151
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Herberth S, Shahriari M, Bruderek M, Hessner F, Müller B, Hülskamp M, Schellmann S. Artificial ubiquitylation is sufficient for sorting of a plasma membrane ATPase to the vacuolar lumen of Arabidopsis cells. PLANTA 2012; 236:63-77. [PMID: 22258747 DOI: 10.1007/s00425-012-1587-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 12/30/2011] [Indexed: 05/21/2023]
Abstract
Sorting of transmembrane proteins into the inner vesicles of multivesicular bodies for subsequent delivery to the vacuole/lysosome can be induced by attachment of a single ubiquitin or K63-linked ubiquitin chains to the cytosolic portion of the cargo in yeast and mammals. In plants, large efforts have been undertaken to elucidate the mechanisms of vacuolar trafficking of soluble proteins. Sorting of transmembrane proteins, by contrast, is still largely unexplored. As a proof of principle, that ubiquitin is involved in vacuolar sorting in plants we show that a translational fusion of a single ubiquitin to the Arabidopsis plasma membrane ATPase PMA-EGFP is sufficient to induce its endocytosis and sorting into the vacuolar lumen. Sorting of the artificial reporter is not dependent on ubiquitin chain formation, but involves ubiquitin's hydrophobic patch and can be inhibited by coexpression of a dominant-negative version of the ESCRT (endosomal sorting complex required for transport) related protein AtSKD1 (SUPPRESSOR OF K+ TRANSPORT GROWTH DEFECT1). Our results suggest that ubiquitin can in principle act as vacuolar sorting signal in plants.
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Affiliation(s)
- Stefanie Herberth
- Botanical Institute III, Biocenter, University of Cologne, Zülpicher Str. 47b, 50674, Cologne, Germany
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152
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Hunt CD. Dietary boron: progress in establishing essential roles in human physiology. J Trace Elem Med Biol 2012; 26:157-60. [PMID: 22658717 DOI: 10.1016/j.jtemb.2012.03.014] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 03/11/2012] [Indexed: 11/20/2022]
Abstract
This review summarizes the progress made in establishing essential roles for boron in human physiology and assesses that progress in view of criteria for essentiality of elements. The evidence to date suggests that humans and at least some higher animals may use boron to support normal biological functions. These include roles in calcium metabolism, bone growth and maintenance, insulin metabolism, and completion of the life cycle. The biochemical mechanisms responsible for these effects are poorly understood but the nature of boron biochemistry suggests further characterization of the cell signaling molecules capable of complexing with boron. Such characterization may provide insights into the biochemical function(s) of boron in humans.
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153
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Liu TY, Huang TK, Tseng CY, Lai YS, Lin SI, Lin WY, Chen JW, Chiou TJ. PHO2-dependent degradation of PHO1 modulates phosphate homeostasis in Arabidopsis. THE PLANT CELL 2012; 24:2168-83. [PMID: 22634761 PMCID: PMC3442594 DOI: 10.1105/tpc.112.096636] [Citation(s) in RCA: 233] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The Arabidopsis thaliana pho2 mutant, which is defective in a ubiquitin-conjugating E2 enzyme, displays inorganic phosphate (Pi) toxicity as a result of enhanced uptake and root-to-shoot translocation of Pi. To elucidate downstream components of the PHO2-dependent regulatory pathway, we identified two pho2 suppressors as carrying missense mutations in PHO1, which has been implicated in Pi loading to the xylem. In support of the genetic interaction between PHO1 and PHO2, we found that the protein level of PHO1 is increased in pho2, whereas such accumulation is ameliorated in both pho2 suppressors. Results from cycloheximide and endosomal Cys protease inhibitor E-64d treatments further suggest that PHO1 degradation is PHO2 dependent and involves multivesicular body-mediated vacuolar proteolysis. Using the transient expression system of tobacco (Nicotiana tabacum) leaves, we demonstrated that PHO1 and PHO2 are partially colocalized and physically interact in the endomembranes, where the ubiquitin conjugase activity of PHO2 is required for PHO1 degradation. In addition, reduced PHO1 expression caused by PHO1 mutations impede Pi uptake, indicating a functional association between xylem loading and acquisition of Pi. Together, our findings uncover a pivotal molecular mechanism by which PHO2 modulates the degradation of PHO1 in the endomembranes to maintain Pi homeostasis in plants.
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Affiliation(s)
- Tzu-Yin Liu
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Teng-Kuei Huang
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung-Hsing University and Academia Sinica, Taipei 115, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 402, Taiwan
| | - Ching-Ying Tseng
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Ya-Shiuan Lai
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Shu-I Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Wei-Yi Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung-Hsing University and Academia Sinica, Taipei 115, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 402, Taiwan
| | - June-Wei Chen
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Tzyy-Jen Chiou
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung-Hsing University and Academia Sinica, Taipei 115, Taiwan
- Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan
- Address correspondence to
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154
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Ganguly A, Sasayama D, Cho HT. Regulation of the polarity of protein trafficking by phosphorylation. Mol Cells 2012; 33:423-30. [PMID: 22453777 PMCID: PMC3887733 DOI: 10.1007/s10059-012-0039-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 02/27/2012] [Accepted: 03/02/2012] [Indexed: 11/30/2022] Open
Abstract
The asymmetry of environmental stimuli and the execution of developmental programs at the organism level require a corresponding polarity at the cellular level, in both unicellular and multicellular organisms. In plants, cell polarity is important in major developmental processes such as cell division, cell enlargement, cell morphogenesis, embryogenesis, axis formation, organ development, and defense. One of the most important factors controlling cell polarity is the asymmetric distribution of polarity determinants. In particular, phosphorylation is implicated in the polar distribution of the determinant protein factors, a mechanism conserved in both prokaryotes and eukaryotes. In plants, formation of local gradients of auxin, the morphogenic hormone, is critical for plant developmental processes exhibiting polarity. The auxin efflux carriers PIN-FORMEDs (PINs) localize asymmetrically in the plasma membrane and cause the formation of local auxin gradients throughout the plant. The asymmetry of PIN distribution in the plasma membrane is determined by phosphorylationmediated polar trafficking of PIN proteins. This review discusses recent studies on the role of phosphorylation in polar PIN trafficking.
