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Abstract
Unconventional protein secretion (UPS) describes secretion pathways that bypass one or several of the canonical secretion pit-stops on the way to the plasma membrane, and/or involve the secretion of leaderless proteins. So far, alternatives to conventional secretion were primarily observed and studied in yeast and animal cells. The sessile lifestyle of plants brings with it unique restraints on how they adapt to adverse conditions and environmental challenges. Recently, attention towards unconventional secretion pathways in plant cells has substantially increased, with the large number of leaderless proteins identified through proteomic studies. While UPS pathways in plants are certainly not yet exhaustively researched, an emerging notion is that induction of UPS pathways is correlated with pathogenesis and stress responses. Given the multitude UPS events observed, comprehensively organizing the routes proteins take to the apoplast in defined UPS categories is challenging. With the establishment of a larger collection of studied plant proteins taking these UPS pathways, a clearer picture of endomembrane trafficking as a whole will emerge. There are several novel enabling technologies, such as vesicle proteomics and chemical genomics, with great potential for dissecting secretion pathways, providing information about the cargo that travels along them and the conditions that induce them.
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Affiliation(s)
- Destiny J Davis
- Department of Plant Sciences, University of California, Asmundson Hall, One Shields Avenue, Davis, CA, 95616, USA
| | - Byung-Ho Kang
- Center for Organelle Biogenesis and Function, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Angelo S Heringer
- Department of Plant Sciences, University of California, Asmundson Hall, One Shields Avenue, Davis, CA, 95616, USA
| | - Thomas E Wilkop
- Department of Plant Sciences, University of California, Asmundson Hall, One Shields Avenue, Davis, CA, 95616, USA.
| | - Georgia Drakakaki
- Department of Plant Sciences, University of California, Asmundson Hall, One Shields Avenue, Davis, CA, 95616, USA.
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Robinson DG, Ding Y, Jiang L. Unconventional protein secretion in plants: a critical assessment. PROTOPLASMA 2016; 253:31-43. [PMID: 26410830 DOI: 10.1007/s00709-015-0887-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 09/18/2015] [Indexed: 05/27/2023]
Abstract
Unconventional protein secretion (UPS) is a collective term for mechanisms by which cytosolic proteins that lack a signal peptide ("leaderless secretory proteins" (LSPs)) can gain access to the cell exterior. Numerous examples of UPS have been well documented in animal and yeast cells. In contrast, our understanding of the mechanism(s) and function of UPS in plants is very limited. This review evaluates the available literature on this subject. The apparent large numbers of LSPs in the plant secretome suggest that UPS also occurs in plants but is not a proof. Although the direct transport of LSPs across the plant plasma membrane (PM) has not yet been described, it is possible that as in other eukaryotes, exosomes may be released from plant cells through fusion of multivesicular bodies (MVBs) with the PM. In this way, LSPs, but also small RNAs (sRNAs), that are passively taken up from the cytosol into the intraluminal vesicles of MVBs, could reach the apoplast. Another possible mechanism is the recently discovered exocyst-positive organelle (EXPO), a double-membrane-bound compartment, distinct from autophagosomes, which appears to sequester LSPs.
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Affiliation(s)
- David G Robinson
- Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, D-69120, Heidelberg, Germany.
