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Chae MJ, Lee JS, Nam MH, Cho K, Hong JY, Yi SA, Suh SC, Yoon IS. A rice dehydration-inducible SNF1-related protein kinase 2 phosphorylates an abscisic acid responsive element-binding factor and associates with ABA signaling. PLANT MOLECULAR BIOLOGY 2007; 63:151-69. [PMID: 16977424 DOI: 10.1007/s11103-006-9079-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 08/19/2006] [Indexed: 05/11/2023]
Abstract
By a differential cDNA screening technique, we have isolated a dehydration-inducible gene (designated OSRK1) that encodes a 41.8 kD protein kinase of SnRK2 family from Oryza sativa. The OSRK1 transcript level was undetectable in vegetative tissues, but significantly increased by hyperosmotic stress and Abscisic acid (ABA). To determine its biochemical properties, we expressed and isolated OSRK1 and its mutants as glutathione S-transferase fusion proteins in Escherichia coli. In vitro kinase assay showed that OSRK1 can phosphorylate itself and generic substrates as well. Interestingly, OSRK1 showed strong substrate preference for rice bZIP transcription factors and uncommon cofactor requirement for Mn(2+) over Mg(2+). By deletion of C-terminus 73 amino acids or mutations of Ser-158 and Thr-159 to aspartic acids (Asp) in the activation loop, the activity of OSRK1 was dramatically decreased. OSRK1 can transphosphorylate the inactive deletion protein. A rice family of abscisic acid-responsive element (ABRE) binding factor, OREB1 was phosphorylated in vitro by OSRK1 at multiple sites of different functional domains. MALDI-TOF analysis identified a phosphorylation site at Ser44 of OREB1 and mutation of the residue greatly decreased the substrate specificity for OSRK1. The recognition motif for OSRK1, RQSS is highly similar to the consensus substrate sequence of AMPK/SNF1 kinase family. We further showed that OSRK1 interacts with OREB1 in a yeast two-hybrid system and co-localized to nuclei by transient expression analysis of GFP-fused protein in onion epidermis. Finally, ectopic expression of OSRK1 in transgenic tobacco resulted in a reduced sensitivity to ABA in seed germination and root elongation. These findings suggest that OSRK1 is associated with ABA signaling, possibly through the phosphorylation of ABF family in vivo. The interaction between SnRK2 family kinases and ABF transcription factors may constitute an important part of cross-talk mechanism in the stress signaling networks in plants.
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Affiliation(s)
- Min-Ju Chae
- Cell and Genetics Division, National Institute of Agricultural Biotechnology, Suwon, 441-707, Republic of Korea
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102
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Calderón-Villalobos LIA, Nill C, Marrocco K, Kretsch T, Schwechheimer C. The evolutionarily conserved Arabidopsis thaliana F-box protein AtFBP7 is required for efficient translation during temperature stress. Gene 2006; 392:106-16. [PMID: 17240087 DOI: 10.1016/j.gene.2006.11.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 11/12/2006] [Accepted: 11/20/2006] [Indexed: 11/30/2022]
Abstract
In eukaryotes, E3 ubiquitin ligases (E3s) mediate the ubiquitylation of proteins that are destined for degradation by the ubiquitin-proteasome system. In SKP1/CDC53/F-box protein (SCF)-type E3 complexes, the interchangeable F-box protein confers specificity to the E3 ligase through direct physical interactions with the degradation substrate. The vast majority of the approximately 700 F-box proteins from the plant model organism Arabidopsis thaliana remain to be characterized. Here, we investigate the previously uncharacterized and evolutionarily conserved Arabidopsis F-box protein 7 (AtFBP7), which is encoded by a unique gene in Arabidopsis (At1g21760). Several apparent fbp7 loss-of-function alleles do not have an obvious phenotype. AtFBP7 is ubiquitously expressed and its expression is induced after cold and heat stress. When following up on a reported co-purification of the eukaryotic elongation factor-2 (eEF-2) with YLR097c, the apparent budding yeast orthologue of AtFBP7, we discovered a general defect in protein biosynthesis after cold and heat stress in fbp7 mutants. Thus, our findings suggest that AtFBP7 is required for protein synthesis during temperature stress.
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Affiliation(s)
- Luz Irina A Calderón-Villalobos
- Department of Developmental Genetics, Centre for Plant Molecular Biology, Tübingen University, Auf der Morgenstelle 5, 72076 Tübingen, Germany
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103
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Potuschak T, Vansiri A, Binder BM, Lechner E, Vierstra RD, Genschik P. The exoribonuclease XRN4 is a component of the ethylene response pathway in Arabidopsis. THE PLANT CELL 2006; 18:3047-57. [PMID: 17085683 PMCID: PMC1693942 DOI: 10.1105/tpc.106.046508] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
EXORIBONUCLEASE4 (XRN4), the Arabidopsis thaliana homolog of yeast XRN1, is involved in the degradation of several unstable mRNAs. Although a role for XRN4 in RNA silencing of certain transgenes has been reported, xrn4 mutant plants were found to lack any apparent visible phenotype. Here, we show that XRN4 is allelic to the unidentified components of the ethylene response pathway ETHYLENE-INSENSITIVE5/ACC-INSENSITIVE1 (EIN5/AIN1) and EIN7. xrn4 mutant seedlings are ethylene-insensitive as a consequence of the upregulation of EIN3 BINDING F-BOX PROTEIN1 (EBF1) and EBF2 mRNA levels, which encode related F-box proteins involved in the turnover of EIN3 protein, a crucial transcriptional regulator of the ethylene response pathway. Epistasis analysis placed XRN4/EIN5/AIN1 downstream of CTR1 and upstream of EBF1/2. XRN4 does not appear to regulate ethylene signaling via an RNA-INDUCED SILENCING COMPLEX-based RNA silencing mechanism but acts by independent means. The identification of XRN4 as an integral new component in ethylene signaling adds RNA degradation as another posttranscriptional process that modulates the perception of this plant hormone.
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Affiliation(s)
- Thomas Potuschak
- Institut de Biologie Moléculaire des Plantes, Laboratoire Propre du Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventioné avec l'Université Louis Pasteur, 67084 Strasbourg, France
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104
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Hua Z, Kao TH. Identification and characterization of components of a putative petunia S-locus F-box-containing E3 ligase complex involved in S-RNase-based self-incompatibility. THE PLANT CELL 2006; 18:2531-53. [PMID: 17028207 PMCID: PMC1626602 DOI: 10.1105/tpc.106.041061] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Petunia inflata S-locus F-box (Pi SLF) is thought to function as a typical F-box protein in ubiquitin-mediated protein degradation and, along with Skp1, Cullin-1, and Rbx1, could compose an SCF complex mediating the degradation of nonself S-RNase but not self S-RNase. We isolated three P. inflata Skp1s (Pi SK1, -2, and -3), two Cullin-1s (Pi CUL1-C and -G), and an Rbx1 (Pi RBX1) cDNAs and found that Pi CUL1-G did not interact with Pi RBX1 and that none of the three Pi SKs interacted with Pi SLF(2). We also isolated a RING-HC protein, S-RNase Binding Protein1 (Pi SBP1), almost identical to Petunia hybrida SBP1, which interacts with Pi SLFs, S-RNases, Pi CUL1-G, and an E2 ubiquitin-conjugating enzyme, suggesting that Pi CUL1-G, SBP1, and SLF may be components of a novel E3 ligase complex, with Pi SBP1 playing the roles of Skp1 and Rbx1. S-RNases interact more with nonself Pi SLFs than with self Pi SLFs, and Pi SLFs also interact more with nonself S-RNases than with self S-RNases. Bacterially expressed S(1)-, S(2)-, and S(3)-RNases are degraded by the 26S proteasomal pathway in a cell-free system, albeit not in an S-allele-specific manner. Native glycosylated S(3)-RNase is not degraded to any significant extent; however, deglycosylated S(3)-RNase is degraded as efficiently as the bacterially expressed S-RNases. Finally, S-RNases are ubiquitinated in pollen tube extracts, but whether this is mediated by the Pi SLF-containing E3 complex is unknown.
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Affiliation(s)
- Zhihua Hua
- Intercollege Graduate Degree Program in Plant Biology, Pensylvania State University, University Park, Pensylvania 16802, USA
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105
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Rook F, Corke F, Baier M, Holman R, May AG, Bevan MW. Impaired sucrose induction1 encodes a conserved plant-specific protein that couples carbohydrate availability to gene expression and plant growth. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 46:1045-58. [PMID: 16805736 DOI: 10.1111/j.1365-313x.2006.02765.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
To identify the molecular mechanisms underlying carbohydrate allocation to storage processes, we have isolated mutants in which the sugar induction of starch biosynthetic gene expression was impaired. Here we describe the IMPAIRED SUCROSE INDUCTION1 (ISI1) gene, which encodes a highly conserved plant-specific protein with structural similarities to Arm repeat proteins. ISI1 is predominantly expressed in the phloem of leaves following the sink-to-source transition during leaf development, but is also sugar-inducible in mesophyll cells. Soil-grown isi1 mutants show reduced plant growth and seed set compared to wild-type Arabidopsis. This growth reduction is not due to reduced carbohydrate availability or a defect in sucrose export from mature leaves, suggesting that isi1 mutant plants do not utilize available carbohydrate resources efficiently. ISI1 interacts synergistically with, but is genetically distinct from, the abscisic acid (ABA) signalling pathway controlling sugar responses via ABI4. Our data show that ISI1 couples the availability of carbohydrates to the control of sugar-responsive gene expression and plant growth.
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Affiliation(s)
- Fred Rook
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
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106
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Wang X, Ni W, Ge X, Zhang J, Ma H, Cao K. Proteomic identification of potential target proteins regulated by an ASK1-mediated proteolysis pathway. Cell Res 2006; 16:489-98. [PMID: 16699544 DOI: 10.1038/sj.cr.7310060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The ASK1 (ARABIDOPSIS SKP1-LIKE) protein is a critical component of the SCF (Skp1-Cullin-F box protein) ubiquitin ligase complexes that recruit target proteins for degradation by the 26S proteosome. To investigate proteins that are affected by the ASK1-mediated proteolysis pathway in Arabidopsis flowers, we compared the proteomes of the Arabidopsis wild type and ask1 mutant flower buds using two-dimensional electrophoresis (2-DE). Ten protein spots with higher or lower abundance in the ask1 mutant flowers compared to wild type flowers were excised and subjected to further mass spectrometry (MS) analysis. The results showed that they were proteins involved in photomorphogenesis, circadian oscillation, post-translation process, stress-responses and cell expansion or elongation, suggesting that those processes were affected in the ask1 mutant. The transcript levels of these genes were also compared based on the Affymetrix gene chip microarray data. No significant difference was observed for most of the genes, suggesting that the proteins with elevated levels of accumulation in the ask1 mutant could be candidate targets regulated by an ASK1-mediated proteolysis pathway. These results help to elucidate the pleiotropic functions of ASK1 in Arabidopsis developmental processes and also demonstrate the importance and necessity of studying protein levels with respect to gene functions.
