501
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Takatsuka C, Inoue Y, Higuchi T, Hillmer S, Robinson DG, Moriyasu Y. Autophagy in tobacco BY-2 cells cultured under sucrose starvation conditions: isolation of the autolysosome and its characterization. PLANT & CELL PHYSIOLOGY 2011; 52:2074-87. [PMID: 22039105 DOI: 10.1093/pcp/pcr137] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Tobacco culture cells carry out a large-scale degradation of intracellular proteins in order to survive under sucrose starvation conditions. We have previously suggested that this bulk degradation of cellular proteins is performed by autophagy, where autolysosomes formed de novo act as the major lytic compartments. The digestion process in autolysosomes can be retarded by addition of the cysteine protease inhibitor E-64c to the culture medium, resulting in the accumulation of autolysosomes. In the present study, we have investigated several properties of autolysosomes in tobacco cells. Electron microscopy showed that the autolysosomes contain osmiophilic particles, some of which resemble partially degraded mitochondria. It also revealed the presence of two kinds of autolysosome precursor structures; one resembled the isolation membrane and the other the autophagosome of mammalian cells. Immunofluorescence microscopy showed that autolysosomes contain acid phosphatase, in accordance with cytochemical enzyme analyses by light and electron microscopy in a previous study. Autolysosomes isolated by cell fractionation on Percoll gradients showed the localization of acid phosphatase, vacuolar H(+)-ATPase and cysteine protease. These results show that starvation-induced autophagy in tobacco cells follows a macroautophagic-type response similar to that described for other eukaryotes. However, our results indicate that, although the plant vacuole is often described as being equivalent to the lysosome of the animal cell, a new low pH lytic compartment-the autolysosome-also contributes to proteolytic degradation when tobacco cells are subjected to sucrose deprivation.
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Affiliation(s)
- Chihiro Takatsuka
- Graduate School of Science and Engineering, Saitama University, Saitama, Japan
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502
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Zhang H, Zhang L, Gao B, Fan H, Jin J, Botella MA, Jiang L, Lin J. Golgi apparatus-localized synaptotagmin 2 is required for unconventional secretion in Arabidopsis. PLoS One 2011; 6:e26477. [PMID: 22140429 PMCID: PMC3225361 DOI: 10.1371/journal.pone.0026477] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 09/27/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Most secretory proteins contain signal peptides that direct their sorting to the ER and secreted via the conventional ER/Golgi transport pathway, while some signal-peptide-lacking proteins have been shown to export through ER/Golgi independent secretory pathways. Hygromycin B is an aminoglycoside antibiotic produced by Streptomyces hygroscopicus that is active against both prokaryotic and eukaryotic cells. The hygromycin phosphotransferase (HYG(R)) can phosphorylate and inactivate the hygromycin B, and has been widely used as a positive selective marker in the construction of transgenic plants. However, the localization and trafficking of HYG(R) in plant cells remain unknown. Synaptotagmins (SYTs) are involved in controlling vesicle endocytosis and exocytosis as calcium sensors in animal cells, while their functions in plant cells are largely unclear. METHODOLOGY/PRINCIPAL FINDINGS We found Arabidopsis synaptotagmin SYT2 was localized on the Golgi apparatus by immunofluorescence and immunogold labeling. Surprisingly, co-expression of SYT2 and HYG(R) caused hypersensitivity of the transgenic Arabidopsis plants to hygromycin B. HYG(R), which lacks a signal sequence, was present in the cytoplasm as well as in the extracellular space in HYG(R)-GFP transgenic Arabidopsis plants and its secretion is not sensitive to brefeldin A treatment, suggesting it is not secreted via the conventional secretory pathway. Furthermore, we found that HYG(R)-GFP was truncated at carboxyl terminus of HYG(R) shortly after its synthesis, and the cells deficient SYT2 failed to efficiently truncate HYG(R)-GFP,resulting in HYG(R)-GFP accumulated in prevacuoles/vacuoles, indicating that SYT2 was involved in HYG(R)-GFP trafficking and secretion. CONCLUSION/SIGNIFICANCE These findings reveal for the first time that SYT2 is localized on the Golgi apparatus and regulates HYG(R)-GFP secretion via the unconventional protein transport from the cytosol to the extracelluar matrix in plant cells.
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Affiliation(s)
- Haiyan Zhang
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Liang Zhang
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijng, China
| | - Bin Gao
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, Shandong Normal University, Jinan, China
| | - Hai Fan
- College of Life Sciences, Shandong Normal University, Jinan, China
| | - Jingbo Jin
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Miguel A. Botella
- Departamento de Biología Moleculary Bioquímica, Universidad de Málaga, Málaga, Spain
| | - Liwen Jiang
- Department of Biology and Molecular Biotechnology Program, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Jinxing Lin
- Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
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503
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Unraveling plant responses to bacterial pathogens through proteomics. J Biomed Biotechnol 2011; 2011:354801. [PMID: 22131803 PMCID: PMC3216475 DOI: 10.1155/2011/354801] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 08/24/2011] [Accepted: 09/02/2011] [Indexed: 12/15/2022] Open
Abstract
Plant pathogenic bacteria cause diseases in important crops and seriously and negatively impact agricultural production. Therefore, an understanding of the mechanisms by which plants resist bacterial infection at the stage of the basal immune response or mount a successful specific R-dependent defense response is crucial since a better understanding of the biochemical and cellular mechanisms underlying these interactions will enable molecular and transgenic approaches to crops with increased biotic resistance. In recent years, proteomics has been used to gain in-depth understanding of many aspects of the host defense against pathogens and has allowed monitoring differences in abundance of proteins as well as posttranscriptional and posttranslational processes, protein activation/inactivation, and turnover. Proteomics also offers a window to study protein trafficking and routes of communication between organelles. Here, we summarize and discuss current progress in proteomics of the basal and specific host defense responses elicited by bacterial pathogens.
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504
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Sharfman M, Bar M, Ehrlich M, Schuster S, Melech-Bonfil S, Ezer R, Sessa G, Avni A. Endosomal signaling of the tomato leucine-rich repeat receptor-like protein LeEix2. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:413-23. [PMID: 21736652 DOI: 10.1111/j.1365-313x.2011.04696.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Extracellular leucine-rich repeat (LRR) receptor-like proteins (RLPs) represent a unique class of cell-surface receptors, as they lack a functional cytoplasmic domain. Our knowledge of how RLPs that do not contain a kinase or Toll domain function is very limited. The tomato RLP receptor LeEix2 signals to induce defense responses mediated by the fungal protein ethylene-inducing xylanase (EIX). The movement of FYVE-positive endosomes before and after EIX application was examined using spinning disc confocal microscopy. We found that while FYVE-positive endosomes generally observe a random movement pattern, following EIX application a subpopulation of FYVE-positive endosomes follow a directional movement pattern. Further, cellular endosomes travel greater distances at higher speeds following EIX application. Time-course experiments conducted with specific inhibitors demonstrate the involvement of endosomal signaling in EIX-triggered defense responses. Abolishing the existence of endosomes or the endocytic event prevented EIX-induced signaling. Endocytosis/endosome inhibitors, such as Dynasore or 1-butanol, inhibit EIX-induced signaling. Moreover, treatment with Endosidin1, which inhibits an early step in plasma membrane/endosome trafficking, enhances the induction of defense responses by EIX. Our data indicate a distinct endosomal signaling mechanism for induction of defense responses in this RLP system.
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Affiliation(s)
- Miya Sharfman
- Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv, Israel
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505
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Qi X, Zheng H. Arabidopsis TRAPPII is functionally linked to Rab-A, but not Rab-D in polar protein trafficking in trans-Golgi network. PLANT SIGNALING & BEHAVIOR 2011; 6:1679-83. [PMID: 22067991 PMCID: PMC3329335 DOI: 10.4161/psb.6.11.17915] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The trans-Golgi network (TGN) in plant cells is an independent organelle, displaying rapid association and dissociation with Golgi bodies. In plant cells, the TGN is the site where secretory and endocytic membrane trafficking meet. Cell wall components, signaling molecules and auxin transporters have been found to undergo intracellular trafficking around the TGN. However, how different trafficking pathways are regulated and how different cargoes are sorted in the TGN is poorly defined in plant cells. Using a combined approach of genetic and in vivo imaging, we recently demonstrated that Arabidopsis TRAPPII acts in the TGN and is required for polar targeting of PIN2, but not PIN1, auxin efflux carrier in root tip cells. Here, we report that, TRAPPII in Arabidopsis is required for polar distribution of AUX1, an auxin influx carrier in protophloem cells and epidermal cells of Arabidopsis root tips. In yeast cells, TRAPPII serves as a guanine-nucleotide exchange factor (GEF) for Ypt1 and Ypt31/32 in late Golgi trafficking, while in mammalian cells, TRAPPII acts as a GEF for Rab1 (homolog of yeast Ypt1) in early Golgi trafficking. We show here that TRAPPII in Arabidopsis is functionally linked to Rab-A proteins, homologs of yeast Ypt31/32, but not Rab-D proteins, homologs of yeast Ypt1 and animal Rab1 proteins.
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506
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Drakakaki G, Robert S, Szatmari AM, Brown MQ, Nagawa S, Van Damme D, Leonard M, Yang Z, Girke T, Schmid SL, Russinova E, Friml J, Raikhel NV, Hicks GR. Clusters of bioactive compounds target dynamic endomembrane networks in vivo. Proc Natl Acad Sci U S A 2011; 108:17850-5. [PMID: 22006339 PMCID: PMC3203817 DOI: 10.1073/pnas.1108581108] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Endomembrane trafficking relies on the coordination of a highly complex, dynamic network of intracellular vesicles. Understanding the network will require a dissection of cargo and vesicle dynamics at the cellular level in vivo. This is also a key to establishing a link between vesicular networks and their functional roles in development. We used a high-content intracellular screen to discover small molecules targeting endomembrane trafficking in vivo in a complex eukaryote, Arabidopsis thaliana. Tens of thousands of molecules were prescreened and a selected subset was interrogated against a panel of plasma membrane (PM) and other endomembrane compartment markers to identify molecules that altered vesicle trafficking. The extensive image dataset was transformed by a flexible algorithm into a marker-by-phenotype-by-treatment time matrix and revealed groups of molecules that induced similar subcellular fingerprints (clusters). This matrix provides a platform for a systems view of trafficking. Molecules from distinct clusters presented avenues and enabled an entry point to dissect recycling at the PM, vacuolar sorting, and cell-plate maturation. Bioactivity in human cells indicated the value of the approach to identifying small molecules that are active in diverse organisms for biology and drug discovery.
