1
|
Jarvis RP, Li J, Lin R, Ling Q, Lyu Y, Sun Y, Yao Z. Reply: Does the polyubiquitination pathway operate inside intact chloroplasts to remove proteins? THE PLANT CELL 2024; 36:2990-2996. [PMID: 38738499 PMCID: PMC11371133 DOI: 10.1093/plcell/koae105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/19/2024] [Indexed: 05/14/2024]
Affiliation(s)
- R Paul Jarvis
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Jialong Li
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Rongcheng Lin
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Qihua Ling
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- CAS-JIC Center of Excellence for Plant and Microbial Sciences (CEPAMS), Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yuping Lyu
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yi Sun
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Zujie Yao
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| |
Collapse
|
2
|
Santana I, Jeon SJ, Kim HI, Islam MR, Castillo C, Garcia GFH, Newkirk GM, Giraldo JP. Targeted Carbon Nanostructures for Chemical and Gene Delivery to Plant Chloroplasts. ACS NANO 2022; 16:12156-12173. [PMID: 35943045 DOI: 10.1021/acsnano.2c02714] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Nanotechnology approaches for improving the delivery efficiency of chemicals and molecular cargoes in plants through plant biorecognition mechanisms remain relatively unexplored. We developed targeted carbon-based nanomaterials as tools for precise chemical delivery (carbon dots, CDs) and gene delivery platforms (single-walled carbon nanotubes, SWCNTs) to chloroplasts, key organelles involved in efforts to improve plant photosynthesis, assimilation of nutrients, and delivery of agrochemicals. A biorecognition approach of coating the nanomaterials with a rationally designed chloroplast targeting peptide improved the delivery of CDs with molecular baskets (TP-β-CD) for delivery of agrochemicals and of plasmid DNA coated SWCNT (TP-pATV1-SWCNT) from 47% to 70% and from 39% to 57% of chloroplasts in leaves, respectively. Plants treated with TP-β-CD (20 mg/L) and TP-pATV1-SWCNT (2 mg/L) had a low percentage of dead cells, 6% and 8%, respectively, similar to controls without nanoparticles, and no permanent cell and chloroplast membrane damage after 5 days of exposure. However, targeted nanomaterials transiently increased leaf H2O2 (0.3225 μmol gFW-1) above control plant levels (0.03441 μmol gFW-1) but within the normal range reported in land plants. The increase in leaf H2O2 levels was associated with oxidative damage in whole plant cell DNA, a transient effect on chloroplast DNA, and a decrease in leaf chlorophyll content (-17%) and carbon assimilation rates at saturation light levels (-32%) with no impact on photosystem II quantum yield. This work provides targeted delivery approaches for carbon-based nanomaterials mediated by biorecognition and a comprehensive understanding of their impact on plant cell and molecular biology for engineering safer and efficient agrochemical and biomolecule delivery tools.
Collapse
Affiliation(s)
- Israel Santana
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Su-Ji Jeon
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Hye-In Kim
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Md Reyazul Islam
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Christopher Castillo
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Gail F H Garcia
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| | - Gregory M Newkirk
- Department of Microbiology and Plant Pathology, University of California-Riverside, Riverside, California 92521, United States
| | - Juan Pablo Giraldo
- Department of Botany and Plant Sciences, University of California-Riverside, Riverside, California 92521, United States
| |
Collapse
|
3
|
Dissecting the Chloroplast Proteome of the Potato (Solanum Tuberosum L.) and Its Comparison with the Tuber Amyloplast Proteome. PLANTS 2022; 11:plants11151915. [PMID: 35893618 PMCID: PMC9332351 DOI: 10.3390/plants11151915] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/02/2022] [Accepted: 07/20/2022] [Indexed: 11/17/2022]
Abstract
The chloroplast, the energy organelle unique to plants and green algae, performs many functions, including photosynthesis and biosynthesis of metabolites. However, as the most critical tuber crop worldwide, the chloroplast proteome of potato (Solanum tuberosum) has not been explored. Here, we use Percoll density gradient centrifugation to isolate intact chloroplasts from leaves of potato cultivar E3 and establish a reference proteome map of potato chloroplast by bottom-up proteomics. A total of 1834 non-redundant proteins were identified in the chloroplast proteome, including 51 proteins encoded by the chloroplast genome. Extensive sequence-based localization prediction revealed over 62% of proteins to be chloroplast resident by at least one algorithm. Sixteen proteins were selected to evaluate the prediction result by transient fluorescence assay, which confirmed that 14 were distributed in distinct internal compartments of the chloroplast. In addition, we identified 136 phosphorylation sites in 61 proteins encoded by chloroplast proteome. Furthermore, we reconstruct the snapshots along starch metabolic pathways in the two different types of plastids by a comparative analysis between chloroplast and previously reported amyloplast proteomes. Altogether, our results establish a comprehensive proteome map with post-translationally modified sites of potato chloroplast, which would provide the theoretical principle for the research of the photosynthesis pathway and starch metabolism.
Collapse
|
4
|
Chin-Fatt A, Menassa R. A V HH-Fc Fusion Targeted to the Chloroplast Thylakoid Lumen Assembles and Neutralizes Enterohemorrhagic E. coli O157:H7. FRONTIERS IN PLANT SCIENCE 2021; 12:686421. [PMID: 34122494 PMCID: PMC8193579 DOI: 10.3389/fpls.2021.686421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
Chimeric fusion proteins comprising a single domain antibody (VHH) fused to a crystallizable fragment (Fc) of an immunoglobulin are modular glycoproteins that are becoming increasingly in demand because of their value as diagnostics, research reagents and passive immunization therapeutics. Because ER-associated degradation and misfolding may potentially be limiting factors in the oxidative folding of VHH-Fc fusion proteins in the ER, we sought to explore oxidative folding in an alternative sub-compartment, the chloroplast thylakoid lumen, and determine its viability in a molecular farming context. We developed a set of in-house expression vectors for transient transformation of Nicotiana benthamiana leaves that target a VHH-Fc to the thylakoid lumen via either secretory (Sec) or twin-arginine translocation (Tat) import pathways. Compared to stromal [6.63 ± 3.41 mg/kg fresh weight (FW)], cytoplasmic (undetectable) and Tat-import pathways (5.43 ± 2.41 mg/kg FW), the Sec-targeted VHH-Fc showed superior accumulation (30.56 ± 5.19 mg/kg FW), but was less than that of the ER (51.16 ± 9.11 mg/kg FW). Additionally, the introduction of a rationally designed de novo disulfide bond enhances in planta accumulation when introduced into the Sec-targeted Fc fusion protein from 50.24 ± 4.08 mg/kg FW to 110.90 ± 6.46 mg/kg FW. In vitro immunofluorescent labeling assays on VHH-Fc purified from Sec, Tat, and stromal pathways demonstrate that the antibody still retains VHH functionality in binding Escherichia coli O157:H7 and neutralizing its intimate adherence to human epithelial type 2 cells. These results overall provide a proof of concept that the oxidative folding environment of the thylakoid lumen may be a viable compartment for stably folding disulfide-containing recombinant VHH-Fc proteins.