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Affiliation(s)
- Anindya Ganguly
- Department of Biological Sciences and Genomics and Breeding Institute, Seoul National University, Seoul 151-742,
Korea
| | - Daisuke Sasayama
- Department of Biological Sciences and Genomics and Breeding Institute, Seoul National University, Seoul 151-742,
Korea
| | - Hyung-Taeg Cho
- Department of Biological Sciences and Genomics and Breeding Institute, Seoul National University, Seoul 151-742,
Korea
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155
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Martinière A, Li X, Runions J, Lin J, Maurel C, Luu DT. Salt stress triggers enhanced cycling of Arabidopsis root plasma-membrane aquaporins. PLANT SIGNALING & BEHAVIOR 2012; 7:529-32. [PMID: 22499180 PMCID: PMC3419046 DOI: 10.4161/psb.19350] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Aquaporins of the plasma membrane intrinsic protein (PIP) subfamily are channels which facilitate the diffusion of water across the plant plasma membrane (PM). Although PIPs have been considered as canonical protein markers of this compartment, their endomembrane trafficking is still not well documented. We recently obtained insights into the constitutive cycling of PIPs in Arabidopsis root cells by means of fluorescence recovery after photobleaching (FRAP). This work also uncovered the behavior of the model isoform AtPIP2;1 in response to NaCl. The present addendum connects these findings to another recent work which describes the dynamic properties of AtPIP2;1 in the PM in normal and salt stress conditions by means of single particle tracking (SPT) and fluorescence correlation spectroscopy (FCS). The results suggest that membrane rafts play an important role in the partitioning of AtPIP2;1 in normal conditions and that clathrin-mediated endocytosis is predominant. In salt stress conditions, the rate of AtPIP2;1 cycling was enhanced and endocytosis was cooperated by a membrane raft-associated salt-induced pathway and a clathrin-dependent pathway.
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Affiliation(s)
- Alexandre Martinière
- Department of Biological and Medical Sciences; Oxford Brookes University; Oxford, UK
- Biochimie et Physiologie Moléculaire des Plantes; Institut de Biologie Intégrative des Plantes; UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2; Montpellier, France
| | - Xiaojuan Li
- Key Laboratory of Plant Molecular Physiology; Institute of Botany; Chinese Academy of Sciences; Beijing, China
| | - John Runions
- Department of Biological and Medical Sciences; Oxford Brookes University; Oxford, UK
| | - Jinxing Lin
- Key Laboratory of Plant Molecular Physiology; Institute of Botany; Chinese Academy of Sciences; Beijing, China
| | - Christophe Maurel
- Biochimie et Physiologie Moléculaire des Plantes; Institut de Biologie Intégrative des Plantes; UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2; Montpellier, France
| | - Doan-Trung Luu
- Biochimie et Physiologie Moléculaire des Plantes; Institut de Biologie Intégrative des Plantes; UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2; Montpellier, France
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156
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Scorei R. Is boron a prebiotic element? A mini-review of the essentiality of boron for the appearance of life on earth. ORIGINS LIFE EVOL B 2012; 42:3-17. [PMID: 22528885 DOI: 10.1007/s11084-012-9269-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 11/02/2011] [Indexed: 01/20/2023]
Abstract
Boron is probably a prebiotic element with special importance in the so-called "sugars world". Boron is not present on Earth in its elemental form. It is found only in compounds, e.g., borax, boric acid, kernite, ulexite, colemanite and other borates. Volcanic spring waters sometimes contain boron-based acids (e.g., boric, metaboric, tetraboric and pyroboric acid). Borates influence the formation of ribofuranose from formaldehyde that feeds the "prebiotic metabolic cycle". The importance of boron in the living world is strongly related to its implications in the prebiotic origins of genetic material; consequently, we believe that throughout the evolution of life, the primary role of boron has been to provide thermal and chemical stability in hostile environments. The complexation of boric acid and borates with organic cis-diols remains the most probable chemical mechanism for the role of this element in the evolution of the living world. Because borates can stabilize ribose and form borate ester nucleotides, boron may have provided an essential contribution to the "pre-RNA world".
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Affiliation(s)
- Romulus Scorei
- Department of Biochemistry, University of Craiova, 13 A.I. Cuza Street, 200585, Craiova, Dolj County, Romania.
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157
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Pérez-Castro R, Kasai K, Gainza-Cortés F, Ruiz-Lara S, Casaretto JA, Peña-Cortés H, Tapia J, Fujiwara T, González E. VvBOR1, the grapevine ortholog of AtBOR1, encodes an efflux boron transporter that is differentially expressed throughout reproductive development of Vitis vinifera L. PLANT & CELL PHYSIOLOGY 2012; 53:485-94. [PMID: 22247248 DOI: 10.1093/pcp/pcs001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Boron (B) is an essential micronutrient for normal development of roots, shoots and reproductive tissues in plants. Due to its role in the structure of rhamnogalacturonan II, a polysaccharide required for pollen tube growth, B deficiency has been associated with the occurrence of parthenocarpic seedless grapes in some varieties of Vitis vinifera L. Despite that, it is unclear how B is mobilized and accumulated in reproductive tissues. Here we describe the characterization of an efflux B transporter, VvBOR1, homolog to AtBOR1, which is involved in B xylem loading in Arabidopsis thaliana roots. VvBOR1-green fluorescent protein (GFP) fusion protein expressed in A. thaliana localizes in the proximal plasma membrane domain in root pericycle cells, and VvBOR1 overexpression restores the wild-type phenotype in A. thaliana bor1-3 mutant plants exposed to B deficiency. Complementation of a mutant yeast strain indicates that VvBOR1 corresponds to a B efflux transporter. Transcriptional analyses during grapevine reproductive development show that the VvBOR1 gene is preferentially expressed in flowers at anthesis and a direct correlation between the expression pattern and B content in grapes was established, suggesting the involvement of this transporter in B accumulation in grapevine berries.