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Affiliation(s)
- Xiaofeng Wang
- 1State Key Laboratory of Genetic Engineering, Department of Biochemistry and Molecular Biology, School of Life Sciences, Fudan University, Shanghai, 200433, China
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107
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Christmann A, Moes D, Himmelbach A, Yang Y, Tang Y, Grill E. Integration of abscisic acid signalling into plant responses. PLANT BIOLOGY (STUTTGART, GERMANY) 2006; 8:314-25. [PMID: 16807823 DOI: 10.1055/s-2006-924120] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The phytohormone abscisic acid (ABA) plays a major role as an endogenous messenger in the regulation of plant's water status. ABA is generated as a signal during a plant's life cycle to control seed germination and further developmental processes and in response to abiotic stress imposed by salt, cold, drought, and wounding. The action of ABA can target specifically guard cells for induction of stomatal closure but may also signal systemically for adjustment towards severe water shortage. At the molecular level, the responses are primarily mediated by regulation of ion channels and by changes in gene expression. In the last years, the molecular complexity of ABA signal transduction surfaced more and more. Many proteins and a plethora of "secondary" messengers that regulate or modulate ABA-responses have been identified by analysis of mutants including gene knock-out plants and by applying RNA interference technology together with protein interaction analysis. The complexity possibly reflects intensive cross-talk with other signal pathways and the role of ABA to be part of and to integrate several responses. Despite the missing unifying concept, it is becoming clear that ABA action enforces a sophisticated regulation at all levels.
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Affiliation(s)
- A Christmann
- Lehrstuhl für Botanik, Technische Universität München, Am Hochanger 4, 85354 Freising, Germany
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108
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Bloom J, Peschiaroli A, DeMartino G, Pagano M. Modification of Cul1 regulates its association with proteasomal subunits. Cell Div 2006; 1:5. [PMID: 16759355 PMCID: PMC1479330 DOI: 10.1186/1747-1028-1-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Accepted: 04/28/2006] [Indexed: 11/17/2022] Open
Abstract
Background Ubiquitylation targets proteins for degradation by the 26S proteasome. Some yeast and plant ubiquitin ligases, including the highly conserved SCF (Skp1/Cul1/F-box protein) complex, have been shown to associate with proteasomes. We sought to characterize interactions between SCF complexes and proteasomes in mammalian cells. Results We found that the binding of SCF complexes to proteasomes is conserved in higher eukaryotes. The Cul1 subunit associated with both sub-complexes of the proteasome, and high molecular weight forms of Cul1 bound to the 19S proteasome. Cul1 is ubiquitylated in vivo. Ubiquitylation of Cul1 promotes its binding to the S5a subunit of the 19S sub-complex without affecting Cul1 stability. Conclusion The association of ubiquitylating enzymes with proteasomes may be an additional means to target ubiquitylated substrates for degradation.
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Affiliation(s)
- Joanna Bloom
- Department of Pathology, New York University Cancer Institute and New York University School of Medicine, New York 10016, USA
- The Rockefeller University, New York 10021, USA
| | - Angelo Peschiaroli
- Department of Pathology, New York University Cancer Institute and New York University School of Medicine, New York 10016, USA
| | - George DeMartino
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
| | - Michele Pagano
- Department of Pathology, New York University Cancer Institute and New York University School of Medicine, New York 10016, USA
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109
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Pazhouhandeh M, Dieterle M, Marrocco K, Lechner E, Berry B, Brault V, Hemmer O, Kretsch T, Richards KE, Genschik P, Ziegler-Graff V. F-box-like domain in the polerovirus protein P0 is required for silencing suppressor function. Proc Natl Acad Sci U S A 2006; 103:1994-9. [PMID: 16446454 PMCID: PMC1413668 DOI: 10.1073/pnas.0510784103] [Citation(s) in RCA: 224] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Indexed: 12/31/2022] Open
Abstract
Plants employ small RNA-mediated posttranscriptional gene silencing as a virus defense mechanism. In response, plant viruses encode proteins that can suppress RNA silencing, but the mode of action of most such proteins is poorly understood. Here, we show that the silencing suppressor protein P0 of two Arabidopsis-infecting poleroviruses interacts by means of a conserved minimal F-box motif with Arabidopsis thaliana orthologs of S-phase kinase-related protein 1 (SKP1), a component of the SCF family of ubiquitin E3 ligases. Point mutations in the F-box-like motif abolished the P0-SKP1 ortholog interaction, diminished virus pathogenicity, and inhibited the silencing suppressor activity of P0. Knockdown of expression of a SKP1 ortholog in Nicotiana benthamiana rendered the plants resistant to polerovirus infection. Together, the results support a model in which P0 acts as an F-box protein that targets an essential component of the host posttranscriptional gene silencing machinery.
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Affiliation(s)
- Maghsoud Pazhouhandeh
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Monika Dieterle
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Katia Marrocco
- Institut für Biologie 2/Botanik, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany; and
| | - Esther Lechner
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Bassam Berry
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Véronique Brault
- Institut National de la Recherche Agronomique, 28 Rue de Herrlisheim, 68021 Colmar, France
| | - Odile Hemmer
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Thomas Kretsch
- Institut für Biologie 2/Botanik, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany; and
| | - Kenneth E. Richards
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Pascal Genschik
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Véronique Ziegler-Graff
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
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110
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Radchuk R, Radchuk V, Weschke W, Borisjuk L, Weber H. Repressing the expression of the SUCROSE NONFERMENTING-1-RELATED PROTEIN KINASE gene in pea embryo causes pleiotropic defects of maturation similar to an abscisic acid-insensitive phenotype. PLANT PHYSIOLOGY 2006; 140:263-78. [PMID: 16361518 PMCID: PMC1326049 DOI: 10.1104/pp.105.071167] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Revised: 11/01/2005] [Accepted: 11/01/2005] [Indexed: 05/05/2023]
Abstract
The classic role of SUCROSE NONFERMENTING-1 (Snf1)-like kinases in eukaryotes is to adapt metabolism to environmental conditions such as nutrition, energy, and stress. During pea (Pisum sativum) seed maturation, developmental programs of growing embryos are adjusted to changing physiological and metabolic conditions. To understand regulation of the switch from cell proliferation to differentiation, SUCROSE NONFERMENTING-1-RELATED PROTEIN KINASE (SnRK1) was antisense repressed in pea seeds. Transgenic seeds show maturation defects, reduced conversion of sucrose into storage products, lower globulin content, frequently altered cotyledon surface, shape, and symmetry, as well as occasional precocious germination. Gene expression analysis of embryos using macroarrays of 5,548 seed-specific genes revealed 183 differentially expressed genes in two clusters, either delayed down-regulated or delayed up-regulated during transition. Delayed down-regulated genes are related to mitotic activity, gibberellic acid/brassinosteroid synthesis, stress response, and Ca2+ signal transduction. This specifies a developmentally younger status and conditional stress. Higher gene expression related to respiration/gluconeogenesis/fermentation is consistent with a role of SnRK1 in repressing energy-consuming processes in maturing cotyledons under low oxygen/energy availability. Delayed up-regulated genes are mainly related to storage protein synthesis and stress tolerance. Most of the phenotype resembles abscisic acid (ABA) insensitivity and may be explained by reduced Abi-3 expression. This may cause a reduction in ABA functions and/or a disconnection between metabolic and ABA signals, suggesting that SnRK1 is a mediator of ABA functions during pea seed maturation. SnRK1 repression also impairs gene expression associated with differentiation, independent from ABA functions, like regulation and signaling of developmental events, chromatin reorganization, cell wall synthesis, biosynthetic activity of plastids, and regulated proteolysis.
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Affiliation(s)
- Ruslana Radchuk
- Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany
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111
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Maupin-Furlow JA, Humbard MA, Kirkland PA, Li W, Reuter CJ, Wright AJ, Zhou G. Proteasomes from Structure to Function: Perspectives from Archaea. Curr Top Dev Biol 2006; 75:125-69. [PMID: 16984812 DOI: 10.1016/s0070-2153(06)75005-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Insight into the world of proteolysis has expanded considerably over the past decade. Energy-dependent proteases, such as the proteasome, are no longer viewed as nonspecific degradative enzymes associated solely with protein catabolism but are intimately involved in controlling biological processes that span life to death. The proteasome maintains this exquisite control by catalyzing the precisely timed and rapid turnover of key regulatory proteins. Proteasomes also interplay with chaperones to ensure protein quality and to readjust the composition of the proteome following stress. Archaea encode proteasomes that are highly related to those of eukaryotes in basic structure and function. Investigations of archaeal proteasomes coupled with those of eukaryotes has greatly facilitated our understanding of the molecular mechanisms that govern regulated protein degradation by this elaborate nanocompartmentalized machine.
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Affiliation(s)
- Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida Gainesville, Florida 32611, USA
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112
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Rolland F, Baena-Gonzalez E, Sheen J. Sugar sensing and signaling in plants: conserved and novel mechanisms. ANNUAL REVIEW OF PLANT BIOLOGY 2006; 57:675-709. [PMID: 16669778 DOI: 10.1146/annurev.arplant.57.032905.105441] [Citation(s) in RCA: 1262] [Impact Index Per Article: 70.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Sugars not only fuel cellular carbon and energy metabolism but also play pivotal roles as signaling molecules. The experimental amenability of yeast as a unicellular model system has enabled the discovery of multiple sugar sensors and signaling pathways. In plants, different sugar signals are generated by photosynthesis and carbon metabolism in source and sink tissues to modulate growth, development, and stress responses. Genetic analyses have revealed extensive interactions between sugar and plant hormone signaling, and a central role for hexokinase (HXK) as a conserved glucose sensor. Diverse sugar signals activate multiple HXK-dependent and HXK-independent pathways and use different molecular mechanisms to control transcription, translation, protein stability and enzymatic activity. Important and complex roles for Snf1-related kinases (SnRKs), extracellular sugar sensors, and trehalose metabolism in plant sugar signaling are now also emerging.
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Affiliation(s)
- Filip Rolland
- Department of Molecular Microbiology, Flanders Interuniversity Institute for Biotechnology (VIB10), and Laboratory of Molecular Cell Biology K.U. Leuven, 3001 Heverlee-Leuven, Belgium.
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113
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Lee SJ, Choi D, Rhim H, Kang S. E3 ubiquitin ligase RNF2 interacts with the S6' proteasomal ATPase subunit and increases the ATP hydrolysis activity of S6'. Biochem J 2005; 389:457-63. [PMID: 15773819 PMCID: PMC1175123 DOI: 10.1042/bj20041982] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We reported previously that the human RNF2 (RING finger protein 2) protein is an E3 ubiquitin ligase that interacts with the human ubiquitin-conjugating enzyme Hip-2/hE2-25K. In the present study, we show that RNF2 interacts with S6' ATPase, a subunit of the proteasomal 19 S regulatory complex. S6' interacts with RNF2 through its N-terminal RING domain, and RNF2 interacts with S6' through its C-terminal region. Interestingly, the RNF2-S6' interaction increases the ATP hydrolysis activity of the S6' protein. Moreover, S6' ATPase activity is highly increased in the presence of ubiquitinated proteins. The present study suggests that the E3 ubiquitin ligase RNF2 might have a dual function: facilitating the ubiquitination of its target substrates and recruiting the substrates to the proteasome. Furthermore, ATP hydrolysis in the E3/proteasome complex might act as an important signal for the protein degradation pathway.