Collapse
Affiliation(s)
- Adam Chin-Fatt
- Agriculture and Agri-Food Canada, London Research and Development Centre, London, ON, Canada
- Department of Biology, University of Western Ontario, London, ON, Canada
| | - Rima Menassa
- Agriculture and Agri-Food Canada, London Research and Development Centre, London, ON, Canada
- Department of Biology, University of Western Ontario, London, ON, Canada
| |
Collapse
|
5
|
Isolation of Intact Chloroplast for Sequencing Plastid Genomes of Five Festuca Species. PLANTS 2019; 8:plants8120606. [PMID: 31847311 PMCID: PMC6963596 DOI: 10.3390/plants8120606] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/08/2019] [Accepted: 12/12/2019] [Indexed: 12/02/2022]
Abstract
Isolation of good quality chloroplast DNA (cpDNA) is a challenge in different plant species, although several methods for isolation are known. Attempts were undertaken to isolate cpDNA from Festuca grass species by using available standard protocols; however, they failed due to difficulties separating intact chloroplasts from the polysaccharides, oleoresin, and contaminated nuclear DNA that are present in the crude homogenate. In this study, we present a quick and inexpensive protocol for isolating intact chloroplasts from seven grass varieties/accessions of five Festuca species using a single layer of 30% Percoll solution. This protocol was successful in isolating high quality cpDNA with the least amount of contamination of other DNA. We performed Illumina MiSeq paired-end sequencing (2 × 300 bp) using 200 ng of cpDNA of each variety/accession. Chloroplast genome mapping showed that 0.28%–11.37% were chloroplast reads, which covered 94%–96% of the reference plastid genomes of the closely related grass species. This improved method delivered high quality cpDNA from seven grass varieties/accessions of five Festuca species and could be useful for other grass species with similar genome complexity.
Collapse
|
6
|
Kwasnik A, Wang VYF, Krzyszton M, Gozdek A, Zakrzewska-Placzek M, Stepniak K, Poznanski J, Tong L, Kufel J. Arabidopsis DXO1 links RNA turnover and chloroplast function independently of its enzymatic activity. Nucleic Acids Res 2019; 47:4751-4764. [PMID: 30949699 PMCID: PMC6511851 DOI: 10.1093/nar/gkz100] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 02/01/2019] [Accepted: 02/07/2019] [Indexed: 01/07/2023] Open
Abstract
The DXO family of proteins participates in eukaryotic mRNA 5'-end quality control, removal of non-canonical NAD+ cap and maturation of fungal rRNA precursors. In this work, we characterize the Arabidopsis thaliana DXO homolog, DXO1. We demonstrate that the plant-specific modification within the active site negatively affects 5'-end capping surveillance properties of DXO1, but has only a minor impact on its strong deNADding activity. Unexpectedly, catalytic activity does not contribute to striking morphological and molecular aberrations observed upon DXO1 knockout in plants, which include growth and pigmentation deficiency, global transcriptomic changes and accumulation of RNA quality control siRNAs. Conversely, these phenotypes depend on the plant-specific N-terminal extension of DXO1. Pale-green coloration of DXO1-deficient plants and our RNA-seq data reveal that DXO1 affects chloroplast-localized processes. We propose that DXO1 mediates the connection between RNA turnover and retrograde chloroplast-to-nucleus signaling independently of its deNADding properties.
Collapse
Affiliation(s)
- Aleksandra Kwasnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland,Correspondence may also be addressed to Aleksandra Kwasnik. Tel: +48 22 5922245; Fax: +48 22 6584176;
| | - Vivien Ya-Fan Wang
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Michal Krzyszton
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Agnieszka Gozdek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Monika Zakrzewska-Placzek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Karolina Stepniak
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Jaroslaw Poznanski
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA,Correspondence may also be addressed to Liang Tong. Tel: +1 212 854 5203; Fax: +1 212 865 8246;
| | - Joanna Kufel
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland,To whom correspondence should be addressed. Tel: +48 22 5922245; Fax: +48 22 6584176;
| |
Collapse
|
7
|
Megias E, do Carmo LST, Nicolini C, Silva LP, Blawid R, Nagata T, Mehta A. Chloroplast Proteome of Nicotiana benthamiana Infected by Tomato Blistering Mosaic Virus. Protein J 2018; 37:290-299. [PMID: 29802510 DOI: 10.1007/s10930-018-9775-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Tymovirus is a genus of plant pathogenic viruses that infects several dicotyledonous plants worldwide, causing serious diseases in economically important crops. The known cytopathic effect on the host cell organelles involves chloroplast membrane deformation and the induction of vesicles in its periphery. These vesicles are known to be the location where tymoviral genomic RNA replication occurs. Tomato blistering mosaic virus (ToBMV) is a tymovirus recently identified in tomato plants in Brazil, which is able to infect several other plants, including tobacco. In this work, we investigated the chloroplast proteomic profile of ToBMV-infected N. benthamiana using bidimensional electrophoresis (2-DE) and mass spectrometry, aiming to study the virus-host interaction related to the virus replication and infection. A total of approximately 200 spots were resolved, out of which 36 were differentially abundant. Differential spots were identified by mass spectrometry including photosynthesis-related and defense proteins. We identified proteins that may be targets of a direct interaction with viral proteins, such as ATP synthase β subunit, RNA polymerase beta-subunit, 50S ribosomal protein L6 and Trigger factor-like protein. The identification of these candidate proteins gives support for future protein-protein interaction studies to confirm their roles in virus replication and disease development.
Collapse
Affiliation(s)
- Esau Megias
- Embrapa Recursos Genéticos e Biotecnologia, Av. W5 Norte final, Brasília, DF, 70770-917, Brazil
| | | | | | - Luciano Paulino Silva
- Embrapa Recursos Genéticos e Biotecnologia, Av. W5 Norte final, Brasília, DF, 70770-917, Brazil
| | - Rosana Blawid
- Departamento de Biologia Celular, Instituto de Biologia, Universidade de Brasília, Brasília, DF, Brazil
| | - Tatsuya Nagata
- Departamento de Biologia Celular, Instituto de Biologia, Universidade de Brasília, Brasília, DF, Brazil
| | - Angela Mehta
- Embrapa Recursos Genéticos e Biotecnologia, Av. W5 Norte final, Brasília, DF, 70770-917, Brazil.
| |
Collapse
|
8
|
Lenarčič T, Albert I, Böhm H, Hodnik V, Pirc K, Zavec AB, Podobnik M, Pahovnik D, Žagar E, Pruitt R, Greimel P, Yamaji-Hasegawa A, Kobayashi T, Zienkiewicz A, Gömann J, Mortimer JC, Fang L, Mamode-Cassim A, Deleu M, Lins L, Oecking C, Feussner I, Mongrand S, Anderluh G, Nürnberger T. Eudicot plant-specific sphingolipids determine host selectivity of microbial NLP cytolysins. Science 2018; 358:1431-1434. [PMID: 29242345 DOI: 10.1126/science.aan6874] [Citation(s) in RCA: 124] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 10/31/2017] [Indexed: 01/05/2023]
Abstract
Necrosis and ethylene-inducing peptide 1-like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity.
