Enhancement of Na+ Uptake Currents, Time-Dependent Inward-Rectifying K+ Channel Currents, and K+Channel Transcripts by K+ Starvation in Wheat Root Cells

Buschmann, P.; Vaidyanathan, Rama; Gassmann, Walter; Schroeder, Julian I.

doi:10.1104/pp.122.4.1387

Cited by 137 publications

(80 citation statements)

References 75 publications

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“…Figures 3 and 4, Table 1). Analysis of these K + currents indicated voltages yielding halfmaximal activation (V 1/2 ) near 2155 mV, close to the value of 2152 6 5 mV obtained in the plant and comparable to similar measurements from protoplasts of wheat (Triticum aestivum; Gassmann and Schroeder, 1994;Buschmann et al, 2000) and rye (Secale cereale) roots (White and Lemtirichlieh, 1995). We also noted that increasing SYP121:KC1 expression ratios progressively displaced the current characteristic to more positive voltages ( Figure 3, Table 1), consistent with a well-defined and saturable stoichiometry of KC1 and SYP121 protein function in modifying channel gating.…”

Section: Syp121-kc1 Interaction Promotes K + Channel Gatingsupporting

confidence: 84%

A Tripartite SNARE-K+ Channel Complex Mediates in Channel-Dependent K+ Nutrition inArabidopsis

et al. 2009

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A few membrane vesicle trafficking (SNARE) proteins in plants are associated with signaling and transmembrane ion transport, including control of plasma membrane ion channels. Vesicle traffic contributes to the population of ion channels at the plasma membrane. Nonetheless, it is unclear whether these SNAREs also interact directly to affect channel gating and, if so, what functional impact this might have on the plant. Here, we report that the Arabidopsis thaliana SNARE SYP121 binds to KC1, a regulatory K + channel subunit that assembles with different inward-rectifying K + channels to affect their activities. We demonstrate that SYP121 interacts preferentially with KC1 over other Kv-like K + channel subunits and that KC1 interacts specifically with SYP121 but not with its closest structural and functional homolog SYP122 nor with another related SNARE SYP111. SYP121 promoted gating of the inward-rectifying K + channel AKT1 but only when heterologously coexpressed with KC1. Mutation in any one of the three genes, SYP121, KC1, and AKT1, selectively suppressed the inwardrectifying K + current in Arabidopsis root epidermal protoplasts as well as K + acquisition and growth in seedlings when channel-mediated K + uptake was limiting. That SYP121 should be important for gating of a K + channel and its role in inorganic mineral nutrition demonstrates an unexpected role for SNARE-ion channel interactions, apparently divorced from signaling and vesicle traffic. Instead, it suggests a role in regulating K + uptake coordinately with membrane expansion for cell growth.

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Section: Syp121-kc1 Interaction Promotes K + Channel Gatingsupporting

confidence: 84%

A Tripartite SNARE-K+ Channel Complex Mediates in Channel-Dependent K+ Nutrition inArabidopsis

et al. 2009

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“…Coexpressing AKT1 and KC1 with wild-type SYP121 that interacts with KC1 ( Figure 1; see also Honsbein et al, 2009), by contrast, yielded a K + current at voltages negative of 2100 mV that was well-fitted to the same Boltzmann function, but with values for d near 2 and V 1/2 close to 2150 mV (Figures 3 and 4). These characteristics were similar to those reported previously on heterologous expression in oocytes and Sf9 insect cells and compare favorably with the characteristics of K + currents obtained in vivo (Gassmann and Schroeder, 1994;White and Lemtirichlieh, 1995;Buschmann et al, 2000;Honsbein et al, 2009).…”