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Affiliation(s)
- Sun-Joo Lee
- *Graduate School of Biotechnology, Korea University, 1,5-ka Anam-dong, Sungbuk-ku, Seoul 136-701, South Korea
| | - Dongwon Choi
- *Graduate School of Biotechnology, Korea University, 1,5-ka Anam-dong, Sungbuk-ku, Seoul 136-701, South Korea
| | - Hyangshuk Rhim
- †Research Institute of Molecular Genetics, College of Medicine, Catholic University of Korea, Seoul 137-701, South Korea
| | - Seongman Kang
- *Graduate School of Biotechnology, Korea University, 1,5-ka Anam-dong, Sungbuk-ku, Seoul 136-701, South Korea
- To whom correspondence should be addressed (email )
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114
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Stolpe T, Süsslin C, Marrocco K, Nick P, Kretsch T, Kircher S. In planta analysis of protein-protein interactions related to light signaling by bimolecular fluorescence complementation. PROTOPLASMA 2005; 226:137-46. [PMID: 16333572 DOI: 10.1007/s00709-005-0122-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 04/22/2005] [Indexed: 05/05/2023]
Abstract
The determination of protein-protein interactions is becoming more and more important in the molecular analysis of signal transduction chains. To this purpose the application of a manageable and simple assay in an appropriate biological system is of major concern. Bimolecular fluorescence complementation (BiFC) is a novel method to analyze protein-protein interactions in vivo. The assay is based on the observation that N- and C-terminal subfragments of the yellow-fluorescent protein (YFP) can only reconstitute a functional fluorophore when they are brought into tight contact. Thus, proteins can be fused to the YFP subfragments and the interaction of the fusion proteins can be monitored by epifluorescence microscopy. Pairs of interacting proteins were tested after transient cotransfection in etiolated mustard seedlings, which is a well characterized plant model system for light signal transduction. BiFC could be demonstrated with the F-box protein EID1 (empfindlicher im dunkelroten Licht 1) and the Arabidopsis S-phase kinase-related protein 1 (ASK1). The interaction of both proteins was specific and strictly dependent on the presence of an intact F-box domain. Our studies also demonstrate that etiolated mustard seedlings provide a versatile transient assay system to study light-induced subcellular localization events.
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Affiliation(s)
- T Stolpe
- Botanik, Institut für Biologie 2, Universität Freiburg, 79104 Freiburg, FR Germany
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Pollock SV, Pootakham W, Shibagaki N, Moseley JL, Grossman AR. Insights into the acclimation of Chlamydomonas reinhardtii to sulfur deprivation. PHOTOSYNTHESIS RESEARCH 2005; 86:475-89. [PMID: 16307308 DOI: 10.1007/s11120-005-4048-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Accepted: 03/17/2005] [Indexed: 05/04/2023]
Abstract
During sulfur deprivation, the photosynthetic green alga Chlamydomonas reinhardtii develops a high-affinity sulfate uptake system and increases the expression of genes encoding proteins involved in sulfur assimilation. Although two regulatory elements, SAC1 and SAC3, have been shown to be required for normal acclimation of C. reinhardtii to sulfur deprivation, a number of other regulatory elements appear to also be involved. The molecular mechanisms by which these regulatory elements function are largely unknown. This manuscript presents our current knowledge of sulfur deprivation responses and the regulation of these responses in C. reinhardtii. In addition, we present preliminary results of a sub-saturation screen for novel sulfur acclimation mutants of C. reinhardtii. A speculative model, incorporating the activities of established regulatory elements with putative novel components of the signal transduction pathway(s) is discussed.
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Affiliation(s)
- Steve V Pollock
- Department of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, CA 94305, USA.
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116
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Raghavan C, Ong EK, Dalling MJ, Stevenson TW. Regulation of genes associated with auxin, ethylene and ABA pathways by 2,4-dichlorophenoxyacetic acid in Arabidopsis. Funct Integr Genomics 2005; 6:60-70. [PMID: 16317577 DOI: 10.1007/s10142-005-0012-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Revised: 09/15/2005] [Accepted: 09/25/2005] [Indexed: 11/29/2022]
Abstract
The chemical 2,4-dichlorophenoxyacetic acid (2,4-D) regulates plant growth and development and mimics auxins in exhibiting a biphasic mode of action. Although gene regulation in response to the natural auxin indole acetic acid (IAA) has been examined, the molecular mode of action of 2,4-D is poorly understood. Data from biochemical studies, (Grossmann (2000) Mode of action of auxin herbicides: a new ending to a long, drawn out story. Trends Plant Sci 5:506-508) proposed that at high concentrations, auxins and auxinic herbicides induced the plant hormones ethylene and abscisic acid (ABA), leading to inhibited plant growth and senescence. Further, in a recent gene expression study (Raghavan et al. (2005) Effect of herbicidal application of 2,4-dichlorophenoxyacetic acid in Arabidopsis. Funct Integr Genomics 5:4-17), we have confirmed that at high concentrations, 2,4-D induced the expression of the gene NCED1, which encodes 9-cis-epoxycarotenoid dioxygenase, a key regulatory enzyme of ABA biosynthesis. To understand the concentration-dependent mode of action of 2,4-D, we further examined the regulation of whole genome of Arabidopsis in response to a range of 2,4-D concentrations from 0.001 to 1.0 mM, using the ATH1-121501 Arabidopsis whole genome microarray developed by Affymetrix. Results of this study indicated that 2,4-D induced the expression of auxin-response genes (IAA1, IAA13, IAA19) at both auxinic and herbicidal levels of application, whereas the TIR1 and ASK1 genes, which are associated with ubiquitin-mediated auxin signalling, were down-regulated in response to low concentrations of 2,4-D application. It was also observed that in response to low concentrations of 2,4-D, ethylene biosynthesis was induced, as suggested by the up-regulation of genes encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. Although genes involved in ethylene biosynthesis were not regulated in response to 0.1 and 1.0 mM 2,4-D, ethylene signalling was induced as indicated by the down-regulation of CTR1 and ERS, both of which play a key role in the ethylene signalling pathway. In response to 1.0 mM 2,4-D, both ABA biosynthesis and signalling were induced, in contrast to the response to lower concentrations of 2,4-D where ABA biosynthesis was suppressed. We present a comprehensive model indicating a molecular mode of action for 2,4-D in Arabidopsis and the effects of this growth regulator on the auxin, ethylene and abscisic acid pathways.
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Affiliation(s)
- Chitra Raghavan
- School of Applied Sciences, RMIT University, Bundoora, Victoria, 3083, Australia
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117
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Sarnowski TJ, Ríos G, Jásik J, Swiezewski S, Kaczanowski S, Li Y, Kwiatkowska A, Pawlikowska K, Koźbiał M, Koźbiał P, Koncz C, Jerzmanowski A. SWI3 subunits of putative SWI/SNF chromatin-remodeling complexes play distinct roles during Arabidopsis development. THE PLANT CELL 2005; 17:2454-72. [PMID: 16055636 PMCID: PMC1197427 DOI: 10.1105/tpc.105.031203] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
SWITCH/SUCROSE NONFERMENTING (SWI/SNF) chromatin-remodeling complexes mediate ATP-dependent alterations of DNA-histone contacts. The minimal functional core of conserved SWI/SNF complexes consists of a SWI2/SNF2 ATPase, SNF5, SWP73, and a pair of SWI3 subunits. Because of early duplication of the SWI3 gene family in plants, Arabidopsis thaliana encodes four SWI3-like proteins that show remarkable functional diversification. Whereas ATSWI3A and ATSWI3B form homodimers and heterodimers and interact with BSH/SNF5, ATSWI3C, and the flowering regulator FCA, ATSWI3D can only bind ATSWI3B in yeast two-hybrid assays. Mutations of ATSWI3A and ATSWI3B arrest embryo development at the globular stage. By a possible imprinting effect, the atswi3b mutations result in death for approximately half of both macrospores and microspores. Mutations in ATSWI3C cause semidwarf stature, inhibition of root elongation, leaf curling, aberrant stamen development, and reduced fertility. Plants carrying atswi3d mutations display severe dwarfism, alterations in the number and development of flower organs, and complete male and female sterility. These data indicate that, by possible contribution to the combinatorial assembly of different SWI/SNF complexes, the ATSWI3 proteins perform nonredundant regulatory functions that affect embryogenesis and both the vegetative and reproductive phases of plant development.
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Affiliation(s)
- Tomasz J Sarnowski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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Quint M, Ito H, Zhang W, Gray WM. Characterization of a novel temperature-sensitive allele of the CUL1/AXR6 subunit of SCF ubiquitin-ligases. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 43:371-83. [PMID: 16045473 PMCID: PMC1363743 DOI: 10.1111/j.1365-313x.2005.02449.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Selective protein degradation by the ubiquitin-proteasome pathway has emerged as a key regulatory mechanism in a wide variety of cellular processes. The selective components of this pathway are the E3 ubiquitin-ligases which act downstream of the ubiquitin-activating and -conjugating enzymes to identify specific substrates for ubiquitinylation. SCF-type ubiquitin-ligases are the most abundant class of E3 enzymes in Arabidopsis. In a genetic screen for enhancers of the tir1-1 auxin response defect, we identified eta1/axr6-3, a recessive and temperature-sensitive mutation in the CUL1 core component of the SCF(TIR1) complex. The axr6-3 mutation interferes with Skp1 binding, thus preventing SCF complex assembly. axr6-3 displays a pleiotropic phenotype with defects in numerous SCF-regulated pathways including auxin signaling, jasmonate signaling, flower development, and photomorphogenesis. We used axr6-3 as a tool for identifying pathways likely to be regulated by SCF-mediated proteolysis and propose new roles for SCF regulation of the far-red light/phyA and sugar signaling pathways. The recessive inheritance and the temperature-sensitive nature of the pleiotropically acting axr6-3 mutation opens promising possibilities for the identification and investigation of SCF-regulated pathways in Arabidopsis.