| | - Yu Ding
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Liwen Jiang
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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Hong D, Jeon BW, Kim SY, Hwang JU, Lee Y. The ROP2-RIC7 pathway negatively regulates light-induced stomatal opening by inhibiting exocyst subunit Exo70B1 in Arabidopsis. THE NEW PHYTOLOGIST 2016; 209:624-35. [PMID: 26451971 DOI: 10.1111/nph.13625] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/30/2015] [Indexed: 05/03/2023]
Abstract
Stomata are the tiny valves on the plant surface that mediate gas exchange between the plant and its environment. Stomatal opening needs to be tightly regulated to facilitate CO2 uptake and prevent excess water loss. Plant Rho-type (ROP) GTPase 2 (ROP2) is a molecular component of the system that negatively regulates light-induced stomatal opening. Previously, ROP-interactive Cdc42- and Rac-interactive binding motif-containing protein 7 (RIC7) was suggested to function downstream of ROP2. However, the underlying molecular mechanism remains unknown. To understand the mechanism by which RIC7 regulates light-induced stomatal opening, we analyzed the stomatal responses of ric7 mutant Arabidopsis plants and identified the target protein of RIC7 using a yeast two-hybrid screen. Light-induced stomatal opening was promoted by ric7 knockout, whereas it was inhibited by RIC7 overexpression, indicating that RIC7 negatively regulates stomatal opening in Arabidopsis. RIC7 interacted with exocyst subunit Exo70 family protein B1 (Exo70B1), a component of the vesicle trafficking machinery. RIC7 and Exo70B1 localized to the plasma membrane region under light or constitutively active ROP2 conditions. The knockout mutant of Exo70B1 and ric7/exo70b1 exhibited retarded light-induced stomatal opening. Our results suggest that ROP2 and RIC7 suppress excess stomatal opening by inhibiting Exo70B1, which most likely participates in the vesicle trafficking required for light-induced stomatal opening.
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Affiliation(s)
- Daewoong Hong
- Division of Molecular Life Sciences, POSTECH, Pohang, 790-784, Korea
| | - Byeong Wook Jeon
- Division of Molecular Life Sciences, POSTECH, Pohang, 790-784, Korea
| | - Soo Young Kim
- Departments of Molecular Biotechnology and Kumho Life Science Laboratory, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 500-757, Korea
| | - Jae-Ung Hwang
- Division of Molecular Life Sciences, POSTECH, Pohang, 790-784, Korea
| | - Youngsook Lee
- Division of Molecular Life Sciences, POSTECH, Pohang, 790-784, Korea
- Division of Integrative Biosciences and Biotechnology, POSTECH, Pohang, 790-784, Korea
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Chen X, Ebbole DJ, Wang Z. The exocyst complex: delivery hub for morphogenesis and pathogenesis in filamentous fungi. CURRENT OPINION IN PLANT BIOLOGY 2015; 28:48-54. [PMID: 26453967 DOI: 10.1016/j.pbi.2015.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/30/2015] [Accepted: 09/05/2015] [Indexed: 06/05/2023]
Abstract
Regulated by several small GTPases, the octameric exocyst complex directs the docking and tethering of exocytic vesicles to the destined plasma membrane sites, providing the precise spatiotemporal control of exocytosis. Although the exocyst components are well conserved among various fungal species, the mechanisms for the regulation of its assembly and activity are diverse. Exocytosis is crucial for the generation of cell polarity as well as the delivery of effector proteins in filamentous fungi, and thus plays an important role for fungal morphogenesis and pathogenicity on plant hosts. This review focuses on current findings about the roles of the exocyst complex in the morphogenesis and pathogenesis of filamentous fungi.