Section: Syp121/syp122 Chimeras Identify the N Terminus Of Syp121 Assupporting

confidence: 77%

A Novel Motif Essential for SNARE Interaction with the K+ Channel KC1 and Channel Gating inArabidopsis

et al. 2010

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The SNARE (for soluble N-ethylmaleimide-sensitive factor protein attachment protein receptor) protein SYP121 (=SYR1/ PEN1) of Arabidopsis thaliana facilitates vesicle traffic, delivering ion channels and other cargo to the plasma membrane, and contributing to plant cell expansion and defense. Recently, we reported that SYP121 also interacts directly with the K + channel subunit KC1 and forms a tripartite complex with a second K + channel subunit, AKT1, to control channel gating and K + transport. Here, we report isolating a minimal sequence motif of SYP121 prerequisite for its interaction with KC1. We made use of yeast mating-based split-ubiquitin and in vivo bimolecular fluorescence complementation assays for proteinprotein interaction and of expression and electrophysiological analysis. The results show that interaction of SYP121 with KC1 is associated with a novel FxRF motif uniquely situated within the first 12 residues of the SNARE sequence, that this motif is the minimal requirement for SNARE-dependent alterations in K + channel gating when heterologously expressed, and that rescue of KC1-associated K + current of the root epidermis in syp121 mutant Arabidopsis plants depends on expression of SNARE constructs incorporating this motif. These results establish the FxRF sequence as a previously unidentified motif required for SNARE-ion channel interactions and lead us to suggest a mechanistic framework for understanding the coordination of vesicle traffic with transmembrane ion transport.

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“…We could not detect any changes in transcript amounts for the ice plant Mkt1, Mkt2, and Kmt1 when the plants were starved for potassium (data not shown). This is consistent with observations of an AKT1 ortholog in Brassica napus (Lagarde et al, 1996), but in contrast with a recent report documenting upregulation of wheat AKT1 in response to potassium starvation (Buschmann et al, 2000). Induction of transcripts by potassium starvation seems more common among potassium transporters: HKT1 (wheat), HvHAK1 (barley), and AtKUP3 (Arabidopsis) respond to K ϩ starvation (Santa-Maria et al, 1997;Fu and Luan, 1998;Kim et al, 1998;Wang et al, 1998).…”

Section: Discussioncontrasting

confidence: 55%

Expression and Stress-Dependent Induction of Potassium Channel Transcripts in the Common Ice Plant

Su¹,

Golldack²,

Katsuhara

et al. 2001

Plant Physiology

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We have characterized transcripts for three potassium channel homologs in the AKT/KAT subfamily (Shaker type) from the common ice plant (Mesembryanthemum crystallinum), with a focus on their expression during salt stress (up to 500 mm NaCl). Mkt1 and 2, Arabidopsis AKT homologs, and Kmt1, a KAT homolog, are members of small gene families with two to three isoforms each. Mkt1 is root specific; Mkt2 is found in leaves, flowers, and seed capsules; and Kmt1 is expressed in leaves and seed capsules. Mkt1 is present in all cells of the root, and in leaves a highly conserved isoform is detected present in all cells with highest abundance in the vasculature. MKT1 for which antibodies were made is localized to the plasma membrane. Following salt stress, MKT1 (transcripts and protein) is drastically down-regulated, Mkt2 transcripts do not change significantly, and Kmt1 is strongly and transiently (maximum at 6 h) up-regulated in leaves and stems. The detection and stress-dependent behavior of abundant transcripts representing subfamilies of potassium channels provides information about tissue specificity and the complex regulation of genes encoding potassium uptake systems in a halophytic plant.

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Enhancement of Na+ Uptake Currents, Time-Dependent Inward-Rectifying K+ Channel Currents, and K+Channel Transcripts by K+ Starvation in Wheat Root Cells

Abstract: Excessive low-affinity Na؉ uptake is toxic to the growth of glycophytic plants. Recently

Cited by 137 publications

References 75 publications

A Tripartite SNARE-K+ Channel Complex Mediates in Channel-Dependent K+ Nutrition inArabidopsis

A Tripartite SNARE-K+ Channel Complex Mediates in Channel-Dependent K+ Nutrition inArabidopsis

A Novel Motif Essential for SNARE Interaction with the K+ Channel KC1 and Channel Gating inArabidopsis

Expression and Stress-Dependent Induction of Potassium Channel Transcripts in the Common Ice Plant

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