101
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Abstract
Plants utilize several families of photoreceptors to fine-tune growth and development over a large range of environmental conditions. The UV-A/blue light sensing phototropins mediate several light responses enabling optimization of photosynthetic yields. The initial event occurring upon photon capture is a conformational change of the photoreceptor that activates its protein kinase activity. The UV-A/blue light sensing cryptochromes and the red/far-red sensing phytochromes coordinately control seedling establishment, entrainment of the circadian clock, and the transition from vegetative to reproductive growth. In addition, the phytochromes control seed germination and shade-avoidance responses. The molecular mechanisms involved include light-regulated subcellular localization of the photoreceptors, a large reorganization of the transcriptional program, and light-regulated proteolytic degradation of several photoreceptors and signaling components.
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Affiliation(s)
- Meng Chen
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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102
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Dodd AN, Love J, Webb AAR. The plant clock shows its metal: circadian regulation of cytosolic free Ca(2+). TRENDS IN PLANT SCIENCE 2005; 10:15-21. [PMID: 15642519 DOI: 10.1016/j.tplants.2004.12.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Signal transduction events that lead to circadian control of physiology are poorly understood. Signalling elements that could transmit time information include transcription factors, reversible phosphorylation, and changes in the concentration of cytosolic free calcium ([Ca(2+)](cyt)). [Ca(2+)](cyt) oscillates with a circadian rhythm in Arabidopsis and Nicotiana, but does not have a defined role in circadian signalling. [Ca(2+)](cyt) oscillations with shorter periods encode specific signals in several cell types, therefore circadian [Ca(2+)](cyt) oscillations provide a potential mechanism for signalling time information. Cell types such as stomatal guard cells and legume pulvini represent attractive model systems for dissecting circadian Ca(2+) signalling.
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Affiliation(s)
- Antony N Dodd
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, UK CB2 3EA.
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103
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Abstract
Photoreceptors allow living organisms to optimize perception of light in the natural environment and thus to gain information about their external world. In this review, we describe blue and red light photoreceptors in bacteria, plants, and animals in relation to their evolution. Analyses performed in different organisms have revealed wonderful examples of structural modifications of the light-sensing proteins themselves, as well as diversification of the signal transduction pathways they use in relation with their evolutionary history and function. In different organisms, the same photoreceptor may have a very conserved role (convergent evolution of function) or may modulate different responses (acquisition of new function). Multiple photoreceptors of the same family in the same organism indicate gene duplication events during evolution, with a consequent enhanced sensitivity to variations in ambient light. Conversely, two different photoreceptors may be involved in the control of the same physiological response. Genomic analysis in marine diatoms, combined with phylogenetic studies, has also revealed the presence of blue and red light photoreceptors in the marine environment. This discovery has intriguing implications for the understanding of light perception and its evolution in photosynthetic organisms. In addition, the characterization of these photoreceptors likely will add to our understanding of photoreceptor diversity as an adaptation to different habitats.
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Affiliation(s)
- Angela Falciatore
- Cell Signalling Laboratory, Stazione Zoologica Anton Dohrn, Villa Comunale, I-80121 Naples, Italy
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104
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Stone BB, Esmon CA, Liscum E. Phototropins, other photoreceptors, and associated signaling: the lead and supporting cast in the control of plant movement responses. Curr Top Dev Biol 2005; 66:215-38. [PMID: 15797455 DOI: 10.1016/s0070-2153(05)66007-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Bethany B Stone
- University of Missouri-Columbia, Columbia, Missouri 65211, USA
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105
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Platten JD, Shabala SN, Elliott RC, Reid JB. A novel mutant with modified tropic responses in Pisum sativum L. PLANTA 2004; 220:222-9. [PMID: 15517358 DOI: 10.1007/s00425-004-1339-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Accepted: 06/09/2004] [Indexed: 05/24/2023]
Abstract
A single-gene recessive mutant which displays increased phototropic and gravitropic responses has been isolated in Pisum sativum L. cv. Torsdag and is provisionally named mtr-1, for its modified tropic response. Mutant plants attain a greater degree of bending during both phototropic and gravitropic induction due to an extension of the curvature phase. In addition to their increase in tropic curvature, mutant plants have longer and narrower leaves as mature plants, attenuated blue-light-induced ion flux responses, and lower levels of PsPK5 mRNA (a PHOT1 orthologue). Possible causes of these effects are discussed.
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Affiliation(s)
- J Damien Platten
- School of Plant Science, University of Tasmania, Private Bag 55, 7001 Hobart, Tasmania, Australia.
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106
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Xiong TC, Jauneau A, Ranjeva R, Mazars C. Isolated plant nuclei as mechanical and thermal sensors involved in calcium signalling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:12-21. [PMID: 15361137 DOI: 10.1111/j.1365-313x.2004.02184.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Calcium signals in the nucleus elicit downstream effects that are distinct from those of cytosolic calcium signals. In the present work, we have evaluated the ability of plant nuclei to sense stimuli directly and to convert them into calcium changes. We show that individual mechanical stimulation of isolated nuclei elicits a single calcium transient at acidic pHs, whereas a series of stimulations leads to oscillations whose frequency reflects that of the stimuli. Conversely, at alkaline pHs, nuclei respond to temperature but not to stretch. The stretch- and the temperature-activated processes differ by their sensitivity to pharmacological drugs known to affect ion channel activities in animal cells. Our data demonstrate that isolated nuclei are able to gauge physical parameters of their environment. This might have a profound influence on the functioning of calcium-dependent processes known to control a large array of molecular events in the nucleus.
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Affiliation(s)
- Tou Cheu Xiong
- UMR CNRS-UPS 5546, Surfaces Cellulaires et Signalisation chez les Végétaux, Pôle de Biotechnologie Végétale, BP 17 Auzeville, 27 Chemin de Borde Rouge, 31326 Castanet-Tolosan, France
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107
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Jeter CR, Tang W, Henaff E, Butterfield T, Roux SJ. Evidence of a novel cell signaling role for extracellular adenosine triphosphates and diphosphates in Arabidopsis. THE PLANT CELL 2004; 16:2652-64. [PMID: 15367717 PMCID: PMC520962 DOI: 10.1105/tpc.104.023945] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 07/20/2004] [Indexed: 05/17/2023]
Abstract
Extracellular ATP is a known receptor agonist in animals and was previously shown to alter plant growth, and so we investigated whether ATP derivatives could function outside plant cells as signaling agents. Signaling responses induced by exogenous nucleotides in animal cells typically include increases in free cytoplasmic calcium concentration ([Ca(2+)](cyt)). We have evaluated the ability of exogenously applied adenosine 5'-[gamma-thio]triphosphate (ATPgammaS), adenosine 5'-[beta-thio]diphosphate (ADPbetaS), and adenosine 5'-O-thiomonophosphate to alter [Ca(2+)](cyt) in intact apoaequorin transgenic Arabidopsis thaliana seedlings. ATPgammaS and ADPbetaS increase [Ca(2+)](cyt), and this increase is enhanced further when the nucleotides are added with the elicitor oligogalacturonic acid. Exogenous treatment with ATP also increases the level of transcripts encoding mitogen-activated protein kinases and proteins involved in ethylene biosynthesis and signal transduction. The increase in [Ca(2+)](cyt) induced by nucleotide derivatives can be ablated by Ca(2+)-channel blocking agents and by the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and the changes in gene expression can be partially blocked by these agents. These observations suggest that extracellular ATP can activate calcium-mediated cell-signaling pathways in plants, potentially playing a physiological role in transducing stress and wound responses.
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Affiliation(s)
- Collene R Jeter
- Section of Molecular Cell and Developmental Biology, University of Texas, Austin, Texas 78712, USA
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108
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Brandizzi F, Irons SL, Evans DE. The plant nuclear envelope: new prospects for a poorly understood structure. THE NEW PHYTOLOGIST 2004; 163:227-246. [PMID: 33873618 DOI: 10.1111/j.1469-8137.2004.01118.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The nuclear envelope (NE) is one of the least characterized cellular structures in plant cells. In particular, knowledge of its dynamic behaviour during the cell cycle and of its protein composition is limited. This review summarizes current views on the plant NE and highlights fundamental differences with other organisms. We also introduce the power of new technology available to investigate the NE and how this has already begun to revolutionize our knowledge of the biology of the plant NE. Contents Summary 227 I. Introduction 227 II. The membranes of the nuclear envelope 228 III. Functions of the nuclear envelope 231 IV. Proteins associated with the nuclear envelope 236 V. New tools for studying the nuclear envelope 239 VI. Conclusions and future prospects 241 Acknowledgements 242 References 242.
