51
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Ratzel SE, Lingard MJ, Woodward AW, Bartel B. Reducing PEX13 expression ameliorates physiological defects of late-acting peroxin mutants. Traffic 2010; 12:121-34. [PMID: 20969679 DOI: 10.1111/j.1600-0854.2010.01136.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Proteins are targeted to the peroxisome matrix via processes that are mechanistically distinct from those used by other organelles. Protein entry into peroxisomes requires peroxin (PEX) proteins, including early-acting receptor (e.g. PEX5) and docking peroxins (e.g. PEX13 and PEX14) and late-acting PEX5-recycling peroxins (e.g. PEX4 and PEX6). We examined genetic interactions among Arabidopsis peroxin mutants and found that the weak pex13-1 allele had deleterious effects when combined with pex5-1 and pex14-2, which are defective in early-acting peroxins, as shown by reduced matrix protein import and enhanced physiological defects. In contrast, combining pex13-1 with pex4-1 or pex6-1, which are defective in late-acting peroxins, unexpectedly ameliorated mutant growth defects. Matrix protein import remained impaired in pex4-1 pex13-1 and pex6-1 pex13-1, suggesting that the partial suppression of pex4-1 and pex6-1 physiological defects by a weak pex13 allele may result from restoring the balance between import and export of PEX5 or other proteins that are retrotranslocated from the peroxisome with the assistance of PEX4 and PEX6. Our results suggest that symptoms caused by pex mutants defective in late-acting peroxins may result not only from defects in matrix protein import but also from inefficient removal of PEX5 from the peroxisomal membrane following cargo delivery.
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Affiliation(s)
- Sarah E Ratzel
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA
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52
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Tognetti VB, Van Aken O, Morreel K, Vandenbroucke K, van de Cotte B, De Clercq I, Chiwocha S, Fenske R, Prinsen E, Boerjan W, Genty B, Stubbs KA, Inzé D, Van Breusegem F. Perturbation of indole-3-butyric acid homeostasis by the UDP-glucosyltransferase UGT74E2 modulates Arabidopsis architecture and water stress tolerance. THE PLANT CELL 2010; 22:2660-79. [PMID: 20798329 PMCID: PMC2947170 DOI: 10.1105/tpc.109.071316] [Citation(s) in RCA: 302] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 07/16/2010] [Accepted: 08/05/2010] [Indexed: 05/18/2023]
Abstract
Reactive oxygen species and redox signaling undergo synergistic and antagonistic interactions with phytohormones to regulate protective responses of plants against biotic and abiotic stresses. However, molecular insight into the nature of this crosstalk remains scarce. We demonstrate that the hydrogen peroxide-responsive UDP-glucosyltransferase UGT74E2 of Arabidopsis thaliana is involved in the modulation of plant architecture and water stress response through its activity toward the auxin indole-3-butyric acid (IBA). Biochemical characterization of recombinant UGT74E2 demonstrated that it strongly favors IBA as a substrate. Assessment of indole-3-acetic acid (IAA), IBA, and their conjugates in transgenic plants ectopically expressing UGT74E2 indicated that the catalytic specificity was maintained in planta. In these transgenic plants, not only were IBA-Glc concentrations increased, but also free IBA levels were elevated and the conjugated IAA pattern was modified. This perturbed IBA and IAA homeostasis was associated with architectural changes, including increased shoot branching and altered rosette shape, and resulted in significantly improved survival during drought and salt stress treatments. Hence, our results reveal that IBA and IBA-Glc are important regulators of morphological and physiological stress adaptation mechanisms and provide molecular evidence for the interplay between hydrogen peroxide and auxin homeostasis through the action of an IBA UGT.