Collapse
Affiliation(s)
- Tea Lenarčič
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Isabell Albert
- Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Hannah Böhm
- Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Vesna Hodnik
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
| | - Katja Pirc
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Apolonija B Zavec
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Marjetka Podobnik
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - David Pahovnik
- Department of Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Ema Žagar
- Department of Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Rory Pruitt
- Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Peter Greimel
- Lipid Biology Laboratory, RIKEN, Wako Saitama 351-0198, Japan.,Laboratory for Cell Function Dynamics, Brain Science Institute, RIKEN Institute, Wako, Saitama 351-0198, Japan
| | - Akiko Yamaji-Hasegawa
- Lipid Biology Laboratory, RIKEN, Wako Saitama 351-0198, Japan.,Molecular Membrane Neuroscience, Brain Science Institute, RIKEN Institute, Wako, Saitama 351-0198, Japan
| | - Toshihide Kobayashi
- Lipid Biology Laboratory, RIKEN, Wako Saitama 351-0198, Japan.,UMR 7213 CNRS, University of Strasbourg, 67401 Illkirch, France
| | - Agnieszka Zienkiewicz
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Germany.,Göttingen Center for Molecular Biosciences, University of Göttingen, Germany
| | - Jasmin Gömann
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Germany.,Göttingen Center for Molecular Biosciences, University of Göttingen, Germany
| | - Jenny C Mortimer
- Joint Bioenergy Institute, Emeryville, CA 94608, USA.,Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Lin Fang
- Joint Bioenergy Institute, Emeryville, CA 94608, USA.,Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Adiilah Mamode-Cassim
- Laboratoire de Biogenèse Membranaire, UMR 5200 CNRS-Université de Bordeaux, 71 Avenue Edouard Bourlaux, 33883 Villenave-d'Ornon Cedex, France
| | - Magali Deleu
- Laboratory of Molecular Biophysics at Interfaces, University of Liège, Gembloux, Belgium
| | - Laurence Lins
- Laboratory of Molecular Biophysics at Interfaces, University of Liège, Gembloux, Belgium
| | - Claudia Oecking
- Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Ivo Feussner
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Germany.,Göttingen Center for Molecular Biosciences, University of Göttingen, Germany
| | - Sébastien Mongrand
- Laboratoire de Biogenèse Membranaire, UMR 5200 CNRS-Université de Bordeaux, 71 Avenue Edouard Bourlaux, 33883 Villenave-d'Ornon Cedex, France
| | - Gregor Anderluh
- Department for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
| | - Thorsten Nürnberger
- Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany.
| |
Collapse
|
9
|
Ling Q, Jarvis P. Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants. J Vis Exp 2016. [PMID: 27842368 DOI: 10.3791/54717] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Chloroplasts are organelles with many vital roles in plants, which include not only photosynthesis but numerous other metabolic and signaling functions. Furthermore, chloroplasts are critical for plant responses to various abiotic stresses, such as salinity and osmotic stresses. A chloroplast may contain up to ~3,000 different proteins, some of which are encoded by its own genome. However, the majority of chloroplast proteins are encoded in the nucleus and synthesized in the cytosol, and these proteins need to be imported into the chloroplast through translocons at the chloroplast envelope membranes. Recent studies have shown that the chloroplast protein import can be actively regulated by stress. To biochemically investigate such regulation of protein import under stress conditions, we developed the method described here as a quick and straightforward procedure that can easily be achieved in any laboratory. In this method, plants are grown under normal conditions and then exposed to stress conditions in liquid culture. Plant material is collected, and chloroplasts are then released by homogenization. The crude homogenate is separated by density gradient centrifugation, enabling isolation of the intact chloroplasts. Chloroplast yield is assessed by counting, and chloroplast intactness is checked under a microscope. For the protein import assays, purified chloroplasts are incubated with 35S radiolabeled in vitro translated precursor proteins, and time-course experiments are conducted to enable comparisons of import rates between genotypes under stress conditions. We present data generated using this method which show that the rate of protein import into chloroplasts from a regulatory mutant is specifically altered under osmotic stress conditions.
Collapse
Affiliation(s)
- Qihua Ling
- Department of Plant Sciences, University of Oxford
| | - Paul Jarvis
- Department of Plant Sciences, University of Oxford;
| |
Collapse
|
10
|
Abstract
Chloroplasts are structurally complex organelles containing ~2000-3000 proteins. They are delimited by a double membrane system or envelope, have an inner aqueous compartment called the stroma, and possess a second internal membrane system called the thylakoids. Thus, determining the suborganellar location of a chloroplast protein is vital to understanding or verifying its function. One way in which protein localization can be addressed is through fractionation. Here we present two rapid and simple methods that may be applied sequentially on the same day: (a) The isolation of intact chloroplasts from Arabidopsis thaliana plants that may be used directly (e.g., for functional studies such as protein import analysis), or for further processing as follows; (b) separation of isolated chloroplasts into three suborganellar fractions (envelope membranes, a soluble fraction containing stromal proteins, and the thylakoids). These methods are routinely used in our laboratory, and they provide a good yield of isolated chloroplasts and suborganellar fractions that can be used for various downstream applications.
Collapse
|
11
|
Increased sensitivity of RT-PCR for Potato virus Y detection using RNA isolated by a procedure with differential centrifugation. J Virol Methods 2015. [DOI: 10.1016/j.jviromet.2015.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
12
|
Zhang H, Zhao X, Li J, Cai H, Deng XW, Li L. MicroRNA408 is critical for the HY5-SPL7 gene network that mediates the coordinated response to light and copper. THE PLANT CELL 2014; 26:4933-53. [PMID: 25516599 PMCID: PMC4311192 DOI: 10.1105/tpc.114.127340] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 11/06/2014] [Accepted: 11/26/2014] [Indexed: 05/18/2023]
Abstract
Light and copper are important environmental determinants of plant growth and development. Despite the wealth of knowledge on both light and copper signaling, the molecular mechanisms that integrate the two pathways remain poorly understood. Here, we use Arabidopsis thaliana to demonstrate an interaction between SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7) and ELONGATED HYPOCOTYL5 (HY5), which mediate copper and light signaling, respectively. Through whole-genome chromatin immunoprecipitation and RNA sequencing analyses, we elucidated the SPL7 regulon and compared it with that of HY5. We found that the two transcription factors coregulate many genes, including those involved in anthocyanin accumulation and photosynthesis. Moreover, SPL7 and HY5 act coordinately to transcriptionally regulate MIR408, which results in differential expression of microRNA408 (miR408) and its target genes in response to changing light and copper conditions. We demonstrate that this regulation is tied to copper allocation to the chloroplast and plastocyanin levels. Finally, we found that constitutively activated miR408 rescues the distinct developmental defects of the hy5, spl7, and hy5 spl7 mutants. These findings revealed the existence of crosstalk between light and copper, mediated by a HY5-SPL7 network. Furthermore, integration of transcriptional and posttranscriptional regulation is critical for governing proper metabolism and development in response to combined copper and light signaling.
Collapse
Affiliation(s)
- Huiyong Zhang
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China Department of Biology, University of Virginia, Charlottesville, Virginia 22904 College of Life Sciences, Henan Agricultural University, Zhengzhou 450002, China
| | - Xin Zhao
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| | - Jigang Li
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520 State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Huaqing Cai
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205
| | - Xing Wang Deng
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Lei Li
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China Department of Biology, University of Virginia, Charlottesville, Virginia 22904
| |
Collapse
|
13
|
Pengelly JJL, Förster B, von Caemmerer S, Badger MR, Price GD, Whitney SM. Transplastomic integration of a cyanobacterial bicarbonate transporter into tobacco chloroplasts. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3071-80. [PMID: 24965541 PMCID: PMC4071830 DOI: 10.1093/jxb/eru156] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Improving global yields of agricultural crops is a complex challenge with evidence indicating benefits in productivity are achieved by enhancing photosynthetic carbon assimilation. Towards improving rates of CO2 capture within leaf chloroplasts, this study shows the versatility of plastome transformation for expressing the Synechococcus PCC7002 BicA bicarbonate transporter within tobacco plastids. Fractionation of chloroplast membranes from transplastomic tob(BicA) lines showed that ~75% of the BicA localized to the thylakoid membranes and ~25% to the chloroplast envelope. BicA levels were highest in young emerging tob(BicA) leaves (0.12 μmol m(-2), ≈7mg m(-2)) accounting for ~0.1% (w/w) of the leaf protein. In these leaves, the molar amount of BicA was 16-fold lower than the abundant thylakoid photosystem II D1 protein (~1.9 μmol m(-2)) which was comparable to the 9:1 molar ratio of D1:BicA measured in air-grown Synechococcus PCC7002 cells. The BicA produced had no discernible effect on chloroplast ultrastructure, photosynthetic CO2-assimilation rates, carbon isotope discrimination, or growth of the tob(BicA) plants, implying that the bicarbonate transporter had little or no activity. These findings demonstrate the utility of plastome transformation for targeting bicarbonate transporter proteins into the chloroplast membranes without impeding growth or plastid ultrastructure. This study establishes the span of experimental measurements required to verify heterologous bicarbonate transporter function and location in chloroplasts and underscores the need for more detailed understanding of BicA structure and function to identify solutions for enabling its activation and operation in leaf chloroplasts.