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Affiliation(s)
- Federica Brandizzi
- Biology Department, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5E2
| | - Sarah L Irons
- Research School of Biological and Molecular Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - David E Evans
- Research School of Biological and Molecular Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
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109
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Babourina O, Godfrey L, Voltchanskii K. Changes in ion fluxes during phototropic bending of etiolated oat coleoptiles. ANNALS OF BOTANY 2004; 94:187-94. [PMID: 15155378 PMCID: PMC4242382 DOI: 10.1093/aob/mch126] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS This work has been conducted to assist theoretical modelling of the different stages of the blue light (BL)-induced phototropic signalling pathway and ion transport activity across plant membranes. Ion fluxes (Ca(2+), H(+), K(+) and Cl(-)) in etiolated oat coleoptiles have been measured continuously before and during unilateral BL exposure. METHODS Changes in ion fluxes at the illuminated (light) and shadowed (dark) sides of etiolated oat coleoptiles (Avena sativa) were studied using a non-invasive ion-selective microelectrode technique (MIFE). The bending response was also measured continuously, and correlations between the changes in various ion fluxes and bending response have been investigated. For each ion the difference (Delta) between the magnitudes of flux at the light and dark sides of the coleoptile was calculated. KEY RESULTS Plants that demonstrated a phototropic bending response also demonstrated Ca(2+) influx into the light side approximately 20 min after the start of BL exposure. This is regarded as part of the perception and transduction stages of the BL-induced signal cascade. The first 10 min of bending were associated with substantial influx of H(+), K(+) and Cl(-) into the light (concave) side of the coleoptiles. CONCLUSIONS The data suggest that Ca(2+) participates in the signalling stage of the BL-induced phototropism, whereas the phototropic bending response is linked to changes in the transport of H(+), K(+) and Cl(-).
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Affiliation(s)
- Olga Babourina
- School of Mathematics and Physics, University of Tasmania, GPO Box 252-21, Hobart, Tasmania 7001, Australia.
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110
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Azad AK, Sawa Y, Ishikawa T, Shibata H. Phosphorylation of Plasma Membrane Aquaporin Regulates Temperature-Dependent Opening of Tulip Petals. ACTA ACUST UNITED AC 2004; 45:608-17. [PMID: 15169943 DOI: 10.1093/pcp/pch069] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The opening and closing of tulip petals was reproduced in the dark by changing the temperature from 5 degrees C to 20 degrees C for opening and 20 degrees C to 5 degrees C for closing. The opening process was accompanied by (3)H(2)O transport through the stem from the incubation medium to the petals. A Ca(2+)-channel blocker and a Ca(2+)-chelator inhibited petal opening and (3)H(2)O transport. Several proteins in the isolated plasma membrane fraction were phosphorylated in the presence of 25 micro M Ca(2+) at 20 degrees C. The 31-kDa protein that was phosphorylated, was suggested immunologically as the putative plasma membrane aquaporin (PM-AQP). This phosphorylated PM-AQP clearly reacted with the anti-phospho-Ser. In-gel assay revealed the presence of a 45-kDa Ca(2+)-dependent protein kinase in the isolated plasma membrane. Phosphorylation of the putative PM-AQP was thought to activate the water channel composed of PM-AQP. Dephosphorylation of the phosphorylated PM-AQP was also observed during petal closing at 5 degrees C, suggesting the inactivation of the water channel.
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Affiliation(s)
- Abul Kalam Azad
- Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, 690-8504 Japan
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111
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Love J, Dodd AN, Webb AAR. Circadian and diurnal calcium oscillations encode photoperiodic information in Arabidopsis. THE PLANT CELL 2004; 16:956-66. [PMID: 15031410 PMCID: PMC412869 DOI: 10.1105/tpc.020214] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 01/30/2004] [Indexed: 05/17/2023]
Abstract
We have tested the hypothesis that circadian oscillations in the concentration of cytosolic free calcium ([Ca2+]cyt) can encode information. We imaged oscillations of [Ca2+]cyt in the cotyledons and leaves of Arabidopsis (Arabidopsis thaliana) that have a 24-h period in light/dark cycles and also constant light. The amplitude, phase, and shape of the oscillations of [Ca2+]cyt and [Ca2+]cyt at critical daily time points were controlled by the light/dark regimes in which the plants were grown. These data provide evidence that 24-h oscillations in [Ca2+]cyt encode information concerning daylength and light intensity, which are two major regulators of plant growth and development.
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Affiliation(s)
- John Love
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK
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112
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Inada S, Ohgishi M, Mayama T, Okada K, Sakai T. RPT2 is a signal transducer involved in phototropic response and stomatal opening by association with phototropin 1 in Arabidopsis thaliana. THE PLANT CELL 2004; 16:887-96. [PMID: 15031408 PMCID: PMC412863 DOI: 10.1105/tpc.019901] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Accepted: 02/08/2004] [Indexed: 05/19/2023]
Abstract
Phototropin 1 (phot1) and phot2, which are blue light receptor kinases, function in blue light-induced hypocotyl phototropism, chloroplast relocation, and stomatal opening in Arabidopsis (Arabidopsis thaliana). Previous studies have shown that the proteins RPT2 (for ROOT PHOTOTROPISM2) and NPH3 (for NONPHOTOTROPIC HYPOCOTYL3) transduce signals downstream of phototropins to induce the phototropic response. However, the involvement of RPT2 and NPH3 in stomatal opening and in chloroplast relocation mediated by phot1 and phot2 was unknown. Genetic analysis of the rpt2 mutant and of a series of double mutants indicates that RPT2 is involved in the phot1-induced phototropic response and stomatal opening but not in chloroplast relocation or phot2-induced movements. Biochemical analyses indicate that RPT2 is purified in the crude microsomal fraction, as well as phot1 and NPH3, and that RPT2 makes a complex with phot1 in vivo. On the other hand, NPH3 is not necessary for stomatal opening or chloroplast relocation. Thus, these results suggest that phot1 and phot2 choose different signal transducers to induce three responses: phototropic response of hypocotyl, stomatal opening, and chloroplast relocation.
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Affiliation(s)
- Sayaka Inada
- RIKEN Plant Science Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
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113
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Folta KM, Lieg EJ, Durham T, Spalding EP. Primary inhibition of hypocotyl growth and phototropism depend differently on phototropin-mediated increases in cytoplasmic calcium induced by blue light. PLANT PHYSIOLOGY 2003; 133:1464-70. [PMID: 14645723 PMCID: PMC300703 DOI: 10.1104/pp.103.024372] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2003] [Revised: 05/26/2003] [Accepted: 08/13/2003] [Indexed: 05/18/2023]
Abstract
The phototropin photoreceptors transduce blue-light signals into several physiological and developmental responses in plants. A transient rise in cytoplasmic calcium (Ca2+) that begins within seconds of phototropin 1 (phot1) excitation is believed to be an important element in the transduction pathways leading to one or more of the phot1-dependent responses. The goal of the present work was to determine whether the Ca2+ response was necessary for (a). the inhibition of hypocotyl elongation that develops within minutes of the irradiation, and (b). hypocotyl phototropism (curved growth of the stem in response to asymmetric illumination). After determining that pulses of light delivering photon fluences of between 1 and 1000 micromol m-2 induced growth inhibition mediated by phot1 without significant interference from other photosensory pathways, the effect of blocking the Ca2+ rise was assessed. Treatment of seedlings with a Ca2+ chelator prevented the rise in cytoplasmic Ca2+ and prevented phot1-mediated growth inhibition. However, the same chelator treatment did not impair phot1-mediated phototropism. Thus, it appears that the early, transient rise in cytoplasmic Ca2+ is an important intermediary process in at least one but not all phot1-signaling pathways.
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Affiliation(s)
- Kevin M Folta
- Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin 53706, USA.
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114
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Catala R, Santos E, Alonso JM, Ecker JR, Martinez-Zapater JM, Salinas J. Mutations in the Ca2+/H+ transporter CAX1 increase CBF/DREB1 expression and the cold-acclimation response in Arabidopsis. THE PLANT CELL 2003; 15:2940-51. [PMID: 14630965 PMCID: PMC282833 DOI: 10.1105/tpc.015248] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Accepted: 09/09/2003] [Indexed: 05/17/2023]
Abstract
Transient increases in cytosolic free calcium concentration ([Ca2+]cyt) are essential for plant responses to a variety of environmental stimuli, including low temperature. Subsequent reestablishment of [Ca2+]cyt to resting levels by Ca2+ pumps and antiporters is required for the correct transduction of the signal [corrected]. C-repeat binding factor/dehydration responsive element binding factor 1 (Ca2+/H+) antiporters is required for the correct transduction of the signal. We have isolated a cDNA from Arabidopsis that corresponds to a new cold-inducible gene, rare cold inducible4 (RCI4), which was identical to calcium exchanger 1 (CAX1), a gene that encodes a vacuolar Ca2+/H+ antiporter involved in the regulation of intracellular Ca2+ levels. The expression of CAX1 was induced in response to low temperature through an abscisic acid-independent pathway. To determine the function of CAX1 in Arabidopsis stress tolerance, we identified two T-DNA insertion mutants, cax1-3 and cax1-4, that display reduced tonoplast Ca2+/H+ antiport activity. The mutants showed no significant differences with respect to the wild type when analyzed for dehydration, high-salt, chilling, or constitutive freezing tolerance. However, they exhibited increased freezing tolerance after cold acclimation, demonstrating that CAX1 plays an important role in this adaptive response. This phenotype correlates with the enhanced expression of CBF/DREB1 genes and their corresponding targets in response to low temperature. Our results indicate that CAX1 ensures the accurate development of the cold-acclimation response in Arabidopsis by controlling the induction of CBF/DREB1 and downstream genes.
