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Ali R, Zielinski RE, Berkowitz GA. Expression of plant cyclic nucleotide-gated cation channels in yeast. JOURNAL OF EXPERIMENTAL BOTANY 2006; 57:125-38. [PMID: 16317039 DOI: 10.1093/jxb/erj012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The functional properties of inwardly conducting plant cyclic nucleotide-gated cation channels (CNGCs) have not been thoroughly characterized due in part to the recalcitrance of their functional expression in heterologous systems. Here, K+ uptake-deficient mutants of yeast (trk1,2) and Escherichia coli (LB650), as well as the Ca2+-uptake yeast mutant mid1,cch1, were used for functional characterization of Arabidopsis thaliana CNGCs, with the aim of identifying some of the cultural and physiological conditions that impact on plant CNGC function in heterologous systems. Use of the Ca2+-uptake yeast mutant provided the first evidence consistent with Ca2+ conduction by the A. thaliana CNGC AtCNGC1. Expression of AtCNGC1 in LB650 demonstrated that mutants of Escherichia coli (which has no endogenous calmodulin) can also be used to study functional properties of CNGCs. Expression of AtCNGC2 and AtCNGC4 enhanced growth of trk1,2 in the presence of hygromycin; AtCNGC1 has less of an effect. Deletion of the AtCNGC1 calmodulin-binding domain enhanced growth of trk1,2 at low external K+ but not of LB650, suggesting that yeast calmodulin may bind to, and down-regulate this plant channel. In vitro binding studies confirmed this physical interaction. Northern analysis, green fluorescent protein:AtCNGC1 fusion protein expression, as well as an antibody raised against a portion of AtCNGC1, were used to monitor expression of AtCNGC1 and deletion constructs of the channel in the heterologous systems. In the presence of the activating ligand cAMP, expression of the AtCNGC1 channel with the calmodulin-binding domain deleted increased intracellular [K+] of trk1,2. Trk1,2 is hypersensitive to the toxic cations spermine, tetramethylamine, and NH4+. These compounds, as well as amiloride, inhibited trk1,2 growth and thereby improved the efficacy of this yeast mutant as a heterologous expression system for CNGCs. In addition to characterizing mutants of yeast and E. coli as assay systems for plant CNGCs, work presented in this report demonstrates, for the first time, that a plant CNGC can retain ion channel function despite (partial) deletion of its calmodulin-binding domain and that yeast calmodulin can bind to and possibly down-regulate a plant CNGC.
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Affiliation(s)
- Rashid Ali
- Agricultural Biotechnology Laboratory, Department of Plant Science, University of Connecticut, U-4067 Storrs Road, Storrs, CT 06269-4067, USA
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Rostoks N, Schmierer D, Mudie S, Drader T, Brueggeman R, Caldwell DG, Waugh R, Kleinhofs A. Barley necrotic locus nec1 encodes the cyclic nucleotide-gated ion channel 4 homologous to the Arabidopsis HLM1. Mol Genet Genomics 2005; 275:159-68. [PMID: 16341885 DOI: 10.1007/s00438-005-0073-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Accepted: 11/02/2005] [Indexed: 10/25/2022]
Abstract
Barley homolog of the Arabidopsis necrotic (disease lesion mimic) mutant HLM1 that encodes the cyclic nucleotide-gated ion channel 4 was cloned. Barley gene was mapped genetically to the known necrotic locus nec1 and subsequent sequence analysis identified mutations in five available nec1 alleles confirming barley homolog of Arabidopsis HLM1 as the NEC1 gene. Two fast neutron (FN) induced mutants had extensive deletions in the gene, while two previously described nec1 alleles had either a STOP codon in exon 1 or a MITE insertion in intron 2 which caused alternative splicing, frame shift and production of a predicted non-functional protein. The MITE insertion was consistent with the reported spontaneous origin of the nec1 Parkland allele. The third FN mutant had a point mutation in the coding sequence which resulted in an amino acid change in the conserved predicted cyclic nucleotide-gated ion channel pore region. The expression of two pathogenesis-related genes, HvPR-1a and beta-1,3-glucanase, was elevated in two FN necrotic lines. Ten other members of the barley cyclic nucleotide-gated ion channel gene family were identified and their position on barley linkage map is reported.
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Affiliation(s)
- Nils Rostoks
- Scottish Crop Research Institute, Genome Dynamics, Invergowrie, Dundee, Scotland, UK.
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McCormack E, Tsai YC, Braam J. Handling calcium signaling: Arabidopsis CaMs and CMLs. TRENDS IN PLANT SCIENCE 2005; 10:383-9. [PMID: 16023399 DOI: 10.1016/j.tplants.2005.07.001] [Citation(s) in RCA: 311] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2005] [Revised: 05/24/2005] [Accepted: 07/01/2005] [Indexed: 05/03/2023]
Abstract
The Arabidopsis genome harbors seven calmodulin (CAM) and 50 CAM-like (CML) genes that encode potential calcium sensors. The CAMs encode only four protein isoforms. Selective pressure to maintain multiple CAMs indicates nonredundancy. Sequence divergence, even in the EF hand calcium-binding motif, exists among the CMLs and, therefore, divergent functions are likely to have evolved. Expression data recently available from Massively Parallel Signature Sequencing and Genevestigator compilation of microarrays are reviewed. The seven Arabidopsis CAMs are highly and relatively uniformly expressed. Differential expression is evident among the distinct CMLs over developmental stages, in various organs and in response to many different stimuli. In spite of the potential importance in mediating plant calcium signaling, the physiological functions of the Arabidopsis CaMs and CMLs remain largely unknown.