Collapse
Affiliation(s)
- J J L Pengelly
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - B Förster
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - S von Caemmerer
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - M R Badger
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - G D Price
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - S M Whitney
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| |
Collapse
|
14
|
Vieira LDN, Faoro H, Fraga HPDF, Rogalski M, de Souza EM, de Oliveira Pedrosa F, Nodari RO, Guerra MP. An improved protocol for intact chloroplasts and cpDNA isolation in conifers. PLoS One 2014; 9:e84792. [PMID: 24392157 PMCID: PMC3879346 DOI: 10.1371/journal.pone.0084792] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 11/27/2013] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Performing chloroplast DNA (cpDNA) isolation is considered a major challenge among different plant groups, especially conifers. Isolating chloroplasts in conifers by such conventional methods as sucrose gradient and high salt has not been successful. So far, plastid genome sequencing protocols for conifer species have been based mainly on long-range PCR, which is known to be time-consuming and difficult to implement. METHODOLOGY/PRINCIPAL FINDINGS We developed a protocol for cpDNA isolation using three different conifer families: Araucaria angustifolia and Araucaria bidwilli (Araucariaceae), Podocarpus lambertii (Podocarpaceae) and Pinus patula (Pinaceae). The present protocol is based on high salt isolation buffer followed by saline Percoll gradient. Combining these two strategies allowed enhanced chloroplast isolation, along with decreased contamination caused by polysaccharides, polyphenols, proteins, and nuclear DNA in cpDNA. Microscopy images confirmed the presence of intact chloroplasts in high abundance. This method was applied to cpDNA isolation and subsequent sequencing by Illumina MiSeq (2×250 bp), using only 50 ng of cpDNA. Reference-guided chloroplast genome mapping showed that high average coverage was achieved for all evaluated species: 24.63 for A. angustifolia, 135.97 for A. bidwilli, 1196.10 for P. lambertii, and 64.68 for P. patula. CONCLUSION Results show that this improved protocol is suitable for enhanced quality and yield of chloroplasts and cpDNA isolation from conifers, providing a useful tool for studies that require isolated chloroplasts and/or whole cpDNA sequences.
Collapse
Affiliation(s)
- Leila do Nascimento Vieira
- Departamento de Fitotecnia, Programa de Pós Graduação em Recursos Genéticos Vegetais, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Helisson Faoro
- Departamento de Bioquímica e Biologia Molecular, Núcleo de Fixação Biológica de Nitrogênio, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
| | - Hugo Pacheco de Freitas Fraga
- Departamento de Fitotecnia, Programa de Pós Graduação em Recursos Genéticos Vegetais, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Marcelo Rogalski
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
| | - Emanuel Maltempi de Souza
- Departamento de Bioquímica e Biologia Molecular, Núcleo de Fixação Biológica de Nitrogênio, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
| | - Fábio de Oliveira Pedrosa
- Departamento de Bioquímica e Biologia Molecular, Núcleo de Fixação Biológica de Nitrogênio, Universidade Federal do Paraná, Curitiba, Paraná, Brazil
| | - Rubens Onofre Nodari
- Departamento de Fitotecnia, Programa de Pós Graduação em Recursos Genéticos Vegetais, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Miguel Pedro Guerra
- Departamento de Fitotecnia, Programa de Pós Graduação em Recursos Genéticos Vegetais, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| |
Collapse
|
15
|
Reumann S, Singhal R. Isolation of leaf peroxisomes from Arabidopsis for organelle proteome analyses. Methods Mol Biol 2014; 1072:541-52. [PMID: 24136545 DOI: 10.1007/978-1-62703-631-3_36] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The isolation of cell organelles from model organisms in high purity is important for biochemical analyses of single proteins, entire metabolic pathways, and protein complexes and is absolutely essential for organelle proteome analyses. The efficient enrichment of nearly all cell organelles is more difficult from Arabidopsis as compared to traditional model plants and especially challenging for peroxisomes. Leaf peroxisomes are generally very instable in aqueous solution due to the presence of a single membrane and (para-)crystalline inclusions in the matrix. Leaf peroxisomes from Arabidopsis are particularly fragile and, moreover, strongly physically adhere to chloroplasts and mitochondria for largely unknown reasons. Here, we provide a detailed protocol for the isolation of Arabidopsis leaf peroxisomes by Percoll followed by sucrose density gradient centrifugation that yields high purity suitable for proteome analyses. Diverse enzymatic and immuno-biochemical methods are summarized to assess purity and intactness.
Collapse
Affiliation(s)
- Sigrun Reumann
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway
| | | |
Collapse
|
16
|
Serrano M, Wang B, Aryal B, Garcion C, Abou-Mansour E, Heck S, Geisler M, Mauch F, Nawrath C, Métraux JP. Export of salicylic acid from the chloroplast requires the multidrug and toxin extrusion-like transporter EDS5. PLANT PHYSIOLOGY 2013; 162:1815-21. [PMID: 23757404 PMCID: PMC3729763 DOI: 10.1104/pp.113.218156] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 06/07/2013] [Indexed: 05/18/2023]
Abstract
Salicylic acid (SA) is central for the defense of plants to pathogens and abiotic stress. SA is synthesized in chloroplasts from chorismic acid by an isochorismate synthase (ICS1); SA biosynthesis is negatively regulated by autoinhibitory feedback at ICS1. Genetic studies indicated that the multidrug and toxin extrusion transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) of Arabidopsis (Arabidopsis thaliana) is necessary for SA accumulation after biotic and abiotic stress, but so far it is not understood how EDS5 controls the biosynthesis of SA. Here, we show that EDS5 colocalizes with a marker of the chloroplast envelope and that EDS5 functions as a multidrug and toxin extrusion-like transporter in the export of SA from the chloroplast to the cytoplasm in Arabidopsis, where it controls the innate immune response. The location at the chloroplast envelope supports a model of the effect of EDS5 on SA biosynthesis: in the eds5 mutant, stress-induced SA is trapped in the chloroplast and inhibits its own accumulation by autoinhibitory feedback.