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Affiliation(s)
- Georgia Drakakaki
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Stéphanie Robert
- Department of Plant Systems Biology, University of Ghent, Flanders Institute for Biotechnology (VIB), 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, University of Ghent, 9052 Ghent, Belgium; and
| | - Anna-Maria Szatmari
- Department of Plant Systems Biology, University of Ghent, Flanders Institute for Biotechnology (VIB), 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, University of Ghent, 9052 Ghent, Belgium; and
| | - Michelle Q. Brown
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Shingo Nagawa
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Daniel Van Damme
- Department of Plant Systems Biology, University of Ghent, Flanders Institute for Biotechnology (VIB), 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, University of Ghent, 9052 Ghent, Belgium; and
| | - Marilyn Leonard
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Zhenbiao Yang
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Thomas Girke
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Sandra L. Schmid
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Eugenia Russinova
- Department of Plant Systems Biology, University of Ghent, Flanders Institute for Biotechnology (VIB), 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, University of Ghent, 9052 Ghent, Belgium; and
| | - Jiří Friml
- Department of Plant Systems Biology, University of Ghent, Flanders Institute for Biotechnology (VIB), 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, University of Ghent, 9052 Ghent, Belgium; and
| | - Natasha V. Raikhel
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
| | - Glenn R. Hicks
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521
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507
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Zhang L, Zhang H, Liu P, Hao H, Jin JB, Lin J. Arabidopsis R-SNARE proteins VAMP721 and VAMP722 are required for cell plate formation. PLoS One 2011; 6:e26129. [PMID: 22022536 PMCID: PMC3191180 DOI: 10.1371/journal.pone.0026129] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 09/20/2011] [Indexed: 11/18/2022] Open
Abstract
Background Cell plate formation during plant cytokinesis is facilitated by SNARE complex-mediated vesicle fusion at the cell-division plane. However, our knowledge regarding R-SNARE components of membrane fusion machinery for cell plate formation remains quite limited. Methodology/Principal Findings We report the in vivo function of Arabidopsis VAMP721 and VAMP722, two closely sequence-related R-SNAREs, in cell plate formation. Double homozygous vamp721vamp722 mutant seedlings showed lethal dwarf phenotypes and were characterized by rudimentary roots, cotyledons and hypocotyls. Furthermore, cell wall stubs and incomplete cytokinesis were frequently observed in vamp721vamp722 seedlings. Confocal images revealed that green fluorescent protein-tagged VAMP721 and VAMP722 were preferentially localized to the expanding cell plates in dividing cells. Drug treatments and co-localization analyses demonstrated that punctuate organelles labeled with VAMP721 and VAMP722 represented early endosomes overlapped with VHA-a1-labeled TGN, which were distinct from Golgi stacks and prevacuolar compartments. In addition, protein traffic to the plasma membrane, but not to the vacuole, was severely disrupted in vamp721vamp722 seedlings by subcellular localization of marker proteins. Conclusion/Significance These observations suggest that VAMP721 and VAMP722 are involved in secretory trafficking to the plasma membrane via TGN/early endosomal compartment, which contributes substantially to cell plate formation during plant cytokinesis.
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Affiliation(s)
- Liang Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Haiyan Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Peng Liu
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Huaiqing Hao
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Jing Bo Jin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Jinxing Lin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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508
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Qi X, Kaneda M, Chen J, Geitmann A, Zheng H. A specific role for Arabidopsis TRAPPII in post-Golgi trafficking that is crucial for cytokinesis and cell polarity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:234-48. [PMID: 21689172 DOI: 10.1111/j.1365-313x.2011.04681.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Cytokinesis and cell polarity are supported by membrane trafficking from the trans-Golgi network (TGN), but the molecular mechanisms that promote membrane trafficking from the TGN are poorly defined in plant cells. Here we show that TRAPPII in Arabidopsis regulates the post-Golgi trafficking that is crucial for assembly of the cell plate and cell polarity. Disruptions of AtTRS120 or AtTRS130, two genes encoding two key subunits of TRAPPII, result in defective cytokinesis and cell polarity in embryogenesis and seedling development. In attrs120 and attrs130, the organization and trafficking in the endoplasmic reticulum (ER)-Golgi interface are normal. However, post-Golgi trafficking to the cell plate and to the cell wall, but not to the vacuole, is impaired. Furthermore, TRAPPII is required for the selective transport of PIN2, but not PIN1, to the plasma membrane. We revealed that AtTRS130 is co-localized with RAB-A1c. Expression of constitutively active RAB-A1c partially rescues attrs130. RAB-A1c, which resides at the TGN, is delocalized to the cytosol in attrs130. We propose that TRAPPII in Arabidopsis acts upstream of Rab-A GTPases in post-Golgi membrane trafficking in plant cells.
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Affiliation(s)
- Xingyun Qi
- Developmental Biology Research Initiatives, Department of Biology, McGill University, 1205 Dr Penfield Avenue, Montreal, Quebec H3A 1B1, Canada
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509
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The trafficking and behavior of cellulose synthase and a glimpse of potential cellulose synthesis regulators. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11515-011-1161-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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510
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Bach L, Gissot L, Marion J, Tellier F, Moreau P, Satiat-Jeunemaître B, Palauqui JC, Napier JA, Faure JD. Very-long-chain fatty acids are required for cell plate formation during cytokinesis in Arabidopsis thaliana. J Cell Sci 2011; 124:3223-34. [PMID: 21896643 DOI: 10.1242/jcs.074575] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Acyl chain length is thought to be crucial for biophysical properties of the membrane, in particular during cell division, when active vesicular fusion is necessary. In higher plants, the process of cytokinesis is unique, because the separation of the two daughter cells is carried out by de novo vesicular fusion to generate a laterally expanding cell plate. In Arabidopsis thaliana, very-long-chain fatty acid (VLCFA) depletion caused by a mutation in the microsomal elongase gene PASTICCINO2 (PAS2) or by application of the selective elongase inhibitor flufenacet altered cytokinesis. Cell plate expansion was delayed and the formation of the endomembrane tubular network altered. These defects were associated with specific aggregation of the cell plate markers YFP-Rab-A2a and KNOLLE during cytokinesis. Changes in levels of VLCFA also resulted in modification of endocytosis and sensitivity to brefeldin A. Finally, the cytokinesis impairment in pas2 cells was associated with reduced levels of very long fatty acyl chains in phospholipids. Together, our findings demonstrate that VLCFA-containing lipids are essential for endomembrane dynamics during cytokinesis.
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Affiliation(s)
- Liên Bach
- Institut Jean-Pierre Bourgin (IJPB), UMR1318 INRA-AgroParisTech, Saclay Plant Science (SPS), INRA Centre de Versailles-Grignon, Route de St-Cyr, 78000 Versailles, France
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511
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Shen Y, Wang J, Ding Y, Lo SW, Gouzerh G, Neuhaus JM, Jiang L. The rice RMR1 associates with a distinct prevacuolar compartment for the protein storage vacuole pathway. MOLECULAR PLANT 2011; 4:854-68. [PMID: 21493745 DOI: 10.1093/mp/ssr025] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Transport of vacuolar proteins from Golgi apparatus or trans-Golgi network (TGN) to vacuoles is a receptor-mediated process via an intermediate membrane-bound prevacuolar compartment (PVC) in plant cells. Both vacuolar sorting receptor (VSR) and receptor homology region-transmembrane domain-RING-H2 (RMR) proteins have been shown to function in transporting storage proteins to protein storage vacuole (PSV), but little is known about the nature of the PVC for the PSV pathway. Here, we use the rice RMR1 (OsRMR1) as a probe to study the PSV pathway in plants. Immunogold electron microscopy (EM) with specific OsRMR1 antibodies showed that OsRMR1 proteins were found in the Golgi apparatus, TGN, and a distinct organelle with characteristics of PVC in both rice culture cells and developing rice seeds, as well as the protein body type II (PBII) or PSV in developing rice seeds. This organelle, also found in both tobacco BY-2 and Arabidopsis suspension cultured cells, is morphologically distinct from the VSR-positive multivesicular lytic PVC or multivesicular body (MVB) and thus represent a PVC for the PSV pathway that we name storage PVC (sPVC). Further in vivo and in vitro interaction studies using truncated OsRMR1 proteins secreted into the culture media of transgenic BY-2 suspension cells demonstrated that OsRMR1 functions as a sorting receptor in transporting vicilin-like storage proteins.
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Affiliation(s)
- Yun Shen
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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512
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Scheuring D, Viotti C, Krüger F, Künzl F, Sturm S, Bubeck J, Hillmer S, Frigerio L, Robinson DG, Pimpl P, Schumacher K. Multivesicular bodies mature from the trans-Golgi network/early endosome in Arabidopsis. THE PLANT CELL 2011; 23:3463-81. [PMID: 21934143 PMCID: PMC3203422 DOI: 10.1105/tpc.111.086918] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 08/19/2011] [Accepted: 08/31/2011] [Indexed: 05/17/2023]
Abstract
The plant trans-Golgi network/early endosome (TGN/EE) is a major hub for secretory and endocytic trafficking with complex molecular mechanisms controlling sorting and transport of cargo. Vacuolar transport from the TGN/EE to multivesicular bodies/late endosomes (MVBs/LEs) is assumed to occur via clathrin-coated vesicles, although direct proof for their participation is missing. Here, we present evidence that post-TGN transport toward lytic vacuoles occurs independently of clathrin and that MVBs/LEs are derived from the TGN/EE through maturation. We show that the V-ATPase inhibitor concanamycin A significantly reduces the number of MVBs and causes TGN and MVB markers to colocalize in Arabidopsis thaliana roots. Ultrastructural analysis reveals the formation of MVBs from the TGN/EE and their fusion with the vacuole. The localization of the ESCRT components VPS28, VPS22, and VPS2 at the TGN/EE and MVBs/LEs indicates that the formation of intraluminal vesicles starts already at the TGN/EE. Accordingly, a dominant-negative mutant of VPS2 causes TGN and MVB markers to colocalize and blocks vacuolar transport. RNA interference-mediated knockdown of the annexin ANNAT3 also yields the same phenotype. Together, these data indicate that MVBs originate from the TGN/EE in a process that requires the action of ESCRT for the formation of intraluminal vesicles and annexins for the final step of releasing MVBs as a transport carrier to the vacuole.