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Affiliation(s)
- Vanesa B. Tognetti
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Olivier Van Aken
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth 6009, Australia
| | - Kris Morreel
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Korneel Vandenbroucke
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Brigitte van de Cotte
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Inge De Clercq
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Sheila Chiwocha
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth 6009, Australia
| | - Ricarda Fenske
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth 6009, Australia
| | - Els Prinsen
- Departement Biologie, Universiteit Antwerpen, 2020 Antwerpen, Belgium
| | - Wout Boerjan
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Bernard Genty
- Centre d'Etudes Atomiques, Centre National de la Recherche Scientifique, Université Aix-Marseille, Unité Mixte de Recherche 6191 Biologie Végétale et Microbiologie Environnementale, Laboratoire d'Ecophysiologie Moléculaire des Plantes, 13108 Saint Paul lez Durance, France
| | - Keith A. Stubbs
- School of Biomedical, Biomolecular, and Chemical Sciences, University of Western Australia, Perth 6009, Australia
| | - Dirk Inzé
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
| | - Frank Van Breusegem
- Department of Plant Systems Biology, VIB, Ghent University, 9052 Gent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium
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53
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Strader LC, Culler AH, Cohen JD, Bartel B. Conversion of endogenous indole-3-butyric acid to indole-3-acetic acid drives cell expansion in Arabidopsis seedlings. PLANT PHYSIOLOGY 2010; 153:1577-86. [PMID: 20562230 PMCID: PMC2923913 DOI: 10.1104/pp.110.157461] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 06/17/2010] [Indexed: 05/18/2023]
Abstract
Genetic evidence in Arabidopsis (Arabidopsis thaliana) suggests that the auxin precursor indole-3-butyric acid (IBA) is converted into active indole-3-acetic acid (IAA) by peroxisomal beta-oxidation; however, direct evidence that Arabidopsis converts IBA to IAA is lacking, and the role of IBA-derived IAA is not well understood. In this work, we directly demonstrated that Arabidopsis seedlings convert IBA to IAA. Moreover, we found that several IBA-resistant, IAA-sensitive mutants were deficient in IBA-to-IAA conversion, including the indole-3-butyric acid response1 (ibr1) ibr3 ibr10 triple mutant, which is defective in three enzymes likely to be directly involved in peroxisomal IBA beta-oxidation. In addition to IBA-to-IAA conversion defects, the ibr1 ibr3 ibr10 triple mutant displayed shorter root hairs and smaller cotyledons than wild type; these cell expansion defects are suggestive of low IAA levels in certain tissues. Consistent with this possibility, we could rescue the ibr1 ibr3 ibr10 short-root-hair phenotype with exogenous auxin. A triple mutant defective in hydrolysis of IAA-amino acid conjugates, a second class of IAA precursor, displayed reduced hypocotyl elongation but normal cotyledon size and only slightly reduced root hair lengths. Our data suggest that IBA beta-oxidation and IAA-amino acid conjugate hydrolysis provide auxin for partially distinct developmental processes and that IBA-derived IAA plays a major role in driving root hair and cotyledon cell expansion during seedling development.
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54
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Abstract
A plant's roots system determines both the capacity of a sessile organism to acquire nutrients and water, as well as providing a means to monitor the soil for a range of environmental conditions. Since auxins were first described, there has been a tight connection between this class of hormones and root development. Here we review some of the latest genetic, molecular, and cellular experiments that demonstrate the importance of generating and maintaining auxin gradients during root development. Refinements in the ability to monitor and measure auxin levels in root cells coupled with advances in our understanding of the sources of auxin that contribute to these pools represent important contributions to our understanding of how this class of hormones participates in the control of root development. In addition, we review the role of identified molecular components that convert auxin gradients into local differentiation events, which ultimately defines the root architecture.
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Affiliation(s)
- Paul Overvoorde
- Department of Biology, Macalester College, St. Paul, MN 55105, USA
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55
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Babujee L, Wurtz V, Ma C, Lueder F, Soni P, van Dorsselaer A, Reumann S. The proteome map of spinach leaf peroxisomes indicates partial compartmentalization of phylloquinone (vitamin K1) biosynthesis in plant peroxisomes. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1441-53. [PMID: 20150517 DOI: 10.1093/jxb/erq014] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Leaf peroxisomes are fragile, low-abundance plant cell organelles that are difficult to isolate from one of the few plant species whose nuclear genome has been sequenced. Leaf peroxisomes were enriched at high purity from spinach (Spinacia oleracea) and approximately 100 protein spots identified from 2-dimensional gels by a combination of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and de novo sequencing. In addition to the predominant enzymes involved in photorespiration and detoxification, several minor enzymes were detected, underscoring the high sensitivity of the protein identification. The tryptic peptides of three unknown proteins shared high sequence similarity with Arabidopsis proteins that carry putative peroxisomal targeting signals type 1 or 2 (PTS1/2). The apparent Arabidopsis orthologues are a short-chain alcohol dehydrogenase (SDRa/IBR1, At4g05530, SRL>) and two enoyl-CoA hydratases/isomerases (ECHIa, At4g16210, SKL>; NS/ECHId, At1g60550, RLx(5)HL). The peroxisomal localization of the three proteins was confirmed in vivo by tagging with enhanced yellow fluorescent protein (EYFP), and the targeting signals were identified. The single Arabidopsis isoform of naphthoate synthase (NS) is orthologous to MenB from cyanobacteria, which catalyses an essential reaction in phylloquinone biosynthesis, a pathway previously assumed to be entirely compartmentalized in plastids in higher plants. In an extension of a previous study, the present in vivo targeting data furthermore demonstrate that the enzyme upstream of NS, chloroplastic acyl-CoA activating enzyme isoform 14 (AAE14, SSL>), is dually targeted to both plastids and peroxisomes. This proteomic study, extended by in vivo subcellular localization analyses, indicates a novel function for plant peroxisomes in phylloquinone biosynthesis.