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Li X, Borsics T, Harrington HM, Christopher DA. Arabidopsis AtCNGC10 rescues potassium channel mutants of E. coli, yeast and Arabidopsis and is regulated by calcium/calmodulin and cyclic GMP in E. coli. FUNCTIONAL PLANT BIOLOGY : FPB 2005; 32:643-653. [PMID: 32689163 DOI: 10.1071/fp04233] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Accepted: 04/15/2005] [Indexed: 05/09/2023]
Abstract
We have isolated and characterised AtCNGC10, one of the 20 members of the family of cyclic nucleotide (CN)-gated and calmodulin (CaM)-regulated channels (CNGCs) from Arabidopsis thaliana (L.) Heynh. AtCNGC10 bound CaM in a C-terminal subregion that contains a basic amphiphillic structure characteristic of CaM-binding proteins and that also overlaps with the predicted CN-binding domain. AtCNGC10 is insensitive to the broad-range K+ channel blocker, tetraethylammonium, and lacks a typical K+-signature motif. However, AtCNGC10 complemented K+ channel uptake mutants of Escherichia coli (LB650), yeast (Saccharomyces cerevisiae CY162) and Arabidopsis (akt1-1). Sense 35S-AtCNGC10 transformed into the Arabidopsis akt1-1 mutant, grew 1.7-fold better on K+-limited medium relative to the vector control. Coexpression of CaM and AtCNGC10 in E. coli showed that Ca2+ / CaM inhibited cell growth by 40%, while cGMP reversed the inhibition by Ca2+ / CaM, in a AtCNGC10-dependent manner. AtCNGC10 did not confer tolerance to Cs+ in E. coli, however, it confers tolerance to toxic levels of Na+ and Cs+ in the yeast K+ uptake mutant grown on low K+ medium. Antisense AtCNGC10 plants had 50% less potassium than wild type Columbia. Taken together, the studies from three evolutionarily diverse species demonstrated a role for the CaM-binding channel, AtCNGC10, in mediating the uptake of K+ in plants.
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Affiliation(s)
- Xinli Li
- University of Hawaii Department of Molecular Biosciences and Bioengineering 1955 East-West Road, Agsciences 218 Honolulu, HI 96822, Hawaii
| | - Tamás Borsics
- University of Hawaii Department of Molecular Biosciences and Bioengineering 1955 East-West Road, Agsciences 218 Honolulu, HI 96822, Hawaii
| | - H Michael Harrington
- University of Hawaii Department of Molecular Biosciences and Bioengineering 1955 East-West Road, Agsciences 218 Honolulu, HI 96822, Hawaii
| | - David A Christopher
- University of Hawaii Department of Molecular Biosciences and Bioengineering 1955 East-West Road, Agsciences 218 Honolulu, HI 96822, Hawaii
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55
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Shang ZL, Ma LG, Zhang HL, He RR, Wang XC, Cui SJ, Sun DY. Ca2+ influx into lily pollen grains through a hyperpolarization-activated Ca2+-permeable channel which can be regulated by extracellular CaM. PLANT & CELL PHYSIOLOGY 2005; 46:598-608. [PMID: 15695439 DOI: 10.1093/pcp/pci063] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Confocal laser scanning microscopy (CLSM) and whole-cell patch-clamp were used to investigate the role of Ca2+ influx in maintaining the cytosolic Ca2+ concentration ([Ca2+]c) and the features of the Ca2+ influx pathway in germinating pollen grains of Lilium davidii D. [Ca2+]c decreased when Ca2+ influx was inhibited by EGTA or Ca2+ channel blockers. A hyperpolarization-activated Ca2+-permeable channel, which can be suppressed by trivalent cations, verapamil, nifedipine or diltiazem, was identified on the plasma membrane of pollen protoplasts with whole-cell patch-clamp recording. Calmodulin (CaM) antiserum and W7-agarose, both of which are cell-impermeable CaM antagonists, lead to a [Ca2+]c decrease, while exogenous purified CaM triggers a transient increase of [Ca2+]c and also remarkably activated the hyperpolarization-activated Ca2+ conductance on plasma membrane of pollen protoplasts in a dose-dependent manner. Both the increase of [Ca2+]c and the activation of Ca2+ conductance which were induced by exogenous CaM were inhibited by EGTA or Ca2+ channel blockers. This primary evidence showed the presence of a voltage-dependent Ca2+-permeable channel, whose activity may be regulated by extracellular CaM, in pollen cells.