Collapse
|
17
|
Bioactivity and Biomodification of Ag, ZnO, and CuO Nanoparticles with Relevance to Plant Performance in Agriculture. Ind Biotechnol (New Rochelle N Y) 2012. [DOI: 10.1089/ind.2012.0028] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
|
18
|
Sun F, Suen PK, Zhang Y, Liang C, Carrie C, Whelan J, Ward JL, Hawkins ND, Jiang L, Lim BL. A dual-targeted purple acid phosphatase in Arabidopsis thaliana moderates carbon metabolism and its overexpression leads to faster plant growth and higher seed yield. THE NEW PHYTOLOGIST 2012; 194:206-219. [PMID: 22269069 DOI: 10.1111/j.1469-8137.2011.04026.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
• Overexpression of AtPAP2, a purple acid phosphatase (PAP) with a unique C-terminal hydrophobic motif in Arabidopsis, resulted in earlier bolting and a higher seed yield. Metabolite analysis showed that the shoots of AtPAP2 overexpression lines contained higher levels of sugars and tricarboxylic acid (TCA) metabolites. Enzyme assays showed that sucrose phosphate synthase (SPS) activity was significantly upregulated in the overexpression lines. The higher SPS activity arose from a higher level of SPS protein, and was independent of SnRK1. • AtPAP2 was found to be targeted to both plastids and mitochondria via its C-terminal hydrophobic motif. Ectopic expression of a truncated AtPAP2 without this C-terminal motif in Arabidopsis indicated that the subcellular localization of AtPAP2 is essential for its biological actions. • Plant PAPs are generally considered to mediate phosphorus acquisition and redistribution. AtPAP2 is the first PAP shown to modulate carbon metabolism and the first shown to be dual-targeted to both plastids and mitochondria by a C-terminal targeting signal. • One PAP-like sequence carrying a hydrophobic C-terminal motif could be identified in the genome of the smallest free-living photosynthetic eukaryote, Ostreococcus tauri. This might reflect a common ancestral function of AtPAP2-like sequences in the regulation of carbon metabolism.
Collapse
Affiliation(s)
- Feng Sun
- School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
| | - Pui Kit Suen
- School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
| | - Youjun Zhang
- School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
| | - Chao Liang
- School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
| | - Chris Carrie
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley WA 6009, Australia
| | - James Whelan
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley WA 6009, Australia
| | - Jane L Ward
- National Centre for Plant and Microbial Metabolomics, Rothamsted Research, West Common, Harpenden, Herts, AL5 2JQ, UK
| | - Nathaniel D Hawkins
- National Centre for Plant and Microbial Metabolomics, Rothamsted Research, West Common, Harpenden, Herts, AL5 2JQ, UK
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell and Developmental Biology, the Chinese University of Hong Kong, Hong Kong, China
| | - Boon Leong Lim
- School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
| |
Collapse
|
19
|
Ajjawi I, Coku A, Froehlich JE, Yang Y, Osteryoung KW, Benning C, Last RL. A J-like protein influences fatty acid composition of chloroplast lipids in Arabidopsis. PLoS One 2011; 6:e25368. [PMID: 22028775 PMCID: PMC3196505 DOI: 10.1371/journal.pone.0025368] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 09/01/2011] [Indexed: 12/26/2022] Open
Abstract
A comprehensive understanding of the lipid and fatty acid metabolic machinery is needed for optimizing production of oils and fatty acids for fuel, industrial feedstocks and nutritional improvement in plants. T-DNA mutants in the poorly annotated Arabidopsis thaliana gene At1g08640 were identified as containing moderately high levels (50–100%) of 16∶1Δ7 and 18∶1Δ9 leaf fatty acids and subtle decreases (5–30%) of 16∶3 and 18∶3 (http://www.plastid.msu.edu/). TLC separation of fatty acids in the leaf polar lipids revealed that the chloroplastic galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were the main lipid types affected by this mutation. Analysis of the inferred amino acid sequence of At1g08640 predicted the presence of a transit peptide, three transmembrane domains and an N-terminal J-like domain, and the gene was named CJD1 for Chloroplast J-like Domain 1. GFP reporter experiments and in vitro chloroplast import assays demonstrated CJD1 is a chloroplast membrane protein. Screening of an Arabidopsis cDNA library by yeast-2-hybrid (Y2H) using the J-like domain of CJD1 as bait identified a plastidial inner envelope protein (Accumulation and Replication of Chloroplasts 6, ARC6) as the primary interacting partner in the Y2H assay. ARC6 plays a central role in chloroplast division and binds CJD1 via its own J-like domain along with an adjacent conserved region whose function is not fully known. These results provide a starting point for future investigations of how mutations in CJD1 affect lipid composition.
Collapse
Affiliation(s)
- Imad Ajjawi
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Ardian Coku
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - John E. Froehlich
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
- Michigan State University (MSU)–Department of Engineering (DOE) Plant Research Laboratories, Michigan State University, East Lansing, Michigan, United States of America
| | - Yue Yang
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Katherine W. Osteryoung
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Christoph Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Robert L. Last
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States of America
- Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
| |
Collapse
|
20
|
Huang W, Ling Q, Bédard J, Lilley K, Jarvis P. In vivo analyses of the roles of essential Omp85-related proteins in the chloroplast outer envelope membrane. PLANT PHYSIOLOGY 2011; 157:147-59. [PMID: 21757633 PMCID: PMC3165866 DOI: 10.1104/pp.111.181891] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 07/12/2011] [Indexed: 05/12/2023]
Abstract
Two different, essential Omp85 (Outer membrane protein, 85 kD)-related proteins exist in the outer envelope membrane of Arabidopsis (Arabidopsis thaliana) chloroplasts: Toc75 (Translocon at the outer envelope membrane of chloroplasts, 75 kD), encoded by atTOC75-III; and OEP80 (Outer Envelope Protein, 80 kD), encoded by AtOEP80/atTOC75-V. The atToc75-III protein is closely related to the originally identified pea (Pisum sativum) Toc75 protein, and it forms a preprotein translocation channel during chloroplast import; the AtOEP80 protein is considerably more divergent from pea Toc75, and its role is unknown. As knockout mutations for atTOC75-III and AtOEP80 are embryo lethal, we employed a dexamethasone-inducible RNA interference strategy (using the pOpOff2 vector) to conduct in vivo studies on the roles of these two proteins in older, postembryonic plants. We conducted comparative studies on plants silenced for atToc75-III (atToc75-III↓) or AtOEP80 (AtOEP80↓), as well as additional studies on a stable, atToc75-III missense allele (toc75-III-3/modifier of altered response to gravity1), and our results indicated that both proteins are important for chloroplast biogenesis at postembryonic stages of development. Moreover, both are important for photosynthetic and nonphotosynthetic development, albeit to different degrees: atToc75-III↓ phenotypes were considerably more severe than those of AtOEP80↓. Qualitative similarity between the atToc75-III↓ and AtOEP80↓ phenotypes may be linked to deficiencies in atToc75-III and other TOC proteins in AtOEP80↓ plants. Detailed analysis of atToc75-III↓ plants, by electron microscopy, immunoblotting, quantitative proteomics, and protein import assays, indicated that these plants are defective in relation to the biogenesis of both photosynthetic and nonphotosynthetic plastids and preproteins, confirming the earlier hypothesis that atToc75-III functions promiscuously in different substrate-specific import pathways.