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Affiliation(s)
- Lavanya Babujee
- Georg-August-University of Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, D-37077 Goettingen, Germany
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56
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Kaur N, Reumann S, Hu J. Peroxisome biogenesis and function. THE ARABIDOPSIS BOOK 2009; 7:e0123. [PMID: 22303249 PMCID: PMC3243405 DOI: 10.1199/tab.0123] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Peroxisomes are small and single membrane-delimited organelles that execute numerous metabolic reactions and have pivotal roles in plant growth and development. In recent years, forward and reverse genetic studies along with biochemical and cell biological analyses in Arabidopsis have enabled researchers to identify many peroxisome proteins and elucidate their functions. This review focuses on the advances in our understanding of peroxisome biogenesis and metabolism, and further explores the contribution of large-scale analysis, such as in sillco predictions and proteomics, in augmenting our knowledge of peroxisome function In Arabidopsis.
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Affiliation(s)
| | - Sigrun Reumann
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, N-4036 Stavanger, Norway
| | - Jianping Hu
- MSU-DOE Plant Research Laboratory and
- Plant Biology Department, Michigan State University, East Lansing, MI 48824
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57
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Zheng Y, Ren N, Wang H, Stromberg AJ, Perry SE. Global identification of targets of the Arabidopsis MADS domain protein AGAMOUS-Like15. THE PLANT CELL 2009; 21:2563-77. [PMID: 19767455 PMCID: PMC2768919 DOI: 10.1105/tpc.109.068890] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 08/06/2009] [Accepted: 08/23/2009] [Indexed: 05/18/2023]
Abstract
AGAMOUS-Like15 (AGL15) is a MADS domain transcriptional regulator that promotes somatic embryogenesis by binding DNA and regulating gene expression. Chromatin immunoprecipitation (ChIP) analysis previously identified DNA fragments with which AGL15 associates in vivo, and a low-throughput approach revealed a role for AGL15 in gibberellic acid catabolism that is relevant to embryogenesis. However, higher throughput methods are needed to identify targets of AGL15. Here, we mapped AGL15 in vivo binding sites using a ChIP-chip approach and the Affymetrix tiling arrays for Arabidopsis thaliana and found that approximately 2000 sites represented in three biological replicates of the experiment are annotated to nearby genes. These results were combined with high-throughput measurement of gene expression in response to AGL15 accumulation to discriminate responsive direct targets from those further downstream in the network. LEAFY COTYLEDON2, FUSCA3, and ABA INSENSITIVE3, which encode B3 domain transcription factors that are key regulators of embryogenesis, were identified and verified as direct target genes of AGL15. Genes identified as targets of the B3 genes are also targets of AGL15, and we found that INDOLEACETIC ACID-INDUCED PROTEIN30 is involved in promotion of somatic embryo development. The data presented here and elsewhere suggest that much cross-regulation occurs in gene regulatory networks underpinning embryogenesis.