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Affiliation(s)
- Rafael Catala
- Departamento de Biotecnología, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28040 Madrid, Spain
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115
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Abstract
Calcium is an essential plant nutrient. It is required for various structural roles in the cell wall and membranes, it is a counter-cation for inorganic and organic anions in the vacuole, and the cytosolic Ca2+ concentration ([Ca2+]cyt) is an obligate intracellular messenger coordinating responses to numerous developmental cues and environmental challenges. This article provides an overview of the nutritional requirements of different plants for Ca, and how this impacts on natural flora and the Ca content of crops. It also reviews recent work on (a) the mechanisms of Ca2+ transport across cellular membranes, (b) understanding the origins and specificity of [Ca2+]cyt signals and (c) characterizing the cellular [Ca2+]cyt-sensors (such as calmodulin, calcineurin B-like proteins and calcium-dependent protein kinases) that allow plant cells to respond appropriately to [Ca2+]cyt signals.
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Affiliation(s)
- Philip J White
- Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK.
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116
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Fuchs I, Philippar K, Ljung K, Sandberg G, Hedrich R. Blue light regulates an auxin-induced K+-channel gene in the maize coleoptile. Proc Natl Acad Sci U S A 2003; 100:11795-800. [PMID: 14500901 PMCID: PMC208837 DOI: 10.1073/pnas.2032704100] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Indexed: 11/18/2022] Open
Abstract
Auxin redistribution along gravistimulated maize coleoptiles causes differential expression of the auxin-induced K+-channel gene ZMK1 (Zea mays K+ channel 1) and precedes the curvature response. To evaluate the role of ZMK1 during phototropism, we here investigated blue light-stimulated coleoptiles. Four hours of blue light stimulation resulted in phototropic bending (23 degrees ). Rotation on a clinostat, at nominally "zero" gravity, and simultaneous stimulation with unidirectional blue light, however, resulted in up to 51 degrees bending toward the light. Differential ZMK1 transcription reached a maximum after 90 min of blue light stimulation under gravity, whereas ZMK1 expression remained asymmetric for at least 180 min in photostimulated coleoptiles on a clinostat. We therefore conclude that the stronger phototropic bending under nominally "zero" gravity results from prolonged differential expression of ZMK1. Under both conditions, asymmetric expression of ZMK1 could be superimposed on the lateral auxin gradient across the coleoptile tip, whereas the gene for the blue light receptor phototropin 1 (PHOT1), expressed in the tip only, was not differentially regulated in response to blue light. The activation of the two different receptors eliciting the photo- and gravitropic response of the coleoptile thus feeds into a common signaling pathway, resulting in auxin redistribution in the coleoptile tip and finally in differential transcription of ZMK1. In the process of signal integration, gravity transduction restricts the magnitude of the blue light-inducible ZMK1 gradient. The spatial and temporal distribution of ZMK1 transcripts and thus differential K+ uptake in both flanks of the coleoptile seem to limit the stimulus-induced bending of this sensory organ.
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Affiliation(s)
- I Fuchs
- Lehrstuhl für Molekulare Pflanzenphysiologie und Biophysik, Universität Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
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117
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Harada A, Sakai T, Okada K. Phot1 and phot2 mediate blue light-induced transient increases in cytosolic Ca2+ differently in Arabidopsis leaves. Proc Natl Acad Sci U S A 2003; 100:8583-8. [PMID: 12821778 PMCID: PMC166272 DOI: 10.1073/pnas.1336802100] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2002] [Accepted: 04/30/2003] [Indexed: 11/18/2022] Open
Abstract
Phototropins (phot1 and phot2) are blue light (BL) receptors that mediate phototropism, chloroplast movements, and stomatal opening in Arabidopsis thaliana. Physiological studies have suggested that Ca2+ in the cytoplasm plays a pivotal role in these BL-induced responses. A phot1-mediated increase in cytosolic Ca2+ was reported in deetiolated seedlings of A. thaliana; however, the contribution of phot2 remains unknown. We examined a BL-induced transient increase in cytosolic free Ca2+ in leaves of transgenic A. thaliana of WT plants, phot1 and phot2 mutants, and phot1 phot2 double mutants expressing the Ca2+-sensitive luminescent protein aequorin. phot1 and phot2 had different photosensitivities: phot1 increased cytosolic Ca2+ at lower fluence rates (0.1-50 micromol x m-2 x s-1) and phot2 increased it at higher fluence rates (1-250 micromol x m-2 x s-1). By using Ca2+ channel blockers, Ca2+ chelating agents, and inhibitors of phospholipase C, we further demonstrated that both phot1 and phot2 could induce Ca2+ influx from the apoplast through the Ca2+ channel in the plasma membrane, whereas phot2 alone induced phospholipase C-mediated phosphoinositide signaling, which might result in Ca2+ release from internal Ca2+ stores. These results suggest that phot1 and phot2 mediate the BL-induced increase in cytosolic free Ca2+ differently.
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Affiliation(s)
- Akiko Harada
- RIKEN Plant Science Center, 1-7-22 Suehiro-cho,
Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; and
Department of Botany, Graduate School of
Sciences, Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502,
Japan
| | - Tatsuya Sakai
- RIKEN Plant Science Center, 1-7-22 Suehiro-cho,
Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; and
Department of Botany, Graduate School of
Sciences, Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502,
Japan
| | - Kiyotaka Okada
- RIKEN Plant Science Center, 1-7-22 Suehiro-cho,
Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan; and
Department of Botany, Graduate School of
Sciences, Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502,
Japan
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118
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Sivaguru M, Pike S, Gassmann W, Baskin TI. Aluminum rapidly depolymerizes cortical microtubules and depolarizes the plasma membrane: evidence that these responses are mediated by a glutamate receptor. PLANT & CELL PHYSIOLOGY 2003; 44:667-75. [PMID: 12881494 DOI: 10.1093/pcp/pcg094] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Efforts to understand how plants respond to aluminum have focused on describing the symptoms of toxicity and elucidating mechanisms of tolerance; however, little is known about the signal transduction steps that initiate the plant's response. Here, we image cortical microtubules and quantify plasma-membrane potential in living, root cells of intact Arabidopsis seedlings. We show that aluminum depolymerizes microtubules and depolarizes the membrane, and that these responses are prevented by calcium channel blockade. Calcium influx might involve glutamate receptors, which in animals are ligand-gated cation channels and are present in the Arabidopsis genome. We show that glutamate depolymerizes microtubules and depolarizes the plasma membrane. These responses, and also the inhibition of root elongation, occur within the first few min of treatment, but are evoked more rapidly by glutamate than by aluminum. Microtubule depolymerization and membrane depolarization, induced by either glutamate or aluminum, are blocked by a specific antagonist of ionotropic glutamate receptors, 2-amino-5-phosphonopentanoate; whereas an antagonist of an aluminum-gated anion channel blocks the two responses to aluminum but not to glutamate. For growth, microtubule integrity, and membrane potential, responses to combined glutamate and aluminum were not greater than to glutamate alone. We propose that signaling in response to aluminum is initiated by efflux of a glutamate-like ligand through an anion channel and the binding of this ligand to a glutamate receptor.
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Affiliation(s)
- Mayandi Sivaguru
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400, USA
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119
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Benjamins R, Ampudia CSG, Hooykaas PJJ, Offringa R. PINOID-mediated signaling involves calcium-binding proteins. PLANT PHYSIOLOGY 2003; 132:1623-30. [PMID: 12857841 PMCID: PMC167099 DOI: 10.1104/pp.103.019943] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2003] [Revised: 02/04/2003] [Accepted: 04/04/2003] [Indexed: 05/18/2023]
Abstract
The plant hormone auxin is a central regulator of plant development. In Arabidopsis, the PINOID (PID) protein serine/threonine kinase is a key component in the signaling of this phytohormone. To further investigate the biological function of PID, we performed a screen for PID-interacting proteins using the yeast two-hybrid system. Here, we show that PID interacts with two calcium-binding proteins: TOUCH3 (TCH3), a calmodulin-related protein, and PID-BINDING PROTEIN 1 (PBP1), a previously uncharacterized protein containing putative EF-hand calcium-binding motifs. The interaction between PID and the calcium-binding proteins is significant because it is calcium dependent and requires an intact PID protein. Furthermore, the expression of all three genes (PID, TCH3, and PBP1) is up-regulated by auxin. TCH3 and PBP1 are not targets for phosphorylation by PID, suggesting that these proteins act upstream of PID. PBP1 was found to stimulate the autophosphorylation activity of PID, and calcium influx and calmodulin inhibitors where found to enhance the activity of PID in vivo. Our results indicate that TCH3 and PBP1 interact with the PID protein kinase and regulate the activity of this protein in response to changes in calcium levels. This work provides the first molecular evidence for the involvement of calcium in auxin-regulated plant development.