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Affiliation(s)
- David Scheuring
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Corrado Viotti
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Falco Krüger
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Fabian Künzl
- Developmental Genetics, Centre for Plant Molecular Biology, University of Tübingen, 72076 Tuebingen, Germany
| | - Silke Sturm
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Julia Bubeck
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Stefan Hillmer
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Lorenzo Frigerio
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - David G. Robinson
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
| | - Peter Pimpl
- Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
- Developmental Genetics, Centre for Plant Molecular Biology, University of Tübingen, 72076 Tuebingen, Germany
- Address correspondence to
| | - Karin Schumacher
- Developmental Biology of Plants, Centre for Organismal Studies, University of Heidelberg, 69120 Heidelberg, Germany
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513
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Fukao Y, Ferjani A. V-ATPase dysfunction under excess zinc inhibits Arabidopsis cell expansion. PLANT SIGNALING & BEHAVIOR 2011; 6:1253-5. [PMID: 21847017 PMCID: PMC3258044 DOI: 10.4161/psb.6.9.16529] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 05/19/2011] [Indexed: 05/18/2023]
Abstract
Although zinc is an essential micronutrient for all living organisms, zinc is harmful to cells at high levels. In the presence of excess zinc, plants exhibit several major symptoms, including root growth inhibition, abnormal root hair morphology and chlorosis. To dissect the molecular mechanisms underlying the effects of excess zinc on plant cells, we used aniTRA Q-based quantitative proteomics approach to analyze the microsomal protein profiles of Arabidopsis roots from wild-type (WT) plants and de-etiolated 3-1 (det3-1), a vacuolar H+ -AT Pase (V-AT Pase) subunit C-defective mutant. A comparative analysis of the iTRA Q data from WT and det3-1 plants exposed to excess zinc suggests that the reduction in V-AT Pase subunit levels and its activity are the cause of the symptoms of zinc toxicity, including the inhibition of cell expansion. Provided that reduced V-AT Pase activity in the trans-Golgi network (TGN) alone can inhibit cell expansion, it is possible that the det3-1 mutant phenotype is caused mainly by a defect in TGN acidification, leading to reduced cell wall component trafficking and cell expansion in the presence of excess zinc. To evaluate the contribution of V-AT Pase activity to vacuolar acidification under excess zinc, the vacuolar pH was measured. Our results indicate clear alkalinization of deep cell vacuoles treated with 300 μM ZnSO4.
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Affiliation(s)
- Yoichiro Fukao
- Plant Global Educational Project, Nara Institute of Science and Technology, Ikoma, Japan.
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514
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Abstract
Being deeply connected to signalling, cell dynamics, growth, regulation, and defence, endocytic processes are linked to almost all aspects of cell life and disease. In this review, we focus on endosomes in the classical endocytic pathway, and on the programme of changes that lead to the formation and maturation of late endosomes/multivesicular bodies. The maturation programme entails a dramatic transformation of these dynamic organelles disconnecting them functionally and spatially from early endosomes and preparing them for their unidirectional role as a feeder pathway to lysosomes.
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515
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Sorieul M, Langhans M, Guetzoyan L, Hillmer S, Clarkson G, Lord JM, Roberts LM, Robinson DG, Spooner RA, Frigerio L. An Exo2 derivative affects ER and Golgi morphology and vacuolar sorting in a tissue-specific manner in arabidopsis. Traffic 2011; 12:1552-62. [PMID: 21801289 DOI: 10.1111/j.1600-0854.2011.01258.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We screened a panel of compounds derived from Exo2 - a drug that perturbs post-Golgi compartments and trafficking in mammalian cells - for their effect on the secretory pathway in Arabidopsis root epidermal cells. While Exo2 and most related compounds had no significant effect, one Exo2 derivative, named LG8, induced severe morphological alterations in both the Golgi (at high concentrations) and the endoplasmic reticulum (ER). LG8 causes the ER to form foci of interconnecting tubules, which at the ultrastructural level appear similar to those previously reported in Arabidopsis roots after treatment with the herbicide oryzalin. In cotyledonary leaves, LG8 causes redistribution of a trans Golgi network (TGN) marker to the vacuole. LG8 affects the anterograde secretory pathway by inducing secretion of vacuolar cargo and preventing the brassinosteroid receptor BRI1 from reaching the plasma membrane. Uptake and arrival at the TGN of the endocytic marker FM4-64 is not affected. Unlike the ADP ribosylation factor-GTP exchange factor (ARF-GEF) inhibitor brefeldin A (BFA), LG8 affects these post-Golgi events without causing the formation of BFA bodies. Up to concentrations of 50 µm, the effects of LG8 are reversible.
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Affiliation(s)
- Mathias Sorieul
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
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516
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Bottanelli F, Foresti O, Hanton S, Denecke J. Vacuolar transport in tobacco leaf epidermis cells involves a single route for soluble cargo and multiple routes for membrane cargo. THE PLANT CELL 2011; 23:3007-25. [PMID: 21856792 PMCID: PMC3180807 DOI: 10.1105/tpc.111.085480] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 06/17/2011] [Accepted: 07/14/2011] [Indexed: 05/15/2023]
Abstract
We tested if different classes of vacuolar cargo reach the vacuole via distinct mechanisms by interference at multiple steps along the transport route. We show that nucleotide-free mutants of low molecular weight GTPases, including Rab11, the Rab5 members Rha1 and Ara6, and the tonoplast-resident Rab7, caused induced secretion of both lytic and storage vacuolar cargo. In situ analysis in leaf epidermis cells indicates a sequential action of Rab11, Rab5, and Rab7 GTPases. Compared with Rab5 members, mutant Rab11 mediates an early transport defect interfering with the arrival of cargo at prevacuoles, while mutant Rab7 inhibits the final delivery to the vacuole and increases cargo levels in prevacuoles. In contrast with soluble cargo, membrane cargo may follow different routes. Tonoplast targeting of an α-TIP chimera was impaired by nucleotide-free Rha1, Ara6, and Rab7 similar to soluble cargo. By contrast, the tail-anchored tonoplast SNARE Vam3 shares only the Rab7-mediated vacuolar deposition step. The most marked difference was observed for the calcineurin binding protein CBL6, which was insensitive to all Rab mutants tested. Unlike soluble cargo, α-TIP and Vam3, CBL6 transport to the vacuole was COPII independent. The results indicate that soluble vacuolar proteins follow a single route to vacuoles, while membrane spanning proteins may use at least three different transport mechanisms.
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Affiliation(s)
| | | | | | - Jürgen Denecke
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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517
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Dhonukshe P. Cell polarity in plants: Linking PIN polarity generation mechanisms to morphogenic auxin gradients. Commun Integr Biol 2011; 2:184-90. [PMID: 20835291 DOI: 10.4161/cib.7715] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 12/23/2008] [Indexed: 12/16/2022] Open
Abstract
Auxin efflux carrier PIN proteins have been intensively investigated as they are the first polar cargos to be identified in plants with a direct relevance for plant patterning. Based on their polar localization; PIN proteins direct the intercellular flow of signaling molecule auxin and thus bear a rate limiting effect on the formation of auxin activity gradients. With this influence on directionality and extent of auxin transport PINs play crucial roles in plant body organization. Many factors such as vesicle trafficking regulator ARF-GEF GNOM, a kinase PINOID, a retromer complex and membrane sterol composition influence polar PIN localization. Recent work uncovers the mechanism that generates default PIN polarity. Real time PIN tracking reveals that PIN polarity is generated from initially non-polar secretion via endocytosis and subsequent polar recycling. In addition, the Rab5 endocytic pathway emerges to be important for polar PIN localization as Rab5 interference causes non-polar distribution of PINs. This non-polar distribution of PINs during embryogenesis transiently alters auxin activity gradients and changes organ identity by transforming embryonic leaf cells to root fates. These findings for the first time link PIN polarity-based auxin activity gradient to cell fate decisions and thus demonstrate morphogen (a substance influencing cell fates on its concentration gradient) characters of auxin. They also suggest an auxin activity distribution-dependent sensing module that executes differential apical and basal developmental program during plant embryogenesis.
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Affiliation(s)
- Pankaj Dhonukshe
- Department of Biology; Utrecht University; Utrecht, The Netherlands
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518
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Klima A, Foissner I. Actin-dependent deposition of putative endosomes and endoplasmic reticulum during early stages of wound healing in characean internodal cells. PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:590-601. [PMID: 21668600 PMCID: PMC3284245 DOI: 10.1111/j.1438-8677.2010.00413.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We investigated the behaviour of organelles stained with FM1-43 (putative endosomes) and/or LysoTracker Red (LTred; acidic compartments) and of the endoplasmic reticulum (ER) during healing of puncture and UV-induced wounds in internodal cells of Nitella flexilis and Chara corallina. Immediately after puncture, wounds were passively sealed with a plug of solid vacuolar inclusions, onto which a bipartite wound wall was actively deposited. The outer, callose-containing amorphous layer consisted of remnants of FM1-43- and LTred-labelled organelles, ER cisternae and polysaccharide-containing secretory vesicles, which became deposited in the absence of membrane retrieval (compound exocytosis). During formation of the inner cellulosic layer, exocytosis of secretory vesicles with the newly formed plasma membrane is coupled to endocytosis via coated vesicles. Migration of FM1-43- and LTred-stained organelles, ER and secretory vesicles towards the cell cortex and deposition of a bipartite wound wall could also be induced by spot-like irradiation with ultraviolet light. Cytochalasin D reversibly inhibited the accumulation and deposition of organelles. Our study indicates that active actin-dependent deposition of putative recycling endosomes is required for wound healing (plasma membrane repair) and supports the hypothesis that deposition of ER cisternae helps to restore wounding-disturbed Ca(2+) metabolism.