Collapse
Affiliation(s)
| | | | | | | | - Paul Jarvis
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom (W.H., Q.L., J.B., P.J.); Cambridge Centre for Proteomics, University of Cambridge, Cambridge CB2 1QW, United Kingdom (K.L.)
| |
Collapse
|
21
|
Rosano GL, Bruch EM, Ceccarelli EA. Insights into the Clp/HSP100 chaperone system from chloroplasts of Arabidopsis thaliana. J Biol Chem 2011; 286:29671-80. [PMID: 21737456 DOI: 10.1074/jbc.m110.211946] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
HSP100 proteins are molecular chaperones involved in protein quality control. They assist in protein (un)folding, prevent aggregation, and are thought to participate in precursor translocation across membranes. Caseinolytic proteins ClpC and ClpD from plant chloroplasts belong to the HSP100 family. Their role has hitherto been investigated by means of physiological studies and reverse genetics. In the present work, we employed an in vitro approach to delve into the structural and functional characteristics of ClpC2 and ClpD from Arabidopsis thaliana (AtClpC2 and AtClpD). They were expressed in Escherichia coli and purified to near-homogeneity. The proteins were detected mainly as dimers in solution, and, upon addition of ATP, the formation of hexamers was observed. Both proteins exhibited basal ATPase activity (K(m), 1.42 mm, V(max), 0.62 nmol/(min × μg) for AtClpC2 and K(m) ∼19.80 mm, V(max) ∼0.19 nmol/(min × μg) for AtClpD). They were able to reactivate the activity of heat-denatured luciferase (∼40% for AtClpC2 and ∼20% for AtClpD). The Clp proteins tightly bound a fusion protein containing a model transit peptide. This interaction was detected by binding assays, where the chaperones were selectively trapped by the transit peptide-containing fusion, immobilized on glutathione-agarose beads. Association of HSP100 proteins to import complexes with a bound transit peptide-containing fusion was also observed in intact chloroplasts. The presented data are useful to understand protein quality control and protein import into chloroplasts in plants.
Collapse
Affiliation(s)
- Germán L Rosano
- Molecular Biology Division, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | | | | |
Collapse
|
22
|
Pathway for lipid A biosynthesis in Arabidopsis thaliana resembling that of Escherichia coli. Proc Natl Acad Sci U S A 2011; 108:11387-92. [PMID: 21709257 DOI: 10.1073/pnas.1108840108] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The lipid A moiety of Escherichia coli lipopolysaccharide is a hexa-acylated disaccharide of glucosamine that makes up the outer monolayer of the outer membrane. Arabidopsis thaliana contains nuclear genes encoding orthologs of key enzymes of bacterial lipid A biosynthesis, including LpxA, LpxC, LpxD, LpxB, LpxK and KdtA. Although structurally related lipid A molecules are found in most other gram-negative bacteria, lipid A and its precursors have not been directly detected in plants previously. However, homozygous insertional knockout mutations or RNAi knock-down constructs of Arabidopsis lpx and kdtA mutants revealed accumulation (or disappearance) of the expected monosaccharide or disaccharide lipid A precursors by mass spectrometry of total lipids extracted from 10-day old seedlings of these mutants. In addition, fluorescence microscopy of lpx-gfp fusions in transgenic Arabidopsis plants suggests that the Lpx and KdtA proteins are expressed and targeted to mitochondria. Although the structure of the lipid A end product generated by plants is still unknown, our work demonstrates that plants synthesize lipid A precursors using the same enzymatic pathway present in E. coli.
Collapse
|
23
|
Wang L, Yu X, Wang H, Lu YZ, de Ruiter M, Prins M, He YK. A novel class of heat-responsive small RNAs derived from the chloroplast genome of Chinese cabbage (Brassica rapa). BMC Genomics 2011; 12:289. [PMID: 21639890 PMCID: PMC3126784 DOI: 10.1186/1471-2164-12-289] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 06/03/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Non-coding small RNAs play critical roles in various cellular processes in a wide spectrum of eukaryotic organisms. Their responses to abiotic stress have become a popular topic of economic and scientific importance in biological research. Several studies in recent years have reported a small number of non-coding small RNAs that map to chloroplast genomes. However, it remains uncertain whether small RNAs are generated from chloroplast genome and how they respond to environmental stress, such as high temperature. Chinese cabbage is an important vegetable crop, and heat stress usually causes great losses in yields and quality. Under heat stress, the leaves become etiolated due to the disruption and disassembly of chloroplasts. In an attempt to determine the heat-responsive small RNAs in chloroplast genome of Chinese cabbage, we carried out deep sequencing, using heat-treated samples, and analysed the proportion of small RNAs that were matched to chloroplast genome. RESULTS Deep sequencing provided evidence that a novel subset of small RNAs were derived from the chloroplast genome of Chinese cabbage. The chloroplast small RNAs (csRNAs) include those derived from mRNA, rRNA, tRNA and intergenic RNA. The rRNA-derived csRNAs were preferentially located at the 3'-ends of the rRNAs, while the tRNA-derived csRNAs were mainly located at 5'-termini of the tRNAs. After heat treatment, the abundance of csRNAs decreased in seedlings, except those of 24 nt in length. The novel heat-responsive csRNAs and their locations in the chloroplast were verified by Northern blotting. The regulation of some csRNAs to the putative target genes were identified by real-time PCR. Our results reveal that high temperature suppresses the production of some csRNAs, which have potential roles in transcriptional or post-transcriptional regulation. CONCLUSIONS In addition to nucleus, the chloroplast is another important organelle that generates a number of small RNAs. Many members of csRNA families are highly sensitive to heat stress. Some csRNAs respond to heat stress by silencing target genes. We suggest that proper temperature is important for production of chloroplast small RNAs, which are associated with plant resistance to abiotic stress.
Collapse
Affiliation(s)
- Lu Wang
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, China
| | | | | | | | | | | | | |
Collapse
|
24
|
Fragnière C, Serrano M, Abou-Mansour E, Métraux JP, L'Haridon F. Salicylic acid and its location in response to biotic and abiotic stress. FEBS Lett 2011; 585:1847-52. [PMID: 21530511 DOI: 10.1016/j.febslet.2011.04.039] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 04/05/2011] [Accepted: 04/14/2011] [Indexed: 11/19/2022]
Abstract
Salicylic acid (SA) is an important signal involved in the activation of plant defence responses against abiotic and biotic stress. SA may derive from the phenylpropanoid pathway or via isochorismate synthase as demonstrated in Nicotiana benthamiana, tomato and Arabidopsis thaliana. The phenylpropanoid pathway as well as isochorismate synthase are localized in the chloroplasts but it remains unknown if the end product SA is in the same organelle. We have studied the localization of SA in A. thaliana using the salicylate hydroxylase (NahG) gene expressed with a chloroplast targeting sequence. Plants expressing NahG in the chloroplasts are unable to accumulate SA induced after pathogen or UV exposure. Our data infer that SA is initially located in the chloroplasts.
