, and KEA3. KEA1 and KEA2 proteins are targeted to the inner envelope membrane of chloroplasts, whereas KEA3 is targeted to the thylakoid membrane. Higher-order but not single mutants showed increasingly impaired photosynthesis along with pale green leaves and severely stunted growth. The pH component of the proton motive force across the thylakoid membrane was significantly decreased in the kea1kea2 mutants, but increased in the kea3 mutant, indicating an altered chloroplast pH homeostasis. Electron microscopy of kea1kea2 leaf cells revealed dramatically swollen chloroplasts with disrupted envelope membranes and reduced thylakoid membrane density. Unexpectedly, exogenous NaCl application reversed the observed phenotypes. Furthermore, the kea1kea2 background enables genetic analyses of the functional significance of other chloroplast transporters as exemplified here in kea1kea2Na + /H + antiporter1 (nhd1) triple mutants. Taken together, the presented data demonstrate a fundamental role of inner envelope KEA1 and KEA2 and thylakoid KEA3 transporters in chloroplast osmoregulation, integrity, and ion and pH homeostasis.

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AtCHX13 Is a Plasma Membrane K+ Transporter

Cited by 96 publications

References 41 publications

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules inArabidopsis

STOP1 Regulates Multiple Genes That Protect Arabidopsis from Proton and Aluminum Toxicities

Plastidial transporters KEA1, -2, and -3 are essential for chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis

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