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Affiliation(s)
- René Benjamins
- Institute of Biology, Leiden University, Wassenaarseweg b4 2333 AL Leiden, The Netherlands
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120
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Huang K, Beck CF. Phototropin is the blue-light receptor that controls multiple steps in the sexual life cycle of the green alga Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2003; 100:6269-74. [PMID: 12716969 PMCID: PMC156361 DOI: 10.1073/pnas.0931459100] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Blue light as an environmental cue plays a pivotal role in controlling the progression of the sexual life cycle in the green alga Chlamydomonas reinhardtii. Phototropin was considered a prime candidate for the blue-light receptor involved. By using the RNA interference method, knockdown strains with reduced phototropin levels were isolated. Those with severely reduced levels of this photoreceptor were partially impaired in three steps of the life cycle: in gametogenesis, the maintenance of mating ability, and the germination of zygotes. These observations suggest that phototropin is the principal sensory molecule used by this alga for the control of its life cycle by light.
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Affiliation(s)
- Kaiyao Huang
- Institute of Biology III, University of Freiburg, Schaenzlestrasse 1, Germany
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121
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Folta KM, Kaufman LS. Phototropin 1 is required for high-fluence blue-light-mediated mRNA destabilization. PLANT MOLECULAR BIOLOGY 2003; 51:609-618. [PMID: 12650626 DOI: 10.1023/a:1022393406204] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Irradiation of etiolated wild-type Arabidopsis thaliana seedlings with a single pulse of blue (B) light with a total fluence equal to that of 1 min of sunlight causes the destabilization of nuclear-encoded Lhcb transcripts. Transcript destabilization is not observed in phototropin1 (phot1, formerly nph1) mutant seedlings, indicating that phot1 is likely the photoreceptor mediating this response. Destabilization is also absent in nph3 mutants, but occurs normally in nph4 mutants. The rates of Lhcb transcription and B low-fluence-induced Lhcb transcript accumulation are normal in phot1 seedlings, confirming that photl regulates destabilization, not a change in transcription. A similar pattern of regulation is observed for the chloroplast-encoded rbcL transcript. The lack of destabilization of a second chloroplast encoded transcript, psbD, indicates that the phot1/B-high-fluence system does not result in a general destabilization of all chloroplast transcripts. Localized sequence similarity between the Lhcb 5'-UTR and the rbcL 3'-UTR suggests a similar mechanism of destabilization even though the two transcripts are located in different sub-cellular compartments. The high-fluence threshold of phot1-mediated RNA destabilization contrasts with the low-fluence threshold required for phot1-directed first-positive phototropic curvature. This study indicates that phot1, like phytochrome, can discriminate between several fluence ranges and direct responses in specific tissues or different sub-cellular compartments.
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Affiliation(s)
- Kevin M Folta
- Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, 900 S. Ashland Avenue M/C 567, Chicago, IL 60607, USA
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122
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Stoelzle S, Kagawa T, Wada M, Hedrich R, Dietrich P. Blue light activates calcium-permeable channels in Arabidopsis mesophyll cells via the phototropin signaling pathway. Proc Natl Acad Sci U S A 2003; 100:1456-61. [PMID: 12540824 PMCID: PMC298794 DOI: 10.1073/pnas.0333408100] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2002] [Indexed: 11/18/2022] Open
Abstract
Light is a central regulator of plant growth and development. Among the processes triggered by blue and UV-A light, phototropism, stomatal movement, and chloroplast orientation rely on the activation of blue-light receptors known as phototropins. So far, these photoreceptors constitute a class of light receptor kinases unique to the plant kingdom. In Arabidopsis thaliana, the two members phot1 and phot2 have been shown to display partially overlapping functions. Up to now little is known about the signaling cascade, which links these phototropins to the physiological responses downstream of blue-light perception. Here, we show that on illumination with blue light, but not red light, voltage-dependent and calcium-permeable channels activate in the plasma membrane of mesophyll cells. Blue-light stimulation in the presence of the photosynthetic electron transport inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, indicates that blue-light receptors rather than photosynthesis control channel activity. Sensitivity toward the protein kinase inhibitor K252a further pointed to the possible involvement of light receptor kinases. In support of this hypothesis, in the photoreceptor mutant phot1-5, blue-light induction of calcium currents was dramatically reduced and was eliminated in the double mutant phot1-5 phot2-1. By contrast, in cry1-304 cry2-1, an Arabidopsis mutant lacking another class of plant blue-light receptors, the channel remained sensitive to blue light. We thus conclude that blue light triggers calcium fluxes via the phototropin-activated calcium-permeable channel.
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Affiliation(s)
- Sonja Stoelzle
- Department of Molecular Plant Physiology and Biophysics, Julius von Sachs Institute of Biosciences, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany
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123
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Sinha RP, Ambasht NK, Sinha JP, Häder DP. Wavelength-dependent induction of a mycosporine-like amino acid in a rice-field cyanobacterium, Nostoc commune: role of inhibitors and salt stress. Photochem Photobiol Sci 2003; 2:171-6. [PMID: 12664980 DOI: 10.1039/b204167g] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Wavelength-dependent induction of a mycosporine-like amino acid (MAA) was studied in a nitrogen-fixing rice-field cyanobacterium, Nostoc commune. HPLC studies showed the presence of shinorine, a bisubstituted MAA containing both glycine and serine groups and having an absorption maximum at 334 nm. Exposure of cultures to simulated solar radiation in combination with various cut-off filters (WG 280, 295, 305, 320, 335, 345, GG 400, 420, 455, 475, OG 515, 530, 570, RG 645, 665; all Schott filter series) clearly indicated that MAAs were induced by UV-B radiation, while UV-A and PAR had very little effect on MAA induction in this organism. The ratio of the absorption at 334 nm (shinorine) to 665 nm (chlorophyll a) and the derived action spectrum also revealed the induction of MAAs to be UV-B dependent with a prominent peak at 290 nm and a second small peak at 310 nm. Various concentrations (50-300 mM) of NaCl were used to test whether another common stress factor, such as osmotic stress, also induces MAAs, as has been reported for other cyanobacterial species. The results indicate that cells grown at high concentration of NaCl but without UV-B did not show any MAA induction. In order to elucidate the possible photoreceptors, the effects of various inhibitors/quenchers on the induction of MAAs were studied. There was a marked reduction in the amount of MAA when the cells were irradiated with UV-B in the presence of inhibitors of the shikimate pathway (glyphosate, 1 mM), photosynthesis [3-(3,4-dichlorophenyl)-1,1-dimethylurea, 20 microM], protein synthesis (chloramphenicol, 25 microg ml(-1)), pterin synthesis (N-acetylserotonin, 5 mM, and 2,4-diamino-6-hydroxypyrimidine, 5 mM) and a quencher of the excited state of flavins and pterins (phenylacetic acid, 1 mM).
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Affiliation(s)
- Rajeshwar P Sinha
- Institut für Botanik und Pharmazeutische Biologie, Friedrich-Alexander-Universität, Staudtstr. 5, D-91058 Erlangen, Germany
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124
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Sato Y, Kadota A, Wada M. Chloroplast movement: dissection of events downstream of photo- and mechano-perception. JOURNAL OF PLANT RESEARCH 2003; 116:1-5. [PMID: 12605293 DOI: 10.1007/s10265-002-0073-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2002] [Accepted: 11/22/2002] [Indexed: 05/24/2023]
Abstract
The study of chloroplast photorelocation movement is progressing rapidly now that mutants for chloroplast movement have become available in Arabidopsis thaliana. However, mechanistic approaches in cell biology still stand to elucidate the mechanisms and regulations of such movement. The fern Adiantum capillus-veneris and the moss Physcomitrella patens are particularly suitable materials for analyzing the kinetics of intracellular chloroplast movement. In these plants, chloroplast movement is induced by red light as well as blue light, mediated by phytochrome and blue light receptor, respectively. In this paper, we review the unique force-generating system for chloroplast motility in P. patens. In addition to light-induced chloroplast movement, we also summarize mechanically induced chloroplast movement in these plants and the motility systems involved. Finally, the different dependency of mechano- and photo-relocation movement on external Ca(2+) is discussed.