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Affiliation(s)
- A Klima
- Division of Plant Physiology, Department of Cell Biology, University of Salzburg, Hellbrunnerstrasse 34, Salzburg, Austria
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519
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Reichardt I, Slane D, El Kasmi F, Knöll C, Fuchs R, Mayer U, Lipka V, Jürgens G. Mechanisms of Functional Specificity Among Plasma-Membrane Syntaxins in Arabidopsis. Traffic 2011; 12:1269-80. [DOI: 10.1111/j.1600-0854.2011.01222.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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520
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Abstract
Subcellular trafficking is required for a multitude of functions in eukaryotic cells. It involves regulation of cargo sorting, vesicle formation, trafficking and fusion processes at multiple levels. Adaptor protein (AP) complexes are key regulators of cargo sorting into vesicles in yeast and mammals but their existence and function in plants have not been demonstrated. Here we report the identification of the protein-affected trafficking 4 (pat4) mutant defective in the putative δ subunit of the AP-3 complex. pat4 and pat2, a mutant isolated from the same GFP imaging-based forward genetic screen that lacks a functional putative AP-3 β, as well as dominant negative AP-3 μ transgenic lines display undistinguishable phenotypes characterized by largely normal morphology and development, but strong intracellular accumulation of membrane proteins in aberrant vacuolar structures. All mutants are defective in morphology and function of lytic and protein storage vacuoles (PSVs) but show normal sorting of reserve proteins to PSVs. Immunoprecipitation experiments and genetic studies revealed tight functional and physical associations of putative AP-3 β and AP-3 δ subunits. Furthermore, both proteins are closely linked with putative AP-3 μ and σ subunits and several components of the clathrin and dynamin machineries. Taken together, these results demonstrate that AP complexes, similar to those in other eukaryotes, exist in plants, and that AP-3 plays a specific role in the regulation of biogenesis and function of vacuoles in plant cells.
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521
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Kim SJ, Bassham DC. TNO1 is involved in salt tolerance and vacuolar trafficking in Arabidopsis. PLANT PHYSIOLOGY 2011; 156:514-26. [PMID: 21521696 PMCID: PMC3177255 DOI: 10.1104/pp.110.168963] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Accepted: 04/26/2011] [Indexed: 05/19/2023]
Abstract
The Arabidopsis (Arabidopsis thaliana) soluble N-ethylmaleimide-sensitive factor attachment protein receptor SYP41 is involved in vesicle fusion at the trans-Golgi network (TGN) and interacts with AtVPS45, SYP61, and VTI12. These proteins are involved in diverse cellular processes, including vacuole biogenesis and stress tolerance. A previously uncharacterized protein, named TNO1 (for TGN-localized SYP41-interacting protein), was identified by coimmunoprecipitation as a SYP41-interacting protein. TNO1 was found to localize to the TGN by immunofluorescence microscopy. A tno1 mutant showed increased sensitivity to high concentrations of NaCl, KCl, and LiCl and also to mannitol-induced osmotic stress. Localization of SYP61, which is involved in the salt stress response, was disrupted in the tno1 mutant. Vacuolar proteins were partially secreted to the apoplast in the tno1 mutant, suggesting that TNO1 is required for efficient protein trafficking to the vacuole. The tno1 mutant had delayed formation of the brefeldin A (BFA) compartment in cotyledons upon application of BFA, suggesting less efficient membrane fusion processes in the mutant. Unlike most TGN proteins, TNO1 does not relocate to the BFA compartment upon BFA treatment. These data demonstrate that TNO1 is involved in vacuolar trafficking and salt tolerance, potentially via roles in vesicle fusion and in maintaining TGN structure or identity.
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Affiliation(s)
| | - Diane C. Bassham
- Department of Genetics, Development, and Cell Biology (S.-J.K., D.C.B.), Plant Sciences Institute (D.C.B.), and Interdepartmental Genetics Program (S.-J.K., D.C.B.), Iowa State University, Ames, Iowa 50011
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522
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Monoubiquitin-dependent endocytosis of the iron-regulated transporter 1 (IRT1) transporter controls iron uptake in plants. Proc Natl Acad Sci U S A 2011; 108:E450-8. [PMID: 21628566 DOI: 10.1073/pnas.1100659108] [Citation(s) in RCA: 312] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Plants take up iron from the soil using the iron-regulated transporter 1 (IRT1) high-affinity iron transporter at the root surface. Sophisticated regulatory mechanisms allow plants to tightly control the levels of IRT1, ensuring optimal absorption of essential but toxic iron. Here, we demonstrate that overexpression of Arabidopsis thaliana IRT1 leads to constitutive IRT1 protein accumulation, metal overload, and oxidative stress. IRT1 is unexpectedly found in trans-Golgi network/early endosomes of root hair cells, and its levels and localization are unaffected by iron nutrition. Using pharmacological approaches, we show that IRT1 cycles to the plasma membrane to perform iron and metal uptake at the cell surface and is sent to the vacuole for proper turnover. We also prove that IRT1 is monoubiquitinated on several cytosol-exposed residues in vivo and that mutation of two putative monoubiquitination target residues in IRT1 triggers stabilization at the plasma membrane and leads to extreme lethality. Together, these data suggest a model in which monoubiquitin-dependent internalization/sorting and turnover keep the plasma membrane pool of IRT1 low to ensure proper iron uptake and to prevent metal toxicity. More generally, our work demonstrates the existence of monoubiquitin-dependent trafficking to lytic vacuoles in plants and points to proteasome-independent turnover of plasma membrane proteins.
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523
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Langhans M, Förster S, Helmchen G, Robinson DG. Differential effects of the brefeldin A analogue (6R)-hydroxy-BFA in tobacco and Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:2949-57. [PMID: 21357769 DOI: 10.1093/jxb/err007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The effects of two brefeldin A (BFA) analogues (BFA lactam; 6(R)-hydroxy-BFA) on plant cells were tested. Although these two compounds elicited BFA-like effects in mammalian cells, the lactam analogue failed to elicit a response in plant cells. By contrast, while the 6(R)-hydroxy-BFA analogue gave rise to a classic BFA response in tobacco mesophyll protoplasts and true leaves of Arabidopsis (redistribution of Golgi enzymes into the ER), it failed to cause the formation of BFA-compartments in Arabidopsis root cells and cotyledonary leaves. Even when the GNL1-LM mutant of Arabidopsis, which has a cis-Golgi located BFA-sensitive ARF-GEF, was used, the 6(R)-hydroxy analogue failed to elicit a response at conventional BFA concentrations. Only at concentrations of over 200 μM did 6(R)-hydroxy-BFA elicit a BFA-like effect. These differences are interpreted in terms of the different properties of the respective TGN- (Arabidopsis roots) and cis-Golgi- (tobacco mesophyll) localized BFA-sensitive ARF-GEFs.
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Affiliation(s)
- Markus Langhans
- Department of Cell Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, D-69120 Heidelberg, Germany
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524
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Conserved Arabidopsis ECHIDNA protein mediates trans-Golgi-network trafficking and cell elongation. Proc Natl Acad Sci U S A 2011; 108:8048-53. [PMID: 21512130 DOI: 10.1073/pnas.1018371108] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Multiple steps of plant growth and development rely on rapid cell elongation during which secretory and endocytic trafficking via the trans-Golgi network (TGN) plays a central role. Here, we identify the ECHIDNA (ECH) protein from Arabidopsis thaliana as a TGN-localized component crucial for TGN function. ECH partially complements loss of budding yeast TVP23 function and a Populus ECH complements the Arabidopsis ech mutant, suggesting functional conservation of the genes. Compared with wild-type, the Arabidopsis ech mutant exhibits severely perturbed cell elongation as well as defects in TGN structure and function, manifested by the reduced association between Golgi bodies and TGN as well as mislocalization of several TGN-localized proteins including vacuolar H(+)-ATPase subunit a1 (VHA-a1). Strikingly, ech is defective in secretory trafficking, whereas endocytosis appears unaffected in the mutant. Some aspects of the ech mutant phenotype can be phenocopied by treatment with a specific inhibitor of vacuolar H(+)-ATPases, concanamycin A, indicating that mislocalization of VHA-a1 may account for part of the defects in ech. Hence, ECH is an evolutionarily conserved component of the TGN with a central role in TGN structure and function.
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525
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Fukao Y, Ferjani A, Tomioka R, Nagasaki N, Kurata R, Nishimori Y, Fujiwara M, Maeshima M. iTRAQ analysis reveals mechanisms of growth defects due to excess zinc in Arabidopsis. PLANT PHYSIOLOGY 2011; 155:1893-907. [PMID: 21325567 PMCID: PMC3091079 DOI: 10.1104/pp.110.169730] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 02/14/2011] [Indexed: 05/18/2023]
Abstract
The micronutrient zinc is essential for all living organisms, but it is toxic at high concentrations. Here, to understand the effects of excess zinc on plant cells, we performed an iTRAQ (for isobaric tags for relative and absolute quantification)-based quantitative proteomics approach to analyze microsomal proteins from Arabidopsis (Arabidopsis thaliana) roots. Our approach was sensitive enough to identify 521 proteins, including several membrane proteins. Among them, IRT1, an iron and zinc transporter, and FRO2, a ferric-chelate reductase, increased greatly in response to excess zinc. The expression of these two genes has been previously reported to increase under iron-deficient conditions. Indeed, the concentration of iron was significantly decreased in roots and shoots under excess zinc. Also, seven subunits of the vacuolar H(+)-ATPase (V-ATPase), a proton pump on the tonoplast and endosome, were identified, and three of them decreased significantly in response to excess zinc. In addition, excess zinc in the wild type decreased V-ATPase activity and length of roots and cells to levels comparable to those of the untreated de-etiolated3-1 mutant, which bears a mutation in V-ATPase subunit C. Interestingly, excess zinc led to the formation of branched and abnormally shaped root hairs, a phenotype that correlates with decreased levels of proteins of several root hair-defective mutants. Our results point out mechanisms of growth defects caused by excess zinc in which cross talk between iron and zinc homeostasis and V-ATPase activity might play a central role.