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Affiliation(s)
- Ramón Pérez-Castro
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
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158
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Laugier E, Bouguyon E, Mauriès A, Tillard P, Gojon A, Lejay L. Regulation of high-affinity nitrate uptake in roots of Arabidopsis depends predominantly on posttranscriptional control of the NRT2.1/NAR2.1 transport system. PLANT PHYSIOLOGY 2012; 158:1067-78. [PMID: 22158677 PMCID: PMC3271743 DOI: 10.1104/pp.111.188532] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 12/06/2011] [Indexed: 05/21/2023]
Abstract
In Arabidopsis (Arabidopsis thaliana), the NRT2.1 gene codes for the main component of the root nitrate (NO(3)(-)) high-affinity transport system (HATS). Due to the strong correlation generally found between high-affinity root NO(3)(-) influx and NRT2.1 mRNA level, it has been postulated that transcriptional regulation of NRT2.1 is a key mechanism for modulation of the HATS activity. However, this hypothesis has never been demonstrated, and is challenged by studies suggesting the occurrence of posttranscriptional regulation at the NRT2.1 protein level. To unambiguously clarify the respective roles of transcriptional and posttranscriptional regulations of NRT2.1, we generated transgenic lines expressing a functional 35S::NRT2.1 transgene in an atnrt2.1 mutant background. Despite a high and constitutive NRT2.1 transcript accumulation in the roots, the HATS activity was still down-regulated in the 35S::NRT2.1 transformants in response to repressive nitrogen or dark treatments that strongly reduce NRT2.1 transcription and NO(3)(-) HATS activity in the wild type. In some treatments, this was associated with a decline of NRT2.1 protein abundance, indicating posttranscriptional regulation of NRT2.1. However, in other instances, NRT2.1 protein level remained constant. Changes in abundance of NAR2.1, a partner protein of NRT2.1, closely followed those of NRT2.1, and thus could not explain the close-to-normal regulation of the HATS in the 35S::NRT2.1 transformants. Even if in certain conditions the transcriptional regulation of NRT2.1 contributes to a limited extent to the control of the HATS, we conclude from this study that posttranscriptional regulation of NRT2.1 and/or NAR2.1 plays a predominant role in the control of the NO(3)(-) HATS in Arabidopsis.
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159
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Yoshinari A, Kasai K, Fujiwara T, Naito S, Takano J. Polar localization and endocytic degradation of a boron transporter, BOR1, is dependent on specific tyrosine residues. PLANT SIGNALING & BEHAVIOR 2012; 7:46-9. [PMID: 22301967 PMCID: PMC3357367 DOI: 10.4161/psb.7.1.18527] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Boron (B) is essential for plants, but is toxic in excess. Plants have to strictly regulate the uptake and translocation of B. In Arabidopsis thaliana root cells, a boric acid channel, NIP5;1, and a boric acid/borate exporter, BOR1, localize to the outer (facing soil) and inner plasma membrane domains, respectively, under B limitation. The opposite polar localizations of the importer and exporter would enable plant roots to transport B efficiently towards the xylem. In addition, accumulation of the B transporters is controlled by B conditions. When plants are shifted from low to high B conditions, NIP5;1 transcript accumulation is down-regulated through mRNA degradation. The BOR1 protein is transported to the trans-Golgi network/early endosome and multivesicular body and finally degraded in the vacuole. We have recently shown that both the polar localization and the endocytic degradation of BOR1 are controlled by at least two tyrosine residues in a large loop located in the cytosol. We also showed that ubiquitination is required for the endocytic degradation of BOR1. Here, we analyzed possible involvement of an additional tyrosine residue (Y414) in the loop region and discuss the pathway of the BOR1 trafficking for polar localization and endocytic degradation of BOR1.
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Affiliation(s)
- Akira Yoshinari
- Division of Life Science; Graduate School of Life Science; Hokkaido University; Sapporo, Japan
| | - Koji Kasai
- Division of Applied Biological Chemistry; Graduate School of Agricultural and Life Science; The University of Tokyo; Tokyo, Japan
| | - Toru Fujiwara
- Division of Applied Biological Chemistry; Graduate School of Agricultural and Life Science; The University of Tokyo; Tokyo, Japan
| | - Satoshi Naito
- Division of Life Science; Graduate School of Life Science; Hokkaido University; Sapporo, Japan
- Division of Applied Bioscience; Graduate School of Agriculture; Hokkaido University; Sapporo, Japan
| | - Junpei Takano
- Division of Applied Bioscience; Graduate School of Agriculture; Hokkaido University; Sapporo, Japan
- Correspondence to: Junpei Takano;
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160
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Contento AL, Bassham DC. Structure and function of endosomes in plant cells. J Cell Sci 2012; 125:3511-8. [DOI: 10.1242/jcs.093559] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Endosomes are a heterogeneous collection of organelles that function in the sorting and delivery of internalized material from the cell surface and the transport of materials from the Golgi to the lysosome or vacuole. Plant endosomes have some unique features, with an organization distinct from that of yeast or animal cells. Two clearly defined endosomal compartments have been studied in plant cells, the trans-Golgi network (equivalent to the early endosome) and the multivesicular body (equivalent to the late endosome), with additional endosome types (recycling endosome, late prevacuolar compartment) also a possibility. A model has been proposed in which the trans-Golgi network matures into a multivesicular body, which then fuses with the vacuole to release its cargo. In addition to basic trafficking functions, endosomes in plant cells are known to function in maintenance of cell polarity by polar localization of hormone transporters and in signaling pathways after internalization of ligand-bound receptors. These signaling functions are exemplified by the BRI1 brassinosteroid hormone receptor and by receptors for pathogen elicitors that activate defense responses. After endocytosis of these receptors from the plasma membrane, endosomes act as a signaling platform, thus playing an essential role in plant growth, development and defense responses. Here we describe the key features of plant endosomes and their differences from those of other organisms and discuss the role of these organelles in cell polarity and signaling pathways.