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Affiliation(s)
- Yoshikatsu Sato
- Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
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125
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Kagawa T. The phototropin family as photoreceptors for blue light-induced chloroplast relocation. JOURNAL OF PLANT RESEARCH 2003; 116:77-82. [PMID: 12605303 DOI: 10.1007/s10265-002-0072-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2002] [Accepted: 11/06/2002] [Indexed: 05/24/2023]
Abstract
Blue light-induced chloroplast accumulation and avoidance relocation movements are controlled by the blue light photoreceptor phototropin. The Arabidopsis thaliana genome has two phototropin genes encoding phot1 and phot2. Each of these photoreceptors contains two LOV (light oxygen and voltage) domains and a kinase domain. The LOV domains absorb blue light though an associated flavin mononucleotide chromophore, while the kinase domain is thought to be associated with signal transduction. The phototropins control not only chloroplast relocation movement, but also blue light-induced phototropic responses, leaf expansion and stomatal opening. Here I review the role of phototropin as a photoreceptor for chloroplast photorelocation movement.
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Affiliation(s)
- Takatoshi Kagawa
- Division of Biological Regulation and Photobiology, National Institute for Basic Biology, 38 Nishigonaka, Myoudaiji-cho, Okazaki 444-8585, Japan.
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126
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Abstract
Cryptochromes are photosensory receptors mediating light regulation of growth and development in plants. Since the isolation of the Arabidopsis CRY1 gene in 1993, cryptochromes have been found in every multicellular eukaryote examined. Most plant cryptochromes have a chromophore-binding domain that shares similar structure with DNA photolyase, and a carboxyl terminal extension that contains a DQXVP-acidic-STAES (DAS) domain conserved from moss, to fern, to angiosperm. In Arabidopsis, cryptochromes are nuclear proteins that mediate light control of stem elongation, leaf expansion, photoperiodic flowering, and the circadian clock. Cryptochromes may act by interacting with proteins such as phytochromes, COP1, and clock proteins, or/and chromatin and DNA. Recent studies suggest that cryptochromes undergo a blue light-dependent phosphorylation that affects the conformation, intermolecular interactions, physiological activities, and protein abundance of the photoreceptors.
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Affiliation(s)
- Chentao Lin
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, California 90095, USA.
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127
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Abstract
The study of chloroplast movement made a quantum leap at the beginning of the twenty-first century. Research based on reverse-genetic approaches using targeted mutants has brought new concepts to this field. One of the most exciting findings has been the discovery of photoreceptors for both accumulation and avoidance responses in Arabidopsis and in the fern Adiantum. Evidence for the adaptive advantage of chloroplast avoidance movements in plant survival has also been found. Additional discoveries include mechano-stress-induced chloroplast movement in ferns and mosses, and microtubule-mediated chloroplast movement in the moss Physcomitrella. The possible ecological significance of chloroplast movement is discussed in the final part of this review.
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Affiliation(s)
- Masamitsu Wada
- Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
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128
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Mithöfer A, Mazars C. Aequorin-based measurements of intracellular Ca2+-signatures in plant cells. Biol Proced Online 2002; 4:105-118. [PMID: 12734562 PMCID: PMC145563 DOI: 10.1251/bpo40] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2002] [Revised: 11/19/2002] [Accepted: 11/21/2002] [Indexed: 11/23/2022] Open
Abstract
Due to the involvement of calcium as a main second messenger in the plant signaling pathway, increasing interest has been focused on the calcium signatures supposed to be involved in the patterning of the specific response associated to a given stimulus. In order to follow these signatures we described here the practical approach to use the non-invasive method based on the aequorin technology. Besides reviewing the advantages and disadvantages of this method we report on results showing the usefulness of aequorin to study the calcium response to biotic (elicitors) and abiotic stimuli (osmotic shocks) in various compartments of plant cells such as cytosol and nucleus.
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Affiliation(s)
- Axel Mithöfer
- Department Biologie I der Ludwig-Maximilians-Universität, Botanik. Menzinger Str. 67, D-80638, München. Germany.Signaux et Messages Cellulaires chez les Végétaux, UMR CNRS/UPS 5546. 24 Chemin de Borde Rouge, BP 17 Auzeville, F-31326 Castanet-Tolosan. France.
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129
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Lecourieux D, Mazars C, Pauly N, Ranjeva R, Pugin A. Analysis and effects of cytosolic free calcium increases in response to elicitors in Nicotiana plumbaginifolia cells. THE PLANT CELL 2002; 14:2627-41. [PMID: 12368509 PMCID: PMC151240 DOI: 10.1105/tpc.005579] [Citation(s) in RCA: 270] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2002] [Accepted: 07/19/2002] [Indexed: 05/17/2023]
Abstract
Cell suspensions obtained from Nicotiana plumbaginifolia plants stably expressing the apoaequorin gene were used to analyze changes in cytosolic free calcium concentrations ([Ca(2+)](cyt)) in response to elicitors of plant defenses, particularly cryptogein and oligogalacturonides. The calcium signatures differ in lag time, peak time, intensity, and duration. The intensities of both signatures depend on elicitor concentration and extracellular calcium concentration. Cryptogein signature is characterized by a long-sustained [Ca(2+)](cyt) increase that should be responsible for sustained mitogen-activated protein kinase activation, microtubule depolymerization, defense gene activation, and cell death. The [Ca(2+)](cyt) increase in elicitor-treated cells first results from a calcium influx, which in turns leads to calcium release from internal stores and additional Ca(2+) influx. H(2)O(2) resulting from the calcium-dependent activation of the NADPH oxidase also participates in [Ca(2+)](cyt) increase and may activate calcium channels from the plasma membrane. Competition assays with different elicitins demonstrate that [Ca(2+)](cyt) increase is mediated by cryptogein-receptor interaction.
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Affiliation(s)
- David Lecourieux
- Unité Mixte de Recherche Institut National de la Recherche Agronomique-Université de Bourgogne, Biochimie, Biologie Cellulaire et Ecologie des Interactions Plantes-Microorganismes, 17 rue de Sully, BP 86510, 21065 Dijon cedex, France
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130
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Dame G, Gloeckner G, Beck CF. Knock-out of a putative transporter results in altered blue-light signalling in Chlamydomonas. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 31:577-587. [PMID: 12207648 DOI: 10.1046/j.1365-313x.2002.01379.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Nitrogen starvation and blue light are the two environmental cues that control sexual differentiation in Chlamydomonas reinhardtii. Insertional mutagenesis was applied to generate mutants that still require nitrogen starvation as the initiating signal for gametogenesis but were no longer dependent on irradiation. In one mutant analysed, sequences adjacent to the site of insertion were cloned and used for the isolation of a genomic clone that, upon transformation, could complement the mutant phenotype. The gene identified (LRG6) encodes two mRNAs that appear to be the products of differential splicing. The two putative gene products derived from these mRNAs differ in their C-terminal ends. Both predicted gene products exhibit multiple hydrophobic domains with alpha-helical secondary structure typical for integral membrane proteins. These proteins may form pores, and may function as transporters of as-yet unknown substrates. Since rendering the LRG6 gene non-functional resulted in light-independence of gamete formation, it is suggested that this transporter may inhibit signal flux from the photoreceptor to target genes - either directly by its activity or indirectly by serving as a scaffold for signalling proteins. Shutting off this transporter may be required for the activation of signal flux in this pathway. This concept is supported by the observed reduction in LRG6 mRNA levels during the first phase of gametic differentiation.
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Affiliation(s)
- Gregory Dame
- Institut für Biologie III, Universität Freiburg, Schaenzlestrasse 1, D-79104 Freiburg, Germany
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131
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Huang K, Merkle T, Beck CF. Isolation and characterization of a Chlamydomonas gene that encodes a putative blue-light photoreceptor of the phototropin family. PHYSIOLOGIA PLANTARUM 2002; 115:613-622. [PMID: 12121468 DOI: 10.1034/j.1399-3054.2002.1150416.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In the search for a Chlamydomonas reinhardtii photoreceptor that may mediate blue-light-induced responses we identified a gene that encodes a protein with a structure typical for that of members of the phototropin family, i.e. two LOV domains that may function in flavin mononucleotide binding and a ser/thr kinase domain. The amino acid sequences of these domains are closely related to those of higher plant phototropins. This single-copy gene (Phot) encodes a protein with a calculated molecular mass of 81.4 kDa which is distinctly smaller than the homologous proteins of higher plants that exhibit molecular masses around 120 kDa. Expression analyses revealed rather constant levels of Phot mRNA and Phot protein in vegetative cells incubated in the dark and in cells undergoing gametogenesis. Only vegetative cells in the light showed a reduced expression of the Phot gene. Cell fractionation studies revealed that the protein is membrane-associated. In higher plants, phototropins were shown to be bound to the plasma membrane. However, the expression of a Phot-GFP gene fusion in tobacco protoplasts revealed an association of the fusion protein with the endogenous membrane network of the cell.
