Potassium transport in fungi and plants

Rodríguez‐Navarro, Alonso

doi:10.1016/s0304-4157(99)00013-1

Cited by 433 publications

(396 citation statements)

References 246 publications

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“…However, in our study, the aforementioned ability of the K ϩ /H ϩ -exchanging ionophores nigericin and monensin to rescue the Letm1-depleted T. brucei presents convincing evidence that it is indeed K ϩ homeostasis that is disrupted. Also, in contrast to K ϩ , which represents the most concentrated intracellular cation (58,59), Ca 2ϩ is a carefully regulated secondary messenger whose intracellular concentration is in the micromolar range (60), making its accumulation in the matrix a less likely cause of the swelling mitochondria phenotype. Finally, yeast still retain an ortholog of the Letm1 gene despite lacking an active Ca 2ϩ uptake mechanism (25)(26)(27)60), presumably removing the evolutionary pressure to maintain the protein in this organellar context.…”

Section: Discussionmentioning

confidence: 99%

Trypanosome Letm1 Protein Is Essential for Mitochondrial Potassium Homeostasis

Hashimi

McDonald

Stříbrná

et al. 2013

Journal of Biological Chemistry

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Background: Letm1 is a mitochondrial protein attributed disparate roles, including cation/proton antiport and translation. Results: Letm1 RNAi silencing in Trypanosoma brucei triggers swelling mitochondria and translation arrest that is ameliorated by chemical potassium/proton exchangers. Conclusion:The ancestral function of Letm1, to maintain mitochondrial potassium homeostasis, shows remarkable conservation. Significance: Results from diverged T. brucei provide a better understanding of Letm1 function throughout eukaryotes.

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Section: Discussionmentioning

confidence: 99%

Trypanosome Letm1 Protein Is Essential for Mitochondrial Potassium Homeostasis

Hashimi

McDonald

Stříbrná

et al. 2013

Journal of Biological Chemistry

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“…OsHKT2;4 permeability to H + was also examined. Since some fungal HKT homologs have been described as H + -K + symporters (Rodríguez-Navarro, 2000), and since K + is the most permeant monovalent cation through OsHKT2;4 (Fig. 3, B-D), we tested whether K + could be cotransported with H + .…”

Section: Oshkt2;4 Is Selective For K + Among Monovalent Cationsmentioning

confidence: 99%

The Rice Monovalent Cation Transporter OsHKT2;4: Revisited Ionic Selectivity

et al. 2012

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The family of plant membrane transporters named HKT (for high-affinity K+ transporters) can be subdivided into subfamilies 1 and 2, which, respectively, comprise Na+-selective transporters and transporters able to function as Na+-K+ symporters, at least when expressed in yeast (Saccharomyces cerevisiae) or Xenopus oocytes. Surprisingly, a subfamily 2 member from rice (Oryza sativa), OsHKT2;4, has been proposed to form cation/K+ channels or transporters permeable to Ca2+ when expressed in Xenopus oocytes. Here, OsHKT2;4 functional properties were reassessed in Xenopus oocytes. A Ca2+ permeability through OsHKT2;4 was not detected, even at very low external K+ concentration, as shown by highly negative OsHKT2;4 zero-current potential in high Ca2+ conditions and lack of sensitivity of OsHKT2;4 zero-current potential and conductance to external Ca2+. The Ca2+ permeability previously attributed to OsHKT2;4 probably resulted from activation of an endogenous oocyte conductance. OsHKT2;4 displayed a high permeability to K+ compared with that to Na+ (permeability sequence: K+ > Rb+ ≈ Cs+ > Na+ ≈ Li+ ≈ NH4 +). Examination of OsHKT2;4 current sensitivity to external pH suggested that H+ is not significantly permeant through OsHKT2;4 in most physiological ionic conditions. Further analyses in media containing both Na+ and K+ indicated that OsHKT2;4 functions as K+-selective transporter at low external Na+, but transports also Na+ at high (>10 mm) Na+ concentrations. These data identify OsHKT2;4 as a new functional type in the K+ and Na+-permeable HKT transporter subfamily. Furthermore, the high permeability to K+ in OsHKT2;4 supports the hypothesis that this system is dedicated to K+ transport in the plant.

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“…Because mostly mutants with great reductions in NaCl tolerance are isolated with the screening method developed in Arabidopsis , it is tempting to speculate that mutants involved in K ϩ nutrition will be preferentially isolated. Because K ϩ is an essential element for plant processes (Rodriguez-Navarro, 2000), it is expected that disruption of K ϩ nutrition results in a drastic inhibition of root growth. Analysis of the mutant segregation within each M2 family allowed us to identify mutants that are moderately more sensitive to NaCl than is the wild type.…”

Section: Identification Of Processes Involved In Salt Tolerance Othermentioning

confidence: 99%

“…The deleterious consequences of high salt concentrations in the external solution of plant cells are hyperosmotic shock and ionic imbalance (Niu et al, 1995;Zhu et al, 1997). When salinity results from an excess of NaCl, homeostasis of not only Na ϩ and Cl Ϫ but also K ϩ and Ca 2 ϩ is disturbed (Serrano et al, 1999;Hasegawa et al, 2000;Rodriguez-Navarro, 2000). Plant survival and growth are dependent on adaptations that reestablish ionic homeostasis, thereby minimizing the duration of cellular exposure to disequilibria of ions.…”

Section: Introductionmentioning

confidence: 99%

Identification of Two Loci in Tomato Reveals Distinct Mechanisms for Salt Tolerance

et al. 2001

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Salt stress is one of the most serious environmental factors limiting the productivity of crop plants. To understand the molecular basis for salt responses, we used mutagenesis to identify plant genes required for salt tolerance in tomato. As a result, three tomato salt-hypersensitive ( tss ) mutants were isolated. These mutants defined two loci and were caused by single recessive nuclear mutations. The tss1 mutant is specifically hypersensitive to growth inhibition by Na ؉ or Li ؉ and is not hypersensitive to general osmotic stress. The tss2 mutant is hypersensitive to growth inhibition by Na ؉ or Li ؉ but, in contrast to tss1 , is also hypersensitive to general osmotic stress. The TSS1 locus is necessary for K ؉ nutrition because tss1 mutants are unable to grow on a culture medium containing low concentrations of K ؉ . Increased Ca 2 ؉ in the culture medium suppresses the growth defect of tss1 on low K ؉ . Measurements of membrane potential in apical root cells were made with an intracellular microelectrode to assess the permeability of the membrane to K ؉ and Na ؉ . K ؉ -dependent membrane potential measurements indicate impaired K ؉ uptake in tss1 but not tss2 , whereas no differences in Na ؉ uptake were found. The TSS2 locus may be a negative regulator of abscisic acid signaling, because tss2 is hypersensitive to growth inhibition by abscisic acid. Our results demonstrate that the TSS1 locus is essential for K ؉ nutrition and NaCl tolerance in tomato. Significantly, the isolation of the tss2 mutant demonstrates that abscisic acid signaling is also important for salt and osmotic tolerance in glycophytic plants.

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Potassium transport in fungi and plants

Cited by 433 publications

References 246 publications

Trypanosome Letm1 Protein Is Essential for Mitochondrial Potassium Homeostasis

Trypanosome Letm1 Protein Is Essential for Mitochondrial Potassium Homeostasis

The Rice Monovalent Cation Transporter OsHKT2;4: Revisited Ionic Selectivity

Identification of Two Loci in Tomato Reveals Distinct Mechanisms for Salt Tolerance

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