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Affiliation(s)
- Xiaofeng Chen
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Daniel J Ebbole
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA
| | - Zonghua Wang
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Fujian Province Key Laboratory of Pathogenic Fungi and Mycotoxins, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Lin Y, Ding Y, Wang J, Shen J, Kung CH, Zhuang X, Cui Y, Yin Z, Xia Y, Lin H, Robinson DG, Jiang L. Exocyst-Positive Organelles and Autophagosomes Are Distinct Organelles in Plants. PLANT PHYSIOLOGY 2015; 169:1917-32. [PMID: 26358417 PMCID: PMC4634068 DOI: 10.1104/pp.15.00953] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/09/2015] [Indexed: 05/23/2023]
Abstract
Autophagosomes are organelles that deliver cytosolic proteins for degradation in the vacuole of the cell. In contrast, exocyst-positive organelles (EXPO) deliver cytosolic proteins to the cell surface and therefore represent a form of unconventional protein secretion. Because both structures have two boundary membranes, it has been suggested that they may have been falsely treated as separate entities. Using suspension culture cells and root tissue cells of transgenic Arabidopsis (Arabidopsis thaliana) plants expressing either the EXPO marker Arabidopsis Exo70E2-GFP or the autophagosome marker yellow fluorescent protein (YFP)-autophagy-related gene 8e/f (ATG8e/f), and using specific antibodies against Exo70E2 and ATG8, we have now established that, in normally growing cells, EXPO and autophagosomes are distinct from one another. However, when cells/roots are subjected to autophagy induction, EXPO as well as autophagosomes fuse with the vacuole. In the presence of concanamycin A, the punctate fluorescent signals from both organelles inside the vacuole remain visible for hours and overlap to a significant degree. Tonoplast staining with FM4-64/YFP-Rab7-like GTPase/YFP-vesicle-associated membrane protein711 confirmed the internalization of tonoplast membrane concomitant with the sequestration of EXPO and autophagosomes. This suggests that EXPO and autophagosomes may be related to one another; however, whereas induction of autophagy led to an increase in the amount of ATG8 recruited to membranes, Exo70E2 did not respond in a similar manner.
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Affiliation(s)
- Youshun Lin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yu Ding
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Juan Wang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Jinbo Shen
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Chun Hong Kung
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Xiaohong Zhuang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yong Cui
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Zhao Yin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yiji Xia
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Hongxuan Lin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - David G Robinson
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Liwen Jiang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
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Woo CH, Gao C, Yu P, Tu L, Meng Z, Banfield DK, Yao X, Jiang L. Conserved function of the lysine-based KXD/E motif in Golgi retention for endomembrane proteins among different organisms. Mol Biol Cell 2015; 26:4280-93. [PMID: 26378254 PMCID: PMC4642860 DOI: 10.1091/mbc.e15-06-0361] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 09/11/2015] [Indexed: 01/06/2023] Open
Abstract
We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) of Arabidopsis endomembrane protein 12 (AtEMP12) as being a crucial Golgi retention mechanism for AtEMP12. This KXD/E motif is conserved in CTs of all EMPs found in plants, yeast, and humans and is also present in hundreds of other membrane proteins. Here, by cloning selective EMP isoforms from plants, yeast, and mammals, we study the localizations of EMPs in different expression systems, since there are contradictory reports on the localizations of EMPs. We show that the N-terminal and C-terminal GFP-tagged EMP fusions are localized to Golgi and post-Golgi compartments, respectively, in plant, yeast, and mammalian cells. In vitro pull-down assay further proves the interaction of the KXD/E motif with COPI coatomer in yeast. COPI loss of function in yeast and plants causes mislocalization of EMPs or KXD/E motif-containing proteins to vacuole. Ultrastructural studies further show that RNA interference (RNAi) knockdown of coatomer expression in transgenic Arabidopsis plants causes severe morphological changes in the Golgi. Taken together, our results demonstrate that N-terminal GFP fusions reflect the real localization of EMPs, and KXD/E is a conserved motif in COPI interaction and Golgi retention in eukaryotes.