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Affiliation(s)
- Marcel Quint
- Department of Plant Biology, University of Minnesota-Twin Cities, St Paul, MN 55108, USA
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119
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Kanegae H, Miyoshi K, Hirose T, Tsuchimoto S, Mori M, Nagato Y, Takano M. Expressions of rice sucrose non-fermenting-1 related protein kinase 1 genes are differently regulated during the caryopsis development. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2005; 43:669-79. [PMID: 16087344 DOI: 10.1016/j.plaphy.2005.06.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2005] [Accepted: 06/07/2005] [Indexed: 05/03/2023]
Abstract
The rice sucrose non-fermenting-1 related protein kinase 1 (SnRK1) family consists of three genes, which were named OSK1, OSK24 and OSK35. In order to elucidate the distinct functions of OSK genes, we identified precise regions for their expression by the promoter: GUS expression analyses as well as in situ mRNA localization experiments. At first, we isolated genomic clones corresponding to each member of OSKs in order to obtain the promoter sequences. All OSK genes house 11 exons and 10 introns and the positions of introns within the coding regions are fully conserved in all these genes. Histochemical analyses using OSK promoter: beta-glucronidase (OSKP:GUS) reporter genes showed that expression patterns of OSK1P:GUS and OSK24P:GUS were quite different in the developing caryopsis. The expression of OSK1P:GUS was nearly restricted in the vascular tissues during the caryopsis development. In contrast, the OSK24P:GUS expression was detected in the pericarp at the early stage with a shift to the endosperm as the endosperm cells were formed, and GUS staining was confined to both aleurone layer and endosperm cells around 15 days after flowering, when cell division of cellular endosperm were almost finished. The shifting pattern of the OSK24 expression was correlated with the appearance of starch granules in each tissue. Similar correlation between OSK24 expression and emergence of starch granules was also observed at another temporal sink organ, the basal part of leaf sheath. These results suggest that OSK24 (rice SnRK1b) most probably have a special role in carbohydrate metabolism of the sink organs.
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Affiliation(s)
- Hiromi Kanegae
- Molecular Genetics Department, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan
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120
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A Triticum tauschii protein kinase related to wheat PKABA1 is associated with ABA signaling and is distributed between the nucleus and cytosol. J Cereal Sci 2005. [DOI: 10.1016/j.jcs.2004.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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121
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Gingerich DJ, Gagne JM, Salter DW, Hellmann H, Estelle M, Ma L, Vierstra RD. Cullins 3a and 3b Assemble with Members of the Broad Complex/Tramtrack/Bric-a-Brac (BTB) Protein Family to Form Essential Ubiquitin-Protein Ligases (E3s) in Arabidopsis. J Biol Chem 2005; 280:18810-21. [PMID: 15749712 DOI: 10.1074/jbc.m413247200] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Selective modification of proteins by ubiquitination is directed by diverse families of ubiquitin-protein ligases (or E3s). A large collection of E3s use Cullins (CULs) as scaffolds to form multisubunit E3 complexes in which the CUL binds a target recognition subcomplex and the RBX1 docking protein, which delivers the activated ubiquitin moiety. Arabidopsis and rice contain a large collection of CUL isoforms, indicating that multiple CUL-based E3s exist in plants. Here we show that Arabidopsis CUL3a and CUL3b associate with RBX1 and members of the broad complex/tramtrack/bric-a-brac (BTB) protein family to form BTB E3s. Eighty genes encoding BTB domain-containing proteins were identified in the Arabidopsis genome, indicating that a diverse array of BTB E3s is possible. In addition to the BTB domain, the encoded proteins also contain various other interaction motifs that likely serve as target recognition elements. DNA microarray analyses show that BTB genes are expressed widely in the plant and that tissue-specific and isoform-specific patterns exist. Arabidopsis defective in both CUL3a and CUL3b are embryo-lethal, indicating that BTB E3s are essential for plant development.
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Affiliation(s)
- Derek J Gingerich
- Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA
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122
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Abstract
BACKGROUND The phytohormone auxin is critical for plant growth and orchestrates many developmental processes. SCOPE This review considers the complex array of mechanisms plants use to control auxin levels, the movement of auxin through the plant, the emerging view of auxin-signalling mechanisms, and several interactions between auxin and other phytohormones. Though many natural and synthetic compounds exhibit auxin-like activity in bioassays, indole-3-acetic acid (IAA) is recognized as the key auxin in most plants. IAA is synthesized both from tryptophan (Trp) using Trp-dependent pathways and from an indolic Trp precursor via Trp-independent pathways; none of these pathways is fully elucidated. Plants can also obtain IAA by beta-oxidation of indole-3-butyric acid (IBA), a second endogenous auxin, or by hydrolysing IAA conjugates, in which IAA is linked to amino acids, sugars or peptides. To permanently inactivate IAA, plants can employ conjugation and direct oxidation. Consistent with its definition as a hormone, IAA can be transported the length of the plant from the shoot to the root; this transport is necessary for normal development, and more localized transport is needed for tropic responses. Auxin signalling is mediated, at least in large part, by an SCFTIR1 E3 ubiquitin ligase complex that accelerates Aux/IAA repressor degradation in response to IAA, thereby altering gene expression. Two classes of auxin-induced genes encode negatively acting products (the Aux/IAA transcriptional repressors and GH3 family of IAA conjugating enzymes), suggesting that timely termination of the auxin signal is crucial. Auxin interaction with other hormone signals adds further challenges to understanding auxin response. CONCLUSIONS Nearly six decades after the structural elucidation of IAA, many aspects of auxin metabolism, transport and signalling are well established; however, more than a few fundamental questions and innumerable details remain unresolved.
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Farràs R, Bossis G, Andermarcher E, Jariel-Encontre I, Piechaczyk M. Mechanisms of delivery of ubiquitylated proteins to the proteasome: new target for anti-cancer therapy? Crit Rev Oncol Hematol 2005; 54:31-51. [PMID: 15780906 DOI: 10.1016/j.critrevonc.2004.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2004] [Indexed: 02/04/2023] Open
Abstract
The proteasome is the main proteolytic machinery of the cell. It is responsible for the basal turnover of many intracellular polypeptides, the elimination of abnormal proteins and the generation of the vast majority of peptides presented by class I major histocompatibility complex molecules. Proteasomal proteolysis is also involved in the control of virtually all cellular functions and major decisions through the spatially and timely regulated destruction of essential cell regulators. Therefore, the elucidation of its molecular mechanisms is crucial for the full understanding of the physiology of cells and whole organisms. Conversely, it is increasingly clear that proteasomal degradation is either altered in numerous pathological situations, including many cancers and diseases resulting from aberrant cell differentiation, or instrumental for the development of these pathologies. This, consequently, makes it an attractive target for therapeutical intervention. There is ample evidence that most cell proteins must be polyubiquitylated prior to proteasomal degradation. If the structure and the mode of functioning of the proteasome, as well as the enzymology of ubiquitylation, are relatively well understood, how substrates are delivered to and recognized by the proteolytic machine has remained mysterious till recently. The recent literature indicates that the mechanisms involved are multiple, complex and exquisitely regulated and provides new potential targets for anti-cancer pharmacological intervention.
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Affiliation(s)
- Rosa Farràs
- Institute of Molecular Genetics of Montpellier (IGMM), UMR 5535-IFR122, CNRS, Montpellier Cedex 05, France
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124
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Wilson ID, Barker GLA, Lu C, Coghill JA, Beswick RW, Lenton JR, Edwards KJ. Alteration of the embryo transcriptome of hexaploid winter wheat (Triticum aestivum cv. Mercia) during maturation and germination. Funct Integr Genomics 2005; 5:144-54. [PMID: 15714317 DOI: 10.1007/s10142-005-0137-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 01/11/2005] [Accepted: 01/12/2005] [Indexed: 11/28/2022]
Abstract
Grain dormancy and germination are areas of biology that are of considerable interest to the cereal community. We have used a 9,155-feature wheat unigene cDNA microarray resource to investigate changes in the wheat embryo transcriptome during late grain development and maturation and during the first 48 h of postimbibition germination. In the embryo 392 mRNAs accumulated by twofold or greater over the time course from 21 days postanthesis (dpa) to 40 dpa and on through 1 and 2 days postgermination. These included mRNAs encoding proteins involved in amino acid biosynthesis and metabolism, cell division and subsequent cell development, signal transduction, lipid metabolism, energy production, protein turnover, respiration, initiation of transcription, initiation of translation and ribosomal composition. A number of mRNAs encoding proteins of unknown function also accumulated over the time course. Conversely 163 sequences showed decreases of twofold or greater over the time course. A small number of mRNAs also showed rapid accumulation specifically during the first 48 h of germination. We also examined alterations in the accumulation of transcripts encoding proteins involved in abscisic acid signalling. Thus, we describe changes in the level of transcripts encoding wheat Viviparous 1 (Vp1) and other interacting proteins. Interestingly, the transcript encoding wheat Viviparous-interacting protein 1 showed a pattern of accumulation that correlates inversely with germination. Our data suggests that the majority of the transcripts required for germination accumulate in the embryo prior to germination and we discuss the implications of these findings with regard to manipulation of germination in wheat.
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Affiliation(s)
- Ian D Wilson
- Department of Biological Sciences, University of Bristol, UK.
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125
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Wang L, Dong L, Zhang Y, Zhang Y, Wu W, Deng X, Xue Y. Genome-wide analysis of S-Locus F-box-like genes in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2004; 56:929-945. [PMID: 15821991 DOI: 10.1007/s11103-004-6236-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Accepted: 11/14/2004] [Indexed: 05/24/2023]
Abstract
The Antirrhinum S-locus F-box gene, AhSLF-S2, has been shown to determine the pollen function of S-RNase-mediated self-incompatibility (SI). Its initial identification led to the discovery of a large family of plant-specific F-box proteins, named the SLF (S-Locus F-box) family, including members from species with or without S-RNase SI system. To investigate the evolution and function of its family members in Arabidopsis, we first identified 92 Arabidopsis F-box proteins related to AhSLF-S2, referred to as AtSFL (S-locus F-box-like) in this report. Phylogenetic analyses with family members from several plant species revealed that they could be classified into five subgroups, and the SLF genes appeared to have had a monophyletic origin. Yeast two-hybrid analyses showed that most AtSFL proteins could interact with one or more ASK (Arabidopsis Skp1-like) proteins, a component of the SCF (Skp1/Cullin or CDC53/F-box) complex, suggesting that AtSFLs may function in the process of ubiquitin/26S proteasome-mediated proteolysis. Transcript analysis found that most of AtSFL genes are expressed ubiquitously and only three of them (AtSFL61, 79 and 85) displayed a tissue-specific pattern. In consistent, phenotypic observations for T-DNA insertion lines of 37 AtSFL genes revealed that most of them are functionally redundant, but inactivation of two AtSFL genes (AtSFL 61 and 70) appears to have caused developmental defects in embryo or female gametophyte. Our results show that a diversified expression and functional pattern are associated with AtSFL genes, indicating that they play important roles in various biological processes in Arabidopsis.
