Cesium Toxicity in Arabidopsis

Hampton, Corrina R.; Bowen, Helen C.; Broadley, Martin R.; Hammond, John P.; Mead, Andrew; Payne, K A; Pritchard, Jeremy; White, Philip J.

doi:10.1104/pp.104.046672

Cited by 169 publications

(162 citation statements)

References 42 publications

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“…It was reported that K + deprivation may induce the transcriptional expression of some K + transporters [41][42][43]. However, K + deficiency did not alter AKT1 transcription [26,44,45]. Our observations showed that overexpressing AKT1 in the 35S::AKT1 Arabidopsis line did not change their phenotype under LK stress (unpublished data).…”

Section: A Complex K + Uptake Regulatory Pathway In Arabidopsis In Resupporting

confidence: 53%

Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress

Wang

et al. 2010

Cell Res

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Potassium transporters play crucial roles in K + uptake and translocation in plants. However, so far little is known about the regulatory mechanism of potassium transporters. Here, we show that a Shaker-like potassium channel AtKC1, encoded by the AtLKT1 gene cloned from the Arabidopsis thaliana low-K + (LK)-tolerant mutant Atlkt1, significantly regulates AKT1-mediated K + uptake under LK conditions. Under LK conditions, the Atkc1 mutants maintained their root growth, whereas wild-type plants stopped their root growth. Lesion of AtKC1 significantly enhanced the tolerance of the Atkc1 mutants to LK stress and markedly increased K + uptake and K + accumulation in the Atkc1-mutant roots under LK conditions. Electrophysiological results showed that AtKC1 inhibited the AKT1-mediated inward K + currents and negatively shifted the voltage dependence of AKT1 channels. These results demonstrate that the 'silent' K + channel α-subunit AtKC1 negatively regulates the AKT1-mediated K + uptake in Arabidopsis roots and consequently alters the ratio of root-to-shoot under LK stress conditions. Keywords: Arabidopsis; potassium channel; low-K + stress; AKT1; AtKC1 Cell Research (2010) IntroductionPotassium is an essential mineral element for plant growth and development, and it plays essential roles in many important physiological and biochemical processes in living plant cells, such as regulation of enzyme activation, electrical neutralization, osmoregulation, control of membrane potential, co-transport of sugars, and so on [1,2]. Plant growth and development need millimolar K + in the soil or growth medium, but typical K + concentration at the interface of roots and soils is within micromolar range [3]. Thus, plants often encounter low-K + (LK) stress under natural conditions. Although different plants or different genotypes of a plant species show varied K + utilization efficiency [4], most plants show K + -deficient symptom under LK stress, typically leaf chlorosis and subsequent inhibition of plant growth and development [5].Absorption of K + by plant cells and K + translocation between different tissues and organs in plants are mediated by plant K + transporters and channels [2,6,7]. Over the past decade, a large number of genes encoding plant K + transporters and channels, particularly for Arabidopsis, have been characterized [6][7][8]. These K + transporters vary in K + affinity, kinetics, transcriptional modulation, regulatory mechanism, etc [2,[6][7][8], and they compose a complex system for plant K + uptake and translocation. Among these K + transporters and channels, members of the Shaker K + channel family are well characterized for their potential functions and are probably the most important for K + uptake and transport in Arabidopsis [8] Recent reports showed that channel heterotetramerization is a key regulatory mechanism for K + channels, which was found not only in animals [14][15][16] but also in plants [17,18]. Different kinds of potassium channel subunits may assemble together to form functional heteromer...

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Section: A Complex K + Uptake Regulatory Pathway In Arabidopsis In Resupporting

confidence: 53%

Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress

Wang

et al. 2010

Cell Res

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“…The chemical similarity of the non-essential alkali cation Cs þ with the essential K þ is a major obstacle for genetic attempts to manipulate radiocaesium accumulation and to prevent it from entry into the food chain 5,6,9 . In this study, however, we demonstrate that specific discrimination against Cs þ is possible in the yeast sec22D mutant, while other cations including K þ are retained at wild-type levels.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies have shown that Cs þ may either inhibit or compete with K þ -dependent processes, and that K þ and Cs þ concentrations are not strictly correlated 9,11,12 . Therefore, alternative transport processes may enable a discrimination between these closely related cations.…”