Collapse
Affiliation(s)
- Cindy Fragnière
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | | | | | | | | |
Collapse
|
25
|
Adhikari ND, Froehlich JE, Strand DD, Buck SM, Kramer DM, Larkin RM. GUN4-porphyrin complexes bind the ChlH/GUN5 subunit of Mg-Chelatase and promote chlorophyll biosynthesis in Arabidopsis. THE PLANT CELL 2011; 23:1449-67. [PMID: 21467578 PMCID: PMC3101535 DOI: 10.1105/tpc.110.082503] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/24/2011] [Accepted: 03/17/2011] [Indexed: 05/19/2023]
Abstract
The GENOMES UNCOUPLED4 (GUN4) protein stimulates chlorophyll biosynthesis by activating Mg-chelatase, the enzyme that commits protoporphyrin IX to chlorophyll biosynthesis. This stimulation depends on GUN4 binding the ChlH subunit of Mg-chelatase and the porphyrin substrate and product of Mg-chelatase. After binding porphyrins, GUN4 associates more stably with chloroplast membranes and was proposed to promote interactions between ChlH and chloroplast membranes-the site of Mg-chelatase activity. GUN4 was also proposed to attenuate the production of reactive oxygen species (ROS) by binding and shielding light-exposed porphyrins from collisions with O₂. To test these proposals, we first engineered Arabidopsis thaliana plants that express only porphyrin binding-deficient forms of GUN4. Using these transgenic plants and particular mutants, we found that the porphyrin binding activity of GUN4 and Mg-chelatase contribute to the accumulation of chlorophyll, GUN4, and Mg-chelatase subunits. Also, we found that the porphyrin binding activity of GUN4 and Mg-chelatase affect the associations of GUN4 and ChlH with chloroplast membranes and have various effects on the expression of ROS-inducible genes. Based on our findings, we conclude that ChlH and GUN4 use distinct mechanisms to associate with chloroplast membranes and that mutant alleles of GUN4 and Mg-chelatase genes cause sensitivity to intense light by a mechanism that is potentially complex.
Collapse
Affiliation(s)
- Neil D. Adhikari
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Genetics Program, Michigan State University, East Lansing, Michigan 48824
| | - John E. Froehlich
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Deserah D. Strand
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824
| | - Stephanie M. Buck
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
| | - David M. Kramer
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Robert M. Larkin
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
- Address correspondence to
| |
Collapse
|
26
|
Aronsson H, Jarvis RP. Rapid isolation of Arabidopsis chloroplasts and their use for in vitro protein import assays. Methods Mol Biol 2011; 774:281-305. [PMID: 21822845 DOI: 10.1007/978-1-61779-234-2_17] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In vitro chloroplast protein import assays have been performed since the late 1970s, initially with plant species (e.g., pea and spinach) that readily provide an abundant source of starting material and also, subsequently, a good yield of chloroplasts for import assays. However, the sequencing of the Arabidopsis genome paved the way for an additional model system that is more amenable to genetic analysis, as a complement to the more biochemically orientated models such as pea and spinach. A prerequisite for this change was an efficient and reliable protocol for the isolation of chloroplasts for use in protein import assays, enabling biochemical approaches to be combined with the genetic potential of the plant. The method described here was developed as a rapid and low-cost procedure that can be accessed by everyone due to its simplicity. Despite its rapidity and simplicity, the method yields highly pure chloroplasts, and in addition works well with mutant plants that exhibit pale or chlorotic phenotypes. The protocol is also optimized for work with material from young plants (10-14 days old), when protein import is believed to be at its peak, and so plant growth can be conducted in vitro on Murashige and Skoog medium. The isolation method has been used not only for protein import assays, but also for proteomic analysis and further subfractionation studies.
Collapse
Affiliation(s)
- Henrik Aronsson
- Department of Plant and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
| | | |
Collapse
|
27
|
George GM, van der Merwe MJ, Nunes-Nesi A, Bauer R, Fernie AR, Kossmann J, Lloyd JR. Virus-induced gene silencing of plastidial soluble inorganic pyrophosphatase impairs essential leaf anabolic pathways and reduces drought stress tolerance in Nicotiana benthamiana. PLANT PHYSIOLOGY 2010; 154:55-66. [PMID: 20605913 PMCID: PMC2938153 DOI: 10.1104/pp.110.157776] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 07/02/2010] [Indexed: 05/18/2023]
Abstract
The role of pyrophosphate in primary metabolism is poorly understood. Here, we report on the transient down-regulation of plastid-targeted soluble inorganic pyrophosphatase in Nicotiana benthamiana source leaves. Physiological and metabolic perturbations were particularly evident in chloroplastic central metabolism, which is reliant on fast and efficient pyrophosphate dissipation. Plants lacking plastidial soluble inorganic pyrophosphatase (psPPase) were characterized by increased pyrophosphate levels, decreased starch content, and alterations in chlorophyll and carotenoid biosynthesis, while constituents like amino acids (except for histidine, serine, and tryptophan) and soluble sugars and organic acids (except for malate and citrate) remained invariable from the control. Furthermore, translation of Rubisco was significantly affected, as observed for the amounts of the respective subunits as well as total soluble protein content. These changes were concurrent with the fact that plants with reduced psPPase were unable to assimilate carbon to the same extent as the controls. Furthermore, plants with lowered psPPase exposed to mild drought stress showed a moderate wilting phenotype and reduced vitality, which could be correlated to reduced abscisic acid levels limiting stomatal closure. Taken together, the results suggest that plastidial pyrophosphate dissipation through psPPase is indispensable for vital plant processes.
Collapse
Affiliation(s)
| | | | | | | | | | | | - James R. Lloyd
- Institute of Plant Biotechnology, University of Stellenbosch, Matieland 7602, Stellenbosch, South Africa (G.M.G., M.J.v.d.M., R.B., J.K., J.R.L.); Max Planck Institute of Molecular Plant Physiology, D–14476 Potsdam-Golm, Germany (A.N.-N., A.R.F.)
| |
Collapse
|
28
|
Aronsson H, Combe J, Patel R, Agne B, Martin M, Kessler F, Jarvis P. Nucleotide binding and dimerization at the chloroplast pre-protein import receptor, atToc33, are not essential in vivo but do increase import efficiency. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 63:297-311. [PMID: 20444229 DOI: 10.1111/j.1365-313x.2010.04242.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The atToc33 protein is one of several pre-protein import receptors in the outer envelope of Arabidopsis chloroplasts. It is a GTPase with motifs characteristic of such proteins, and its loss in the plastid protein import 1 (ppi1) mutant interferes with the import of photosynthesis-related pre-proteins, causing a chlorotic phenotype in mutant plants. To assess the significance of GTPase cycling by atToc33, we generated several atToc33 point mutants with predicted effects on GTP binding (K49R, S50N and S50N/S51N), GTP hydrolysis (G45R, G45V, Q68A and N101A), both binding and hydrolysis (G45R/K49N/S50R), and dimerization or the functional interaction between dimeric partners (R125A, R130A and R130K). First, a selection of these mutants was assessed in vitro, or in yeast, to confirm that the mutations have the desired effects: in relation to nucleotide binding and dimerization, the mutants behaved as expected. Then, activities of selected mutants were tested in vivo, by assessing for complementation of ppi1 in transgenic plants. Remarkably, all tested mutants mediated high levels of complementation: complemented plants were similar to the wild type in growth rate, chlorophyll accumulation, photosynthetic performance, and chloroplast ultrastructure. Protein import into mutant chloroplasts was also complemented to >50% of the wild-type level. Overall, the data indicate that neither nucleotide binding nor dimerization at atToc33 is essential for chloroplast import (in plants that continue to express the other TOC receptors in native form), although both processes do increase import efficiency. Absence of atToc33 GTPase activity might somehow be compensated for by that of the Toc159 receptors. However, overexpression of atToc33 (or its close relative, atToc34) in Toc159-deficient plants did not mediate complementation, indicating that the receptors do not share functional redundancy in the conventional sense.