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Affiliation(s)
- Lei Wang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100080, P.R. China
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126
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Umezawa T, Yoshida R, Maruyama K, Yamaguchi-Shinozaki K, Shinozaki K. SRK2C, a SNF1-related protein kinase 2, improves drought tolerance by controlling stress-responsive gene expression in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2004; 101:17306-11. [PMID: 15561775 PMCID: PMC535404 DOI: 10.1073/pnas.0407758101] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein phosphorylation/dephosphorylation are major signaling events induced by osmotic stress in higher plants. Here, we showed that a SNF1-related protein kinase 2 (SnRK2), SRK2C, is an osmotic-stress-activated protein kinase in Arabidopsis thaliana that can significantly impact drought tolerance of Arabidopsis plants. Knockout mutants of SRK2C exhibited drought hypersensitivity in their roots, suggesting that SRK2C is a positive regulator of drought tolerance in Arabidopsis roots. Additionally, transgenic plants with CaMV35S promoter::SRK2C-GFP displayed higher overall drought tolerance than control plants. Whereas stomatal regulation in 35S::SRK2C-GFP plants was not altered, microarray analysis revealed that their drought tolerance coincided with up-regulation of many stress-responsive genes, for example, RD29A, COR15A, and DREB1A/CBF3. From these results, we concluded that SRK2C is capable of mediating signals initiated during drought stress, resulting in appropriate gene expression. Our present study reveals new insights around signal output from osmotic-stress-activated SnRK2 protein kinase as well as supporting feasibility of manipulating SnRK2 toward improving plant osmotic-stress tolerance.
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Affiliation(s)
- Taishi Umezawa
- Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, 3-1-1 Kouyadai, Tsukuba 305-0074, Japan
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127
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Han L, Mason M, Risseeuw EP, Crosby WL, Somers DE. Formation of an SCF(ZTL) complex is required for proper regulation of circadian timing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:291-301. [PMID: 15447654 DOI: 10.1111/j.1365-313x.2004.02207.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The circadian timing system involves an autoregulatory transcription/translation feedback loop that incorporates a diverse array of factors to maintain a 24-h periodicity. In Arabidopsis a novel F-box protein, ZEITLUPE (ZTL), plays an important role in the control of the free-running period of the circadian clock. As a class, F-box proteins are well-established components of the Skp/Cullin/F-box (SCF) class of E3 ubiquitin ligases that link the target substrates to the core ubiquitinating activity of the ligase complex via direct association with the Skp protein. Here we identify and characterize the SCFZTL complex in detail. Yeast two-hybrid tests demonstrate the sufficiency and necessity of the F-box domain for Arabidopsis Skp-like protein (ASK) interactions and the dispensability of the unique N-terminal LOV domain in this association. Co-immunoprecipitation of full-length (FL) ZTL with the three known core components of SCF complexes (ASK1, AtCUL1 and AtRBX1) demonstrates that ZTL can assemble into an SCF complex in vivo. F-box-containing truncated versions of ZTL (LOV-F and F-kelch) can complex with SCF components in vivo, whereas stably expressed LOV or kelch domains alone cannot. Stable expression of F-box-mutated FL ZTL eliminates the shortened period caused by mild ZTL overexpression and also abolishes ASK1 interaction in vivo. Reduced levels of the core SCF component AtRBX1 phenocopy the long period phenotype of ztl loss-of-function mutations, demonstrating the functional significance of the SCFZTL complex. Taken together, our data establish SCFZTL as an essential SCF class E3 ligase controlling circadian period in plants.
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Affiliation(s)
- Linqu Han
- Department of Plant Cellular and Molecular Biology, Ohio State University, Columbus, OH, USA
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128
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Ketcham C, Wang F, Fisher SZ, Ercan A, van der Wel H, Locke RD, Sirajud-Doulah K, Matta KL, West CM. Specificity of a soluble UDP-galactose: fucoside alpha1,3-galactosyltransferase that modifies the cytoplasmic glycoprotein Skp1 in Dictyostelium. J Biol Chem 2004; 279:29050-9. [PMID: 15123660 DOI: 10.1074/jbc.m313858200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Skp1 is an adaptor-like protein in E3(SCF)-ubiquitin ligases and other multiprotein complexes of the cytoplasm and nucleus. In Dictyostelium, Skp1 is modified by an unusual pentasaccharide containing a Galalpha1-Fuc linkage, whose formation is examined here. A cytosolic extract from Dictyostelium was found to yield, after 2400-fold purification, an activity that could transfer Gal from UDP-Gal to both a Fuc-terminated glycoform of Skp1 and synthetic Fuc conjugates in the presence of Mn(2+) and dithiothreitol. The microsomal fraction was devoid of activity. The linkage formed was Galalpha1,3Fuc based on co-chromatography with only this synthetic isomer conjugate, and sensitivity to alpha1,3/6-galactosidase. Skp1 exhibited an almost 1000-fold lower K(m) and 35-fold higher V(max) compared with a simple alpha-fucoside, but this advantage was abolished by denaturation or alkylation of Cys residues. A comparison of a complete series of synthetic glycosides representing the non-reducing terminal mono-, di-, and trisaccharides of Skp1 revealed, surprisingly, that the disaccharide is most active owing primarily to a V(max) advantage, but still much less active than Skp1 itself because of a K(m) difference. These findings indicate that alpha-GalT1 is a cytoplasmic enzyme whose modification of Skp1 requires proper presentation of the terminal acceptor disaccharide by a folded Skp1 polypeptide, which correlates with previous evidence that the Galalpha1,3Fuc linkage is deficient in expressed mutant Skp1 proteins.
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Affiliation(s)
- Catherine Ketcham
- Department of Anatomy & Cell Biology, University of Florida College of Medicine, Gainesville, Florida 32610-0235, USA
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129
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Ni W, Xie D, Hobbie L, Feng B, Zhao D, Akkara J, Ma H. Regulation of flower development in Arabidopsis by SCF complexes. PLANT PHYSIOLOGY 2004; 134:1574-85. [PMID: 15047903 PMCID: PMC419832 DOI: 10.1104/pp.103.031971] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2003] [Revised: 11/03/2003] [Accepted: 01/12/2004] [Indexed: 05/17/2023]
Abstract
SCF complexes are the largest and best studied family of E3 ubiquitin protein ligases that facilitate the ubiquitylation of proteins targeted for degradation. The SCF core components Skp1, Cul1, and Rbx1 serve in multiple SCF complexes involving different substrate-specific F-box proteins that are involved in diverse processes including cell cycle and development. In Arabidopsis, mutations in the F-box gene UNUSUAL FLORAL ORGANS (UFO) result in a number of defects in flower development. However, functions of the core components Cul1 and Rbx1 in flower development are poorly understood. In this study we analyzed floral phenotypes caused by altering function of Cul1 or Rbx1, as well as the effects of mutations in ASK1 and ASK2. Plants homozygous for a point mutation in the AtCUL1 gene showed reduced floral organ number and several defects in each of the four whorls. Similarly, plants with reduced AtRbx1 expression due to RNA interference also exhibited floral morphological defects. In addition, compared to the ask1 mutant, plants homozygous for ask1 and heterozygous for ask2 displayed enhanced reduction of B function, as well as other novel defects of flower development, including carpelloid sepals and an inhibition of petal development. Genetic analyses demonstrate that AGAMOUS (AG) is required for the novel phenotypes observed in the first and second whorls. Furthermore, the genetic interaction between UFO and AtCUL1 supports the idea that UFO regulates multiple aspects of flower development as a part of SCF complexes. These results suggest that SCF complexes regulate several aspects of floral development in Arabidopsis.
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Affiliation(s)
- Weimin Ni
- Department of Biology and the Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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130
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Lai CP, Lee CL, Chen PH, Wu SH, Yang CC, Shaw JF. Molecular analyses of the Arabidopsis TUBBY-like protein gene family. PLANT PHYSIOLOGY 2004; 134:1586-97. [PMID: 15064372 PMCID: PMC419833 DOI: 10.1104/pp.103.037820] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 01/29/2004] [Accepted: 01/29/2004] [Indexed: 05/20/2023]
Abstract
In mammals, TUBBY-like proteins play an important role in maintenance and function of neuronal cells during postdifferentiation and development. We have identified a TUBBY-like protein gene family with 11 members in Arabidopsis, named AtTLP1-11. Although seven of the AtTLP genes are located on chromosome I, no local tandem repeats or gene clusters are identified. Except for AtTLP4, reverse transcription-PCR analysis indicates that all these genes are expressed in various organs in 6-week-old Arabidopsis. AtTLP1, 2, 3, 6, 7, 9, 10, and 11 are expressed ubiquitously in all the organs tested, but the expression of AtTLP5 and 8 shows dramatic organ specificity. These 11 family members share 30% to 80% amino acid similarities across their conserved C-terminal tubby domains. Unlike the highly diverse N-terminal region of animal TUBBY-like proteins, all AtTLP members except AtTLP8 contain a conserved F-box domain (51-57 residues). The interaction between AtTLP9 and ASK1 (Arabidopsis Skp1-like 1) is confirmed via yeast (Saccharomyces cerevisiae) two-hybrid assays. Abscisic acid (ABA)-insensitive phenotypes are observed for two independent AtTLP9 mutant lines, whereas transgenic plants overexpressing AtTLP9 are hypersensitive to ABA. These results suggest that AtTLP9 may participate in the ABA signaling pathway.
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Affiliation(s)
- Chia-Ping Lai
- Institute of Microbiology and Biochemistry, National Taiwan University, Taipei 106, Taiwan
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131
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Potuschak T, Lechner E, Parmentier Y, Yanagisawa S, Grava S, Koncz C, Genschik P. EIN3-dependent regulation of plant ethylene hormone signaling by two arabidopsis F box proteins: EBF1 and EBF2. Cell 2004; 115:679-89. [PMID: 14675533 DOI: 10.1016/s0092-8674(03)00968-1] [Citation(s) in RCA: 443] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The plant hormone ethylene regulates a wide range of developmental processes and the response of plants to stress and pathogens. Genetic studies in Arabidopsis led to a partial elucidation of the mechanisms of ethylene action. Ethylene signal transduction initiates with ethylene binding at a family of ethylene receptors and terminates in a transcription cascade involving the EIN3/EIL and ERF families of plant-specific transcription factors. Here, we identify two Arabidopsis F box proteins called EBF1 and EBF2 that interact physically with EIN3/EIL transcription factors. EBF1 overexpression results in plants insensitive to ethylene. In contrast, plants carrying the ebf1 and ebf2 mutations display a constitutive ethylene response and accumulate the EIN3 protein in the absence of the hormone. Our work places EBF1 and EBF2 within the genetic framework of the ethylene-response pathway and supports a model in which ethylene action depends on EIN3 protein stabilization.
