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

Cellier, Françoise; Conéjéro, Geneviève; Ricaud, Lilian; Luu, Doan‐Trung; Lepetit, Marc; Gosti, Françoise; Casse, Francine

doi:10.1111/j.1365-313x.2004.02177.x

Cited by 157 publications

(115 citation statements)

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“…Our results and model are consistent with genetic studies of a related protein, CHX17. K 1 starvation induced an increase of CHX17 transcripts in wild-type plants; and K 1 starvation caused a 20% decrease in K 1 content of chx17 mutant roots (Cellier et al, 2004). To offset alkalization of the cytosol in yeast grown at pH 7.5, we suggest that antiporters, like CHX20, neutralize cytosolic pH by mediating K 1 exchange for H 1 release from acidified compartments.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies showed 18 CHXs are preferentially expressed in pollen and six AtCHXs are highly expressed in roots and/or shoots (Cellier et al, 2004;Sze et al, 2004;Hall et al, 2006). However, a discrepancy in the spatial expression of CHX23 mainly in either pollen (Sze et al, 2004) or sporophytic tissues (Song et al, 2004) raises concerns about unconfirmed results.…”

Section: Discussionmentioning

confidence: 99%

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Participation of Endomembrane Cation/H+ Exchanger AtCHX20 in Osmoregulation of Guard Cells

et al. 2007

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Guard cell movement is induced by environmental and hormonal signals that cause changes in turgor through changes in uptake or release of solutes and water. Several transporters mediating these fluxes at the plasma membrane have been characterized; however, less is known about transport at endomembranes. CHX20, a member of a poorly understood cation/H+ exchanger gene family in Arabidopsis (Arabidopsis thaliana), is preferentially and highly expressed in guard cells as shown by promoter∷β-glucuronidase activity and by whole-genome microarray. Interestingly, three independent homozygous mutants carrying T-DNA insertions in CHX20 showed 35% reduction in light-induced stomatal opening compared to wild-type plants. To test the biochemical function of CHX20, cDNA was expressed in a yeast (Saccharomyces cerevisiae) mutant that lacks Na+(K+)/H+ antiporters (Δnhx1 Δnha1 Δkha1) and plasma membrane Na+ pumps (Δena1-4). Curiously, CHX20 did not enhance tolerance of mutants to moderate Na+ or high K+ stress. Instead, it restored growth of the mutant on medium with low K+ at slightly alkaline pH, but had no effect on growth at acidic pH. Green fluorescent protein-tagged CHX20 expressed in mesophyll protoplasts was localized mainly to membranes of the endosomal system. Furthermore, light-induced stomatal opening of the Arabidopsis mutants was insensitive to external pH and was impaired at high KCl. The results are consistent with the idea that, in exchanging K+ for H+, CHX20 maintains K+ homeostasis and influences pH under certain conditions. Together, these results provide genetic and biochemical evidence that one CHX protein plays a critical role in osmoregulation through K+ fluxes and possibly pH modulation of an active endomembrane system in guard cells.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Participation of Endomembrane Cation/H+ Exchanger AtCHX20 in Osmoregulation of Guard Cells

et al. 2007

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“…However, since the aha2 mutant plants show growth differences such as reduced sensitivity to toxic cations and an enhanced sensitivity to environmental stresses that challenge the plasma membrane PMF, the identities of these 27 genes could provide useful information on the plant's responses to genetically induced changes in plasma membrane energetics. Among the up-regulated mRNAs observed in aha2 mutants are, notably, a potassium transporter (AtHAK5) and a proton/potassium antiporter (K + /H + exchanger 17) known to be induced under potassium starvation (Cellier et al, 2004;Gierth et al, 2005;Maresova and Sychrova, 2006). Changes in the expression of potassium transporter genes may provide avenues by which the plant cells compensate for reductions in turgor caused by a reduced membrane potential in the mutant.…”

Section: Transcriptome Analysis Of Aha1-6 and Aha2-4 Mutantsmentioning

confidence: 99%

The Effect of a Genetically Reduced Plasma Membrane Protonmotive Force on Vegetative Growth of Arabidopsis