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Affiliation(s)
- Zhong-lin Shang
- Institute of Molecular and Cell Biology, Hebei Normal University, Shijiazhuang 050016, PR China
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56
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Cyclic nucleotide binding proteins in the Arabidopsis thaliana and Oryza sativa genomes. BMC Bioinformatics 2005; 6:6. [PMID: 15644130 PMCID: PMC545951 DOI: 10.1186/1471-2105-6-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Accepted: 01/11/2005] [Indexed: 11/25/2022] Open
Abstract
Background Cyclic nucleotides are ubiquitous intracellular messengers. Until recently, the roles of cyclic nucleotides in plant cells have proven difficult to uncover. With an understanding of the protein domains which can bind cyclic nucleotides (CNB and GAF domains) we scanned the completed genomes of the higher plants Arabidopsis thaliana (mustard weed) and Oryza sativa (rice) for the effectors of these signalling molecules. Results Our analysis found that several ion channels and a class of thioesterases constitute the possible cyclic nucleotide binding proteins in plants. Contrary to some reports, we found no biochemical or bioinformatic evidence for a plant cyclic nucleotide regulated protein kinase, suggesting that cyclic nucleotide functions in plants have evolved differently than in mammals. Conclusion This paper provides a molecular framework for the discussion of cyclic nucleotide function in plants, and resolves a longstanding debate about the presence of a cyclic nucleotide dependent kinase in plants.
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57
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Yamniuk AP, Vogel HJ. Calmodulin's flexibility allows for promiscuity in its interactions with target proteins and peptides. Mol Biotechnol 2004; 27:33-57. [PMID: 15122046 DOI: 10.1385/mb:27:1:33] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The small bilobal calcium regulatory protein calmodulin (CaM) activates numerous target enzymes in response to transient changes in intracellular calcium concentrations. Binding of calcium to the two helix-loop-helix calcium-binding motifs in each of the globular domains induces conformational changes that expose a methionine-rich hydrophobic patch on the surface of each domain of the protein, which it uses to bind to peptide sequences in its target enzymes. Although these CaM-binding domains typically have little sequence identity, the positions of several bulky hydrophobic residues are often conserved, allowing for classification of CaM-binding domains into recognition motifs, such as the 1-14 and 1-10 motifs. For calcium-independent binding of CaM, a third motif known as the IQ motif is also common. Many CaM-peptide complexes have globular conformations, where CaM's central linker connecting the two domains unwinds, allowing the protein to wrap around a single predominantly alpha-helical target peptide sequence. However, novel structures have recently been reported where the conformation of CaM is highly dissimilar to these globular complexes, in some instances with less than a full compliment of bound calcium ions, as well as novel stoichiometries. Furthermore, many divergent CaM isoforms from yeast and plant species have been discovered with unique calcium-binding and enzymatic activation characteristics compared to the single CaM isoform found in mammals.
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Affiliation(s)
- Aaron P Yamniuk
- Structural Biology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada
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58
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Abstract
The natural occurrence of cyclic nucleotides in higher plants, formerly a topic of fierce debate, is now established, as is the presence of nucleotidyl cyclases and cyclic nucleotide phosphodiesterases capable of their synthesis and breakdown. Here we describe the significant properties of cyclic nucleotides, also outlining their second messenger functions and the history of plant cyclic nucleotide research over its first three decades. Findings of the last five years are detailed within the context of the functional role of cyclic nucleotides in higher plants, with particular emphasis upon nucleotidyl cyclases and cyclic nucleotide-responsive protein kinases, -binding proteins and -gated ion channels, with future objectives and strategies discussed.
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Affiliation(s)
- Russell P Newton
- Biochemistry Group, School of Biological Sciences, Wallace Building, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK.
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59
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Nagata T, Iizumi S, Satoh K, Ooka H, Kawai J, Carninci P, Hayashizaki Y, Otomo Y, Murakami K, Matsubara K, Kikuchi S. Comparative analysis of plant and animal calcium signal transduction element using plant full-length cDNA data. Mol Biol Evol 2004; 21:1855-70. [PMID: 15215322 DOI: 10.1093/molbev/msh197] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We obtained 32K full-length cDNA sequence data from the rice full-length cDNA project and performed a homology search against NCBI GenBank data. We have also searched homologs of Arabidopsis and other plants' genes with the databases. Comparative analysis of calcium ion transport proteins revealed that the genes specific for muscle and nerve calcium signal transduction systems (VDCC, IP3 receptor, ryanodine receptor) are very different in animals and plants. In contrast, Ca elements with basic functions in cell responses (CNGC, iGlu receptor, Ca(2+)ATPase, Ca2+/Na(+)-K+ ion exchanger) are basically conserved between plants and animals. We also performed comparative analyses of calcium ion binding and/or controlling signal transduction proteins. Many genes specific for muscle and nerve tissue do not exist in plants. However, calcium ion signal transduction genes of basic functions of cell homeostasis and responses were well conserved; plants have developed a calcium ion interacting system that is more direct than in animals. Many species of plants have specifically modified calcium ion binding proteins (CPK, CRK), Ca2+/phospholipid-binding domains, and calcium storage proteins.