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161
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Ito E, Fujimoto M, Ebine K, Uemura T, Ueda T, Nakano A. Dynamic behavior of clathrin in Arabidopsis thaliana unveiled by live imaging. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 69:204-16. [PMID: 21910772 DOI: 10.1111/j.1365-313x.2011.04782.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Clathrin-coated vesicles (CCV) are necessary for selective transport events, including receptor-mediated endocytosis on the plasma membrane and cargo molecule sorting in the trans-Golgi network (TGN). Components involved in CCV formation include clathrin heavy and light chains and several adaptor proteins that are conserved among plants. Clathrin-dependent endocytosis has been shown to play an integral part in plant endocytosis. However, little information is known about clathrin dynamics in living plant cells. In this study, we have visualized clathrin in Arabidopsis thaliana by tagging clathrin light chain with green fluorescent protein (CLC-GFP). Quantitative evaluations of colocalization demonstrate that the majority of CLC-GFP is localized to the TGN, and a minor population is associated with multivesicular endosomes and the Golgi trans-cisternae. Live imaging further demonstrated the presence of highly dynamic clathrin-positive tubules and vesicles, which appeared to mediate interactions between the TGNs. CLC-GFP is also targeted to cell plates and the plasma membrane. Although CLC-GFP colocalizes with a dynamin isoform at the plasma membrane, these proteins exhibit distinct distributions at newly forming cell plates. This finding indicates independent functions of CLC (clathrin light chains) and dynamin during the formation of cell plates. We have also found that brefeldin A and wortmannin treatment causes distinctly different alterations in the dynamics and distribution of clathrin-coated domains at the plasma membrane. This could account for the different effects of these drugs on plant endocytosis.
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Affiliation(s)
- Emi Ito
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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162
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Nussaume L, Kanno S, Javot H, Marin E, Pochon N, Ayadi A, Nakanishi TM, Thibaud MC. Phosphate Import in Plants: Focus on the PHT1 Transporters. FRONTIERS IN PLANT SCIENCE 2011; 2:83. [PMID: 22645553 PMCID: PMC3355772 DOI: 10.3389/fpls.2011.00083] [Citation(s) in RCA: 281] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 11/03/2011] [Indexed: 05/17/2023]
Abstract
The main source of phosphorus for plants is inorganic phosphate (Pi), which is characterized by its poor availability and low mobility. Uptake of this element from the soil relies heavily upon the PHT1 transporters, a specific family of plant plasma membrane proteins that were identified by homology with the yeast PHO84 Pi transporter. Since the discovery of PHT1 transporters in 1996, various studies have revealed that their function is controlled by a highly complex network of regulation. This review will summarize the current state of research on plant PHT1 multigenic families, including physiological, biochemical, molecular, cellular, and genetics studies.
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Affiliation(s)
- Laurent Nussaume
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
| | - Satomi Kanno
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-kuTokyo, Japan 113-8657
| | - Hélène Javot
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
| | - Elena Marin
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
| | - Nathalie Pochon
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
| | - Amal Ayadi
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
| | - Tomoko M. Nakanishi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-kuTokyo, Japan 113-8657
| | - Marie-Christine Thibaud
- IBEB-SBVME Laboratoire de Biologie du Développement des Plantes, UMR6191 CNRS-Commissariat à l’Energie Atomique et aux Energies Alternatives Cadarache, Université Aix-Marseille, F-13108 Saint-Paul-lez-DuranceFrance
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163
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Boron stress activates the general amino acid control mechanism and inhibits protein synthesis. PLoS One 2011; 6:e27772. [PMID: 22114689 PMCID: PMC3219688 DOI: 10.1371/journal.pone.0027772] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 10/25/2011] [Indexed: 12/01/2022] Open
Abstract
Boron is an essential micronutrient for plants, and it is beneficial for animals. However, at high concentrations boron is toxic to cells although the mechanism of this toxicity is not known. Atr1 has recently been identified as a boron efflux pump whose expression is upregulated in response to boron treatment. Here, we found that the expression of ATR1 is associated with expression of genes involved in amino acid biosynthesis. These mechanisms are strictly controlled by the transcription factor Gcn4 in response to boron treatment. Further analyses have shown that boron impaired protein synthesis by promoting phosphorylation of eIF2α in a Gcn2 kinase dependent manner. The uncharged tRNA binding domain (HisRS) of Gcn2 is necessary for the phosphorylation of eIF2α in the presence of boron. We postulate that boron exerts its toxic effect through activation of the general amino acid control system and inhibition of protein synthesis. Since the general amino acid control pathway is conserved among eukaryotes, this mechanism of boron toxicity may be of general importance.
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164
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Abstract
Protein turnover is fundamental both for development and cellular homeostasis. The mechanisms responsible for the turnover of integral membrane proteins in plant cells are however still largely unknown. Recently, considerable attention has been devoted to the degradation of plasma membrane proteins. We have now studied the turnover of a tonoplast protein, the potassium channel TPK1, in fully differentiated Arabidopsis leaf cells and showed that its degradation occurs upon internalization into the vacuole. Here, we discuss the possible mechanisms and triggering events involved.