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Affiliation(s)
- Yoichiro Fukao
- Plant Science Education Unit, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
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526
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Gu Y, Innes RW. The KEEP ON GOING protein of Arabidopsis recruits the ENHANCED DISEASE RESISTANCE1 protein to trans-Golgi network/early endosome vesicles. PLANT PHYSIOLOGY 2011; 155:1827-38. [PMID: 21343429 PMCID: PMC3091131 DOI: 10.1104/pp.110.171785] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Accepted: 02/18/2011] [Indexed: 05/20/2023]
Abstract
Loss-of-function mutations in the Arabidopsis (Arabidopsis thaliana) ENHANCED DISEASE RESISTANCE1 (EDR1) gene confer enhanced resistance to powdery mildew infection, enhanced senescence, and enhanced programmed cell death under both abiotic and biotic stress conditions. All edr1-mediated phenotypes can be suppressed by a specific missense mutation (keg-4) in the KEEP ON GOING (KEG) gene, which encodes a multidomain protein that includes a RING E3 ligase domain, a kinase domain, ankyrin repeats, and HERC2-like (for HECT and RCC1-like) repeats. The molecular and cellular mechanisms underlying this suppression are poorly understood. Using confocal laser scanning microscopy and fluorescent protein fusions, we determined that KEG localizes to trans-Golgi network/early endosome (TGN/EE) vesicles. Both the keg-4 mutation, which is located in the carboxyl-terminal HERC2-like repeats, and deletion of the entire HERC2-like repeats reduced endosomal localization of KEG and increased localization to the endoplasmic reticulum and cytosol, indicating that the HERC2-like repeats facilitate the TGN/EE targeting of KEG. EDR1 colocalized with KEG to the TGN/EE when coexpressed but localized primarily to the endoplasmic reticulum when expressed alone. Yeast two-hybrid and coimmunoprecipitation analyses revealed that EDR1 and KEG physically interact. Deletion of the HERC2-like repeats abolished the interaction between KEG and EDR1 as well as the KEG-induced TGN/EE localization of EDR1, indicating that the recruitment of EDR1 to the TGN/EE is based on a direct interaction between EDR1 and KEG mediated by the HERC2-like repeats. Collectively, these data suggest that EDR1 and KEG function together to regulate endocytic trafficking and/or the formation of signaling complexes on TGN/EE vesicles during stress responses.
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Affiliation(s)
| | - Roger W. Innes
- Department of Biology, Indiana University, Bloomington, Indiana 47405–7107
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527
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Bayle V, Arrighi JF, Creff A, Nespoulous C, Vialaret J, Rossignol M, Gonzalez E, Paz-Ares J, Nussaume L. Arabidopsis thaliana high-affinity phosphate transporters exhibit multiple levels of posttranslational regulation. THE PLANT CELL 2011; 23:1523-35. [PMID: 21521698 PMCID: PMC3101552 DOI: 10.1105/tpc.110.081067] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 02/15/2011] [Accepted: 04/06/2011] [Indexed: 05/18/2023]
Abstract
In Arabidopsis thaliana, the PHOSPHATE TRANSPORTER1 (PHT1) family encodes the high-affinity phosphate transporters. They are transcriptionally induced by phosphate starvation and require PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR (PHF1) to exit the endoplasmic reticulum (ER), indicating intracellular traffic as an additional level of regulation of PHT1 activity. Our study revealed that PHF1 acts on PHT1, upstream of vesicle coat protein COPII formation, and that additional regulatory events occur during PHT1 trafficking and determine its ER exit and plasma membrane stability. Phosphoproteomic and mutagenesis analyses revealed modulation of PHT1;1 ER export by Ser-514 phosphorylation status. Confocal microscopy analysis of root tip cells showed that PHT1;1 is localized to the plasma membrane and is present in intracellular endocytic compartments. More precisely, PHT1;1 was localized to sorting endosomes associated with prevacuolar compartments. Kinetic analysis of PHT1;1 stability and targeting suggested a modulation of PHT1 internalization from the plasma membrane to the endosomes, followed by either subsequent recycling (in low Pi) or vacuolar degradation (in high Pi). For the latter condition, we identified a rapid mechanism that reduces the pool of PHT1 proteins present at the plasma membrane. This mechanism is regulated by the Pi concentration in the medium and appears to be independent of degradation mechanisms potentially regulated by the PHO2 ubiquitin conjugase. We propose a model for differential trafficking of PHT1 to the plasma membrane or vacuole as a function of phosphate concentration.
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Affiliation(s)
- Vincent Bayle
- Commissariat à l’Energie Atomique Cadarache, Institut de Biologie Environnementale et Biotechnologie-Service de Biologie Végétale et de Microbiologie Environnementales, Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 6191 Centre National de la Recherche Scientifique–Commissariat à l’Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lez-Durance Cedex, France
| | - Jean-François Arrighi
- Commissariat à l’Energie Atomique Cadarache, Institut de Biologie Environnementale et Biotechnologie-Service de Biologie Végétale et de Microbiologie Environnementales, Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 6191 Centre National de la Recherche Scientifique–Commissariat à l’Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lez-Durance Cedex, France
| | - Audrey Creff
- Commissariat à l’Energie Atomique Cadarache, Institut de Biologie Environnementale et Biotechnologie-Service de Biologie Végétale et de Microbiologie Environnementales, Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 6191 Centre National de la Recherche Scientifique–Commissariat à l’Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lez-Durance Cedex, France
| | - Claude Nespoulous
- Laboratoire de Protéomique Fonctionnelle, Institut National de la Recherche Agronomique UR1199, Place Viala, F-34060 Montpellier Cedex 1, France
| | - Jérôme Vialaret
- Laboratoire de Protéomique Fonctionnelle, Institut National de la Recherche Agronomique UR1199, Place Viala, F-34060 Montpellier Cedex 1, France
| | - Michel Rossignol
- Laboratoire de Protéomique Fonctionnelle, Institut National de la Recherche Agronomique UR1199, Place Viala, F-34060 Montpellier Cedex 1, France
| | - Esperanza Gonzalez
- Centro Nacional de Biotecnologia–Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, Madrid E-28049, Spain
| | - Javier Paz-Ares
- Centro Nacional de Biotecnologia–Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, Madrid E-28049, Spain
| | - Laurent Nussaume
- Commissariat à l’Energie Atomique Cadarache, Institut de Biologie Environnementale et Biotechnologie-Service de Biologie Végétale et de Microbiologie Environnementales, Laboratoire de Biologie du Développement des Plantes, Unité Mixte de Recherche 6191 Centre National de la Recherche Scientifique–Commissariat à l’Energie Atomique, Aix-Marseille II, F-13108 Saint-Paul-lez-Durance Cedex, France
- Address correspondence to
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528
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Cai Y, Jia T, Lam SK, Ding Y, Gao C, San MWY, Pimpl P, Jiang L. Multiple cytosolic and transmembrane determinants are required for the trafficking of SCAMP1 via an ER-Golgi-TGN-PM pathway. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 65:882-96. [PMID: 21251105 DOI: 10.1111/j.1365-313x.2010.04469.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
How polytopic plasma membrane (PM) proteins reach their destination in plant cells remains elusive. Using transgenic tobacco BY-2 cells, we previously showed that the rice secretory carrier membrane protein 1 (SCAMP1), an integral membrane protein with four transmembrane domains (TMDs), is localized to the PM and trans-Golgi network (TGN). Here, we study the transport pathway and sorting signals of SCAMP1 by following its transient expression in tobacco BY-2 protoplasts and show that SCAMP1 reaches the PM via an endoplasmic reticulum (ER)-Golgi-TGN-PM pathway. Loss-of-function and gain-of-function analysis of various green fluorescent protein (GFP) fusions with SCAMP1 mutations further demonstrates that: (i) the cytosolic N-terminus of SCAMP1 contains an ER export signal; (ii) the transmembrane domain 2 (TMD2) and TMD3 of SCAMP1 are essential for Golgi export; (iii) SCAMP1 TMD1 is essential for TGN-to-PM targeting; (iv) the predicted topology of SCAMP1 and its various mutants remain identical as demonstrated by protease protection assay. Therefore, both the cytosolic N-terminus and TMD sequences of SCAMP1 play integral roles in mediating its transport to the PM via an ER-Golgi-TGN pathway.
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Affiliation(s)
- Yi Cai
- School of Life Sciences, Centre for Cell and Developmental Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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529
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Kang BH, Nielsen E, Preuss ML, Mastronarde D, Staehelin LA. Electron Tomography of RabA4b- and PI-4Kβ1-Labeled Trans Golgi Network Compartments in Arabidopsis. Traffic 2011; 12:313-29. [DOI: 10.1111/j.1600-0854.2010.01146.x] [Citation(s) in RCA: 213] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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530
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531
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Kim HJ, Ok SH, Bahn SC, Jang J, Oh SA, Park SK, Twell D, Ryu SB, Shin JS. Endoplasmic reticulum- and Golgi-localized phospholipase A2 plays critical roles in Arabidopsis pollen development and germination. THE PLANT CELL 2011; 23:94-110. [PMID: 21278126 PMCID: PMC3051258 DOI: 10.1105/tpc.110.074799] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 12/31/2010] [Accepted: 01/11/2011] [Indexed: 05/18/2023]
Abstract
The phospholipase A(2) (PLA(2)) superfamily of lipolytic enzymes is involved in a number of essential biological processes, such as inflammation, development, host defense, and signal transduction. Despite the proven involvement of plant PLA(2)s in many biological functions, including senescence, wounding, elicitor and stress responses, and pathogen defense, relatively little is known about plant PLA(2)s, and their genes essentially remain uncharacterized. We characterized three of four Arabidopsis thaliana PLA(2) paralogs (PLA(2)-β, -γ, and -δ) and found that they (1) are expressed during pollen development, (2) localize to the endoplasmic reticulum and/or Golgi, and (3) play critical roles in pollen development and germination and tube growth. The suppression of PLA(2) using the RNA interference approach resulted in pollen lethality. The inhibition of pollen germination by pharmacological PLA(2) inhibitors was rescued by a lipid signal molecule, lysophosphatidyl ethanolamine. Based on these results, we propose that plant reproduction, in particular, male gametophyte development, requires the activities of the lipid-modifying PLA(2)s that are conserved in other organisms.
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Affiliation(s)
- Hae Jin Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
| | - Sung Han Ok
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
| | - Sung Chul Bahn
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
| | - Juno Jang
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
| | - Sung Aeong Oh
- Division of Plant Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - Soon Ki Park
- Division of Plant Biosciences, Kyungpook National University, Daegu 702-701, Korea
| | - David Twell
- Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Stephen Beungtae Ryu
- Environmental Biotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, South Korea
| | - Jeong Sheop Shin
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
- Address correspondence to
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532
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Park M, Jürgens G. Membrane traffic and fusion at post-Golgi compartments. FRONTIERS IN PLANT SCIENCE 2011; 2:111. [PMID: 22645561 PMCID: PMC3355779 DOI: 10.3389/fpls.2011.00111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 12/19/2011] [Indexed: 05/18/2023]
Abstract
Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysis of various biological processes including membrane traffic by which many proteins are delivered to their sites of action and turnover. In particular, membrane traffic between post-Golgi compartments plays an important role in cell signaling, taking care of receptor-ligand interaction and inactivation, which requires secretion, endocytosis, and recycling or targeting to the vacuole for degradation. Here, we discuss recent studies that address the identity of post-Golgi compartments, the machinery involved in traffic and fusion or functionally characterized cargo proteins that are delivered to or pass through post-Golgi compartments. We also provide an outlook on future challenges in this area of research.