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Affiliation(s)
- Yumei Zheng
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546-0312
| | - Na Ren
- Department of Statistics, University of Kentucky, Lexington, Kentucky 40506-0027
| | - Huai Wang
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546-0312
| | - Arnold J. Stromberg
- Department of Statistics, University of Kentucky, Lexington, Kentucky 40506-0027
| | - Sharyn E. Perry
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546-0312
- Address correspondence to
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58
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Strader LC, Bartel B. The Arabidopsis PLEIOTROPIC DRUG RESISTANCE8/ABCG36 ATP binding cassette transporter modulates sensitivity to the auxin precursor indole-3-butyric acid. THE PLANT CELL 2009; 21:1992-2007. [PMID: 19648296 PMCID: PMC2729616 DOI: 10.1105/tpc.109.065821] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 06/27/2009] [Accepted: 07/14/2009] [Indexed: 05/18/2023]
Abstract
Plants have developed numerous mechanisms to store hormones in inactive but readily available states, enabling rapid responses to environmental changes. The phytohormone auxin has a number of storage precursors, including indole-3-butyric acid (IBA), which is apparently shortened to active indole-3-acetic acid (IAA) in peroxisomes by a process similar to fatty acid beta-oxidation. Whereas metabolism of auxin precursors is beginning to be understood, the biological significance of the various precursors is virtually unknown. We identified an Arabidopsis thaliana mutant that specifically restores IBA, but not IAA, responsiveness to auxin signaling mutants. This mutant is defective in PLEIOTROPIC DRUG RESISTANCE8 (PDR8)/PENETRATION3/ABCG36, a plasma membrane-localized ATP binding cassette transporter that has established roles in pathogen responses and cadmium transport. We found that pdr8 mutants display defects in efflux of the auxin precursor IBA and developmental defects in root hair and cotyledon expansion that reveal previously unknown roles for IBA-derived IAA in plant growth and development. Our results are consistent with the possibility that limiting accumulation of the IAA precursor IBA via PDR8-promoted efflux contributes to auxin homeostasis.
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Affiliation(s)
- Lucia C Strader
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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59
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Wiszniewski AAG, Zhou W, Smith SM, Bussell JD. Identification of two Arabidopsis genes encoding a peroxisomal oxidoreductase-like protein and an acyl-CoA synthetase-like protein that are required for responses to pro-auxins. PLANT MOLECULAR BIOLOGY 2009; 69:503-15. [PMID: 19043666 DOI: 10.1007/s11103-008-9431-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Accepted: 11/08/2008] [Indexed: 05/09/2023]
Abstract
Indole-3-butyric acid (IBA) and 2,4-dichlorophenoxybutyric acid (2,4-DB) are metabolised by peroxisomal beta-oxidation to active auxins that inhibit root growth. We screened Arabidopsis mutants for resistance to IBA and 2,4-DB and identified two new 2,4-DB resistant mutants. The mutant genes encode a putative oxidoreductase (SDRa) and a putative acyl-activating enzyme (AAE18). Both proteins are localised to peroxisomes. SDRa is coexpressed with core beta-oxidation genes, but germination, seedling growth and the fatty acid profile of sdra seedlings are indistinguishable from wild type. The sdra mutant is also resistant to IBA, but aae18 is not. AAE18 is the first example of a gene required for response to 2,4-DB but not IBA. The closest relative of AAE18 is AAE17. AAE17 is predicted to be peroxisomal, but an aae17 aae18 double mutant responded similarly to aae18 for all assays. We propose that AAE18 is capable of activating 2,4-DB but IBA activating enzymes remain to be discovered. We present an updated model for peroxisomal pro-auxin metabolism in Arabidopsis that includes SDRa and AAE18.
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60
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Kiel JAKW, van den Berg MA, Fusetti F, Poolman B, Bovenberg RAL, Veenhuis M, van der Klei IJ. Matching the proteome to the genome: the microbody of penicillin-producing Penicillium chrysogenum cells. Funct Integr Genomics 2009; 9:167-84. [PMID: 19156454 DOI: 10.1007/s10142-009-0110-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 01/05/2009] [Accepted: 01/05/2009] [Indexed: 10/21/2022]
Abstract
In the filamentous fungus Penicillium chrysogenum, microbodies are essential for penicillin biosynthesis. To better understand the role of these organelles in antibiotics production, we determined the matrix enzyme contents of P. chrysogenum microbodies. Using a novel in silico approach, we first obtained a catalogue of 200 P. chrysogenum proteins with putative microbody targeting signals (PTSs). This included two orthologs of proteins involved in cephalosporin biosynthesis, which we demonstrate to be bona fide microbody matrix constituents. Subsequently, we performed a proteomics based inventory of P. chrysogenum microbody matrix proteins using nano-LC-MS/MS analysis. We identified 89 microbody proteins, 79 with a PTS, including the two known microbody-borne penicillin biosynthesis enzymes, isopenicillin N:acyl CoA acyltransferase and phenylacetyl-CoA ligase. Comparative analysis revealed that 69 out of 79 PTS proteins identified experimentally were in the reference list. A prominent microbody protein was identified as a novel fumarate reductase-cytochrome b5 fusion protein, which contains an internal PTS2 between the two functional domains. We show that this protein indeed localizes to P. chrysogenum microbodies.