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165
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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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166
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Li X, Wang X, Yang Y, Li R, He Q, Fang X, Luu DT, Maurel C, Lin J. Single-molecule analysis of PIP2;1 dynamics and partitioning reveals multiple modes of Arabidopsis plasma membrane aquaporin regulation. THE PLANT CELL 2011; 23:3780-97. [PMID: 22010034 PMCID: PMC3229149 DOI: 10.1105/tpc.111.091454] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 09/09/2011] [Accepted: 10/03/2011] [Indexed: 05/17/2023]
Abstract
PIP2;1 is an integral membrane protein that facilitates water transport across plasma membranes. To address the dynamics of Arabidopsis thaliana PIP2;1 at the single-molecule level as well as their role in PIP2;1 regulation, we tracked green fluorescent protein-PIP2;1 molecules by variable-angle evanescent wave microscopy and fluorescence correlation spectroscopy (FCS). Single-particle tracking analysis revealed that PIP2;1 presented four diffusion modes with large dispersion of diffusion coefficients, suggesting that partitioning and dynamics of PIP2;1 are heterogeneous and, more importantly, that PIP2;1 can move into or out of membrane microdomains. In response to salt stress, the diffusion coefficients and percentage of restricted diffusion increased, implying that PIP2;1 internalization was enhanced. This was further supported by the decrease in PIP2;1 density on plasma membranes by FCS. We additionally demonstrated that PIP2;1 internalization involves a combination of two pathways: a tyrphostin A23-sensitive clathrin-dependent pathway and a methyl-β-cyclodextrin-sensitive, membrane raft-associated pathway. The latter was efficiently stimulated under NaCl conditions. Taken together, our findings demonstrate that PIP2;1 molecules are heterogeneously distributed on the plasma membrane and that clathrin and membrane raft pathways cooperate to mediate the subcellular trafficking of PIP2;1, suggesting that the dynamic partitioning and recycling pathways might be involved in the multiple modes of regulating water permeability.
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Affiliation(s)
- Xiaojuan Li
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaohua Wang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yong Yang
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Key Laboratory of Molecular Nanostructures and Nanotechnology, Chinese Academy of Sciences, Beijing 100190, China
| | - Ruili Li
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qihua He
- Peking University Health Science Center, Beijing 100191, China
| | - Xiaohong Fang
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Key Laboratory of Molecular Nanostructures and Nanotechnology, Chinese Academy of Sciences, Beijing 100190, China
| | - Doan-Trung Luu
- Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, Unité Mixte de Recherche 5004 Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique/Montpellier SupAgro/Université Montpellier 2, F-34060 Montpellier Cedex 2, France
| | - Christophe Maurel
- Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, Unité Mixte de Recherche 5004 Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique/Montpellier SupAgro/Université Montpellier 2, F-34060 Montpellier Cedex 2, France
| | - Jinxing Lin
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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167
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Zelazny E, Barberon M, Curie C, Vert G. Ubiquitination of transporters at the forefront of plant nutrition. PLANT SIGNALING & BEHAVIOR 2011; 6:1597-9. [PMID: 21918375 PMCID: PMC3256394 DOI: 10.4161/psb.6.10.17134] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In plants, the tight regulation of plasma membrane transporters is essential to maintain nutrient homeostasis. The mechanisms controlling the abundance of transporters, and other integral plasma membrane proteins, now come to light. Ubiquitination appears as a major signal initiating cargo endocytosis and sorting into multivesicular bodies prior to degradation in the vacuole. We have indeed demonstrated that the root iron transporter IRT1 is subjected to ubiquitin-dependent trafficking in root epidermal cells. This control is crucial to keep IRT1 levels at the cell surface low and to cope with the toxicity associated with other readily available metal substrates of IRT1. Our work combined with recent report on the BOR1 boron transporter establishes ubiquitination as a conserved mechanism of plasma membrane protein trafficking in plants, and highlights its importance for plant nutrition.
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Affiliation(s)
- Enric Zelazny
- Biochimie et Physiologie Moléculaire des Plantes, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5004, Institut de Biologie Intégrative des Plantes, Montpellier, France
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168
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Dettmer J, Friml J. Cell polarity in plants: when two do the same, it is not the same.... Curr Opin Cell Biol 2011; 23:686-96. [PMID: 21962973 DOI: 10.1016/j.ceb.2011.09.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/19/2011] [Accepted: 09/09/2011] [Indexed: 01/12/2023]
Abstract
In unicellular and multicellular organisms, cell polarity is essential for a wide range of biological processes. An important feature of cell polarity is the asymmetric distribution of proteins in or at the plasma membrane. In plants such polar localized proteins play various specific roles ranging from organizing cell morphogenesis, asymmetric cell division, pathogen defense, nutrient transport and establishment of hormone gradients for developmental patterning. Moreover, flexible respecification of cell polarities enables plants to adjust their physiology and development to environmental changes. Having evolved multicellularity independently and lacking major cell polarity mechanisms of animal cells, plants came up with alternative solutions to generate and respecify cell polarity as well as to regulate polar domains at the plasma membrane.
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Affiliation(s)
- Jan Dettmer
- Department of Plant Systems Biology, VIB, 9052 Gent, Belgium
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169
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Tanaka M, Takano J, Chiba Y, Lombardo F, Ogasawara Y, Onouchi H, Naito S, Fujiwara T. Boron-dependent degradation of NIP5;1 mRNA for acclimation to excess boron conditions in Arabidopsis. THE PLANT CELL 2011; 23:3547-59. [PMID: 21908722 PMCID: PMC3203445 DOI: 10.1105/tpc.111.088351] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 08/05/2011] [Accepted: 08/24/2011] [Indexed: 05/02/2023]
Abstract
Boron (B) is an essential plant micronutrient that is toxic at higher levels. NIP5;1 is a boric acid channel required for B uptake and growth under B deficiency. Accumulation of the NIP5;1 transcript is upregulated under B deficiency in Arabidopsis thaliana roots. To elucidate the mechanism of regulation, the 5' untranslated region (UTR) of NIP5;1 was tested for its ability to confer B-dependent regulation using β-glucuronidase and green fluorescent protein as reporters. This analysis showed that the 5' UTR was involved in NIP5;1 transcript accumulation in response to B conditions. We also found that high-B conditions trigger NIP5;1 mRNA degradation and that the sequence from +182 to +200 bp in the 5' UTR is required for this mRNA destabilization. In the nip5;1-1 mutant background, a NIP5;1 complementation construct without the 5' UTR produced high levels of mRNA accumulation, increased B concentrations in tissues, and reduced growth under high-B conditions. These data suggest that the 5' UTR controls B-dependent NIP5;1 mRNA degradation and that NIP5;1 mRNA degradation is important for plant acclimation to high-B conditions.