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Affiliation(s)
- Kaiyao Huang
- Institut für Biologie III, Institut für Biologie II, Universität Freiburg, Schaenzlestrasse 1, D-79104 Freiburg, Germany
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132
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Sakamoto K, Briggs WR. Cellular and subcellular localization of phototropin 1. THE PLANT CELL 2002; 14:1723-35. [PMID: 12172018 PMCID: PMC151461 DOI: 10.1105/tpc.003293] [Citation(s) in RCA: 293] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2002] [Accepted: 04/19/2002] [Indexed: 05/18/2023]
Abstract
Phototropin 1 (phot1) is a Ser/Thr photoreceptor kinase that binds two molecules of flavin mononucleotide as its chromophores and undergoes autophosphorylation in response to blue light. Phot1 is plasma membrane associated and, as with phot2, has been shown to function as a photoreceptor for phototropism, blue light-induced chloroplast movement, and blue light-induced stomatal opening. Phot1 likely also plays a redundant role with phot2 in regulating the rate of leaf expansion. Understanding the mechanism(s) by which phot1 initiates these four different responses requires, at minimum, knowledge of where the photoreceptor is located. Therefore, we transformed a phot1 null mutant of Arabidopsis with a construct encoding translationally fused phot1-green fluorescent protein (GFP) under the control of the endogenous PHOT1 promoter and investigated its cellular and subcellular distribution. This PHOT1-GFP construct complements the mutant phenotype, restoring second positive curvature. Phot1 is expressed strongly in dividing and elongating cortical cells in the apical hook and in the root elongation zone in etiolated seedlings. It is localized evenly to the plasma membrane region in epidermal cells but is confined largely to the plasma membrane region of the transverse cell walls in the cortical cells of both root and hypocotyl. It is found at both apical and basal ends of these cortical cells. In light-grown plants, phot1-GFP is localized largely in the plasma membrane regions adjacent to apical and basal cell end walls in the elongating inflorescence stem, where the photoreceptor is expressed strongly in the vascular parenchyma and leaf vein parenchyma. Phot1 also is localized to the plasma membrane region of leaf epidermal cells, mesophyll cells, and guard cells, where its distribution is uniform. Although phot1 is localized consistently to the plasma membrane region in etiolated seedlings, a fraction becomes released to the cytoplasm in response to blue light. Possible relationships between observed phot1 distribution and the various physiological responses activated by blue light are discussed.
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Affiliation(s)
- Koji Sakamoto
- Department of Plant Biology, Carnegie Institution of Washington, 260 Panama Street, Stanford, CA 94305, USA
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133
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Allen GJ, Murata Y, Chu SP, Nafisi M, Schroeder JI. Hypersensitivity of abscisic acid-induced cytosolic calcium increases in the Arabidopsis farnesyltransferase mutant era1-2. THE PLANT CELL 2002; 14:1649-62. [PMID: 12119381 PMCID: PMC150713 DOI: 10.1105/tpc.010448] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2001] [Accepted: 03/21/2002] [Indexed: 05/18/2023]
Abstract
Cytosolic calcium increases were analyzed in guard cells of the Arabidopsis farnesyltransferase deletion mutant era1-2 (enhanced response to abscisic acid). At low abscisic acid (ABA) concentrations (0.1 microM), increases of guard cell cytosolic calcium and stomatal closure were activated to a greater extent in the era1-2 mutant compared with the wild type. Patch clamping of era1-2 guard cells showed enhanced ABA sensitivity of plasma membrane calcium channel currents. These data indicate that the ERA1 farnesyltransferase targets a negative regulator of ABA signaling that acts between the points of ABA perception and the activation of plasma membrane calcium influx channels. Experimental increases of cytosolic calcium showed that the activation of S-type anion currents downstream of cytosolic calcium and extracellular calcium-induced stomatal closure were unaffected in era1-2, further supporting the positioning of era1-2 upstream of cytosolic calcium in the guard cell ABA signaling cascade. Moreover, the suppression of ABA-induced calcium increases in guard cells by the dominant protein phosphatase 2C mutant abi2-1 was rescued partially in era1-2 abi2-1 double mutant guard cells, further reinforcing the notion that ERA1 functions upstream of cytosolic calcium and indicating the genetic interaction of these two mutations upstream of ABA-induced calcium increases.
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Affiliation(s)
- Gethyn J Allen
- Cell and Developmental Biology Section, Division of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116, USA
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134
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Plieth C, Trewavas AJ. Reorientation of seedlings in the earth's gravitational field induces cytosolic calcium transients. PLANT PHYSIOLOGY 2002; 129:786-96. [PMID: 12068119 PMCID: PMC161701 DOI: 10.1104/pp.011007] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2001] [Revised: 12/17/2001] [Accepted: 01/30/2002] [Indexed: 05/19/2023]
Abstract
The gravitational field controls plant growth, morphology, and development. However, the underlying transduction mechanisms are not well understood. Much indirect evidence has implicated the cytoplasmic free calcium concentration ([Ca(2+)](c)) as an important factor, but direct evidence for changes in [Ca(2+)](c) is currently lacking. We now have made measurements of [Ca(2+)](c) in groups of young seedlings of Arabidopsis expressing aequorin in the cytoplasm and reconstituted in vivo with cp-coelenterazine, a synthetic high-affinity luminophore. Distinct [Ca(2+)](c) signaling occurs in response to gravistimulation with kinetics very different from [Ca(2+)](c) transients evoked by other mechanical stimuli (e.g. movement and wind). [Ca(2+)](c) changes produced in response to gravistimulation are transient but with a duration of many minutes and dependent on stimulus strength (i.e. the angle of displacement). The auxin transport blockers 2,3,5-tri-iodo benzoic acid and N-(1-naphthyl) phthalamic acid interfere with gravi-induced [Ca(2+)](c) responses and addition of methyl indole-3-acetic acid to whole seedlings induces long-lived [Ca(2+)](c) transients, suggesting that changes in auxin transport may interact with [Ca(2+)](c). Permanent nonaxial rotation of seedlings on a two-dimensional clinostat, however, produced a sustained elevation of the [Ca(2+)](c) level. This probably reflects permanent displacement of gravity-sensing cellular components and/or disturbance of cytoskeletal tension. It is concluded that [Ca(2+)](c) is part of the gravity transduction mechanism in young Arabidopsis seedlings.
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Affiliation(s)
- Christoph Plieth
- Zentrum für Biochemie und Molekularbiologie, Christian-Albrechts-Universität, Am Botanischen Garten 1-9 (Room 517), D-24118 Kiel, Germany.
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135
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Talbott LD, Zhu J, Han SW, Zeiger E. Phytochrome and blue light-mediated stomatal opening in the orchid, paphiopedilum. PLANT & CELL PHYSIOLOGY 2002; 43:639-46. [PMID: 12091717 DOI: 10.1093/pcp/pcf075] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Guard cells of the orchid genus, Paphiopedilum have been reported to lack developed chloroplasts and detectable chlorophyll a autofluorescence. Paphiopedilum stomata lack a photosynthesis-dependent opening response but have a blue light-specific opening. The present study found that low fluence rate green and red light elicited stomatal opening in Paphiopedilum and this opening was reversed by far red light, indicating the presence of a phytochrome-mediated opening response. Phytochrome-dependent, red light-stimulated opening was largest under low fluence rates and decreased to near zero as fluence rate increased. A recently discovered green light reversibility of blue light-specific stomatal opening was used to probe the properties of the blue light response in Paphiopedilum stomata. Blue light-stimulated opening was completely reversed by green light in the presence of far red light. Red light enhanced the blue light response of Paphiopedilum guard cells when given as a pretreatment or together with blue light. Analysis of guard cell pigments showed that guard cells have small amounts of chlorophyll a and b, zeaxanthin, violaxanthin, antheraxanthin and lutein. Zeaxanthin content increased in response to blue light or ascorbate and declined in the dark or under illumination in the presence of dithiothreitol, indicating the presence of an active xanthophyll cycle. Thus Paphiopedilum stomata possess both a blue light-mediated opening response with characteristics similar to species with normal chloroplast development and a novel phytochrome-mediated opening response.
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Affiliation(s)
- Lawrence D Talbott
- Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA 90024, USA
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136
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Briggs WR, Christie JM. Phototropins 1 and 2: versatile plant blue-light receptors. TRENDS IN PLANT SCIENCE 2002; 7:204-10. [PMID: 11992825 DOI: 10.1016/s1360-1385(02)02245-8] [Citation(s) in RCA: 467] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Blue and ultraviolet-A light regulate a wide range of responses in plants, including phototropism, chloroplast migration and stomatal opening. However, the photoreceptors for these light responses have been identified only recently. The phototropins (phot1 and phot2) represent a new class of receptor kinases that appear to be exclusive to plants. Recent genetic analysis has shown that phot1 and phot2 exhibit partially overlapping functions in mediating phototropism, chloroplast migration, and stomatal opening in Arabidopsis. Although significant progress has been made in understanding the early photochemical and biochemical events that follow phototropin excitation, the details of how this excitation activates such different responses remain to be elucidated.
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Affiliation(s)
- Winslow R Briggs
- Dept Plant Biology, Carnegie Institution of Washington, Stanford, CA 94305, USA.
