<b>Cytosolic acidification but not auxin at physiological concentration is an activator of MAP kinases in tobacco cells</b>

Tena, Guillaume; Renaudin, Jean-Pierre

doi:10.1046/j.1365-313x.1998.00283.x

Cited by 59 publications

(37 citation statements)

References 64 publications

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“…In maize, propionic acid and auxin treatments resulted in cytosolic acidification (69). In tobacco BY-2 cells, cytosolic acidification was observed after the addition of high concentration of auxin and other lipophilic acid (70). In plant cells, changes in the cytosolic pH are closely related to tonoplast K ϩ influx and efflux (11).…”

Section: Discussionmentioning

confidence: 99%

Characterization of a Tobacco TPK-type K+ Channel as a Novel Tonoplast K+ Channel Using Yeast Tonoplasts

Hamamoto

Marui

Matsuoka

et al. 2008

Journal of Biological Chemistry

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The tonoplast K ؉ membrane transport system plays a crucial role in maintaining K ؉ homeostasis in plant cells. Here, we isolated cDNAs encoding a two-pore K ؉ channel (NtTPK1) from Nicotiana tabacum cv. SR1 and cultured BY-2 tobacco cells. Two of the four variants of NtTPK1 contained VHG and GHG instead of the GYG signature sequence in the second pore region. All four products were functional when expressed in the Escherichia coli cell membrane, and NtTPK1 was targeted to the tonoplast in tobacco cells. Two of the three promoter sequences isolated from N. tabacum cv. SR1 were active, and expression from these was increased ϳ2-fold by salt stress or high osmotic shock. To determine the properties of NtTPK1, we enlarged mutant yeast cells with inactivated endogenous tonoplast channels and prepared tonoplasts suitable for patch clamp recording allowing the NtTPK1-related channel conductance to be distinguished from the small endogenous currents. NtTPK1 exhibited strong selectivity for K ؉ over Na ؉ . NtTPK1 activity was sensitive to spermidine and spermine, which were shown to be present in tobacco cells. NtTPK1 was active in the absence of Ca 2؉ , but a cytosolic concentration of 45 M Ca 2؉ resulted in a 2-fold increase in the amplitude of the K ؉ current. Acidification of the cytosol to pH 5.5 also markedly increased NtTPK1-mediated K ؉ currents. These results show that NtTPK1 is a novel tonoplast K ؉ channel belonging to a different group from the previously characterized vacuolar channels SV, FV, and VK.Plants take up potassium (K ϩ ) from the soil and plant cells accumulate K ϩ to regulate the membrane potential and turgor pressure. The cytoplasmic K ϩ concentration is tightly controlled at ϳ100 mM (1). Vacuoles are major subcellular reservoirs for controlling K ϩ homeostasis in plant cells (1). During cell expansion, for instance during stomata opening or cell growth, tonoplast transport system moves K ϩ into the vacuole, whereas, under conditions of salinity stress, K ϩ is replaced by Na ϩ (2-5).Several kinds of genes encoding K ϩ channels and K ϩ transporters have been identified in the Arabidopsis thaliana genome, and their function and tissue and cellular distribution have been extensively studied. They consist of two families, the Shaker-type channels, with six hydrophobic transmembrane domains and a single pore domain, and the two-pore K ϩ channel (TPK) 2 family, with four transmembrane and two pore domains. Six different genes encoding TPK-type channels are present in A. thaliana. AtTPK4 is targeted to the plasma membrane (6), while the other five, AtTPK1, AtTPK2, AtTPK3, AtTPK5, and AtKCO3, are localized in the vacuolar membrane (7). AtTPK1 and AtTPK4 have been functionally characterized. AtTPK4 shows a voltage-independent K ϩ profile in Xenopus laevis ooctyes and in yeast, and the K ϩ current is inhibited by extracellular Ca 2ϩ and reduced by shifting the cytosolic pH from 7.5 to 6.3, but is not affected by the external pH (6). AtTPK1 has different properties to AtTPK4 (7,8). In the yeast and plant ...