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Affiliation(s)
- Mayuki Tanaka
- Graduate School of Agricultural and Life Science, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Junpei Takano
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Yukako Chiba
- Creative Research Initiative, Hokkaido University, Sapporo 001-0021, Japan
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-8589, Japan
| | - Fabien Lombardo
- Graduate School of Agricultural and Life Science, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yuki Ogasawara
- Graduate School of Agricultural and Life Science, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hitoshi Onouchi
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
- Core Research for Evolutional Science and Technology, Japanese Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Satoshi Naito
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-8589, Japan
| | - Toru Fujiwara
- Graduate School of Agricultural and Life Science, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
- Division of Life Science, Graduate School of Life Science, Hokkaido University, Sapporo 060-8589, Japan
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170
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Maîtrejean M, Wudick MM, Voelker C, Prinsi B, Mueller-Roeber B, Czempinski K, Pedrazzini E, Vitale A. Assembly and sorting of the tonoplast potassium channel AtTPK1 and its turnover by internalization into the vacuole. PLANT PHYSIOLOGY 2011; 156:1783-96. [PMID: 21697507 PMCID: PMC3149923 DOI: 10.1104/pp.111.177816] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 06/18/2010] [Indexed: 05/18/2023]
Abstract
The assembly, sorting signals, and turnover of the tonoplast potassium channel AtTPK1 of Arabidopsis (Arabidopsis thaliana) were studied. We used transgenic Arabidopsis expressing a TPK1-green fluorescent protein (GFP) fusion or protoplasts transiently transformed with chimeric constructs based on domain exchange between TPK1 and TPK4, the only TPK family member not located at the tonoplast. The results show that TPK1-GFP is a dimer and that the newly synthesized polypeptides transiently interact with a thus-far unidentified 20-kD polypeptide. A subset of the TPK1-TPK4 chimeras were unable to assemble correctly and these remained located in the endoplasmic reticulum where they interacted with the binding protein chaperone. Therefore, TPK1 must assemble correctly to pass endoplasmic reticulum quality control. Substitution of the cytosolic C terminus of TPK4 with the corresponding domain of TPK1 was sufficient to allow tonoplast delivery, indicating that this domain contains tonoplast sorting information. Pulse-chase labeling indicated that TPK1-GFP has a half-life of at least 24 h. Turnover of the fusion protein involves internalization into the vacuole where the GFP domain is released. This indicates a possible mechanism for the turnover of tonoplast proteins.
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171
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Camacho-Cristóbal JJ, Rexach J, Herrera-Rodríguez MB, Navarro-Gochicoa MT, González-Fontes A. Boron deficiency and transcript level changes. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 181:85-9. [PMID: 21683871 DOI: 10.1016/j.plantsci.2011.05.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 05/03/2011] [Accepted: 05/04/2011] [Indexed: 05/02/2023]
Abstract
Boron (B) is an essential element for plant growth whose deficiency causes an alteration in the expression of a wide range of genes involved in several physiological processes. However, our understanding of the signal transduction pathways that trigger the B-deficiency responses in plants is still poor. The aims of this review are (i) to summarize the genes whose transcript levels are affected by B deficiency and (ii) to provide an update on recent findings that could help to understand how the signal(s) triggered by B deficiency is transferred to the nucleus to modulate gene expression. In this contribution we review the effects of B deficiency on the transcript level of genes related to B uptake and translocation, maintenance of cell wall and membrane function, nitrogen assimilation and stress response. In addition, we discuss the possible mediation of calcium, arabinogalactan-proteins and other cis-diol containing compounds in the signaling mechanisms that transfer the signal of B deficiency to nuclei. Finally, we conclude that the advance in the knowledge of the molecular basis of B deficiency response in plants will allow improving the tolerance of crops to B deficiency stress.
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Affiliation(s)
- Juan J Camacho-Cristóbal
- Departamento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, E-41013 Sevilla, Spain.
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172
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De Caroli M, Lenucci MS, Di Sansebastiano GP, Dalessandro G, De Lorenzo G, Piro G. Dynamic protein trafficking to the cell wall. PLANT SIGNALING & BEHAVIOR 2011; 6:1012-5. [PMID: 21701253 PMCID: PMC3257782 DOI: 10.4161/psb.6.7.15550] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 03/21/2011] [Indexed: 05/16/2023]
Abstract
Recently we have studied the secretion pattern of a pectin methylesterase inhibitor protein (PMEI1) and a polygalacturonase inhibitor protein (PGIP2) in tobacco protoplast using the protein fusions, secGFP-PMEI1 and PGIP2-GFP. Both chimeras reach the cell wall by passing through the endomembrane system but using distinct mechanisms and through a pathway distinguishable from the default sorting of a secreted GFP. After reaching the apoplast, sec-GFP-PMEI1 is stably accumulated in the cell wall, while PGIP2-GFP undergoes endocytic trafficking. Here we describe the final localization of PGIP2-GFP in the vacuole, evidenced by co-localization with the marker Aleu-RFP, and show a graphic elaboration of its sorting pattern. A working model taking into consideration the presence of a regulated apoplast-targeted secretion pathway is proposed.