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Affiliation(s)
- Cheuk Hang Woo
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, and
| | - Caiji Gao
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, and
| | - Ping Yu
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Linna Tu
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Zhaoyue Meng
- School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - David K Banfield
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xiaoqiang Yao
- School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China
| | - Liwen Jiang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, and CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China )
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58
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Chi Y, Yang Y, Li G, Wang F, Fan B, Chen Z. Identification and characterization of a novel group of legume-specific, Golgi apparatus-localized WRKY and Exo70 proteins from soybean. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:3055-70. [PMID: 25805717 PMCID: PMC4449531 DOI: 10.1093/jxb/erv104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Many plant genes belong to families that arise from extensive proliferation and diversification allowing the evolution of functionally new proteins. Here we report the characterization of a group of proteins evolved from WRKY and exocyst complex subunit Exo70 proteins through fusion with a novel transmembrane (TM) domain in soybean (Glycine max). From the soybean genome, we identified a novel WRKY-related protein (GmWRP1) that contains a WRKY domain with no binding activity for W-box sequences. GFP fusion revealed that GmWRP1 was targeted to the Golgi apparatus through its N-terminal TM domain. Similar Golgi-targeting TM domains were also identified in members of a new subfamily of Exo70J proteins involved in vesicle trafficking. The novel TM domains are structurally most similar to the endosomal cytochrome b561 from birds and close homologues of GmWRP1 and GmEx070J proteins with the novel TM domain have only been identified in legumes. Transient expression of some GmExo70J proteins or the Golgi-targeting TM domain in tobacco altered the subcellular structures labelled by a fluorescent Golgi marker. GmWRP1 transcripts were detected at high levels in roots, flowers, pods, and seeds, and the expression levels of GmWRP1 and GmExo70J genes were elevated with increased age in leaves. The legume-specific, Golgi apparatus-localized GmWRP1 and GmExo70J proteins are probably involved in Golgi-mediated vesicle trafficking of biological molecules that are uniquely important to legumes.
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Affiliation(s)
- Yingjun Chi
- Department of Horticulture, Zijingang Campus, 866 Yuhangtang Road, Zhejiang University, Hangzhou, 310058, China
| | - Yan Yang
- Department of Horticulture, Zijingang Campus, 866 Yuhangtang Road, Zhejiang University, Hangzhou, 310058, China
| | - Guiping Li
- Department of Horticulture, Zijingang Campus, 866 Yuhangtang Road, Zhejiang University, Hangzhou, 310058, China
| | - Fei Wang
- Department of Botany and Plant Pathology, 915W. State Street, Purdue University, West Lafayette, IN 47907, USA
| | - Baofang Fan
- Department of Botany and Plant Pathology, 915W. State Street, Purdue University, West Lafayette, IN 47907, USA
| | - Zhixiang Chen
- Department of Horticulture, Zijingang Campus, 866 Yuhangtang Road, Zhejiang University, Hangzhou, 310058, China Department of Botany and Plant Pathology, 915W. State Street, Purdue University, West Lafayette, IN 47907, USA
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Zhao Q, Gao C, Lee P, Liu L, Li S, Hu T, Shen J, Pan S, Ye H, Chen Y, Cao W, Cui Y, Zeng P, Yu S, Gao Y, Chen L, Mo B, Liu X, Xiao S, Zhao Y, Zhong S, Chen X, Jiang L. Fast-suppressor screening for new components in protein trafficking, organelle biogenesis and silencing pathway in Arabidopsis thaliana using DEX-inducible FREE1-RNAi plants. J Genet Genomics 2015; 42:319-30. [PMID: 26165498 DOI: 10.1016/j.jgg.2015.03.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 03/21/2015] [Accepted: 03/27/2015] [Indexed: 12/20/2022]
Abstract
Membrane trafficking is essential for plant growth and responses to external signals. The plant unique FYVE domain-containing protein FREE1 is a component of the ESCRT complex (endosomal sorting complex required for transport). FREE1 plays multiple roles in regulating protein trafficking and organelle biogenesis including the formation of intraluminal vesicles of multivesicular body (MVB), vacuolar protein transport and vacuole biogenesis, and autophagic degradation. FREE1 knockout plants show defective MVB formation, abnormal vacuolar transport, fragmented vacuoles, accumulated autophagosomes, and seedling lethality. To further uncover the underlying mechanisms of FREE1 function in plants, we performed a forward genetic screen for mutants that suppressed the seedling lethal phenotype of FREE1-RNAi transgenic plants. The obtained mutants are termed as suppressors of free1 (sof). To date, 229 putative sof mutants have been identified. Barely detecting of FREE1 protein with M3 plants further identified 84 FREE1-related suppressors. Also 145 mutants showing no reduction of FREE1 protein were termed as RNAi-related mutants. Through next-generation sequencing (NGS) of bulked DNA from F2 mapping population of two RNAi-related sof mutants, FREE1-RNAi T-DNA inserted on chromosome 1 was identified and the causal mutation of putative sof mutant is being identified similarly. These FREE1- and RNAi-related sof mutants will be useful tools and resources for illustrating the underlying mechanisms of FREE1 function in intracellular trafficking and organelle biogenesis, as well as for uncovering the new components involved in the regulation of silencing pathways in plants.