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Section: Discussionmentioning

confidence: 99%

Characterization of a Tobacco TPK-type K+ Channel as a Novel Tonoplast K+ Channel Using Yeast Tonoplasts

Hamamoto

Marui

Matsuoka

et al. 2008

Journal of Biological Chemistry

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“…Our experience with intact plants rather than cell suspension cultures leads us to posit that neither JA nor ethylene has any feedback effect on MAPKs, as these compounds are located downstream of MAPKs. We propose that the differences observed in suspension cells and intact plants are due to the specificity of MAPK signaling in different tissues, although these differences may also reflect the easily disturbed physiology of cell suspension culture, for example, an easily changed cytosolic pH (Tena and Renaudin, 1998).…”

Section: Activation Of Sipk and Wipk And Accumulation Of Phytohormonesmentioning

confidence: 99%

Herbivory Rapidly Activates MAPK Signaling in Attacked and Unattacked Leaf Regions but Not between Leaves ofNicotiana attenuata

et al. 2007

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Mitogen-activated protein kinase (MAPK) signaling plays a central role in transducing extracellular stimuli into intracellular responses, but its role in mediating plant responses to herbivore attack remains largely unexplored. When Manduca sexta larvae attack their host plant, Nicotiana attenuata, the plant's wound response is reconfigured at transcriptional, phytohormonal, and defensive levels due to the introduction of oral secretions (OS) into wounds during feeding. We show that OS dramatically amplify wound-induced MAPK activity and that fatty acid-amino acid conjugates in M. sexta OS are the elicitors. Virus-induced gene silencing of salicylic acid-induced protein kinase (SIPK) and wound-induced protein kinase revealed their importance in mediating wound and OS-elicited hormonal responses and transcriptional regulation of defense-related genes. We found that after applying OS to wounds created in one portion of a leaf, SIPK is activated in both wounded and specific unwounded regions of the leaf but not in phylotactically connected adjacent leaves. We propose that M. sexta attack elicits a mobile signal that travels to nonwounded regions of the attacked leaf where it activates MAPK signaling and, thus, downstream responses; subsequently, a different signal is transported by the vascular system to systemic leaves to initiate defense responses without activating MAPKs in systemic leaves.

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“…Our initial ACC treatment experiments were performed using ACC stock solutions with an adjusted pH of 5.8, which is the same as the pH of the medium for growing Arabidopsis seedlings. It was documented that some weak acids can disturb the cellular pH and cause the activation of MAPK (Tena and Renaudin, 1998). As a result, we also performed the experiments using ACC stock solutions with an unadjusted pH.…”

Section: Acc Treatment Does Not Activate Mpk6 In Arabidopsis Seedlingsmentioning

confidence: 99%

Phosphorylation of 1-Aminocyclopropane-1-Carboxylic Acid Synthase by MPK6, a Stress-Responsive Mitogen-Activated Protein Kinase, Induces Ethylene Biosynthesis in Arabidopsis[W]

2004

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Mitogen-activated protein kinases (MAPKs) are implicated in regulating plant growth, development, and response to the environment. However, the underlying mechanisms are unknown because of the lack of information about their substrates. Using a conditional gain-of-function transgenic system, we demonstrated that the activation of SIPK, a tobacco (Nicotiana tabacum) stress-responsive MAPK, induces the biosynthesis of ethylene. Here, we report that MPK6, the Arabidopsis thaliana ortholog of tobacco SIPK, is required for ethylene induction in this transgenic system. Furthermore, we found that selected isoforms of 1-aminocyclopropane-1-carboxylic acid synthase (ACS), the rate-limiting enzyme of ethylene biosynthesis, are substrates of MPK6. Phosphorylation of ACS2 and ACS6 by MPK6 leads to the accumulation of ACS protein and, thus, elevated levels of cellular ACS activity and ethylene production. Expression of ACS6 DDD , a gain-of-function ACS6 mutant that mimics the phosphorylated form of ACS6, confers constitutive ethylene production and ethylene-induced phenotypes. Increasing numbers of stress stimuli have been shown to activate Arabidopsis MPK6 or its orthologs in other plant species. The identification of the first plant MAPK substrate in this report reveals one mechanism by which MPK6/ SIPK regulates plant stress responses. Equally important, this study uncovers a signaling pathway that modulates the biosynthesis of ethylene, an important plant hormone, in plants under stress.

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Cytosolic acidification but not auxin at physiological concentration is an activator of MAP kinases in tobacco cells

Cited by 59 publications

References 64 publications

Characterization of a Tobacco TPK-type K+ Channel as a Novel Tonoplast K+ Channel Using Yeast Tonoplasts

Characterization of a Tobacco TPK-type K+ Channel as a Novel Tonoplast K+ Channel Using Yeast Tonoplasts

Herbivory Rapidly Activates MAPK Signaling in Attacked and Unattacked Leaf Regions but Not between Leaves ofNicotiana attenuata

Phosphorylation of 1-Aminocyclopropane-1-Carboxylic Acid Synthase by MPK6, a Stress-Responsive Mitogen-Activated Protein Kinase, Induces Ethylene Biosynthesis in Arabidopsis[W]

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