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Affiliation(s)
- Thomas Potuschak
- Institut de Biologie Moléculaire des Plantes du CNRS, 12 rue du Général Zimmer, 67084 Cédex, Strasbourg, France
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132
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Yang Z, Zhang L, Diao F, Huang M, Wu N. Sucrose regulates elongation of carrot somatic embryo radicles as a signal molecule. PLANT MOLECULAR BIOLOGY 2004; 54:441-459. [PMID: 15284498 DOI: 10.1023/b:plan.0000036375.40006.d3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Elongation of carrot somatic embryo radicles was inhibited by sucrose at or above 5% (145 mM). This effect would not be released until the sucrose concentration was lowered again. Morphological and cytological studies as well as determination of ABA content and analysis of the expression mode of a Lea gene, all point to its similarity to natural dormancy and germination of seeds. Use of monosaccharides (glucose and fructose), other disaccharide (maltose), and isomolar concentration of osmotica (mannitol and sorbitol), did not show similar regulatory effect. It is thus clear that the regulatory effect is not a result of simple osmotic stress. Hexokinase inhibitors such as glucosamine and N -acetyl-glucosamine did not exert any influence on the regulation-deregulation effects of sucrose. Mannose, which inhibits germination of Arabidopsis seeds, did not prevent carrot somatic embryo radicles from elongating. It is thus inferred that this sucrose-signaling pathway may be independent of hexokinase. As a first step to understand the molecular mechanism of this process, a carrot sucrose transporter gene ( cSUT ) expressed in the embryos and roots specifically was isolated. Studies on transformed yeast mutant with cSUT cDNA identified its sucrose transport activity. Northern hybridization and gel retardation experiment revealed that there is a marked increase in expression of cSUT at the beginning of somatic embryo germination, and this is attributed to regulation on the level of transcription. This suggested the possibility that cSUT has an important role in this sucrose signal regulation system.
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Affiliation(s)
- Zhipan Yang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100080, China
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133
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Takahashi N, Kuroda H, Kuromori T, Hirayama T, Seki M, Shinozaki K, Shimada H, Matsui M. Expression and interaction analysis of Arabidopsis Skp1-related genes. PLANT & CELL PHYSIOLOGY 2004; 45:83-91. [PMID: 14749489 DOI: 10.1093/pcp/pch009] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Specific protein degradation has been observed in several aspects of development and differentiation in many organisms. One example of such proteolysis is regulated by protein polyubiquitination that is promoted by the SCF complex consisting of Skp1, cullin, and an F-box protein. We examined the activities of the Arabidopsis Skp1-related proteins (ASKs). Among 19 annotated ASK genes, we isolated 16 of the corresponding cDNAs (ASK1, 2, 3, 4, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19), and examined their gene products for interactions with 24 representatives of F-box proteins carrying various classes of the C-terminal domains using the yeast two-hybrid system. As a result, we found diverse binding specificities: ASK1, ASK2, ASK11 and ASK12 interacted well with COI1, FKF1, UFO-like protein, LRR-containing F-box proteins, and other F-box proteins with unknown C-terminal motifs. We also observed specific interaction between F-box proteins and ASK3, ASK9, ASK13, ASK14, ASK16 and ASK18. In contrast, we detected no interaction between any of the 12 ASK proteins and F-box proteins containing CRFA, CRFB or CRFC domains. Both histochemical and RT-PCR analysis of eight ASK genes expression revealed unique expression patterns for the respective genes.
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Affiliation(s)
- Naoki Takahashi
- Plant Function Exploration Team, Plant Functional Genomics Research Group, Genomic Sciences Center, RIKEN Yokohama Institute, 1-7-22 Suyehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045 Japan
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134
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Liu F, Ni W, Griffith ME, Huang Z, Chang C, Peng W, Ma H, Xie D. The ASK1 and ASK2 genes are essential for Arabidopsis early development. THE PLANT CELL 2004; 16:5-20. [PMID: 14688296 PMCID: PMC301391 DOI: 10.1105/tpc.017772] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The requirement of CUL1 for Arabidopsis embryogenesis suggests that Skp1-CUL1-F-box protein (SCF) complexes play important roles during embryo development. Among the 21 Arabidopsis Skp1-like genes (ASKs), it is unknown which ASK gene(s) is essential for embryo development. In this study, we demonstrate a vital role for ASK1 and ASK2 in Arabidopsis embryogenesis and postembryonic development through analysis of the ask1 ask2 double mutant. Our detailed analysis indicates that the double mutations in both ASK1 and ASK2 affect cell division and cell expansion/elongation and cause a developmental delay during embryogenesis and lethality in seedling growth. The expression patterns of ASK1 and ASK2 were examined further and found to be consistent with their roles in embryogenesis and seedling development. We propose that mutations in ASK1 and ASK2 abolish all of the ASK1- and ASK2-based SCF and non-SCF complexes, resulting in alteration of gene expression and leading to defects in growth and development.
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Affiliation(s)
- Fuquan Liu
- Laboratory of Plant Signal Transduction, Institute of Molecular and Cell Biology, 117609 Republic of Singapore
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135
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Abstract
Much of plant physiology, growth, and development is controlled by the selective removal of short-lived regulatory proteins. One important proteolytic pathway involves the small protein ubiquitin (Ub) and the 26S proteasome, a 2-MDa protease complex. In this pathway, Ub is attached to proteins destined for degradation; the resulting Ub-protein conjugates are then recognized and catabolized by the 26S proteasome. This review describes our current understanding of the pathway in plants at the biochemical, genomic, and genetic levels, using Arabidopsis thaliana as the model. Collectively, these analyses show that the Ub/26S proteasome pathway is one of the most elaborate regulatory mechanisms in plants. The genome of Arabidopsis encodes more than 1400 (or >5% of the proteome) pathway components that can be connected to almost all aspects of its biology. Most pathway components participate in the Ub-ligation reactions that choose with exquisite specificity which proteins should be ubiquitinated. What remains to be determined is the identity of the targets, which may number in the thousands in plants.
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Affiliation(s)
- Jan Smalle
- Department of Genetics, 445 Henry Mall, University of Wisconsin-Madison, Madison, Wisconsin 53706-1574, USA
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136
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Kong H, Leebens-Mack J, Ni W, dePamphilis CW, Ma H. Highly heterogeneous rates of evolution in the SKP1 gene family in plants and animals: functional and evolutionary implications. Mol Biol Evol 2003; 21:117-28. [PMID: 14595103 DOI: 10.1093/molbev/msh001] [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] [Indexed: 01/14/2023] Open
Abstract
Skp1 (S-phase kinase-associated protein 1) is a core component of SCF ubiquitin ligases and mediates protein degradation, thereby regulating eukaryotic fundamental processes such as cell cycle progression, transcriptional regulation, and signal transduction. Among the four components of the SCF complexes, Rbx1 and Cullin form a core catalytic complex, an F-box protein acts as a receptor for target proteins, and Skp1 is an adaptor between one of the variable F-box proteins and Cullin. Whereas protists, fungi, and some vertebrates have a single SKP1 gene, many animal and plant species possess multiple SKP1 homologs. It has been shown that the same Skp1 homolog can interact with two or more F-box proteins, and different Skp1 homologs from the same species sometimes can interact with the same F-box protein. In this paper, we demonstrate that multiple Skp1 homologs from the same species have evolved at highly heterogeneous rates. Parametric bootstrap analyses suggested that the differences in evolutionary rate are so large that true phylogenies were not recoverable from the full data set. Only when the original data set were partitioned into sets of genes with slow, medium, and rapid rates of evolution and analyzed separately, better-resolved relationships were observed. The slowly evolving Skp1 homologs, which are relatively highly conserved in sequence and expressed widely and/or at high levels, usually have very low d(N)/d(S) values, suggesting that they have evolved under functional constraint and serve the most fundamental function(s). On the other hand, the rapidly evolving members are structurally more diverse and usually have limited expression patterns and higher d(N)/d(S) values, suggesting that they may have evolved under relaxed or altered constraint, or even under positive selection. Some rapidly evolving members may have lost their original function(s) and/or acquired new function(s) or become pseudogenes, as suggested by their expression patterns, d(N)/d(S) values, and amino acid changes at key positions. In addition, our analyses revealed several monophyletic groups within the SKP1 gene family, one for each of protists, fungi, animals, and plants, as well as nematodes, arthropods, and angiosperms, suggesting that the extant SKP1 genes within each of these eukaryote groups shared only one common ancestor.
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Affiliation(s)
- Hongzhi Kong
- Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing, China
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137
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Himmelbach A, Yang Y, Grill E. Relay and control of abscisic acid signaling. CURRENT OPINION IN PLANT BIOLOGY 2003; 6:470-9. [PMID: 12972048 DOI: 10.1016/s1369-5266(03)00090-6] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Insights into the signal transduction of the phytohormone abscisic acid (ABA) have unfolded dramatically in the past few years and reveal an unanticipated complexity. Knockout lines and RNA-interference technology, together with protein interaction analyses, have been used to identify many of the cellular components that regulate or modulate ABA responses. ABA signaling is characterized by a plethora of intracellular messengers. This may reflect the function of ABA in integrating several stress responses and antagonizing pathways via cross-talk, but it hampers the establishment of a unifying concept. Transcriptome analyses have unraveled more than a thousand genes that are differentially regulated by ABA, and these ABA-mediated changes in gene expression translate to major changes in proteome expression. ABA-induced mechanisms that re-adjust cellular protein expression are just surfacing. ABA-response-specific transcription factors have a well-established function in that process and, recently, it has also become clear that phytohormone signaling enforces a sophisticated interference with protein expression at the posttranscriptional level. This interference includes both targeted proteolysis and the regulation of the translation of specific mRNAs by RNA-binding proteins.
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Affiliation(s)
- Axel Himmelbach
- Lehrstuhl für Botanik, Technische Universität München, Biologikum Weihenstephan, Am Hochanger 4, 85354 Freising, Germany
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138
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Itoh H, Matsuoka M, Steber CM. A role for the ubiquitin-26S-proteasome pathway in gibberellin signaling. TRENDS IN PLANT SCIENCE 2003; 8:492-7. [PMID: 14557046 DOI: 10.1016/j.tplants.2003.08.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The gibberellin (GA) signaling pathway, like auxin and jasmonate signaling, uses the ubiquitin-proteasome pathway to control expression through protein degradation. A conserved F-box protein of an SCF E3 ubiquitin ligase is a positive regulator of GA signaling in Arabidopsis and rice. GA apparently stimulates stem elongation by causing this SCF complex to regulate negatively a family of negative regulators of GA response (the DELLA family of putative transcription factors). The DELLA family members AtRGA or (Repressor of ga1-3) and OsSLR1 (SLENDER RICE1) proteins both appear to be subject to GA-induced proteolysis. The need to have the F-box genes AtSLY1 and OsGID2 for this proteolysis suggests that GA causes proteolysis of AtRGA/OsSLR1 via the SCF(AtSLY1/OsGID2) ubiquitin ligase.
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Affiliation(s)
- Hironori Itoh
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya 464-8601, Japan
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139
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Hare PD, Seo HS, Yang JY, Chua NH. Modulation of sensitivity and selectivity in plant signaling by proteasomal destabilization. CURRENT OPINION IN PLANT BIOLOGY 2003; 6:453-62. [PMID: 12972046 DOI: 10.1016/s1369-5266(03)00080-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The ubiquitin (Ub) system of intracellular protein degradation regulates the abundance of numerous proteins that control plant growth and development. Recent advances have begun to illustrate how environmental and endogenous signals affect plant responses through Ub-related proteolysis, the importance of combinatorial control in regulated protein destruction and how multiprotein complexes confer sensitivity and selectivity to ubiquitination. Further insight into the cell biology of Ub-chain assembly and proteasomal degradation, as well as into the relationship between proteolysis and other regulatory modifications, will be essential for understanding the mechanistic basis of the integration of diverse plant signals.