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Affiliation(s)
- Qiong Zhao
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Caiji Gao
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - PoShing Lee
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Lin Liu
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Shaofang Li
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Tangjin Hu
- CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
| | - Jinbo Shen
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Shuying Pan
- CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
| | - Hao Ye
- CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
| | - Yunru Chen
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Wenhan Cao
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yong Cui
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Peng Zeng
- Beijing Genomics Institute at Shenzhen, Shenzhen 518083, China
| | - Sheng Yu
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yangbin Gao
- Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Liang Chen
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Beixin Mo
- Shenzhen Key Laboratory of Microbial Genetic Engineering, College of Life Sciences, Shenzhen University, Shenzhen 518060, China
| | - Xin Liu
- Beijing Genomics Institute at Shenzhen, Shenzhen 518083, China
| | - Shi Xiao
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Yunde Zhao
- Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Silin Zhong
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Xuemei Chen
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Liwen Jiang
- Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China.
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60
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Kulich I, Vojtíková Z, Glanc M, Ortmannová J, Rasmann S, Žárský V. Cell wall maturation of Arabidopsis trichomes is dependent on exocyst subunit EXO70H4 and involves callose deposition. PLANT PHYSIOLOGY 2015; 168:120-31. [PMID: 25767057 PMCID: PMC4424025 DOI: 10.1104/pp.15.00112] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2015] [Accepted: 03/10/2015] [Indexed: 05/22/2023]
Abstract
Arabidopsis (Arabidopsis thaliana) leaf trichomes are single-cell structures with a well-studied development, but little is understood about their function. Developmental studies focused mainly on the early shaping stages, and little attention has been paid to the maturation stage. We focused on the EXO70H4 exocyst subunit, one of the most up-regulated genes in the mature trichome. We uncovered EXO70H4-dependent development of the secondary cell wall layer, highly autofluorescent and callose rich, deposited only in the upper part of the trichome. The boundary is formed between the apical and the basal parts of mature trichome by a callose ring that is also deposited in an EXO70H4-dependent manner. We call this structure the Ortmannian ring (OR). Both the secondary cell wall layer and the OR are absent in the exo70H4 mutants. Ecophysiological aspects of the trichome cell wall thickening include interference with antiherbivore defense and heavy metal accumulation. Ultraviolet B light induces EXO70H4 transcription in a CONSTITUTIVE PHOTOMORPHOGENIC1-dependent way, resulting in stimulation of trichome cell wall thickening and the OR biogenesis. EXO70H4-dependent trichome cell wall hardening is a unique phenomenon, which may be conserved among a variety of the land plants. Our analyses support a concept that Arabidopsis trichome is an excellent model to study molecular mechanisms of secondary cell wall deposition.
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Affiliation(s)
- Ivan Kulich
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
| | - Zdeňka Vojtíková
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
| | - Matouš Glanc
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
| | - Jitka Ortmannová
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
| | - Sergio Rasmann
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
| | - Viktor Žárský
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, 12844 Prague, Czech Republic (I.K., Z.V., M.G., J.O., V.Z.);Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 16502 Prague, Czech Republic (J.O., V.Z.); andDepartment of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland (S.R.)
