Physical and functional interaction of the Arabidopsis K+ channel AKT2 and phosphatase AtPP2CA. Plant Cell

Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004 Agro-M/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Montpellier II, France.
The Plant Cell (Impact Factor: 9.58). 06/2002; 14(5):1133-46.
Source: PubMed

ABSTRACT The AKT2 K(+) channel is endowed with unique functional properties, being the only weak inward rectifier characterized to date in Arabidopsis. The gene is expressed widely, mainly in the phloem but also at lower levels in leaf epiderm, mesophyll, and guard cells. The AKT2 mRNA level is upregulated by abscisic acid. By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of AKT2. We further confirmed the interaction by in vitro binding studies. The expression of AtPP2CA (beta-glucuronidase reporter gene) displayed a pattern largely overlapping that of AKT2 and was upregulated by abscisic acid. Coexpression of AtPP2CA with AKT2 in COS cells and Xenopus laevis oocytes was found to induce both an inhibition of the AKT2 current and an increase of the channel inward rectification. Site-directed mutagenesis and pharmacological analysis revealed that this functional interaction involves AtPP2CA phosphatase activity. Regulation of AKT2 activity by AtPP2CA in planta could allow the control of K(+) transport and membrane polarization during stress situations.

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Available from: Jean-Baptiste Thibaud, Jan 23, 2014
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    • "The various combinations of CBLs-CIPKs may be able to control diverse biological processes since Arabidopsis has ten CBL proteins (Kudla et al., 1999) and at least 25 CIPKs (Luan et al., 2009). More examples of complexities in the regulation of K+ channels are also provided by the interaction of K+ channels with PROTEIN PHOSPHATASE 2C (PP2C) (Cherel et al., 2002; Lan et al., 2011) and SNARE proteins (Honsbein et al., 2009). PP2Cs directly interact with the kinase domain of CIPK in the CBLCIPK complex and dephosphorylate CIPK, resulting in the inactivation of AKT1 (Cherel et al., 2002; Lan et al., 2011). "
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    ABSTRACT: Potassium is a macronutrient that is crucial for healthy plant growth. Potassium availability, however, is often limited in agricultural fields and thus crop yields and quality are reduced. Therefore, improving the efficiency of potassium uptake and transport, as well as its utilization, in plants is important for agricultural sustainability. This review summarizes the current knowledge on the molecular mechanisms involved in potassium uptake and transport in plants, and the molecular response of plants to different levels of potassium availability. Based on this information, four strategies for improving potassium use efficiency in plants are proposed; 1) increased root volume, 2) increasing efficiency of potassium uptake from the soil and translocation in planta, 3) increasing mobility of potassium in soil, and 4) molecular breeding new varieties with greater potassium efficiency through marker assisted selection which will require identification and utilization of potassium associated quantitative trait loci.
    Molecules and Cells 06/2014; 37(8). DOI:10.14348/molcells.2014.0141 · 2.24 Impact Factor
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    • "AKT2 regulates transport of K+ and other small molecules in phloem through its roles in electric cell signaling and membrane excitability [28]. AKT2 may be involved in plant stress responses by adjusting potassium gradients that are important energy sources in plant vascular tissues [28,32-34]. "
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    ABSTRACT: Background Soybean mosaic virus (SMV) is the most prevalent viral disease in many soybean production areas. Due to a large number of SMV resistant loci and alleles, SMV strains and the rapid evolution in avirulence/effector genes, traditional breeding for SMV resistance is complex. Genetic engineering is an effective alternative method for improving SMV resistance in soybean. Potassium (K+) is the most abundant inorganic solute in plant cells, and is involved in plant responses to abiotic and biotic stresses. Studies have shown that altering the level of K+ status can reduce the spread of the viral diseases. Thus K+ transporters are putative candidates to target for soybean virus resistance. Results The addition of K+ fertilizer significantly reduced SMV incidence. Analysis of K+ channel gene expression indicated that GmAKT2, the ortholog of Arabidopsis K+ weak channel encoding gene AKT2, was significantly induced by SMV inoculation in the SMV highly-resistant genotype Rsmv1, but not in the susceptible genotype Ssmv1. Transgenic soybean plants overexpressing GmAKT2 were produced and verified by Southern blot and RT-PCR analysis. Analysis of K+ concentrations on different leaves of both the transgenic and the wildtype (Williams 82) plants revealed that overexpression of GmAKT2 significantly increased K+ concentrations in young leaves of plants. In contrast, K+ concentrations in the old leaves of the GmAKT2-Oe plants were significantly lower than those in WT plants. These results indicated that GmAKT2 acted as a K+ transporter and affected the distribution of K+ in soybean plants. Starting from 14 days after inoculation (DAI) of SMV G7, severe mosaic symptoms were observed on the WT leaves. In contrast, the GmAKT2-Oe plants showed no symptom of SMV infection. At 14 and 28 DAI, the amount of SMV RNA in WT plants increased 200- and 260- fold relative to GmAKT2-Oe plants at each time point. Thus, SMV development was significantly retarded in GmAKT2-overexpressing transgenic soybean plants. Conclusions Overexpression of GmAKT2 significantly enhanced SMV resistance in transgenic soybean. Thus, alteration of K+ transporter expression is a novel molecular approach for enhancing SMV resistance in soybean.
    BMC Plant Biology 06/2014; 14(1):154. DOI:10.1186/1471-2229-14-154 · 3.94 Impact Factor
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    • "It is now known that shaker-like potassium channels are the major players regulating K+ transport in guard cells. These K+-selective channels typically consist of six trans-membrane domains, a cyclic nucleotide binding domain, and some have an ankyrin repeat domain, and have been characterized in both animals and plants [3,4]. "
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    ABSTRACT: Potassium is the most abundant cation and a myriad of transporters regulate K(+) homeostasis in plant. Potassium plays a role as a major osmolyte to regulate stomatal movements that control water utility of land plants. Here we report the characterization of two inward rectifying shaker-like potassium channels, OsKAT2 and OsKAT3, expressed in guard cell of rice plants. While OsKAT2 showed typical potassium channel activity, like that of Arabidopsis KAT1, OsKAT3 did not despite high sequence similarity between the two channel proteins. Interestingly, the two potassium channels physically interacted with each other and such interaction negatively regulated the OsKAT2 channel activity in CHO cell system. Furthermore, deletion of the C-terminal domain recovered the channel activity of OsKAT3, suggesting that the C-terminal region was regulatory domain that inhibited channel activity. Two homologous channels with antagonistic interaction has not been previously reported and presents new information for potassium channel regulation in plants, especially in stomatal regulation.
    PLoS ONE 08/2013; 8(8):e72541. DOI:10.1371/journal.pone.0072541 · 3.23 Impact Factor
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