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Affiliation(s)
- Jan A K W Kiel
- Molecular Cell Biology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, AA Haren, The Netherlands.
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61
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Abstract
Auxin controls numerous plant growth processes by directing cell division and expansion. Auxin-response mutants, including iba response5 (ibr5), exhibit a long root and decreased lateral root production in response to exogenous auxins. ibr5 also displays resistance to the phytohormone abscisic acid (ABA). We found that the sar3 suppressor of auxin resistant1 (axr1) mutant does not suppress ibr5 auxin-response defects, suggesting that screening for ibr5 suppressors might reveal new components important for phytohormone responsiveness. We identified two classes of Arabidopsis thaliana mutants that suppressed ibr5 resistance to indole-3-butyric acid (IBA): those with restored responses to both the auxin precursor IBA and the active auxin indole-3-acetic acid (IAA) and those with restored response to IBA but not IAA. Restored IAA sensitivity was accompanied by restored ABA responsiveness, whereas suppressors that remained IAA resistant also remained ABA resistant. Some suppressors restored sensitivity to both natural and synthetic auxins; others restored responsiveness only to auxin precursors. We used positional information to determine that one ibr5 suppressor carried a mutation in PLEIOTROPIC DRUG RESISTANCE9 (PDR9/ABCG37/At3g53480), which encodes an ATP-binding cassette transporter previously implicated in cellular efflux of the synthetic auxin 2,4-dichlorophenoxyacetic acid.
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62
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Zolman BK, Martinez N, Millius A, Adham AR, Bartel B. Identification and characterization of Arabidopsis indole-3-butyric acid response mutants defective in novel peroxisomal enzymes. Genetics 2008; 180:237-51. [PMID: 18725356 PMCID: PMC2535678 DOI: 10.1534/genetics.108.090399] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Accepted: 07/08/2008] [Indexed: 01/04/2023] Open
Abstract
Genetic evidence suggests that indole-3-butyric acid (IBA) is converted to the active auxin indole-3-acetic acid (IAA) by removal of two side-chain methylene units in a process similar to fatty acid beta-oxidation. Previous studies implicate peroxisomes as the site of IBA metabolism, although the enzymes that act in this process are still being identified. Here, we describe two IBA-response mutants, ibr1 and ibr10. Like the previously described ibr3 mutant, which disrupts a putative peroxisomal acyl-CoA oxidase/dehydrogenase, ibr1 and ibr10 display normal IAA responses and defective IBA responses. These defects include reduced root elongation inhibition, decreased lateral root initiation, and reduced IBA-responsive gene expression. However, peroxisomal energy-generating pathways necessary during early seedling development are unaffected in the mutants. Positional cloning of the genes responsible for the mutant defects reveals that IBR1 encodes a member of the short-chain dehydrogenase/reductase family and that IBR10 resembles enoyl-CoA hydratases/isomerases. Both enzymes contain C-terminal peroxisomal-targeting signals, consistent with IBA metabolism occurring in peroxisomes. We present a model in which IBR3, IBR10, and IBR1 may act sequentially in peroxisomal IBA beta-oxidation to IAA.
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Affiliation(s)
- Bethany K Zolman
- Department of Biology, University of Missouri, St. Louis, Missouri 63121, USA.
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63
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Arent S, Pye VE, Henriksen A. Structure and function of plant acyl-CoA oxidases. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2008; 46:292-301. [PMID: 18272379 DOI: 10.1016/j.plaphy.2007.12.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Indexed: 05/08/2023]
Abstract
Acyl-CoA oxidases (in peroxisomes) and acyl-CoA dehydrogenases (in mitochondria) catalyse the first step in fatty acid beta-oxidation, the pathway responsible for lipid catabolism and plant hormone biosynthesis. The interplay and differences between peroxisomal and mitochondrial beta-oxidation processes are highlighted by the variation in the enzymes involved. Structure and sequence comparisons are made with a focus on the enzyme's mechanistic means to control electron transfer paths, reactivity towards molecular oxygen, and spatial and architectural requirements for substrate discrimination.