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Affiliation(s)
- Misoon Park
- Entwicklungsgenetik, Zentrum für Molekularbiologie der Pflanzen, University of TübingenTübingen, Germany
| | - Gerd Jürgens
- Entwicklungsgenetik, Zentrum für Molekularbiologie der Pflanzen, University of TübingenTübingen, Germany
- *Correspondence: Gerd Jürgens, Entwicklungsgenetik, Zentrum für Molekularbiologie der Pflanzen, University of Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany. e-mail:
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533
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Qi X, Droste T, Kao CC. Cell-penetrating peptides derived from viral capsid proteins. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:25-36. [PMID: 21138375 DOI: 10.1094/mpmi-07-10-0147] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Cell-penetrating peptides (CPP) can translocate across the cell membrane and have been extensively studied for the delivery of proteins, nucleic acids, and therapeutics in mammalian cells. However, characterizations of CPP in plants have only recently been initiated. We showed that the intact virion and a recombinant capsid protein (CaP) from a plant-infecting nonenveloped icosahedral RNA virus, Brome mosaic virus (BMV), can penetrate the membranes of plant protoplasts but are trapped by the extracellular matrix. Furthermore, a 22-residue peptide derived from the N-terminal region of the CaP (CPNT) can enter barley protoplasts and cells of intact barley and Arabidopsis roots. An inhibitor of the macropinocytosis reduced CPNT entry, while treatment with NiCl(2) changed the cellular localization of CPNT. CPNT increased uptake of the green flourescent protein (GFP) into the cell when covalently fused to GFP or when present in trans of GFP. The BMV CPNT overlaps with the sequence known to bind BMV RNA, and it can deliver BMV RNAs into cells, resulting in viral replication, as well as deliver double-stranded RNAs that can induce gene silencing.
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Affiliation(s)
- Xiaopeng Qi
- Department of Molecular & Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA
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534
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Olins AL, Langhans M, Monestier M, Schlotterer A, Robinson DG, Viotti C, Zentgraf H, Zwerger M, Olins DE. An epichromatin epitope: persistence in the cell cycle and conservation in evolution. Nucleus 2011; 2:47-60. [PMID: 21647299 PMCID: PMC3104809 DOI: 10.4161/nucl.2.1.13271] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 09/15/2010] [Accepted: 09/16/2010] [Indexed: 11/19/2022] Open
Abstract
Interphase nuclear architecture is disrupted and rapidly reformed with each cell division cycle. Successive cell generations exhibit a "memory" of this nuclear architecture, as well as for gene expression. Furthermore, many features of nuclear and mitotic chromosome structure are recognizably species and tissue specific. We wish to know what properties of the underlying chromatin structure may determine these conserved features of nuclear architecture. Employing a particular mouse autoimmune anti-nucleosome monoclonal antibody (PL2-6), combined with deconvolution immunofluorescence microscopy, we present evidence for a unique epitope (involving a ternary complex of histones H2A and H2B and DNA) which is localized only at the exterior chromatin surface of interphase nuclei and mitotic chromosomes in mammalian, invertebrate and plant systems. As only the surface chromatin region is identified with antibody PL2-6, we have assigned it the name "epichromatin". We describe an "epichromatin hypothesis", suggesting that epichromatin may have a unique evolutionary conserved conformation which facilitates interaction with the reforming post-mitotic nuclear envelope and a rapid return of interphase nuclear architecture.
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Affiliation(s)
- Ada L Olins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, ME USA. ted proteins (ARPs), a
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535
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Bassil E, Ohto MA, Esumi T, Tajima H, Zhu Z, Cagnac O, Belmonte M, Peleg Z, Yamaguchi T, Blumwald E. The Arabidopsis intracellular Na+/H+ antiporters NHX5 and NHX6 are endosome associated and necessary for plant growth and development. THE PLANT CELL 2011; 23:224-39. [PMID: 21278129 PMCID: PMC3051250 DOI: 10.1105/tpc.110.079426] [Citation(s) in RCA: 201] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/20/2010] [Accepted: 01/03/2011] [Indexed: 05/18/2023]
Abstract
Intracellular Na(+)/H(+) antiporters (NHXs) play important roles in cellular pH and Na(+) and K(+) homeostasis in all eukaryotes. Based on sequence similarity, the six intracellular Arabidopsis thaliana members are divided into two groups. Unlike the vacuolar NHX1-4, NHX5 and NHX6 are believed to be endosomal; however, little data exist to support either their function or localization. Using reverse genetics, we show that whereas single knockouts nhx5 or nhx6 did not differ from the wild type, the double knockout nhx5 nhx6 showed reduced growth, with smaller and fewer cells and increased sensitivity to salinity. Reduced growth of nhx5 nhx6 was due to slowed cell expansion. Transcriptome analysis indicated that nhx5, nhx6, and the wild type had similar gene expression profiles, whereas transcripts related to vesicular trafficking and abiotic stress were enriched in nhx5 nhx6. We show that unlike other intracellular NHX proteins, NHX5 and NHX6 are associated with punctate, motile cytosolic vesicles, sensitive to Brefeldin A, that colocalize to known Golgi and trans-Golgi network markers. We provide data to show that vacuolar trafficking is affected in nhx5 nhx6. Possible involvements of NHX5 and NHX6 in maintaining organelle pH and ion homeostasis with implications in endosomal sorting and cellular stress responses are discussed.
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Affiliation(s)
- Elias Bassil
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Masa-aki Ohto
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Tomoya Esumi
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Hiromi Tajima
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Zhu Zhu
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Olivier Cagnac
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Mark Belmonte
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - Zvi Peleg
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Toshio Yamaguchi
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Eduardo Blumwald
- Department of Plant Sciences, University of California, Davis, California 95616
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536
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Katz E, Fon M, Eigenheer RA, Phinney BS, Fass JN, Lin D, Sadka A, Blumwald E. A label-free differential quantitative mass spectrometry method for the characterization and identification of protein changes during citrus fruit development. Proteome Sci 2010; 8:68. [PMID: 21162737 PMCID: PMC3017515 DOI: 10.1186/1477-5956-8-68] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 12/16/2010] [Indexed: 01/03/2023] Open
Abstract
Background Citrus is one of the most important and widely grown commodity fruit crops. In this study a label-free LC-MS/MS based shot-gun proteomics approach was taken to explore three main stages of citrus fruit development. These approaches were used to identify and evaluate changes occurring in juice sac cells in various metabolic pathways affecting citrus fruit development and quality. Results Protein changes in citrus juice sac cells were identified and quantified using label-free shotgun methodologies. Two alternative methods, differential mass-spectrometry (dMS) and spectral counting (SC) were used to analyze protein changes occurring during earlier and late stages of fruit development. Both methods were compared in order to develop a proteomics workflow that could be used in a non-model plant lacking a sequenced genome. In order to resolve the bioinformatics limitations of EST databases from species that lack a full sequenced genome, we established iCitrus. iCitrus is a comprehensive sequence database created by merging three major sources of sequences (HarvEST:citrus, NCBI/citrus/unigenes, NCBI/citrus/proteins) and improving the annotation of existing unigenes. iCitrus provided a useful bioinformatics tool for the high-throughput identification of citrus proteins. We have identified approximately 1500 citrus proteins expressed in fruit juice sac cells and quantified the changes of their expression during fruit development. Our results showed that both dMS and SC provided significant information on protein changes, with dMS providing a higher accuracy. Conclusion Our data supports the notion of the complementary use of dMS and SC for label-free comparative proteomics, broadening the identification spectrum and strengthening the identification of trends in protein expression changes during the particular processes being compared.
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Affiliation(s)
- Ehud Katz
- Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
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537
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Takác T, Pechan T, Richter H, Müller J, Eck C, Böhm N, Obert B, Ren H, Niehaus K, Samaj J. Proteomics on brefeldin A-treated Arabidopsis roots reveals profilin 2 as a new protein involved in the cross-talk between vesicular trafficking and the actin cytoskeleton. J Proteome Res 2010; 10:488-501. [PMID: 21090759 DOI: 10.1021/pr100690f] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The growing importance of vesicular trafficking and cytoskeleton dynamic reorganization during plant development requires the exploitation of novel experimental approaches. Several genetic and cell biological studies have used diverse pharmaceutical drugs that inhibit vesicular trafficking and secretion to study these phenomena. Here, proteomic and cell biology approaches were applied to study effects of brefeldin A (BFA), an inhibitor of vesicle recycling and secretion, in Arabidopsis roots. The main aim of this study was to obtain an overview of proteins affected by BFA, but especially to identify new proteins involved in the vesicular trafficking and its cross-talk to the actin cytoskeleton. The results showed that BFA altered vesicular trafficking and caused the formation of BFA-compartments which was accompanied by differential expression of several proteins in root cells. Some of the BFA-up-regulated proteins belong to the class of the vesicular trafficking proteins, such as V-ATPase and reversibly glycosylated polypeptide, while others, such as profilin 2 and elongation factor 1 alpha, are rather involved in the remodeling of the actin cytoskeleton. Upregulation of profilin 2 by BFA was verified by immunoblot and live imaging at subcellular level. The latter approach also revealed that profilin 2 accumulated in BFA-compartments which was accompanied by remodeling of the actin cytoskeleton in BFA-treated root cells. Thus, profilin 2 seems to be involved in the cross-talk between vesicular trafficking and the actin cytoskeleton, in a BFA-dependent manner.
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Affiliation(s)
- Tomás Takác
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Department of Cell Biology, Palacký University, Olomouc, Czech Republic.