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137
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McClung CR, Salomé PA, Michael TP. The Arabidopsis circadian system. THE ARABIDOPSIS BOOK 2002; 1:e0044. [PMID: 22303209 PMCID: PMC3243369 DOI: 10.1199/tab.0044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Rhythms with periods of approximately 24 hr are widespread in nature. Those that persist in constant conditions are termed circadian rhythms and reflect the activity of an endogenous biological clock. Plants, including Arabidopsis, are richly rhythmic. Expression analysis, most recently on a genomic scale, indicates that the Arabidopsis circadian clock regulates a number of key metabolic pathways and stress responses. A number of sensitive and high-throughput assays have been developed to monitor the Arabidopsis clock. These assays have facilitated the identification of components of plant circadian systems through genetic and molecular biological studies. Although much remains to be learned, the framework of the Arabidopsis circadian system is coming into focus.DedicationThis review is dedicated to the memory of DeLill Nasser, a wonderful mentor and an unwavering advocate of both Arabidopsis and circadian rhythms research.
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Affiliation(s)
- C. Robertson McClung
- Department of Biological Sciences, 6044 Gilman Laboratories, Dartmouth College, Hanover, New Hampshire 03755-3576
- Corresponding Author: telephone: 603-646-3940; fax: 603-646-1347;
| | - Patrice A. Salomé
- Department of Biological Sciences, 6044 Gilman Laboratories, Dartmouth College, Hanover, New Hampshire 03755-3576
| | - Todd P. Michael
- Department of Biological Sciences, 6044 Gilman Laboratories, Dartmouth College, Hanover, New Hampshire 03755-3576
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138
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Babourina O, Newman I, Shabala S. Blue light-induced kinetics of H+ and Ca2+ fluxes in etiolated wild-type and phototropin-mutant Arabidopsis seedlings. Proc Natl Acad Sci U S A 2002; 99:2433-8. [PMID: 11854534 PMCID: PMC122382 DOI: 10.1073/pnas.042294599] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ion flux kinetics associated with blue light (BL) treatment of two wild types (WTs) and the phot1, phot2 and phot1/phot2 mutants of Arabidopsis were studied by using the MIFE noninvasive ion-selective microelectrode technique. BL induced significant changes in activity of H(+) and Ca(2+) transporters within the first 10 min of BL onset, peaking between 3 and 5 min. In all WT plants and in phot2 mutants, BL induced immediate Ca(2+) influx. In phot1 and phot1/phot2 mutants, net Ca(2+) flux remained steady. It is suggested that PHOT1 regulates Ca(2+) uptake into the cytoplasm from the apoplast. Changes in ion fluxes were measured from cotyledons of intact seedlings and from the cut top of the hypocotyl of decapitated seedlings. Thus the photoreceptors mediating BL-induced Ca(2+) and H(+) fluxes are present in the rest of the decapitated seedling and probably in the cotyledons as well. The H(+) and Ca(2+) flux responses to BL appear not to be linked because, (i) when changes were observed for both ions, Ca(2+) flux changed almost immediately, whereas H(+) flux lagged by about 1.5 min; (ii) in the Wassilewskija ecotype, changes in H(+) fluxes were small. Finally, wave-like changes in Ca(2+) and H(+) concentrations were observed along the cotyledon-hook axis regardless of its orientation to the light.
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Affiliation(s)
- Olga Babourina
- School of Mathematics and Physics, and School of Agricultural Science, University of Tasmania, GPO Box 252-21, Hobart, Tasmania 7001, Australia.
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139
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Lin C. Blue light receptors and signal transduction. THE PLANT CELL 2002; 14 Suppl:S207-25. [PMID: 12045278 PMCID: PMC151256 DOI: 10.1105/tpc.000646] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2001] [Accepted: 03/17/2002] [Indexed: 05/18/2023]
Affiliation(s)
- Chentao Lin
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA.
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140
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Sanders D, Pelloux J, Brownlee C, Harper JF. Calcium at the crossroads of signaling. THE PLANT CELL 2002; 14 Suppl:S401-17. [PMID: 12045291 PMCID: PMC151269 DOI: 10.1105/tpc.002899] [Citation(s) in RCA: 712] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2002] [Accepted: 03/21/2002] [Indexed: 05/17/2023]
Affiliation(s)
- Dale Sanders
- Biology Department, University of York, York YO10 5YW, United Kingdom.
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141
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Kinoshita T, Doi M, Suetsugu N, Kagawa T, Wada M, Shimazaki K. Phot1 and phot2 mediate blue light regulation of stomatal opening. Nature 2001; 414:656-60. [PMID: 11740564 DOI: 10.1038/414656a] [Citation(s) in RCA: 562] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The stomatal pores of higher plants allow for gaseous exchange into and out of leaves. Situated in the epidermis, they are surrounded by a pair of guard cells which control their opening in response to many environmental stimuli, including blue light. Opening of the pores is mediated by K(+) accumulation in guard cells through a K(+) channel and driven by an inside-negative electrical potential. Blue light causes phosphorylation and activation of the plasma membrane H(+)-ATPase that creates this potential. Thus far, no blue light receptor mediating stomatal opening has been identified, although the carotenoid, zeaxanthin, has been proposed. Arabidopsis mutants deficient in specific blue-light-mediated responses have identified four blue light receptors, cryptochrome 1 (cry1), cryptochrome 2 (cry2), phot1 and phot2. Here we show that in a double mutant of phot1 and phot2 stomata do not respond to blue light although single mutants are phenotypically normal. These results demonstrate that phot1 and phot2 act redundantly as blue light receptors mediating stomatal opening.
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Affiliation(s)
- T Kinoshita
- Department of Biology, Faculty of Science, Kyushu University, Ropponmatsu, Fukuoka 810-8560, Japan
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142
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Pauly N, Knight MR, Thuleau P, Graziana A, Muto S, Ranjeva R, Mazars C. The nucleus together with the cytosol generates patterns of specific cellular calcium signatures in tobacco suspension culture cells. Cell Calcium 2001; 30:413-21. [PMID: 11728136 DOI: 10.1054/ceca.2001.0250] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Plant cell suspension cultures respond to osmotic changes by alterations in levels of free cellular calcium. Using the aequorin recombinant method, we have measured the spatial and temporal characteristics of calcium signatures in the nucleus and the cytosol of BY-2 tobacco suspension cells challenged with hypo- or hyper-osmotic shock. We show here that the nuclear compartment contributes together with the cytosol to produce calcium signal patterns that discriminate hypo- from hyper-osmotic treatments, i.e. turgor from tension. We also demonstrate that calcium responses in the nucleus and the cytosol are differentially modulated by the strength and the nature of hyper-osmotic treatments. We conclude that qualitative and quantitative changes in the parameters of an external stimulus such as osmotic changes are converted into calcium signatures, distinctive in their temporal and subcellular characteristics, involving both the nucleus and the cytosol. Our results illustrate the versatility of calcium signaling in plant cells. In addition to the physiological 'address' of the cell, the compartmentation of the calcium signal is probably an important parameter in encoding response specificity.
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Affiliation(s)
- N Pauly
- Signaux et Messages Cellulaires chez les Végétaux, Centre National de la Recherche Scientifique, Université Paul Sabatier, Castanet-Tolosan, France
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143
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Allen GJ, Schroeder JI. Combining Genetics and Cell Biology to Crack the Code of Plant Cell Calcium Signaling. Sci Signal 2001. [DOI: 10.1126/scisignal.1022001re13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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144
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Allen GJ, Schroeder JI. Combining genetics and cell biology to crack the code of plant cell calcium signaling. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2001; 2001:re13. [PMID: 11584126 DOI: 10.1126/stke.2001.102.re13] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Plant hormones, light receptors, pathogens, and abiotic signals trigger elevations in the cytosolic calcium concentration, which mediate physiological and developmental responses. Recent studies are reviewed here that reveal how specific genetic mutations impair or modify stimulus-induced calcium elevations in plant cells. These studies provide genetic evidence for the importance of calcium as a second messenger in plant signal transduction. A fundamental question arises: How can different stimuli use the same second messenger, calcium, to mediate different responses? Recent research and models are reviewed that suggest that several important mechanisms contribute to specificity in calcium signaling in plant cells. These mechanisms include (i) activation of different calcium channels in the plasma membrane and organellar membranes, (ii) stimulus-specific calcium oscillation parameters, (iii) cell type-specific responses, and (iv) intracellular localization of calcium gradients and calcium elevations in plant cells.
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Affiliation(s)
- G J Allen
- The Division of Biology, Cell and Developmental Biology Section, University of California, San Diego, La Jolla, CA 92093-0116, USA.