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Affiliation(s)
- Toshifumi Nagata
- Department of Molecular Genetics, National Institute of Agrobiological Sciences, 2-1-2 Kannon dai, Tsukuba, Ibaraki, 305-8602 Japan
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60
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Lemtiri-Chlieh F, Berkowitz GA. Cyclic adenosine monophosphate regulates calcium channels in the plasma membrane of Arabidopsis leaf guard and mesophyll cells. J Biol Chem 2004; 279:35306-12. [PMID: 15199067 DOI: 10.1074/jbc.m400311200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effect of cAMP on Ca(2+)-permeable channels from Arabidopsis thaliana leaf guard cell and mesophyll cell protoplasts was studied using the patch clamp technique. In the whole cell configuration, dibutyryl cAMP was found to increase a hyperpolarization-activated Ba(2+) conductance (I(Ba)). The increase of I(Ba) was blocked by the addition of GdCl(3). In excised outside-out patches, the addition of dibutyryl cAMP consistently activated a channel with particularly fast gating kinetics. Current/voltage analyses indicated a single channel conductance of approximately 13 picosiemens. In patches where we measured some channel activity prior to cAMP application, the data suggest that cAMP enhances channel activity without affecting the single channel conductance. The cAMP activation of these channels was reversible upon washout. The results obtained with excised patches indicate that the cAMP-activated I(Ba) seen in the whole cell configuration could be explained by a direct effect of cAMP on the Ca(2+) channel itself or a close entity to the channel. This work represents the first demonstration using patch clamp analysis of the presence in plant cell membranes of an ion channel directly activated by cAMP.
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Affiliation(s)
- Fouad Lemtiri-Chlieh
- Agricultural Biotechnology Laboratory, Department of Plant Science, University of Connecticut, Storrs, Connecticut 06269-4067, USA
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61
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Jurkowski GI, Smith RK, Yu IC, Ham JH, Sharma SB, Klessig DF, Fengler KA, Bent AF. Arabidopsis DND2, a second cyclic nucleotide-gated ion channel gene for which mutation causes the "defense, no death" phenotype. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:511-20. [PMID: 15141955 DOI: 10.1094/mpmi.2004.17.5.511] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A previous mutant screen identified Arabidopsis dnd1 and dnd2 "defense, no death" mutants, which exhibit loss of hypersensitive response (HR) cell death without loss of gene-for-gene resistance. The dnd1 phenotype is caused by mutation of the gene encoding cyclic nucleotide-gated (CNG) ion channel AtCNGC2. This study characterizes dnd2 plants. Even in the presence of high titers of Pseudomonas syringae expressing avrRpt2, most leaf mesophyll cells in the dnd2 mutant exhibited no HR. These plants retained strong RPS2-, RPM1-, or RPS4-mediated restriction of P. syringae pathogen growth. Mutant dnd2 plants also exhibited enhanced broad-spectrum resistance against virulent P. syringae and constitutively elevated levels of salicylic acid, and pathogenesis-related (PR) gene expression. Unlike the wild type, dnd2 plants responding to virulent and avirulent P. syringae exhibited elevated expression of both salicylate-dependent PR-1 and jasmonate and ethylene-dependent PDF1.2. Introduction of nahG+ (salicylate hydroxylase) into the dnd2 background, which removes salicylic acid and causes other defense alterations, eliminated constitutive disease resistance and PR gene expression but only weakly impacted the HR- phenotype. Map-based cloning revealed that dnd2 phenotypes are caused by mutation of a second CNG ion channel gene, AtCNGC4. Hence, loss of either of two functionally nonredundant CNG ion channels can cause dnd phenotypes. The dnd mutants provide a unique genetic background for dissection of defense signaling.
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Affiliation(s)
- Grace I Jurkowski
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA
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62
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Becker JD, Boavida LC, Carneiro J, Haury M, Feijó JA. Transcriptional profiling of Arabidopsis tissues reveals the unique characteristics of the pollen transcriptome. PLANT PHYSIOLOGY 2003; 133:713-25. [PMID: 14500793 PMCID: PMC219046 DOI: 10.1104/pp.103.028241] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2003] [Revised: 07/07/2003] [Accepted: 07/09/2003] [Indexed: 05/18/2023]
Abstract
Pollen tubes are a good model for the study of cell growth and morphogenesis because of their extreme elongation without cell division. Yet, knowledge about the genetic basis of pollen germination and tube growth is still lagging behind advances in pollen physiology and biochemistry. In an effort to reduce this gap, we have developed a new method to obtain highly purified, hydrated pollen grains of Arabidopsis through flowcytometric sorting, and we used GeneChips (Affymetrix, Santa Clara, CA; representing approximately 8,200 genes) to compare the transcriptional profile of sorted pollen with those of four vegetative tissues (seedlings, leaves, roots, and siliques). We present a new graphical tool allowing genomic scale visualization of the unique transcriptional profile of pollen. The 1,584 genes expressed in pollen showed a 90% overlap with genes expressed in these vegetative tissues, whereas one-third of the genes constitutively expressed in the vegetative tissues were not expressed in pollen. Among the 469 genes enriched in pollen, 162 were selectively expressed, and most of these had not been associated previously with pollen. Their functional classification reveals several new candidate genes, mainly in the categories of signal transduction and cell wall biosynthesis and regulation. Thus, the results presented improve our knowledge of the molecular mechanisms underlying pollen germination and tube growth and provide new directions for deciphering their genetic basis. Because pollen expresses about one-third of the number of genes expressed on average in other organs, it may constitute an ideal system to study fundamental mechanisms of cell biology and, by omission, of cell division.