Collapse
Affiliation(s)
- Henrik Aronsson
- Department of Plant and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Gothenburg, Sweden
| | - Jonathan Combe
- Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Ramesh Patel
- Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Birgit Agne
- Laboratoire de Physiologie Végétale, Université de Neuchâtel, Rue Emile-Argand 11, 2007 Neuchâtel, Switzerland
| | - Meryll Martin
- Laboratoire de Physiologie Végétale, Université de Neuchâtel, Rue Emile-Argand 11, 2007 Neuchâtel, Switzerland
| | - Felix Kessler
- Laboratoire de Physiologie Végétale, Université de Neuchâtel, Rue Emile-Argand 11, 2007 Neuchâtel, Switzerland
| | - Paul Jarvis
- Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK
| |
Collapse
|
29
|
Ahsan N, Nanjo Y, Sawada H, Kohno Y, Komatsu S. Ozone stress-induced proteomic changes in leaf total soluble and chloroplast proteins of soybean reveal that carbon allocation is involved in adaptation in the early developmental stage. Proteomics 2010; 10:2605-19. [PMID: 20443193 DOI: 10.1002/pmic.201000180] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 04/16/2010] [Indexed: 12/25/2022]
Abstract
Considerable soybean yield losses caused by ozone (O3) stress have been demonstrated by large-scale meta-analyses of free-gas concentration enrichment systems. In this study, comparative proteomic approach was employed to explore the differential changes of proteins in O3 target structures such as leaf and chloroplasts of soybean seedlings. Acute O3 exposure (120 parts-per-billion) for 3 days did not cause any visible symptoms in developing leaves. However, higher amounts of ROS and lipid peroxidation indicated that severe oxidative burst occurred. Immunoblot analysis of O3-induced known proteins revealed that proteins were modulated before symptoms became visible. Proteomic analysis identified a total of 20 and 32 differentially expressed proteins from O3-treated leaf and chloroplast, respectively. Proteins associated with photosynthesis, including photosystem I/II and carbon assimilation decreased following exposure to O3. In contrast, proteins involved in antioxidant defense and carbon metabolism increased. The activity of enzymes involved in carbohydrate metabolism increased following exposure to O3, which is consistent with the decrease in starch and increase in sucrose concentrations. Taken together, these results suggest that carbon allocation is tightly programmed, and starch degradation probably feeds the tricarboxylic acid cycle while the photosynthesis pathway is severely affected during O3 stress.
Collapse
Affiliation(s)
- Nagib Ahsan
- National Institute of Crop Science, Tsukuba, Japan
| | | | | | | | | |
Collapse
|
30
|
Stitt M, Lunn J, Usadel B. Arabidopsis and primary photosynthetic metabolism - more than the icing on the cake. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:1067-91. [PMID: 20409279 DOI: 10.1111/j.1365-313x.2010.04142.x] [Citation(s) in RCA: 203] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Historically speaking, Arabidopsis was not the plant of choice for investigating photosynthesis, with physiologists and biochemists favouring other species such as Chlorella, spinach and pea. However, its inherent advantages for forward genetics rapidly led to its adoption for photosynthesis research. In the last ten years, the availability of the Arabidopsis genome sequence - still the gold-standard for plant genomes - and the rapid expansion of genetic and genomic resources have further increased its importance. Research in Arabidopsis has not only provided comprehensive information about the enzymes and other proteins involved in photosynthesis, but has also allowed transcriptional responses, protein levels and compartmentation to be analysed at a global level for the first time. Emerging technical and theoretical advances offer another leap forward in our understanding of post-translational regulation and the control of metabolism. To illustrate the impact of Arabidopsis, we provide a historical review of research in primary photosynthetic metabolism, highlighting the role of Arabidopsis in elucidation of the pathway of photorespiration and the regulation of RubisCO, as well as elucidation of the pathways of starch turnover and studies of the significance of starch for plant growth.
Collapse
Affiliation(s)
- Mark Stitt
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, Potsdam-Golm, Germany.
| | | | | |
Collapse
|
31
|
Lee J, Han CT, Hur Y. Overexpression of BrMORN, a novel 'membrane occupation and recognition nexus' motif protein gene from Chinese cabbage, promotes vegetative growth and seed production in Arabidopsis. Mol Cells 2010; 29:113-22. [PMID: 20016940 DOI: 10.1007/s10059-010-0006-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 10/14/2009] [Accepted: 10/28/2009] [Indexed: 10/20/2022] Open
Abstract
Proteins that contain membrane occupation and recognition nexus (MORN) motifs regulate various aspects of cellular metabolism by localizing proteins in different cellular organelles. The full-length Brassica rapa MORN motif protein (BrMORN) cDNA consists of 1,510 bp encoding 502 deduced amino acids with a predicted molecular mass of 55.8 kDa and an isoelectric point of 9.72. BrMORN is a novel protein composed of two N-terminal transmembrane helices and seven C-terminal MORN motifs and it appears to be localized on the plastid envelope. BrMORN expression was relatively high in actively-growing tissues, but low in mature tissues and under some abiotic stresses. Arabidopsis thaliana plants overexpressing BrMORN showed an enhanced rate of growth, hypocotyl elongation, and increases in the size of vegetative organs and seed productivity under normal growth conditions. In addition, cell size in Arabidopsis plants overexpressing BrMORN was 24% larger than that of wild-type plants, implying that the increase in the size of vegetative organs is due to cell enlargement. The increased size of the vegetative organs also led to increased seed production. Our data suggest that the MORN motif of BrMORN may act at the plastid envelope and facilitate plant growth via cell enlargement.
Collapse
Affiliation(s)
- Jeongyeo Lee
- Plant Genomics Institute, College of Biosystems Science, Chungnam National University, Daejeon, 305-764, Korea
| | | | | |
Collapse
|
32
|
Schelbert S, Aubry S, Burla B, Agne B, Kessler F, Krupinska K, Hörtensteiner S. Pheophytin pheophorbide hydrolase (pheophytinase) is involved in chlorophyll breakdown during leaf senescence in Arabidopsis. THE PLANT CELL 2009; 21:767-85. [PMID: 19304936 PMCID: PMC2671698 DOI: 10.1105/tpc.108.064089] [Citation(s) in RCA: 332] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 02/12/2009] [Accepted: 03/08/2009] [Indexed: 05/08/2023]
Abstract
During leaf senescence, chlorophyll is removed from thylakoid membranes and converted in a multistep pathway to colorless breakdown products that are stored in vacuoles. Dephytylation, an early step of this pathway, increases water solubility of the breakdown products. It is widely accepted that chlorophyll is converted into pheophorbide via chlorophyllide. However, chlorophyllase, which converts chlorophyll to chlorophyllide, was found not to be essential for dephytylation in Arabidopsis thaliana. Here, we identify pheophytinase (PPH), a chloroplast-located and senescence-induced hydrolase widely distributed in algae and land plants. In vitro, Arabidopsis PPH specifically dephytylates the Mg-free chlorophyll pigment, pheophytin (phein), yielding pheophorbide. An Arabidopsis mutant deficient in PPH (pph-1) is unable to degrade chlorophyll during senescence and therefore exhibits a stay-green phenotype. Furthermore, pph-1 accumulates phein during senescence. Therefore, PPH is an important component of the chlorophyll breakdown machinery of senescent leaves, and we propose that the sequence of early chlorophyll catabolic reactions be revised. Removal of Mg most likely precedes dephytylation, resulting in the following order of early breakdown intermediates: chlorophyll --> pheophytin --> pheophorbide. Chlorophyllide, the last precursor of chlorophyll biosynthesis, is most likely not an intermediate of breakdown. Thus, chlorophyll anabolic and catabolic reactions are metabolically separated.
Collapse
Affiliation(s)
- Silvia Schelbert
- Institute of Plant Biology, University of Zürich, CH-8008 Zurich, Switzerland
| | | | | | | | | | | | | |
Collapse
|