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Affiliation(s)
- Peter D Hare
- The Laboratory of Plant Molecular Biology, The Rockefeller University, 1230 York Avenue, New York, New York 10021-6399, USA
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140
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Zhao D, Ni W, Feng B, Han T, Petrasek MG, Ma H. Members of the Arabidopsis-SKP1-like gene family exhibit a variety of expression patterns and may play diverse roles in Arabidopsis. PLANT PHYSIOLOGY 2003; 133:203-17. [PMID: 12970487 PMCID: PMC196598 DOI: 10.1104/pp.103.024703] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2003] [Revised: 04/25/2003] [Accepted: 05/29/2003] [Indexed: 05/18/2023]
Abstract
Ubiquitin-mediated proteolysis by the proteasome is a critical regulatory mechanism controlling many biological processes. In particular, SKP1, cullin/CDC53, F-box protein (SCF) complexes play important roles in selecting substrates for proteolysis by facilitating the ligation of ubiquitin to specific proteins. In plants, SCF complexes have been found to regulate auxin responses and jasmonate signaling and may be involved in several other processes, such as flower development, circadian clock, and gibberellin signaling. Although 21 Skp1-related genes, called Arabidopsis-SKP1-like (ASK), have been uncovered in the Arabidopsis genome, ASK1 is the only gene that has been analyzed genetically. As a first step toward understanding their functions, we tested for expression of 20 ASK genes using reverse transcription-polymerase chain reaction experiments. Also, we examined the expression patterns of 11 ASK genes by in situ hybridizations. The ASK genes exhibit a spectrum of expression levels and patterns, with a large subset showing expression in the flower and/or fruit. In addition, the ASK genes that have similar sequences tend to have similar expression patterns. On the basis of the expression results, we selectively suppressed the expression of a few ASK genes using RNA interference. Compared with the ask1 mutant, the strong ASK1 RNA interference (RNAi) line exhibited similar or enhanced phenotypes in both vegetative and floral development, whereas ASK11 RNAi plants had normal vegetative growth but mild defects in flower development. The diverse expression patterns and distinct defects observed in RNAi plants suggest that the ASK gene family may collectively perform a range of functions and may regulate different developmental and physiological processes.
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Affiliation(s)
- Dazhong Zhao
- Department of Biology and Huck Institute for Life Sciences, 313 Wartik Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
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141
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Zhao D, Han T, Risseeuw E, Crosby WL, Ma H. Conservation and divergence of ASK1 and ASK2 gene functions during male meiosis in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2003; 53:163-173. [PMID: 14756314 DOI: 10.1023/b:plan.0000009273.81702.b5] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Selective proteolysis of regulatory proteins mediated by the ubiquitin pathway is an important mechanism for controlling many biological events. The SCF (Skpl-Cullin-F-box protein) class of E3 ubiquitin ligases controls the ubiquitination of a wide variety of substrates, thereby mediating their degradation by the 26S proteasome. The Arabidopsis genome contains 21 genes encoding Skp1-like proteins that are named as ASKs (Arabidopsis Skp1-like). So far, only the ASK1 gene has been characterized genetically, and is known to be required for male meiosis, flower development, and auxin response. The ASK2 gene is most similar to ASK1 in terms of both the amino acid sequence and expression pattern. To compare ASK2 with ASK1 functionally in male meiosis, different transgenic lines over-expressing ASK1 and ASK2 were tested for their ability to complement the male meiosis defect of the ask1-1 mutant. The genomic ASK1 rescued the ask1-1 mutant defects. The 35S::ASK1 transgene restored male fertility to the ask1-1 mutant, although the percentages of normal pollen grains and tetrads were reduced. 35S::ASK2 lines in the ask1-1 background exhibited partial fertility with even fewer normal pollen grains and tetrads than those of the 35S::ASK1 lines. Detailed analysis of chromosome behavior during male meiosis demonstrated that 35S::ASK1 and 35S::ASK2 lines had different fractions of pollen mother cells undergoing normal meiosis. Our results suggest that ASK2 partially substitutes for ASK1 if expressed at higher than normal levels.
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Affiliation(s)
- Dazhong Zhao
- Department of Biology, Huck Institute for Life Sciences, 315 Wartik Laboratory, Pennsylvania State University, University Park, PA 16802, USA
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142
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Tiessen A, Prescha K, Branscheid A, Palacios N, McKibbin R, Halford NG, Geigenberger P. Evidence that SNF1-related kinase and hexokinase are involved in separate sugar-signalling pathways modulating post-translational redox activation of ADP-glucose pyrophosphorylase in potato tubers. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:490-500. [PMID: 12904211 DOI: 10.1046/j.1365-313x.2003.01823.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We recently discovered that post-translational redox modulation of ADP-glucose pyrophosphorylase (AGPase) is a powerful new mechanism to adjust the rate of starch synthesis to the availability of sucrose in growing potato tubers. A strong correlation was observed between the endogenous levels of sucrose and the redox-activation state of AGPase. To identify candidate components linking AGPase redox modulation to sugar supply, we used potato tuber discs as a model system. When the discs were cut from growing wild-type potato tubers and incubated for 2 h in the absence of sugars, redox activation of AGPase decreased because of a decrease in internal sugar levels. The decrease in AGPase redox activation could be prevented when glucose or sucrose was supplied to the discs. Both sucrose uptake and redox activation of AGPase were increased when EDTA was used to prepare the tuber discs. However, EDTA treatment of discs had no effect on glucose uptake. Feeding of different glucose analogues revealed that the phosphorylation of hexoses by hexokinase is an essential component in the glucose-dependent redox activation of AGPase. In contrast to this, feeding of the non-metabolisable sucrose analogue, palatinose, leads to a similar activation as with sucrose, indicating that metabolism of sucrose is not necessary in the sucrose-dependent AGPase activation. The influence of sucrose and glucose on redox activation of AGPase was also investigated in discs cut from tubers of antisense plants with reduced SNF1-related protein kinase activity (SnRK1). Feeding of sucrose to tuber discs prevented AGPase redox inactivation in the wild type but not in SnRK1 antisense lines. However, feeding of glucose leads to a similar activation of AGPase in the wild type and in SnRK1 transformants. AGPase redox activation was also increased in transgenic tubers with ectopic overexpression of invertase, containing high levels of glucose and low sucrose levels. Expression of a bacterial glucokinase in the invertase-expressing background led to a decrease in AGPase activation state and tuber starch content. These results show that both sucrose and glucose lead to post-translational redox activation of AGPase, and that they do this by two different pathways involving SnRK1 and an endogenous hexokinase, respectively.
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Affiliation(s)
- Axel Tiessen
- Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany.
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143
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Tokumoto T, Kondo A, Miwa J, Horiguchi R, Tokumoto M, Nagahama Y, Okida N, Ishikawa K. Regulated interaction between polypeptide chain elongation factor-1 complex with the 26S proteasome during Xenopus oocyte maturation. BMC BIOCHEMISTRY 2003; 4:6. [PMID: 12864926 PMCID: PMC179889 DOI: 10.1186/1471-2091-4-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Accepted: 07/16/2003] [Indexed: 11/10/2022]
Abstract
BACKGROUND During Xenopus oocyte maturation, the amount of a 48 kDa protein detected in the 26S proteasome fraction (p48) decreased markedly during oocyte maturation to the low levels seen in unfertilized eggs. The results indicate that the interaction of at least one protein with the 26S proteasome changes during oocyte maturation and early development. An alteration in proteasome function may be important for the regulation of developmental events, such as the rapid cell cycle, in the early embryo. In this study, we identified p48. RESULTS p48 was purified by conventional column chromatography. The resulting purified fraction contained two other proteins with molecular masses of 30 (p30) and 37 (p37) kDa. cDNAs encode elongation factor-1gamma and delta were obtained by an immuno-screening method using polyclonal antibodies against purified p48 complex, which recognized p48 and p37. N-terminal amino acid sequence analysis of p30 revealed that it was identical to EF-1beta. To identify the p48 complex bound to the 26S proteasome as EF-1betagammadelta, antibodies were raised against the components of purified p48 complex. Recombinant EF-1 beta,gamma and delta were expressed in Escherichia coli, and an antibody was raised against purified recombinant EF-1gamma. Cross-reactivity of the antibodies toward the p48 complex and recombinant proteins showed it to be specific for each component. These results indicate that the p48 complex bound to the 26S proteasome is the EF-1 complex. MPF phosphorylated EF-1gamma was shown to bind to the 26S proteasome. When EF-1gamma is phosphorylated by MPF, the association is stabilized. CONCLUSION p48 bound to the 26S proteasome is identified as the EF-1gamma. EF-1 complex is associated with the 26S proteasome in Xenopus oocytes and the interaction is stabilized by MPF-mediated phosphorylation.
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Affiliation(s)
- Toshinobu Tokumoto
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
- CREST Research Project, Japan Science and Technology Corporation, Japan
| | - Ayami Kondo
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
| | - Junko Miwa
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
| | - Ryo Horiguchi
- Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan
- Department of Molecular Biomechanics, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Mika Tokumoto
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
- CREST Research Project, Japan Science and Technology Corporation, Japan
| | - Yoshitaka Nagahama
- CREST Research Project, Japan Science and Technology Corporation, Japan
- Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Noriyuki Okida
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
| | - Katsutoshi Ishikawa
- Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
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144
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Hellmann H, Hobbie L, Chapman A, Dharmasiri S, Dharmasiri N, del Pozo C, Reinhardt D, Estelle M. Arabidopsis AXR6 encodes CUL1 implicating SCF E3 ligases in auxin regulation of embryogenesis. EMBO J 2003; 22:3314-25. [PMID: 12839993 PMCID: PMC165659 DOI: 10.1093/emboj/cdg335] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2003] [Revised: 05/14/2003] [Accepted: 05/15/2003] [Indexed: 12/24/2022] Open
Abstract
The AXR6 gene is required for auxin signaling in the Arabidopsis embryo and during postembryonic development. One of the effects of auxin is to stimulate degradation of the Aux/IAA auxin response proteins through the action of the ubiquitin protein ligase SCF(TIR1). Here we show that AXR6 encodes the SCF subunit CUL1. The axr6 mutations affect the ability of mutant CUL1 to assemble into stable SCF complexes resulting in reduced degradation of the SCF(TIR1) substrate AXR2/IAA7. In addition, we show that CUL1 is required for lateral organ initiation in the shoot apical meristem and the inflorescence meristem. These results indicate that the embryonic axr6 phenotype is related to a defect in SCF function and accumulation of Aux/IAA proteins such as BDL/IAA12. In addition, we show that CUL1 has a role in auxin response throughout the life cycle of the plant.