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Affiliation(s)
- Jörg D Becker
- Instituto Gulbenkian de Ciência, PT-2780-156 Oeiras, Portugal
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63
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Abstract
Various extracellular stimuli elicit specific calcium signatures that can be recognized by different calcium sensors. Calmodulin, the predominant calcium receptor, is one of the best-characterized calcium sensors in eukaryotes. In recent years, completion of the Arabidopsis genome project and advances in functional genomics have helped to identify and characterize numerous calmodulin-binding proteins in plants. There are some similarities in Ca(2+)/calmodulin-mediated signaling in plants and animals. However, plants possess multiple calmodulin genes and many calmodulin target proteins, including unique protein kinases and transcription factors. Some of these proteins are likely to act as "hubs" during calcium signal transduction. Hence, a better understanding of the function of these calmodulin target proteins should help in deciphering the Ca(2+)/calmodulin-mediated signal network and its role in plant growth, development and response to environmental stimuli.
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Affiliation(s)
- Tianbao Yang
- Center for Integrated Biotechnology and Department of Horticulture, Washington State University, Pullman, WA 99164-6414, USA
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64
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McCormack E, Braam J. Calmodulins and related potential calcium sensors of Arabidopsis. NEW PHYTOLOGIST 2003; 159:585-598. [PMID: 0 DOI: 10.1046/j.1469-8137.2003.00845.x] [Citation(s) in RCA: 202] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- Elizabeth McCormack
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005–1892, USA
| | - Janet Braam
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005–1892, USA
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65
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Hua BG, Mercier RW, Leng Q, Berkowitz GA. Plants do it differently. A new basis for potassium/sodium selectivity in the pore of an ion channel. PLANT PHYSIOLOGY 2003; 132:1353-61. [PMID: 12857817 PMCID: PMC167075 DOI: 10.1104/pp.103.020560] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2003] [Revised: 02/12/2003] [Accepted: 04/02/2003] [Indexed: 05/18/2023]
Abstract
Understanding of the molecular architecture necessary for selective K(+) permeation through the pore of ion channels is based primarily on analysis of the crystal structure of the bacterial K(+) channel KcsA, and structure:function studies of cloned animal K(+) channels. Little is known about the conduction properties of a large family of plant proteins with structural similarities to cloned animal cyclic nucleotide-gated channels (CNGCs). Animal CNGCs are nonselective cation channels that do not discriminate between Na(+) and K(+) permeation. These channels all have the same triplet of amino acids in the channel pore ion selectivity filter, and this sequence is different from that of the selectivity filter found in K(+)-selective channels. Plant CNGCs have unique pore selectivity filters; unlike those found in any other family of channels. At present, the significance of the unique pore selectivity filters of plant CNGCs, with regard to discrimination between Na(+) and K(+) permeation is unresolved. Here, we present an electrophysiological analysis of several members of this protein family; identifying the first cloned plant channel (AtCNGC1) that conducts Na(+). Another member of this ion channel family (AtCNGC2) is shown to have a selectivity filter that provides a heretofore unknown molecular basis for discrimination between K(+) and Na(+) permeation. Specific amino acids within the AtCNGC2 pore selectivity filter (Asn-416, Asp-417) are demonstrated to facilitate K(+) over Na(+) conductance. The selectivity filter of AtCNGC2 represents an alternative mechanism to the well-known GYG amino acid triplet of K(+) channels that has been identified as the critical basis for K(+) over Na(+) permeation through the pore of ion channels.
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Affiliation(s)
- Bao-Guang Hua
- Agricultural Biotechnology Laboratory, Department of Plant Science, University of Connecticut, Connecticut 06269-4163, USA
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66
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Abstract
Recently nitric oxide (NO) has emerged as a key signalling molecule in plants. Here we review the potential sources of endogenous NO, outline the biological processes likely to be mediated by NO, and discuss the downstream signalling processes by which NO exerts its cellular effects. It will be important to develop methods to quantify intracellular NO synthesis and release. Clasification of the biosynthetic origins of NO is also required. NO can be synthesised from nitrite via nitrate reductase (NR) and although biochemical and immunological data indicate the presence of enzyme(s) similar to mammalian nitric oxide synthase (NOS), no NOS genes have been identified. NO can induce various processes in plants, including the expression of defence-related genes and programmed cell death (PCD), stomatal closure, seed germination and root development. Intracellular signalling responses to NO involve generation of cGMP, cADPR and elevation of cytosolic calcium, but in many cases, the precise biochemical and cellular nature of these responses has not been detailed. Research priorities here must be the reliable quantification of downstream signalling molecules in NO-responsive cells, and cloning and manipulation of the enzymes responsible for synthesis and degradation of these molecules. Contents Summary 11 1 Introduction 12 2 Why does NO make a good signal? 12 3 NO biosynthesis 13 4 NO biology 17 5 NO signal transduction 23 6 Conclusion 30 Acknowledgements 31 References 31.