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Affiliation(s)
| | | | | | | | - Giulia De Lorenzo
- Dipartimento di Biologia e Biotecnologie “C. Darwin”; Università “La Sapienza”; Roma, Italy
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173
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A membrane trafficking pathway regulated by the plant-specific RAB GTPase ARA6. Nat Cell Biol 2011; 13:853-9. [PMID: 21666683 DOI: 10.1038/ncb2270] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 04/28/2011] [Indexed: 12/29/2022]
Abstract
Endosomal trafficking plays an integral role in various eukaryotic cell activities and serves as a basis for higher-order functions in multicellular organisms. An understanding of the importance of endosomal trafficking in plants is rapidly developing, but its molecular mechanism is mostly unknown. Several key regulators of endosomal trafficking, including RAB5, which regulates diverse endocytic events in animal cells, are highly conserved. However, the identification of lineage-specific regulators in eukaryotes indicates that endosomal trafficking is diversified according to distinct body plans and lifestyles. In addition to orthologues of metazoan RAB5, land plants possess a unique RAB5 molecule, which is one of the most prominent features of plant RAB GTPase organization. Plants have also evolved a unique repertoire of SNAREs, the most distinctive of which are diverse VAMP7-related longins, including plant-unique VAMP72 derivatives. Here, we demonstrate that a plant-unique RAB5 protein, ARA6, acts in an endosomal trafficking pathway in Arabidopsis thaliana. ARA6 modulates the assembly of a distinct SNARE complex from conventional RAB5, and has a functional role in the salinity stress response. Our results indicate that plants possess a unique endosomal trafficking network and provide the first indication of a functional link between a specific RAB and a specific SNARE complex in plants.
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174
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Cloning and characterization of boron transporters in Brassica napus. Mol Biol Rep 2011; 39:1963-73. [PMID: 21660474 DOI: 10.1007/s11033-011-0930-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 05/24/2011] [Indexed: 10/18/2022]
Abstract
Six full-length cDNA encoding boron transporters (BOR) were isolated from Brassica napus (AACC) by rapid amplification of cDNA ends (RACE). The phylogenic analysis revealed that the six BORs were the orthologues of AtBOR1, which formed companying with the triplication and allotetra-ploidization process of B. napus, and were divided into three groups in B. napus. Each group was comprised of two members, one of which was originated from Brassica rapa (AA) and the other from Brassica oleracea (CC). Based on the phylogenetic relationships, the six genes were named as BnBOR1;1a, BnBOR1;1c, BnBOR1;2a, BnBOR1;2c, BnBOR1;3a and BnBOR1;3c, respectively. The deduced BnBOR1 s had extensive similarity with other plant BORs, with the identity of 74-96.8% in amino acid sequence. The BnBOR1;3a and BnBOR1;3c resembled AtBOR1 in number and positions of the 11 introns, but the others only have 9 introns. After the gene duplication, there was evidence of purifying selection under a divergent selective pressure. The expression patterns of the six BnBOR1 s were detected by semi-quantitative RT-PCR. The BnBOR1;3a and BnBOR1;3c showed a ubiquitous expression in all of the investigated tissues, whereas the other four genes showed similar tissue-specific expression profile. Unlike the non-transcriptional regulation of AtBOR1, the expression of BnBOR1;1c and BnBOR1;2a were obviously induced by boron deficiency. This study suggested that the BOR1 s had undergone a divergent expression pattern in the genome of B. napus after that the B. napus diverged from Arabidopsis thaliana.
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175
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Markham JE, Molino D, Gissot L, Bellec Y, Hématy K, Marion J, Belcram K, Palauqui JC, Satiat-JeuneMaître B, Faure JD. Sphingolipids containing very-long-chain fatty acids define a secretory pathway for specific polar plasma membrane protein targeting in Arabidopsis. THE PLANT CELL 2011; 23:2362-78. [PMID: 21666002 PMCID: PMC3160045 DOI: 10.1105/tpc.110.080473] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 04/15/2011] [Accepted: 05/20/2011] [Indexed: 05/18/2023]
Abstract
Sphingolipids are a class of structural membrane lipids involved in membrane trafficking and cell polarity. Functional analysis of the ceramide synthase family in Arabidopsis thaliana demonstrates the existence of two activities selective for the length of the acyl chains. Very-long-acyl-chain (C > 18 carbons) but not long-chain sphingolipids are essential for plant development. Reduction of very-long-chain fatty acid sphingolipid levels leads in particular to auxin-dependent inhibition of lateral root emergence that is associated with selective aggregation of the plasma membrane auxin carriers AUX1 and PIN1 in the cytosol. Defective targeting of polar auxin carriers is characterized by specific aggregation of Rab-A2(a)- and Rab-A1(e)-labeled early endosomes along the secretory pathway. These aggregates correlate with the accumulation of membrane structures and vesicle fragmentation in the cytosol. In conclusion, sphingolipids with very long acyl chains define a trafficking pathway with specific endomembrane compartments and polar auxin transport protein cargoes.
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Affiliation(s)
| | - Diana Molino
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Lionel Gissot
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Yannick Bellec
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Kian Hématy
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Jessica Marion
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, F-91198 Gif-sur-Yvette Cedex, France
| | - Katia Belcram
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Jean-Christophe Palauqui
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
| | - Béatrice Satiat-JeuneMaître
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, F-91198 Gif-sur-Yvette Cedex, France
| | - Jean-Denis Faure
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique–AgroParisTech, Centre de Versailles-Grignon, 78000 Versailles, France
- Address correspondence to
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176
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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: 326] [Impact Index Per Article: 25.1] [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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177
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Nielsen FH, Meacham SL. Growing Evidence for Human Health Benefits of Boron. J Evid Based Complementary Altern Med 2011. [DOI: 10.1177/2156587211407638] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Growing evidence from a variety of experimental models shows that boron is a bioactive and beneficial (perhaps essential) element for humans. Reported beneficial actions of boron include arthritis alleviation or risk reduction, bone growth and maintenance, central nervous system function, cancer risk reduction, hormone facilitation, and immune response, inflammation, and oxidative stress modulation. The diverse effects of boron indicate that it influences the formation and/or activity of an entity that is involved in many biochemical processes. Formation of boroesters with the ribose moiety of compounds involved in numerous reactions, such as S-adenosylmethionine and oxidized nicotinamide adenine dinucleotide (NAD+) might be the reason for boron bioactivity. Both animal and human data suggest that boron intakes should be >1.0 mg/d. Many people consume less than this amount. Thus, a low boron intake should be considered a health concern, which can be prevented by diets rich in fruits, vegetables, nuts, and pulses.