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61
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Gendre D, Jonsson K, Boutté Y, Bhalerao RP. Journey to the cell surface--the central role of the trans-Golgi network in plants. PROTOPLASMA 2015; 252:385-98. [PMID: 25187082 DOI: 10.1007/s00709-014-0693-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 08/21/2014] [Indexed: 05/11/2023]
Abstract
The secretion of proteins, lipids, and carbohydrates to the cell surface is essential for plant development and adaptation. Secreted substances synthesized at the endoplasmic reticulum pass through the Golgi apparatus and trans-Golgi network (TGN) en route to the plasma membrane via the conventional secretion pathway. The TGN is morphologically and functionally distinct from the Golgi apparatus. The TGN is located at the crossroads of many trafficking pathways and regulates a range of crucial processes including secretion to the cell surface, transport to the vacuole, and the reception of endocytic cargo. This review outlines the TGN's central role in cargo secretion, showing that its behavior is more complex and controlled than the bulk-flow hypothesis suggests. Its formation, structure, and maintenance are discussed along with the formation and release of secretory vesicles.
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Affiliation(s)
- Delphine Gendre
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden,
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62
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Ebine K, Ueda T. Roles of membrane trafficking in plant cell wall dynamics. FRONTIERS IN PLANT SCIENCE 2015; 6:878. [PMID: 26539200 PMCID: PMC4609830 DOI: 10.3389/fpls.2015.00878] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 10/02/2015] [Indexed: 05/18/2023]
Abstract
The cell wall is one of the characteristic components of plant cells. The cell wall composition differs among cell types and is modified in response to various environmental conditions. To properly generate and modify the cell wall, many proteins are transported to the plasma membrane or extracellular space through membrane trafficking, which is one of the key protein transport mechanisms in eukaryotic cells. Given the diverse composition and functions of the cell wall in plants, the transport of the cell wall components and proteins that are involved in cell wall-related events could be specialized for each cell type, i.e., the machinery for cell wall biogenesis, modification, and maintenance could be transported via different trafficking pathways. In this review, we summarize the recent progress in the current understanding of the roles and mechanisms of membrane trafficking in plant cells and focus on the biogenesis and regulation of the cell wall.
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Affiliation(s)
- Kazuo Ebine
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- *Correspondence: Kazuo Ebine,
| | - Takashi Ueda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology, Kawaguchi, Japan
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63
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Shen J, Ding Y, Gao C, Rojo E, Jiang L. N-linked glycosylation of AtVSR1 is important for vacuolar protein sorting in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 80:977-92. [PMID: 25293377 DOI: 10.1111/tpj.12696] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 05/18/2023]
Abstract
Vacuolar sorting receptors (VSRs) in Arabidopsis mediate the sorting of soluble proteins to vacuoles in the secretory pathway. The VSRs are post-translationally modified by the attachment of N-glycans, but the functional significance of such a modification remains unknown. Here we have studied the role(s) of glycosylation in the stability, trafficking and vacuolar protein transport of AtVSR1 in Arabidopsis protoplasts. AtVSR1 harbors three complex-type N-glycans, which are located in the N-terminal 'PA domain', the central region and the C-terminal epidermal growth factor repeat domain, respectively. We have demonstrated that: (i) the N-glycans do not affect the targeting of AtVSR1 to pre-vacuolar compartments (PVCs) and its vacuolar degradation; and (ii) N-glycosylation alters the binding affinity of AtVSR1 to cargo proteins and affects the transport of cargo into the vacuole. Hence, N-glycosylation of AtVSR1 plays a critical role in its function as a VSR in plants.