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Affiliation(s)
- Steven J Neill
- Centre for Research in Plant Science, University of the West of England (UWE), Bristol, Coldharbour Lane, Bristol BS16 1QY, UK
| | - Radhika Desikan
- Centre for Research in Plant Science, University of the West of England (UWE), Bristol, Coldharbour Lane, Bristol BS16 1QY, UK
| | - John T Hancock
- Centre for Research in Plant Science, University of the West of England (UWE), Bristol, Coldharbour Lane, Bristol BS16 1QY, UK
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67
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Abstract
In vivo analyses have identified different functional types of ion channels in various plant tissues and cells. The Arabidopsis genome contains approximately 70 genes for ion channels, of which 57 might be cation-selective channels (K(+), Ca(2+) or poorly discriminating channels). Here, we describe the different families of (putative) cation channels: the Shakers, the two-P-domain and Kir K(+) channels (encoded by the KCO genes), the cyclic-nucleotide-gated channels, the glutamate receptors, and the Ca(2+) channel TPC1. We also compare molecular data with the data obtained in planta, which should lead to a better understanding of the identity of these channels and provide clues about their roles in plant nutrition and cell signalling.
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Affiliation(s)
- Anne Aliénor Véry
- Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, CNRS/ENSA-M/INRA/UM2, Place Viala, F-34060 Montpellier Cedex 2, France.
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Reddy VS, Ali GS, Reddy ASN. Genes encoding calmodulin-binding proteins in the Arabidopsis genome. J Biol Chem 2002; 277:9840-52. [PMID: 11782485 DOI: 10.1074/jbc.m111626200] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Analysis of the recently completed Arabidopsis genome sequence indicates that approximately 31% of the predicted genes could not be assigned to functional categories, as they do not show any sequence similarity with proteins of known function from other organisms. Calmodulin (CaM), a ubiquitous and multifunctional Ca(2+) sensor, interacts with a wide variety of cellular proteins and modulates their activity/function in regulating diverse cellular processes. However, the primary amino acid sequence of the CaM-binding domain in different CaM-binding proteins (CBPs) is not conserved. One way to identify most of the CBPs in the Arabidopsis genome is by protein-protein interaction-based screening of expression libraries with CaM. Here, using a mixture of radiolabeled CaM isoforms from Arabidopsis, we screened several expression libraries prepared from flower meristem, seedlings, or tissues treated with hormones, an elicitor, or a pathogen. Sequence analysis of 77 positive clones that interact with CaM in a Ca(2+)-dependent manner revealed 20 CBPs, including 14 previously unknown CBPs. In addition, by searching the Arabidopsis genome sequence with the newly identified and known plant or animal CBPs, we identified a total of 27 CBPs. Among these, 16 CBPs are represented by families with 2-20 members in each family. Gene expression analysis revealed that CBPs and CBP paralogs are expressed differentially. Our data suggest that Arabidopsis has a large number of CBPs including several plant-specific ones. Although CaM is highly conserved between plants and animals, only a few CBPs are common to both plants and animals. Analysis of Arabidopsis CBPs revealed the presence of a variety of interesting domains. Our analyses identified several hypothetical proteins in the Arabidopsis genome as CaM targets, suggesting their involvement in Ca(2+)-mediated signaling networks.
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Affiliation(s)
- Vaka S Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
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69
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Reddy ASN, Day IS, Narasimhulu SB, Safadi F, Reddy VS, Golovkin M, Harnly MJ. Isolation and characterization of a novel calmodulin-binding protein from potato. J Biol Chem 2002; 277:4206-14. [PMID: 11684678 DOI: 10.1074/jbc.m104595200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tuberization in potato is controlled by hormonal and environmental signals. Ca(2+), an important intracellular messenger, and calmodulin (CaM), one of the primary Ca(2+) sensors, have been implicated in controlling diverse cellular processes in plants including tuberization. The regulation of cellular processes by CaM involves its interaction with other proteins. To understand the role of Ca(2+)/CaM in tuberization, we have screened an expression library prepared from developing tubers with biotinylated CaM. This screening resulted in isolation of a cDNA encoding a novel CaM-binding protein (potato calmodulin-binding protein (PCBP)). Ca(2+)-dependent binding of the cDNA-encoded protein to CaM is confirmed by (35)S-labeled CaM. The full-length cDNA is 5 kb long and encodes a protein of 1309 amino acids. The deduced amino acid sequence showed significant similarity with a hypothetical protein from another plant, Arabidopsis. However, no homologs of PCBP are found in nonplant systems, suggesting that it is likely to be specific to plants. Using truncated versions of the protein and a synthetic peptide in CaM binding assays we mapped the CaM-binding region to a 20-amino acid stretch (residues 1216-1237). The bacterially expressed protein containing the CaM-binding domain interacted with three CaM isoforms (CaM2, CaM4, and CaM6). PCBP is encoded by a single gene and is expressed differentially in the tissues tested. The expression of CaM, PCBP, and another CaM-binding protein is similar in different tissues and organs. The predicted protein contained seven putative nuclear localization signals and several strong PEST motifs. Fusion of the N-terminal region of the protein containing six of the seven nuclear localization signals to the reporter gene beta-glucuronidase targeted the reporter gene to the nucleus, suggesting a nuclear role for PCBP.