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145
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Sato Y, Wada M, Kadota A. External Ca(2+) is essential for chloroplast movement induced by mechanical stimulation but not by light stimulation. PLANT PHYSIOLOGY 2001. [PMID: 11598224 DOI: 10.1104/pp.010405] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In the fern Adiantum capillus-veneris, chloroplast movement is induced by mechanical stimulation as well as by light stimulation. Directional movement of both types depends on an actin-based motile system. To investigate the physiological relationship between mechanical and light signaling in the regulation of chloroplast movement, we examined the mechano-response of chloroplasts whose motility had been already restricted after photo-relocation. Chloroplast mechano-avoidance movement was induced under all of the photo-relocation conditions tested, indicating that mechano-specific signals generated by mechanical stimulation dominate over the light signals and reactivate the motility of chloroplasts. When the effects of external Ca(2+) on the induction of mechano- and light responses were examined, strikingly different requirements of external Ca(2+) were found for each. In medium without Ca(2+), the mechano-response was suppressed but no effects were observed on photo-response. Mechano-relocation movement of chloroplasts was inhibited by 100 microM lanthanum (La(3+)), a plasma membrane calcium channel blocker, and by 10 microM gadolinium (Gd(3+)), a stretch-activated channel blocker. However, the same concentrations of these drugs did not affect the photo-relocation movement at all. These results suggest that the influx of external Ca(2+) is crucial for the early signaling step of chloroplast mechano-relocation but not for that of photo-relocation. This is the first report showing the separation of signaling pathways in mechano- and photo-relocation of chloroplasts.
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Affiliation(s)
- Y Sato
- Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan
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146
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Jenkins GI, Long JC, Wade HK, Shenton MR, Bibikova TN. UV and blue light signalling: pathways regulating chalcone synthase gene expression in Arabidopsis. THE NEW PHYTOLOGIST 2001; 151:121-131. [PMID: 33873370 DOI: 10.1046/j.1469-8137.2001.00151.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
UV-B, UV-A and blue light control a variety of aspects of plant development via distinct photoreceptors and signalling pathways. The known photoreceptors for UV-A/blue light are cryptochrome (cry)1 and cry2, and the phototropism photoreceptor, phototropin. Redox processes are important in cry and phototropin signal transduction. A specific photoreceptor for UV-B has not been identified and there appear to be several possible UV-B signalling pathways. We are investigating the UV and blue light regulation of transcription of the chalcone synthase gene (CHS) in Arabidopsis. Experiments with photoreceptor mutants show that distinct UV-A/blue (cry mediated) and UV-B photoreception systems control CHS expression. Experiments with an Arabidopsis cell suspension culture show that the UV-B and cry1 signalling pathways differ kinetically and pharmacologically. In contrast to some other UV-B responses, the UV-B induction of CHS does not appear to involve oxidative stress signalling. Promoter elements and candidate transcription factors that effect CHS induction have been identified. Interactions within a network of UV-B, cry and phytochrome signalling pathways regulate CHS expression. Synergistic interactions between the UV-B pathway and distinct UV-A and blue-light pathways maximize the response. In addition, specific phytochromes positively control the cry1 pathway via distinct potentiation and coaction effects, and negatively regulate the UV-B pathway.
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Affiliation(s)
- Gareth I Jenkins
- Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Joanne C Long
- present address: Department of Botany, North Carolina State University, Box 7612, Raleigh, NC 27695-7612, USA
| | - Helena K Wade
- Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Matthew R Shenton
- Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Tatiana N Bibikova
- present address: Biology Department, Pennsylvania State University, University Park, PA 16802, USA
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147
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Rudd JJ, Franklin-Tong VE. Unravelling response-specificity in Ca 2+ signalling pathways in plant cells. THE NEW PHYTOLOGIST 2001; 151:7-33. [PMID: 33873376 DOI: 10.1046/j.1469-8137.2001.00173.x] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Considerable advances have been made, both in the technologies available to study changes in intracellular cytosolic free Ca2+ ([Ca2+ ]i ), and in our understanding of Ca2+ signalling cascades in plant cells, but how specificity can be generated from such a ubiquitous component as Ca2+ is questionable. Recently the concept of 'Ca2+ signatures' has been formulated; tight control of the temporal and spatial characteristics of alterations in [Ca2+ ]i signals is thought to be responsible, at least in part, for the specificity of the response. However, the way in which Ca2+ signatures are decoded, which depends on the nature and location of the targets of the Ca2+ signals, has received little attention. In a few key systems, progress is being made on how diverse Ca2+ signatures might be transduced within cells in response to specific signals. Valuable pieces of the signal-specificity puzzle are being put together and this is illustrated here using some key examples; these emphasize the global importance of Ca2+ -mediated signal-transduction cascades in the responses of plants to a wide diversity of extracellular signals. However, the way in which signal specificity is encoded and transduced is still far from clear. Contents Summary 7 I. Introduction: Ca2+ as a signal transducer 8 II. Alterations in intracellular [Ca2+ ] 8 1. Measuring alterations in [Ca2+ ] 8 Imaging [Ca2+ ]i using Ca2+ -sensitive dyes 8 Measuring [Ca2+ ]i using aequorin 9 Imaging [Ca2+ ]i using cameleon 10 2. The concept of the 'Ca2+ signature 10 3. How might specific Ca2+ signatures be generated? 11 Control of intracellular Ca2+ release 11 Control of influx of extracellular Ca2+ 12 4. Examples of Ca2+ signatures and cellular responses to increases in [Ca2+ ] 13 Ca2+ signatures in stomatal guard cells in response to abscisic acid signals 14 Ca2+ signals in response to abiotic stimuli1 8 Ca2+ signatures involved in plant-pathogen responses 19 Ca2+ signatures in control of plant reproduction 20 Ca2+ signatures in root hairs in response to nodulation signals 23 III. Decoding the [Ca2+ ]i signatures 24 1. Coupling Ca2+ signals to responses through CaM 26 2. Coupling Ca2+ signals to responses through CDPK 27 3. Novel Ca2+ binding proteins as primary Ca2+ sensors 28 Conclusions and Perspective 28 References 29.
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Affiliation(s)
- Jason J Rudd
- Institut fur Pflanzenbiochemie, Weinberg 3, D-06120 Halle/Saale, Germany
| | - Vernonica E Franklin-Tong
- Wolfson Laboratory for Plant Molecular Biology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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148
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McClung CR. CIRCADIAN RHYTHMS IN PLANTS. ANNUAL REVIEW OF PLANT PHYSIOLOGY AND PLANT MOLECULAR BIOLOGY 2001; 52:139-162. [PMID: 11337395 DOI: 10.1146/annurev.arplant.52.1.139] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Circadian rhythms, endogenous rhythms with periods of approximately 24 h, are widespread in nature. Although plants have provided many examples of rhythmic outputs and our understanding of photoreceptors of circadian input pathways is well advanced, studies with plants have lagged in the identification of components of the central circadian oscillator. Nonetheless, genetic and molecular biological studies, primarily in Arabidopsis, have begun to identify the components of plant circadian systems at an accelerating pace. There also is accumulating evidence that plants and other organisms house multiple circadian clocks both in different tissues and, quite probably, within individual cells, providing unanticipated complexity in circadian systems.
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Affiliation(s)
- C Robertson McClung
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755-3576; e-mail:
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149
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Sakai T, Kagawa T, Kasahara M, Swartz TE, Christie JM, Briggs WR, Wada M, Okada K. Arabidopsis nph1 and npl1: blue light receptors that mediate both phototropism and chloroplast relocation. Proc Natl Acad Sci U S A 2001; 98:6969-74. [PMID: 11371609 PMCID: PMC34462 DOI: 10.1073/pnas.101137598] [Citation(s) in RCA: 503] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
UV-A/blue light acts to regulate a number of physiological processes in higher plants. These include light-driven chloroplast movement and phototropism. The NPH1 gene of Arabidopsis encodes an autophosphorylating protein kinase that functions as a photoreceptor for phototropism in response to low-intensity blue light. However, nph1 mutants have been reported to exhibit normal phototropic curvature under high-intensity blue light, indicating the presence of an additional phototropic receptor. A likely candidate is the nph1 homologue, npl1, which has recently been shown to mediate the avoidance response of chloroplasts to high-intensity blue light in Arabidopsis. Here we demonstrate that npl1, like nph1, noncovalently binds the chromophore flavin mononucleotide (FMN) within two specialized PAS domains, termed LOV domains. Furthermore, when expressed in insect cells, npl1, like nph1, undergoes light-dependent autophosphorylation, indicating that npl1 also functions as a light receptor kinase. Consistent with this conclusion, we show that a nph1 npl1 double mutant exhibits an impaired phototropic response under both low- and high-intensity blue light. Hence, npl1 functions as a second phototropic receptor under high fluence rate conditions and is, in part, functionally redundant to nph1. We also demonstrate that both chloroplast accumulation in response to low-intensity light and chloroplast avoidance movement in response to high-intensity light are lacking in the nph1 npl1 double mutant. Our findings therefore indicate that nph1 and npl1 show partially overlapping functions in two different responses, phototropism and chloroplast relocation, in a fluence rate-dependent manner.
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Affiliation(s)
- T Sakai
- RIKEN (The Institute of Physical and Chemical Research) Plant Science Center, Sakyo-ku, Kyoto 606-8502, Japan
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150
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Affiliation(s)
- J M Christie
- Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305, USA
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