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Affiliation(s)
- Hanjo Hellmann
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA
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145
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Bradford KJ, Downie AB, Gee OH, Alvarado V, Yang H, Dahal P. Abscisic acid and gibberellin differentially regulate expression of genes of the SNF1-related kinase complex in tomato seeds. PLANT PHYSIOLOGY 2003; 132:1560-76. [PMID: 12857836 PMCID: PMC167094 DOI: 10.1104/pp.102.019141] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2002] [Revised: 01/20/2003] [Accepted: 03/12/2003] [Indexed: 05/17/2023]
Abstract
The SNF1/AMP-activated protein kinase subfamily plays central roles in metabolic and transcriptional responses to nutritional or environmental stresses. In yeast (Saccharomyces cerevisiae) and mammals, activating and anchoring subunits associate with and regulate the activity, substrate specificity, and cellular localization of the kinase subunit in response to changing nutrient sources or energy demands, and homologous SNF1-related kinase (SnRK1) proteins are present in plants. We isolated cDNAs corresponding to the kinase (LeSNF1), regulatory (LeSNF4), and localization (LeSIP1 and LeGAL83) subunits of the SnRK1 complex from tomato (Lycopersicon esculentum Mill.). LeSNF1 and LeSNF4 complemented yeast snf1 and snf4 mutants and physically interacted with each other and with LeSIP1 in a glucose-dependent manner in yeast two-hybrid assays. LeSNF4 mRNA became abundant at maximum dry weight accumulation during seed development and remained high when radicle protrusion was blocked by abscisic acid (ABA), water stress, far-red light, or dormancy, but was low or undetected in seeds that had completed germination or in gibberellin (GA)-deficient seeds stimulated to germinate by GA. In leaves, LeSNF4 was induced in response to ABA or dehydration. In contrast, LeSNF1 and LeGAL83 genes were essentially constitutively expressed in both seeds and leaves regardless of the developmental, hormonal, or environmental conditions. Regulation of LeSNF4 expression by ABA and GA provides a potential link between hormonal and sugar-sensing pathways controlling seed development, dormancy, and germination.
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Affiliation(s)
- Kent J Bradford
- Department of Vegetable Crops, One Shields Avenue, University of California, Davis, California 95616-8631, USA.
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146
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Hrabak EM, Chan CWM, Gribskov M, Harper JF, Choi JH, Halford N, Kudla J, Luan S, Nimmo HG, Sussman MR, Thomas M, Walker-Simmons K, Zhu JK, Harmon AC. The Arabidopsis CDPK-SnRK superfamily of protein kinases. PLANT PHYSIOLOGY 2003; 132:666-80. [PMID: 12805596 PMCID: PMC167006 DOI: 10.1104/pp.102.011999] [Citation(s) in RCA: 644] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2002] [Revised: 10/02/2002] [Accepted: 02/17/2003] [Indexed: 05/17/2023]
Abstract
The CDPK-SnRK superfamily consists of seven types of serine-threonine protein kinases: calcium-dependent protein kinase (CDPKs), CDPK-related kinases (CRKs), phosphoenolpyruvate carboxylase kinases (PPCKs), PEP carboxylase kinase-related kinases (PEPRKs), calmodulin-dependent protein kinases (CaMKs), calcium and calmodulin-dependent protein kinases (CCaMKs), and SnRKs. Within this superfamily, individual isoforms and subfamilies contain distinct regulatory domains, subcellular targeting information, and substrate specificities. Our analysis of the Arabidopsis genome identified 34 CDPKs, eight CRKs, two PPCKs, two PEPRKs, and 38 SnRKs. No definitive examples were found for a CCaMK similar to those previously identified in lily (Lilium longiflorum) and tobacco (Nicotiana tabacum) or for a CaMK similar to those in animals or yeast. CDPKs are present in plants and a specific subgroup of protists, but CRKs, PPCKs, PEPRKs, and two of the SnRK subgroups have been found only in plants. CDPKs and at least one SnRK have been implicated in decoding calcium signals in Arabidopsis. Analysis of intron placements supports the hypothesis that CDPKs, CRKs, PPCKs and PEPRKs have a common evolutionary origin; however there are no conserved intron positions between these kinases and the SnRK subgroup. CDPKs and SnRKs are found on all five Arabidopsis chromosomes. The presence of closely related kinases in regions of the genome known to have arisen by genome duplication indicates that these kinases probably arose by divergence from common ancestors. The PlantsP database provides a resource of continuously updated information on protein kinases from Arabidopsis and other plants.
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Affiliation(s)
- Estelle M Hrabak
- Department of Plant Biology and Program in Genetics, University of New Hampshire, 46 College Road, Durham 03824, USA.
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147
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Risseeuw EP, Daskalchuk TE, Banks TW, Liu E, Cotelesage J, Hellmann H, Estelle M, Somers DE, Crosby WL. Protein interaction analysis of SCF ubiquitin E3 ligase subunits from Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 34:753-767. [PMID: 12795696 DOI: 10.1046/j.1365-313x.2003.01768.x] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Ubiquitin E3 ligases are a diverse family of protein complexes that mediate the ubiquitination and subsequent proteolytic turnover of proteins in a highly specific manner. Among the several classes of ubiquitin E3 ligases, the Skp1-Cullin-F-box (SCF) class is generally comprised of three 'core' subunits: Skp1 and Cullin, plus at least one F-box protein (FBP) subunit that imparts specificity for the ubiquitination of selected target proteins. Recent genetic and biochemical evidence in Arabidopsis thaliana suggests that post-translational turnover of proteins mediated by SCF complexes is important for the regulation of diverse developmental and environmental response pathways. In this report, we extend upon a previous annotation of the Arabidopsis Skp1-like (ASK) and FBP gene families to include the Cullin family of proteins. Analysis of the protein interaction profiles involving the products of all three gene families suggests a functional distinction between ASK proteins in that selected members of the protein family interact generally while others interact more specifically with members of the F-box protein family. Analysis of the interaction of Cullins with FBPs indicates that CUL1 and CUL2, but not CUL3A, persist as components of selected SCF complexes, suggesting some degree of functional specialization for these proteins. Yeast two-hybrid analyses also revealed binary protein interactions between selected members of the FBP family in Arabidopsis. These and related results are discussed in terms of their implications for subunit composition, stoichiometry and functional diversity of SCF complexes in Arabidopsis.
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Affiliation(s)
- Eddy P Risseeuw
- Gene Expression Group, NRC Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK, Canada S7N-0W9
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148
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Hrabak EM, Chan CWM, Gribskov M, Harper JF, Choi JH, Halford N, Kudla J, Luan S, Nimmo HG, Sussman MR, Thomas M, Walker-Simmons K, Zhu JK, Harmon AC. The Arabidopsis CDPK-SnRK superfamily of protein kinases. PLANT PHYSIOLOGY 2003; 132:666-680. [PMID: 12805596 DOI: 10.1104/pp.102.011999.666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The CDPK-SnRK superfamily consists of seven types of serine-threonine protein kinases: calcium-dependent protein kinase (CDPKs), CDPK-related kinases (CRKs), phosphoenolpyruvate carboxylase kinases (PPCKs), PEP carboxylase kinase-related kinases (PEPRKs), calmodulin-dependent protein kinases (CaMKs), calcium and calmodulin-dependent protein kinases (CCaMKs), and SnRKs. Within this superfamily, individual isoforms and subfamilies contain distinct regulatory domains, subcellular targeting information, and substrate specificities. Our analysis of the Arabidopsis genome identified 34 CDPKs, eight CRKs, two PPCKs, two PEPRKs, and 38 SnRKs. No definitive examples were found for a CCaMK similar to those previously identified in lily (Lilium longiflorum) and tobacco (Nicotiana tabacum) or for a CaMK similar to those in animals or yeast. CDPKs are present in plants and a specific subgroup of protists, but CRKs, PPCKs, PEPRKs, and two of the SnRK subgroups have been found only in plants. CDPKs and at least one SnRK have been implicated in decoding calcium signals in Arabidopsis. Analysis of intron placements supports the hypothesis that CDPKs, CRKs, PPCKs and PEPRKs have a common evolutionary origin; however there are no conserved intron positions between these kinases and the SnRK subgroup. CDPKs and SnRKs are found on all five Arabidopsis chromosomes. The presence of closely related kinases in regions of the genome known to have arisen by genome duplication indicates that these kinases probably arose by divergence from common ancestors. The PlantsP database provides a resource of continuously updated information on protein kinases from Arabidopsis and other plants.
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Affiliation(s)
- Estelle M Hrabak
- Department of Plant Biology and Program in Genetics, University of New Hampshire, 46 College Road, Durham 03824, USA.
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149
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Diaz-Camino C, Risseeuw EP, Liu E, Crosby WL. A high-throughput system for two-hybrid screening based on growth curve analysis in microtiter plates. Anal Biochem 2003; 316:171-4. [PMID: 12711337 DOI: 10.1016/s0003-2697(02)00706-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The yeast two-hybrid system is a powerful tool for identifying novel protein-protein interactions. In general, biochemical marker genes such as lacZ are exploited for indirect quantification of the interaction, and commonly involve the conduct of rather laborious beta-galactosidase assays. This paper describes a simple alternative method based on growth curve analysis of yeast cultures that is amenable to microtiter plate format, and therefore allows the quantification of large numbers of yeast two-hybrid combinations. The analyzed results of yeast cultures grown in microtiter plates were compared with those obtained from the classical beta-galactosidase assay. We conclude that the method presented here is reproducible, of equal or greater sensitivity than the beta-galactosidase assay, and can be further adapted for application to the conduct of large-scale, automated yeast two-hybrid experiments.
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Affiliation(s)
- Claudia Diaz-Camino
- Gene Expression Group, Plant Biotechnology Institute, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK, Canada S7N 0W9
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150
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Min KW, Hwang JW, Lee JS, Park Y, Tamura TA, Yoon JB. TIP120A associates with cullins and modulates ubiquitin ligase activity. J Biol Chem 2003; 278:15905-10. [PMID: 12609982 DOI: 10.1074/jbc.m213070200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cullin-containing ubiquitin-protein isopeptide ligases (E3s) play an important role in regulating the abundance of key proteins involved in cellular processes such as cell cycle and cytokine signaling. They have multisubunit modular structures in which substrate recognition and the catalysis of ubiquitination are carried out by distinct polypeptides. In a search for proteins involved in regulation of cullin-containing E3 ubiquitin ligases we immunopurified CUL4B-containing complex from HeLa cells and identified TIP120A as an associated protein by mass spectrometry. Immunoprecipitation of cullins revealed that all cullins tested specifically interacted with TIP120A. Reciprocal immunoaffinity purification of TIP120A confirmed the stable interaction of TIP120A with cullin family proteins. TIP120A formed a complex with CUL1 and Rbx1, but interfered with the binding of Skp1 and F-box proteins to CUL1. TIP120A greatly reduced the ubiquitination of phosphorylated IkappaBalpha by SCF(beta-TrCP) ubiquitin ligase. These results suggest that TIP120A functions as a negative regulator of SCF E3 ubiquitin ligases and may modulate other cullin ligases in a similar fashion.
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Affiliation(s)
- Kyoeng-Woo Min
- Department of Biochemistry and Protein Network Research Center, Yonsei University, Seoul 120-749, Korea
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