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Affiliation(s)
- Anireddy S N Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
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70
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Leng Q, Mercier RW, Hua BG, Fromm H, Berkowitz GA. Electrophysiological analysis of cloned cyclic nucleotide-gated ion channels. PLANT PHYSIOLOGY 2002; 128:400-10. [PMID: 11842144 PMCID: PMC148903 DOI: 10.1104/pp.010832] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2001] [Revised: 10/12/2001] [Accepted: 11/27/2001] [Indexed: 05/04/2023]
Abstract
Electrophysiological studies were conducted on the cloned plant cyclic nucleotide-gated ion channels AtCNGC2 and AtCNGC1 from Arabidopsis, and NtCBP4 from tobacco (Nicotiana tobacum). The nucleotide coding sequences for these proteins were expressed in Xenopus laevis oocytes or HEK 293 cells. Channel characteristics were evaluated using voltage clamp analysis of currents in the presence of cAMP. AtCNGC2 was demonstrated to conduct K(+) and other monovalent cations, but exclude Na(+); this conductivity profile is unique for any ion channel not possessing the amino acid sequence found in the selectivity filter of K(+)-selective ion channels. Application of cAMP evoked currents in membrane patches of oocytes injected with AtCNGC2 cRNA. Direct activation of the channel by cyclic nucleotide, demonstrated by application of cyclic nucleotide to patches of membranes expressing such channels, is a hallmark characteristic of this ion channel family. Voltage clamp studies (two-electrode configuration) demonstrated that AtCNGC1 and NtCBP4 are also cyclic nucleotide-gated channels. Addition of a lipophilic analog of cAMP to the perfusion bath of oocytes injected with NtCBP4 and AtCNGC1 cRNAs induced inward rectified, noninactivating K(+) currents.
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Affiliation(s)
- Qiang Leng
- Department of Plant Science, University of Connecticut, Storrs, CT 06269-4067, USA
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71
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Abstract
Nonselective cation channels are a diverse group of ion channels characterized by their low discrimination between many essential and toxic cations. They are ubiquitous in plant tissues and are active in the plasma membrane, tonoplast, and other endomembranes. Members of this group are likely to function in low-affinity nutrient uptake, in distribution of cations within and between cells, and as plant Ca2+ channels. They are gated by diverse mechanisms, which can include voltage, cyclic nucleotides, glutamate, reactive oxygen species, and stretch. These channels dominate tonoplast cation transport, and the selectivity and gating mechanisms of tonoplast nonselective cation channels are comprehensively reviewed here. This review presents the first classification of plant nonselective cation channels and the first full description of nonselective cation channel candidate sequences in the Arabidopsis genome.
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Affiliation(s)
- Vadim Demidchik
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, United Kingdom.
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72
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Furuichi T, Cunningham KW, Muto S. A putative two pore channel AtTPC1 mediates Ca(2+) flux in Arabidopsis leaf cells. PLANT & CELL PHYSIOLOGY 2001; 42:900-5. [PMID: 11577183 DOI: 10.1093/pcp/pce145] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The gene encoding voltage-gated channel with high affinity for Ca(2+) permeation has not been cloned from plants. In the present study, we isolated a full-length cDNA encoding a putative Ca(2+ )channel (AtTPC1) from Arabidopsis. AtTPC1 has two conserved homologous domains, both of which contain six transmembrane segments (S1-S6) and a pore loop (P) between S5 and S6 in each domain, and has the highest homology with the two pore channel TPC1 recently cloned from rat. The overall structure is similar to the half of the general structure of alpha-subunits of voltage-activated Ca(2+) channels from animals. AtTPC1 rescued the Ca(2+) uptake activity of a yeast mutant cch1. Sucrose-induced luminescence, which reflects a cytosolic free Ca(2+) increase in aequorin-expressing Arabidopsis leaves, was enhanced by overexpression of AtTPC1 and suppressed by antisense expression of it. Sucrose-H(+) symporters AtSUC1 and 2, which depolarize membrane potential of cells receiving sucrose, also depressed a Ca(2+) increase by their antisense expression. These results suggest that AtTPC1 mediates a voltage-activated Ca(2+ )influx in Arabidopsis leaf cells.
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Affiliation(s)
- T Furuichi
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan
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73
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Mäser P, Thomine S, Schroeder JI, Ward JM, Hirschi K, Sze H, Talke IN, Amtmann A, Maathuis FJ, Sanders D, Harper JF, Tchieu J, Gribskov M, Persans MW, Salt DE, Kim SA, Guerinot ML. Phylogenetic relationships within cation transporter families of Arabidopsis. PLANT PHYSIOLOGY 2001; 126:1646-67. [PMID: 11500563 PMCID: PMC117164 DOI: 10.1104/pp.126.4.1646] [Citation(s) in RCA: 719] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2001] [Revised: 04/12/2001] [Accepted: 05/01/2001] [Indexed: 05/17/2023]
Abstract
Uptake and translocation of cationic nutrients play essential roles in physiological processes including plant growth, nutrition, signal transduction, and development. Approximately 5% of the Arabidopsis genome appears to encode membrane transport proteins. These proteins are classified in 46 unique families containing approximately 880 members. In addition, several hundred putative transporters have not yet been assigned to families. In this paper, we have analyzed the phylogenetic relationships of over 150 cation transport proteins. This analysis has focused on cation transporter gene families for which initial characterizations have been achieved for individual members, including potassium transporters and channels, sodium transporters, calcium antiporters, cyclic nucleotide-gated channels, cation diffusion facilitator proteins, natural resistance-associated macrophage proteins (NRAMP), and Zn-regulated transporter Fe-regulated transporter-like proteins. Phylogenetic trees of each family define the evolutionary relationships of the members to each other. These families contain numerous members, indicating diverse functions in vivo. Closely related isoforms and separate subfamilies exist within many of these gene families, indicating possible redundancies and specialized functions. To facilitate their further study, the PlantsT database (http://plantst.sdsc.edu) has been created that includes alignments of the analyzed cation transporters and their chromosomal locations.