2012

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The plasma membrane proton gradient is an essential feature of plant cells. In Arabidopsis (Arabidopsis thaliana), this gradient is generated by the plasma membrane proton pump encoded by a family of 11 genes (abbreviated as AHA, for Arabidopsis H + -ATPase), of which AHA1 and AHA2 are the two most predominantly expressed in seedlings and adult plants. Although double knockdown mutant plants containing T-DNA insertions in both genes are embryonic lethal, under ideal laboratory growth conditions, single knockdown mutant plants with a 50% reduction in proton pump concentration complete their life cycle without any observable growth alteration. However, when grown under conditions that induce stress on the plasma membrane protonmotive force (PMF), such as high external potassium to reduce the electrical gradient or high external pH to reduce the proton chemical gradient, aha2 mutant plants show a growth retardation compared with wild-type plants. In this report, we describe the results of studies that examine in greater detail AHA2's specific role in maintaining the PMF during seedling growth. By comparing the wild type and aha2 mutants, we have measured the effects of a reduced PMF on root and hypocotyl growth, ATP-induced skewed root growth, and rapid cytoplasmic calcium spiking. In addition, genome-wide gene expression profiling revealed the up-regulation of potassium transporters in aha2 mutants, indicating, as predicted, a close link between the PMF and potassium uptake at the plasma membrane. Overall, this characterization of aha2 mutants provides an experimental and theoretical framework for investigating growth and signaling processes that are mediated by PMF-coupled energetics at the cell membrane.

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“…• C with a light intensity maintained above 300 µE · s −1 · m −2 and a day/night regime of 16 h/8 h. For determining the expression pattern of ACO genes, wild-type (Col ecotype) plants were grown under hydroponic conditions for 5 weeks as described in [23]. The other studies were performed on 10-day-old plantlets grown in liquid medium under sterile conditions [13].…”

Section: Plant Culturementioning

confidence: 99%

The iron-responsive element (IRE)/iron-regulatory protein 1 (IRP1)–cytosolic aconitase iron-regulatory switch does not operate in plants

Arnaud

Ravet

Borlotti

et al. 2007

Biochemical Journal

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Animal cytosolic ACO (aconitase) and bacteria ACO are able to switch to RNA-binding proteins [IRPs (iron-regulatory proteins)], thereby playing a key role in the regulation of iron homoeostasis. In the model plant Arabidopsis thaliana, we have identified three IRP1 homologues, named ACO1-3. To determine whether or not they may encode functional IRP proteins and regulate iron homoeostasis in plants, we have isolated loss-of-function mutants in the three genes. The aco1-1 and aco3-1 mutants show a clear decrease in cytosolic ACO activity. However, none of the mutants is affected in respect of the accumulation of the ferritin transcript or protein in response to iron excess. cis-acting elements potentially able to bind to the IRP have been searched for in silico in the Arabidopsis genome. They appear to be very rare sequences, found in the 5 -UTR (5 -untranslated region) or 3 -UTR of a few genes unrelated to iron metabolism. They are therefore unlikely to play a functional role in the regulation of iron homoeostasis. Taken together, our results demonstrate that, in plants, the cytosolic ACO is not converted into an IRP and does not regulate iron homoeostasis. In contrast with animals, the RNA binding activity of plant ACO, if any, would be more likely to be attributable to a structural element, rather than to a canonical sequence.

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

Cited by 157 publications

References 55 publications

Participation of Endomembrane Cation/H+ Exchanger AtCHX20 in Osmoregulation of Guard Cells

Participation of Endomembrane Cation/H+ Exchanger AtCHX20 in Osmoregulation of Guard Cells

The Effect of a Genetically Reduced Plasma Membrane Protonmotive Force on Vegetative Growth of Arabidopsis

The iron-responsive element (IRE)/iron-regulatory protein 1 (IRP1)–cytosolic aconitase iron-regulatory switch does not operate in plants

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