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Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Dräxl

Müller

et al. 2013

Nat Commun

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The non-essential cation caesium (Cs þ ) is assimilated by all organisms. Thus, anthropogenically released radiocaesium is of concern to agriculture. Cs þ accumulates owing to its chemical similarity to the potassium ion (K þ ). The apparent lack of a Cs þ -specific uptake mechanism has obstructed attempts to manipulate Cs þ accumulation without causing pleiotropic effects. Here we show that the SNARE protein Sec22p/SEC22 specifically impacts Cs þ accumulation in yeast and in plants. Loss of Saccharomyces cerevisiae Sec22p does not affect K þ homeostasis, yet halves Cs þ concentration compared with the wild type. Mathematical modelling of the uptake time course predicts a compromised vacuolar Cs þ deposition in sec22D. Biochemical fractionation confirms this and indicates a new feature of Sec22p in enhancing non-selective cation deposition. A developmentally controlled loss-of-function mutant of the orthologous Arabidopsis thaliana SEC22 phenocopies the reduced Cs þ uptake without affecting plant growth. This finding provides a new strategy to reduce radiocaesium entry into the food chain.

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“…The choice of concentrations of inhibitors was based on previous studies: 500 mM 8-bromocAMP (Maathuis and Sanders, 2001), 10 mM CaCl 2 , 10 mM LiCl (Rubio et al, 2004), 10 mM TEA-Cl (Essah et al, 2003), 3 mM CsCl (Hampton et al, 2004), and 5 mM BaCl 2 (Garciadeblas et al, 2003). Each treatment, which lasted between 48 and 144 h (see figure and table legends or the text for details) under the conditions described above, had eight replicates with three plants per beaker.…”

Section: Plant Materials and Treatmentsmentioning

confidence: 99%

Low-Affinity Na+ Uptake in the HalophyteSuaeda maritima

2007

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Na+ uptake by plant roots has largely been explored using species that accumulate little Na+ into their shoots. By way of contrast, the halophyte Suaeda maritima accumulates, without injury, concentrations of the order of 400 mm NaCl in its leaves. Here we report that cAMP and Ca2+ (blockers of nonselective cation channels) and Li+ (a competitive inhibitor of Na+ uptake) did not have any significant effect on the uptake of Na+ by the halophyte S. maritima when plants were in 25 or 150 mm NaCl (150 mm NaCl is near optimal for growth). However, the inhibitors of K+ channels, TEA+ (10 mm), Cs+ (3 mm), and Ba2+ (5 mm), significantly reduced the net uptake of Na+ from 150 mm NaCl over 48 h, by 54%, 24%, and 29%, respectively. TEA+ (10 mm), Cs+ (3 mm), and Ba2+ (1 mm) also significantly reduced 22Na+ influx (measured over 2 min in 150 mm external NaCl) by 47%, 30%, and 31%, respectively. In contrast to the situation in 150 mm NaCl, neither TEA+ (1–10 mm) nor Cs+ (0.5–10 mm) significantly reduced net Na+ uptake or 22Na+ influx in 25 mm NaCl. Ba2+ (at 5 mm) did significantly decrease net Na+ uptake (by 47%) and 22Na+ influx (by 36% with 1 mm Ba2+) in 25 mm NaCl. K+ (10 or 50 mm) had no effect on 22Na+ influx at concentrations below 75 mm NaCl, but the influx of 22Na+ was inhibited by 50 mm K+ when the external concentration of NaCl was above 75 mm. The data suggest that neither nonselective cation channels nor a low-affinity cation transporter are major pathways for Na+ entry into root cells. We propose that two distinct low-affinity Na+ uptake pathways exist in S. maritima: Pathway 1 is insensitive to TEA+ or Cs+, but sensitive to Ba2+ and mediates Na+ uptake under low salinities (25 mm NaCl); pathway 2 is sensitive to TEA+, Cs+, and Ba2+ and mediates Na+ uptake under higher external salt concentrations (150 mm NaCl). Pathway 1 might be mediated by a high-affinity K transporter-type transporter and pathway 2 by an AKT1-type channel.

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Cesium Toxicity in Arabidopsis

Cited by 169 publications

References 42 publications

Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress

Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Low-Affinity Na+ Uptake in the HalophyteSuaeda maritima

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