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538
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Naramoto S, Kleine-Vehn J, Robert S, Fujimoto M, Dainobu T, Paciorek T, Ueda T, Nakano A, Van Montagu MCE, Fukuda H, Friml J. ADP-ribosylation factor machinery mediates endocytosis in plant cells. Proc Natl Acad Sci U S A 2010; 107:21890-21895. [PMID: 21118984 DOI: 10.2307/25756979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
Endocytosis is crucial for various cellular functions and development of multicellular organisms. In mammals and yeast, ADP-ribosylation factor (ARF) GTPases, key components of vesicle formation, and their regulators ARF-guanine nucleotide exchange factors (GEFs) and ARF-GTPase-activating protein (GAPs) mediate endocytosis. A similar role has not been established in plants, mainly because of the lack of the canonical ARF and ARF-GEF components that are involved in endocytosis in other eukaryotes. In this study, we revealed a regulatory mechanism of endocytosis in plants based on ARF GTPase activity. We identified that ARF-GEF GNOM and ARF-GAP vascular network defective 3 (VAN3), both of which are involved in polar auxin transport-dependent morphogenesis, localize at the plasma membranes as well as in intracellular structures. Variable angle epifluorescence microscopy revealed that GNOM and VAN3 localize to partially overlapping discrete foci at the plasma membranes that are regularly associated with the endocytic vesicle coat clathrin. Genetic studies revealed that GNOM and VAN3 activities are required for endocytosis and internalization of plasma membrane proteins, including PIN-FORMED auxin transporters. These findings identified ARF GTPase-based regulatory mechanisms for endocytosis in plants. GNOM and VAN3 previously were proposed to function solely at the recycling endosomes and trans-Golgi networks, respectively. Therefore our findings uncovered an additional cellular function of these prominent developmental regulators.
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Affiliation(s)
- Satoshi Naramoto
- Department of Plant Systems Biology, Flanders Institute for Biotechnology, 9052 Ghent, Belgium
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539
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The gametic central cell of Arabidopsis determines the lifespan of adjacent accessory cells. Proc Natl Acad Sci U S A 2010; 107:22350-5. [PMID: 21135240 DOI: 10.1073/pnas.1012795108] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Plant germ cells develop in specialized haploid structures, termed gametophytes. The female gametophyte patterns of flowering plants are diverse, with often unknown adaptive value. Here we present the Arabidopsis fiona mutant, which forms a female gametophyte that is structurally and functionally reminiscent of a phylogenetic distant female gametophyte. The respective changes include a modified reproductive behavior of one of the female germ cells (central cell) and an extended lifespan of three adjacent accessory cells (antipodals). FIONA encodes the cysteinyl t-RNA synthetase SYCO ARATH (SYCO), which is expressed and required in the central cell but not in the antipodals, suggesting that antipodal lifespan is controlled by the adjacent gamete. SYCO localizes to the mitochondria, and ultrastructural analysis of mutant central cells revealed that the protein is necessary for mitochondrial cristae integrity. Furthermore, a dominant ATP/ADP translocator caused mitochondrial cristae degeneration and extended antipodal lifespan when expressed in the central cell of wild-type plants. Notably, this construct did not affect antipodal lifespan when expressed in antipodals. Our results thus identify an unexpected noncell autonomous role for mitochondria in the regulation of cellular lifespan and provide a basis for the coordinated development of gametic and nongametic cells.
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540
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Stefano G, Renna L, Rossi M, Azzarello E, Pollastri S, Brandizzi F, Baluska F, Mancuso S. AGD5 is a GTPase-activating protein at the trans-Golgi network. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:790-799. [PMID: 21105926 DOI: 10.1111/j.1365-313x.2010.04369.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
ARF-GTPases are important proteins that control membrane trafficking events. Their activity is largely influenced by the interplay between guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), which facilitate the activation or inactivation of ARF-GTPases, respectively. There are 15 predicted proteins that contain an ARF-GAP domain within the Arabidopsis thaliana genome, and these are classified as ARF-GAP domain (AGD) proteins. The function and subcellular distribution of AGDs, including the ability to activate ARF-GTPases in vivo, that remain largely uncharacterized to date. Here we show that AGD5 is localised to the trans-Golgi network (TGN), where it co-localises with ARF1, a crucial GTPase that is involved in membrane trafficking and which was previously shown to be distributed on Golgi and post-Golgi structures of unknown nature. Taking advantage of the in vivo AGD5-ARF1 interaction at the TGN, we show that mutation of an arginine residue that is critical for ARF-GAP activity of AGD5 leads to longer residence of ARF1 on the membranes, as expected if GTP hydrolysis on ARF1 was impaired due to a defective GAP. Our results establish the nature of the post-Golgi compartments in which ARF1 localises, as well as identifying the role of AGD5 in vivo as a TGN-localised GAP. Furthermore, in vitro experiments established the promiscuous interaction between AGD5 and the plasma membrane-localised ADP ribosylation factor B (ARFB), confirming that ARF-GAP specificity for ARF-GTPases within the cell environment may be spatially regulated.
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Affiliation(s)
- Giovanni Stefano
- Department of Plant, Soil and Environmental Science, viale delle Idee, University of Florence, Sesto Fiorentino, FI 50019, Italy.
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541
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Wang J, Ding Y, Wang J, Hillmer S, Miao Y, Lo SW, Wang X, Robinson DG, Jiang L. EXPO, an exocyst-positive organelle distinct from multivesicular endosomes and autophagosomes, mediates cytosol to cell wall exocytosis in Arabidopsis and tobacco cells. THE PLANT CELL 2010; 22:4009-30. [PMID: 21193573 PMCID: PMC3027174 DOI: 10.1105/tpc.110.080697] [Citation(s) in RCA: 209] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2010] [Revised: 11/29/2010] [Accepted: 12/09/2010] [Indexed: 05/17/2023]
Abstract
The exocyst protein complex mediates vesicle fusion with the plasma membrane. By expressing an (X)FP-tagged Arabidopsis thaliana homolog of the exocyst protein Exo70 in suspension-cultured Arabidopsis and tobacco (Nicotiana tabacum) BY-2 cells, and using antibodies specific for Exo70, we detected a compartment, which we term EXPO (for exocyst positive organelles). Standard markers for the Golgi apparatus, the trans-Golgi network/early endosome, and the multivesicular body/late endosome in plants do not colocalize with EXPO. Inhibitors of the secretory and endocytic pathways also do not affect EXPO. Exo70E2-(X)FP also locates to the plasma membrane (PM) as discrete punctae and is secreted outside of the cells. Immunogold labeling of sections cut from high-pressure frozen samples reveal EXPO to be spherical double membrane structures resembling autophagosomes. However, unlike autophagosomes, EXPOs are not induced by starvation and do not fuse with the lytic compartment or with endosomes. Instead, they fuse with the PM, releasing a single membrane vesicle into the cell wall. EXPOs are also found in other cell types, including root tips, root hair cells, and pollen grains. EXPOs therefore represent a form of unconventional secretion unique to plants.
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Affiliation(s)
- Juan Wang
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yu Ding
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Junqi Wang
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Stefan Hillmer
- Department of Cell Biology, Heidelberg Institute for Plant Science, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Yansong Miao
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Sze Wan Lo
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Xiangfeng Wang
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - David G. Robinson
- Department of Cell Biology, Heidelberg Institute for Plant Science, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell and Developmental Biology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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542
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Pourcher M, Santambrogio M, Thazar N, Thierry AM, Fobis-Loisy I, Miège C, Jaillais Y, Gaude T. Analyses of sorting nexins reveal distinct retromer-subcomplex functions in development and protein sorting in Arabidopsis thaliana. THE PLANT CELL 2010; 22:3980-91. [PMID: 21156856 PMCID: PMC3027177 DOI: 10.1105/tpc.110.078451] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 10/26/2010] [Accepted: 11/24/2010] [Indexed: 05/18/2023]
Abstract
Sorting nexins (SNXs) are conserved eukaryotic proteins that associate with three types of vacuolar protein sorting (VPS) proteins to form the retromer complex. How SNXs act in this complex and whether they might work independently of the retromer remains elusive. Here, we show by genetic and cell imaging approaches that the Arabidopsis thaliana SNX1 protein recruits SNX2 at the endosomal membrane, a process required for SNX1-SNX2 dimer activity. We report that, in contrast with the mammalian retromer, SNXs are dispensable for membrane binding and function of the retromer complex. We also show that VPS retromer components can work with or independently of SNXs in the trafficking of seed storage proteins, which reveals distinct functions for subcomplexes of the plant retromer. Finally, we provide compelling evidence that the combined loss of function of SNXs and VPS29 leads to embryo or seedling lethality, underlining the essential role of these proteins in development.
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Affiliation(s)
- Mikael Pourcher
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Martina Santambrogio
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Nelcy Thazar
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Anne-Marie Thierry
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Isabelle Fobis-Loisy
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Christine Miège
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Yvon Jaillais
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
| | - Thierry Gaude
- Université de Lyon, F-69007 Lyon, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5667, Institut Fédératif de Recherche 128, F-69342 Lyon, France
- Ecole Normale Supérieure de Lyon, F-69342 Lyon, France
- Institut National de la Recherche Agronomique, F-69364 Lyon, France
- Université Lyon 1, F-69622 Villeurbanne, France
- Address correspondence to
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543
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Schumacher K, Krebs M. The V-ATPase: small cargo, large effects. CURRENT OPINION IN PLANT BIOLOGY 2010; 13:724-30. [PMID: 20801076 DOI: 10.1016/j.pbi.2010.07.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 07/20/2010] [Accepted: 07/30/2010] [Indexed: 05/18/2023]
Abstract
About 30 years ago seminal reports of anion-sensitive proton-pumping activity associated with microsomal membranes initiated research on the plant vacuolar-type H(+)-ATPase (V-ATPase, VHA). Since, it has been firmly established that these complex molecular machines are essential for what can be defined as cellular logistics. In a eukaryotic cell, the flow of goods between compartments is achieved either by protein-mediated membrane transport or via vesicular trafficking. Over the past years, it has become increasingly clear that V-ATPases do not only energize secondary active transport but are also important regulators of membrane trafficking.
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Affiliation(s)
- Karin Schumacher
- Heidelberg Institute for Plant Sciences (HIP), Universität Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany.