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Affiliation(s)
- Susan Arent
- Biostructure Group, Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby, Denmark
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64
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Reumann S, Babujee L, Ma C, Wienkoop S, Siemsen T, Antonicelli GE, Rasche N, Lüder F, Weckwerth W, Jahn O. Proteome analysis of Arabidopsis leaf peroxisomes reveals novel targeting peptides, metabolic pathways, and defense mechanisms. THE PLANT CELL 2007; 19:3170-93. [PMID: 17951448 PMCID: PMC2174697 DOI: 10.1105/tpc.107.050989] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Revised: 09/12/2007] [Accepted: 09/24/2007] [Indexed: 05/18/2023]
Abstract
We have established a protocol for the isolation of highly purified peroxisomes from mature Arabidopsis thaliana leaves and analyzed the proteome by complementary gel-based and gel-free approaches. Seventy-eight nonredundant proteins were identified, of which 42 novel proteins had previously not been associated with plant peroxisomes. Seventeen novel proteins carried predicted peroxisomal targeting signals (PTS) type 1 or type 2; 11 proteins contained PTS-related peptides. Peroxisome targeting was supported for many novel proteins by in silico analyses and confirmed for 11 representative full-length fusion proteins by fluorescence microscopy. The targeting function of predicted and unpredicted signals was investigated and SSL>, SSI>, and ASL> were established as novel functional PTS1 peptides. In contrast with the generally accepted confinement of PTS2 peptides to the N-terminal domain, the bifunctional transthyretin-like protein was demonstrated to carry internally a functional PTS2. The novel enzymes include numerous enoyl-CoA hydratases, short-chain dehydrogenases, and several enzymes involved in NADP and glutathione metabolism. Seven proteins, including beta-glucosidases and myrosinases, support the currently emerging evidence for an important role of leaf peroxisomes in defense against pathogens and herbivores. The data provide new insights into the biology of plant peroxisomes and improve the prediction accuracy of peroxisome-targeted proteins from genome sequences.
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Affiliation(s)
- Sigrun Reumann
- Department of Plant Biochemistry, Georg-August-University of Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, D-37077 Goettingen, Germany.
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65
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Woodward AW, Ratzel SE, Woodward EE, Shamoo Y, Bartel B. Mutation of E1-CONJUGATING ENZYME-RELATED1 decreases RELATED TO UBIQUITIN conjugation and alters auxin response and development. PLANT PHYSIOLOGY 2007; 144:976-87. [PMID: 17449645 PMCID: PMC1914210 DOI: 10.1104/pp.107.100404] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The ubiquitin-like protein RELATED TO UBIQUITIN (RUB) is conjugated to CULLIN (CUL) proteins to modulate the activity of Skp1-Cullin-F-box (SCF) ubiquitylation complexes. RUB conjugation to specific target proteins is necessary for the development of many organisms, including Arabidopsis (Arabidopsis thaliana). Here, we report the isolation and characterization of e1-conjugating enzyme-related1-1 (ecr1-1), an Arabidopsis mutant compromised in RUB conjugation. The ecr1-1 mutation causes a missense change located two amino acid residues from the catalytic site cysteine, which normally functions to form a thioester bond with activated RUB. A higher ratio of unmodified CUL1 relative to CUL1-RUB is present in ecr1-1 compared to wild type, suggesting that the mutation reduces ECR1 function. The ecr1-1 mutant is resistant to the auxin-like compound indole-3-propionic acid, produces fewer lateral roots than wild type, displays reduced adult height, and stabilizes a reporter fusion protein that is degraded in response to auxin, suggesting reduced auxin signaling in the mutant. In addition, ecr1-1 hypocotyls fail to elongate normally when seedlings are grown in darkness, a phenotype shared with certain other RUB conjugation mutants that is not general to auxin-response mutants. The suite of ecr1-1 molecular and morphological phenotypes reflects roles for RUB conjugation in many aspects of plant growth and development. Certain ecr1-1 elongation defects are restored by treatment with the ethylene-response inhibitor silver nitrate, suggesting that the short ecr1-1 root and hypocotyl result from aberrant ethylene accumulation. Further, silver nitrate supplementation in combination with various auxins and auxin-like compounds reveals that members of this growth regulator family may differentially rely on ethylene signaling to inhibit root growth.
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Affiliation(s)
- Andrew W Woodward
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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