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Affiliation(s)
- Jinbo Shen
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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64
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Ding Y, Robinson DG, Jiang L. Unconventional protein secretion (UPS) pathways in plants. Curr Opin Cell Biol 2014; 29:107-15. [PMID: 24949560 DOI: 10.1016/j.ceb.2014.05.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 04/09/2014] [Accepted: 05/22/2014] [Indexed: 02/09/2023]
Abstract
As in yeast and mammalian cells, novel unconventional protein secretion (UPS) or unconventional membrane trafficking pathways are now known to operate in plants. UPS in plants is generally associated with stress conditions such as pathogen attack, but little is known about its underlying mechanism and function. Here, we present an update on the current knowledge of UPS in the plants in terms of its transport pathways, possible functions and its relationship to autophagy.
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Affiliation(s)
- Yu Ding
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - David G Robinson
- Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China.
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65
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Shen J, Fu J, Ma J, Wang X, Gao C, Zhuang C, Wan J, Jiang L. Isolation, culture, and transient transformation of plant protoplasts. CURRENT PROTOCOLS IN CELL BIOLOGY 2014; 63:2.8.1-17. [PMID: 24894837 DOI: 10.1002/0471143030.cb0208s63] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Transient gene expression in protoplasts, which has been used in several plant species, is an important and versatile tool for rapid functional gene analysis, protein subcellular localization, and biochemical manipulations. This unit describes transient gene expression by electroporation of DNA into protoplasts of Arabidopsis or tobacco suspension-cultured cells and by polyethylene glycol (PEG)-mediated DNA transformation into protoplasts derived from rice leaf sheaths. PEG-mediated DNA transformation for transient gene expression in rice protoplasts in suspension culture is also described as an alternative technique. Methods for collecting intracellular and secreted proteins are also provided.
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Affiliation(s)
- Jinbo Shen
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
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66
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Cui Y, Zhao Q, Gao C, Ding Y, Zeng Y, Ueda T, Nakano A, Jiang L. Activation of the Rab7 GTPase by the MON1-CCZ1 Complex Is Essential for PVC-to-Vacuole Trafficking and Plant Growth in Arabidopsis. THE PLANT CELL 2014; 26:2080-2097. [PMID: 24824487 PMCID: PMC4079370 DOI: 10.1105/tpc.114.123141] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 04/12/2014] [Accepted: 04/22/2014] [Indexed: 05/17/2023]
Abstract
Rab GTPases serve as multifaceted organizers during vesicle trafficking. Rab7, a member of the Rab GTPase family, has been shown to perform various essential functions in endosome trafficking and in endosome-to-lysosome trafficking in mammalian systems. The Arabidopsis thaliana genome encodes eight putative Rab7 homologs; however, the detailed function and activation mechanism of Rab7 in plants remain unknown. Here, we demonstrate that Arabidopsis RABG3f, a member of the plant Rab7 small GTPase family, localizes to prevacuolar compartments (PVCs) and the tonoplast. The proper activation of Rab7 is essential for both PVC-to-vacuole trafficking and vacuole biogenesis. Expression of a dominant-negative Rab7 mutant (RABG3fT22N) induces the formation of enlarged PVCs and affects vacuole morphology in plant cells. We also identify Arabidopsis MON1 (MONENSIN SENSITIVITY1) and CCZ1 (CALCIUM CAFFEINE ZINC SENSITIVITY1) proteins as a dimeric complex that functions as the Rab7 guanine nucleotide exchange factor. The MON1-CCZ1 complex also serves as the Rab5 effector to mediate Rab5-to-Rab7 conversion on PVCs. Loss of functional MON1 causes the formation of enlarged Rab5-positive PVCs that are separated from Rab7-positive endosomes. Similar to the dominant-negative Rab7 mutant, the mon1 mutants show pleiotropic growth defects, fragmented vacuoles, and altered vacuolar trafficking. Thus, Rab7 activation by the MON1-CCZ1 complex is critical for vacuolar trafficking, vacuole biogenesis, and plant growth.
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Affiliation(s)
- Yong Cui
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Qiong Zhao
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Caiji Gao
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yu Ding
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Yonglun Zeng
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Takashi Ueda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Akihiko Nakano
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China
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