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544
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Foresti O, Gershlick DC, Bottanelli F, Hummel E, Hawes C, Denecke J. A recycling-defective vacuolar sorting receptor reveals an intermediate compartment situated between prevacuoles and vacuoles in tobacco. THE PLANT CELL 2010; 22:3992-4008. [PMID: 21177482 PMCID: PMC3027165 DOI: 10.1105/tpc.110.078436] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 10/04/2010] [Accepted: 11/11/2010] [Indexed: 05/18/2023]
Abstract
Plant vacuolar sorting receptors (VSRs) display cytosolic Tyr motifs (YMPL) for clathrin-mediated anterograde transport to the prevacuolar compartment. Here, we show that the same motif is also required for VSR recycling. A Y612A point mutation in Arabidopsis thaliana VSR2 leads to a quantitative shift in VSR2 steady state levels from the prevacuolar compartment to the trans-Golgi network when expressed in Nicotiana tabacum. By contrast, the L615A mutant VSR2 leaks strongly to vacuoles and accumulates in a previously undiscovered compartment. The latter is shown to be distinct from the Golgi stacks, the trans-Golgi network, and the prevacuolar compartment but is characterized by high concentrations of soluble vacuolar cargo and the rab5 GTPase Rha1(RabF2a). The results suggest that the prevacuolar compartment matures by gradual receptor depletion, leading to the formation of a late prevacuolar compartment situated between the prevacuolar compartment and the vacuole.
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Affiliation(s)
- Ombretta Foresti
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - David C. Gershlick
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Francesca Bottanelli
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Eric Hummel
- School of Life Sciences, Oxford Brookes, Oxford OX3 0BP, United Kingdom
| | - Chris Hawes
- School of Life Sciences, Oxford Brookes, Oxford OX3 0BP, United Kingdom
| | - Jürgen Denecke
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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545
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Hicks GR, Raikhel NV. Advances in dissecting endomembrane trafficking with small molecules. CURRENT OPINION IN PLANT BIOLOGY 2010; 13:706-13. [PMID: 20851666 DOI: 10.1016/j.pbi.2010.08.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 08/06/2010] [Accepted: 08/25/2010] [Indexed: 05/08/2023]
Abstract
Chemical genomics is relatively new to plant biology in academia; however, the ability of this approach to present novel discoveries is being demonstrated clearly. One particularly suitable application of this approach is plant endomembrane trafficking. The rapid and dynamic nature of vesicular trafficking plus genetic redundancy has hampered effective study of this complex network. The ability of small molecules to act quickly to inhibit or arrest vesicular trafficking should permit the association of specific vesicles, especially endosome compartments, with their cargoes, particularly those destined for the plasma membrane. This approach and the large target space presented by the endomembrane trafficking network require the discovery of many new bioactive molecules. Advances in high-throughput chemical screening in plants are making this a reality. However, successful chemical genomic approaches in plants must be coupled with improvements in automated microscopy, image analysis, and target identification. In addition, the ability to correlate specific molecules with complex phenotypic data will be crucial. The data obtained from these experiments will be composed of a matrix of intracellular markers displaying complex chemically induced phenotypes as well as whole plant and perhaps data generated by genomics, proteomics, and metabolomics. In this manner, it should be possible to view endomembrane trafficking and its interactions as a systems-based network.
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Affiliation(s)
- Glenn R Hicks
- Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.
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546
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ADP-ribosylation factor machinery mediates endocytosis in plant cells. Proc Natl Acad Sci U S A 2010; 107:21890-5. [PMID: 21118984 DOI: 10.1073/pnas.1016260107] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Endocytosis is crucial for various cellular functions and development of multicellular organisms. In mammals and yeast, ADP-ribosylation factor (ARF) GTPases, key components of vesicle formation, and their regulators ARF-guanine nucleotide exchange factors (GEFs) and ARF-GTPase-activating protein (GAPs) mediate endocytosis. A similar role has not been established in plants, mainly because of the lack of the canonical ARF and ARF-GEF components that are involved in endocytosis in other eukaryotes. In this study, we revealed a regulatory mechanism of endocytosis in plants based on ARF GTPase activity. We identified that ARF-GEF GNOM and ARF-GAP vascular network defective 3 (VAN3), both of which are involved in polar auxin transport-dependent morphogenesis, localize at the plasma membranes as well as in intracellular structures. Variable angle epifluorescence microscopy revealed that GNOM and VAN3 localize to partially overlapping discrete foci at the plasma membranes that are regularly associated with the endocytic vesicle coat clathrin. Genetic studies revealed that GNOM and VAN3 activities are required for endocytosis and internalization of plasma membrane proteins, including PIN-FORMED auxin transporters. These findings identified ARF GTPase-based regulatory mechanisms for endocytosis in plants. GNOM and VAN3 previously were proposed to function solely at the recycling endosomes and trans-Golgi networks, respectively. Therefore our findings uncovered an additional cellular function of these prominent developmental regulators.
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547
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Elgass K, Caesar K, Harter K, Meixner AJ, Schleifenbaum F. Combining ocFLIM and FIDSAM reveals fast and dynamic physiological responses at subcellular resolution in living plant cells. J Microsc 2010; 242:124-31. [DOI: 10.1111/j.1365-2818.2010.03446.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K Elgass
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle, Tübingen, Germany
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548
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Olins AL, Ernst A, Zwerger M, Herrmann H, Olins DE. An in vitro model for Pelger-Huët anomaly: stable knockdown of lamin B receptor in HL-60 cells. Nucleus 2010; 1:506-12. [PMID: 21327094 PMCID: PMC3027054 DOI: 10.4161/nucl.1.6.13271] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 08/03/2010] [Accepted: 08/06/2010] [Indexed: 11/19/2022] Open
Abstract
The principal human blood granulocyte (neutrophil) possesses a lobulated and deformable nucleus, important to facilitate rapid egress from blood vessels as these cells migrate to sites of bacterial or fungal infection. This unusual nuclear shape is a product of elevated levels of an integral membrane protein of the nuclear envelope lamin B receptor (LBR) and of decreased amounts of lamin A/C. In humans, a genetic deficiency of LBR produces Pelger-Huët anomaly, resulting in blood neutrophils that exhibit hypolobulated nuclei with redistributed heterochromatin. Structural changes in nuclear architecture occur during granulopoiesis within bone marrow. The exact mechanisms of this nuclear shape change and of heterochromatin redistribution remain largely unknown. As a tool to facilitate analysis of these mechanisms, a stable LBR knockdown subline of HL-60 cells was established. During in vitro granulopoiesis induced with retinoic acid, the LBR knockdown cells retain an ovoid shaped nucleus with reduced levels of lamin A/C; while, the parent cells develop highly lobulated nuclei. In contrast, macrophage forms induced in LBR knockdown cells by in vitro treatment with phorbol ester were indistinguishable from the parent cells, judged by both nuclear shape and attached cell morphology. The capability of differentiation of LBR knockdown HL-60 cells should facilitate a detailed analysis of the molecular relationship between LBR levels, granulocyte nuclear shape and heterochromatin distribution.
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Affiliation(s)
- Ada L Olins
- Department of Biology, Bowdoin College, Brunswick, ME, USA
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549
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Xiong G, Li R, Qian Q, Song X, Liu X, Yu Y, Zeng D, Wan J, Li J, Zhou Y. The rice dynamin-related protein DRP2B mediates membrane trafficking, and thereby plays a critical role in secondary cell wall cellulose biosynthesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 64:56-70. [PMID: 20663087 DOI: 10.1111/j.1365-313x.2010.04308.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Membrane trafficking between the plasma membrane (PM) and intracellular compartments is an important process that regulates the deposition and metabolism of cell wall polysaccharides. Dynamin-related proteins (DRPs), which function in membrane tubulation and vesiculation are closely associated with cell wall biogenesis. However, the molecular mechanisms by which DRPs participate in cell wall formation are poorly understood. Here, we report the functional characterization of Brittle Culm3 (BC3), a gene encoding OsDRP2B. Consistent with the expression of BC3 in mechanical tissues, the bc3 mutation reduces mechanical strength, which results from decreased cellulose content and altered secondary wall structure. OsDRP2B, one of three members of the DRP2 subfamily in rice (Oryza sativa L.), was identified as an authentic membrane-associated dynamin via in vitro biochemical analyses. Subcellular localization of fluorescence-tagged OsDRP2B and several compartment markers in protoplast cells showed that this protein not only lies at the PM and the clathrin-mediated vesicles, but also is targeted to the trans-Golgi network (TGN). An FM4-64 uptake assay in transgenic plants that express green fluorescent protein-tagged OsDRP2B verified its involvement in an endocytic pathway. BC3 mutation and overexpression altered the abundance of cellulose synthase catalytic subunit 4 (OsCESA4) in the PM and in the endomembrane systems. All of these findings lead us to conclude that OsDRP2B participates in the endocytic pathway, probably as well as in post-Golgi membrane trafficking. Mutation of OsDRP2B disturbs the membrane trafficking that is essential for normal cellulose biosynthesis of the secondary cell wall, thereby leading to inferior mechanical properties in rice plants.
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Affiliation(s)
- Guangyan Xiong
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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550
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Thellmann M, Rybak K, Thiele K, Wanner G, Assaad FF. Tethering factors required for cytokinesis in Arabidopsis. PLANT PHYSIOLOGY 2010; 154:720-32. [PMID: 20713617 PMCID: PMC2948999 DOI: 10.1104/pp.110.154286] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
At the end of the cell cycle, the nascent cross wall is laid down within a transient membrane compartment referred to as the cell plate. Tethering factors, which act by capturing vesicles and holding them in the vicinity of their target membranes, are likely to play an important role in the first stages of cell plate assembly. Factors required for cell plate biogenesis, however, remain to be identified. In this study, we used a reverse genetic screen to isolate tethering factors required for cytokinesis in Arabidopsis (Arabidopsis thaliana). We focused on the TRAPPI and TRAPPII (for transport protein particle) tethering complexes, which are thought to be required for the flow of traffic through the Golgi and for trans-Golgi network function, as well as on the GARP complex, thought to be required for the tethering of endocytotic vesicles to the trans-Golgi network. We found weak cytokinesis defects in some TRAPPI mutants and strong cytokinesis defects in all the TRAPPII lines we surveyed. Indeed, four insertion lines at the TRAPPII locus AtTRS120 had canonical cytokinesis-defective seedling-lethal phenotypes, including cell wall stubs and incomplete cross walls. Confocal and electron microscopy showed that in trs120 mutants, vesicles accumulated at the equator of dividing cells yet failed to assemble into a cell plate. This shows that AtTRS120 is required for cell plate biogenesis. In contrast to the TRAPP complexes, we found no conclusive evidence for cytokinesis defects in seven GARP insertion lines. We discuss the implications of these findings for the origin and identity of cell plate membranes.
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