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Affiliation(s)
- P Mäser
- Division of Biology, Cell and Developmental Biology Section and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116, USA
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74
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Smith CJ, Gallon JR. Living in the real world: how plants perceive their environment. THE NEW PHYTOLOGIST 2001; 151:1-6. [PMID: 33873390 DOI: 10.1046/j.1469-8137.2001.00176.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Chris J Smith
- School of Biological Sciences, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK (tel +44 1792295 378; fax +44 1792295 447 email )
| | - John R Gallon
- School of Biological Sciences, University of Wales, Swansea, Singleton Park, Swansea SA2 8PP, UK (tel +44 1792295376; fax +44 1792295447 email )
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Snedden WA, Fromm H. Calmodulin as a versatile calcium signal transducer in plants. THE NEW PHYTOLOGIST 2001; 151:35-66. [PMID: 33873389 DOI: 10.1046/j.1469-8137.2001.00154.x] [Citation(s) in RCA: 264] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The complexity of Ca2+ patterns observed in eukaryotic cells, including plants, has led to the hypothesis that specific patterns of Ca2+ propagation, termed Ca2+ signatures, encode information and relay it to downstream elements (effectors) for translation into appropriate cellular responses. Ca2+ -binding proteins (sensors) play a key role in decoding Ca2+ signatures and transducing signals by activating specific targets and pathways. Calmodulin is a Ca2+ sensor known to modulate the activity of many mammalian proteins, whose targets in plants are now being actively characterized. Plants possess an interesting and rapidly growing list of calmodulin targets with a variety of cellular roles. Nevertheless, many targets appear to be unique to plants and remain uncharacterized, calling for a concerted effort to elucidate their functions. Moreover, the extended family of calmodulin-related proteins in plants consists of evolutionarily divergent members, mostly of unknown function, although some have recently been implicated in stress responses. It is hoped that advances in functional genomics, and the research tools it generates, will help to explain themultiplicity of calmodulin genes in plants, and to identify their downstream effectors. This review summarizes current knowledge of the Ca2+ -calmodulin messenger system in plants and presents suggestions for future areas of research. Contents I. Introduction 36 II. CaM isoforms and CaM-like proteins 37 III. CaM-target proteins 42 IV. CaM and nuclear functions 46 V. Regulation of ion transport 49 VI. CaM and plant responses to environmental stimuli 52 VII. Conclusions and future studies 58 Acknowledgements 59 References 59.
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Affiliation(s)
- Wayne A Snedden
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
| | - Hillel Fromm
- Centre for Plant Sciences, Leeds Institute for Biotechnology and Agriculture (LIBA), School of Biology, University of Leeds, Leeds LS2 9JT, UK
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76
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Reddy AS. Calcium: silver bullet in signaling. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2001; 160:381-404. [PMID: 11166425 DOI: 10.1016/s0168-9452(00)00386-1] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Accumulating evidence suggests that Ca(2+) serves as a messenger in many normal growth and developmental process and in plant responses to biotic and abiotic stresses. Numerous signals have been shown to induce transient elevation of [Ca(2+)](cyt) in plants. Genetic, biochemical, molecular and cell biological approaches in recent years have resulted in significant progress in identifying several Ca(2+)-sensing proteins in plants and in understanding the function of some of these Ca(2+)-regulated proteins at the cellular and whole plant level. As more and more Ca(2+)-sensing proteins are identified it is becoming apparent that plants have several unique Ca(2+)-sensing proteins and that the downstream components of Ca(2+) signaling in plants have novel features and regulatory mechanisms. Although the mechanisms by which Ca(2+) regulates diverse biochemical and molecular processes and eventually physiological processes in response to diverse signals are beginning to be understood, recent studies have raised many interesting questions. Despite the fact that Ca(2+) sensing proteins are being identified at a rapid pace, progress on the function(s) of many of them is limited. Studies on plant 'signalome' - the identification of all signaling components in all messengers mediated transduction pathways, analysis of their function and regulation, and cross talk among these components - should help in understanding the inner workings of plant cell responses to diverse signals. New functional genomics approaches such as reverse genetics, microarray analyses coupled with in vivo protein-protein interaction studies and proteomics should not only permit functional analysis of various components in Ca(2+) signaling but also enable identification of a complex network of interactions.
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Affiliation(s)
- A S.N. Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, 80523, Fort Collins, CO, USA
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