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Affiliation(s)
- Forrest H. Nielsen
- USDA, ARS, Grand Forks Human Nutrition Research Center, Grand Forks, ND, USA
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178
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Kitakura S, Vanneste S, Robert S, Löfke C, Teichmann T, Tanaka H, Friml J. Clathrin mediates endocytosis and polar distribution of PIN auxin transporters in Arabidopsis. THE PLANT CELL 2011; 23:1920-31. [PMID: 21551390 PMCID: PMC3123958 DOI: 10.1105/tpc.111.083030] [Citation(s) in RCA: 242] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 03/15/2011] [Accepted: 04/18/2011] [Indexed: 05/18/2023]
Abstract
Endocytosis is a crucial mechanism by which eukaryotic cells internalize extracellular and plasma membrane material, and it is required for a multitude of cellular and developmental processes in unicellular and multicellular organisms. In animals and yeast, the best characterized pathway for endocytosis depends on the function of the vesicle coat protein clathrin. Clathrin-mediated endocytosis has recently been demonstrated also in plant cells, but its physiological and developmental roles remain unclear. Here, we assessed the roles of the clathrin-mediated mechanism of endocytosis in plants by genetic means. We interfered with clathrin heavy chain (CHC) function through mutants and dominant-negative approaches in Arabidopsis thaliana and established tools to manipulate clathrin function in a cell type-specific manner. The chc2 single mutants and dominant-negative CHC1 (HUB) transgenic lines were defective in bulk endocytosis as well as in internalization of prominent plasma membrane proteins. Interference with clathrin-mediated endocytosis led to defects in constitutive endocytic recycling of PIN auxin transporters and their polar distribution in embryos and roots. Consistent with this, these lines had altered auxin distribution patterns and associated auxin transport-related phenotypes, such as aberrant embryo patterning, imperfect cotyledon specification, agravitropic growth, and impaired lateral root organogenesis. Together, these data demonstrate a fundamental role for clathrin function in cell polarity, growth, patterning, and organogenesis in plants.
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Affiliation(s)
- Saeko Kitakura
- Department of Plant Systems Biology, VIB, B-9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Steffen Vanneste
- Department of Plant Systems Biology, VIB, B-9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Stéphanie Robert
- Department of Plant Systems Biology, VIB, B-9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Christian Löfke
- Department of Plant Cell Biology, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University, 37073 Gottingen, Germany
| | - Thomas Teichmann
- Department of Plant Cell Biology, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University, 37073 Gottingen, Germany
| | - Hirokazu Tanaka
- Department of Plant Systems Biology, VIB, B-9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Jiří Friml
- Department of Plant Systems Biology, VIB, B-9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
- Address correspondence to
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179
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Chen Z, Grefen C, Donald N, Hills A, Blatt MR. A bicistronic, Ubiquitin-10 promoter-based vector cassette for transient transformation and functional analysis of membrane transport demonstrates the utility of quantitative voltage clamp studies on intact Arabidopsis root epidermis. PLANT, CELL & ENVIRONMENT 2011; 34:554-64. [PMID: 21251017 DOI: 10.1111/j.1365-3040.2010.02262.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
To date the use of fluorescent reporter constructs in analysing membrane transport has been limited primarily to cell lines expressing stably either the tagged transporter protein(s) or markers to identify lineages of interest. Strategies for transient expression have yet to be exploited in transport analysis, despite their wide application in cellular imaging studies. Here we describe a Gateway-compatible, bicistronic vector, incorporating the constitutive Ubiqutin-10 gene promoter of Arabidopsis that gives prolonged expression after transient transformation and enables fluorescence marking of cells without a fusion construct. We show that Arabidopsis root epidermal cells are readily transformed by co-cultivation with Agrobacterium and are tractable for quantitative electrophysiological analysis. As a proof of principle, we transiently transformed Arabidopsis with the bicistronic vector carrying GFP as the fluorescent marker and, separately, the integral plasma membrane protein SYP121 essential for the inward K+ channel current. We demonstrate that transient expression of SYP121 in syp121 mutant plants is sufficient to rescue the K+ current in vivo. The combination of transient expression and use of the bicistronic vector promises significant advantages for studies of membrane transport and nutrient acquisition in roots.
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Affiliation(s)
- Zhonghua Chen
- Laboratory of Plant Physiology and Biophysics, MCSB-Plant Sciences, Bower Building, University of Glasgow, Glasgow G128QQ, UK
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180
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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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181
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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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182
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De Caroli M, Lenucci MS, Di Sansebastiano GP, Dalessandro G, De Lorenzo G, Piro G. Protein trafficking to the cell wall occurs through mechanisms distinguishable from default sorting in tobacco. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 65:295-308. [PMID: 21223393 DOI: 10.1111/j.1365-313x.2010.04421.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The secretory pathway in plants involves sustained traffic to the cell wall, as matrix components, polysaccharides and proteins reach the cell wall through the endomembrane system. We studied the secretion pattern of cell-wall proteins in tobacco protoplasts and leaf epidermal cells using fluorescent forms of a pectin methylesterase inhibitor protein (PMEI1) and a polygalacturonase inhibitor protein (PGIP2). The two most representative protein fusions, secGFP-PMEI1 and PGIP2-GFP, reached the cell wall by passing through ER and Golgi stacks but using distinct mechanisms. secGFP-PMEI1 was linked to a glycosylphosphatidylinositol (GPI) anchor and stably accumulated in the cell wall, regulating the activity of the endogenous pectin methylesterases (PMEs) that are constitutively present in this compartment. A mannosamine-induced non-GPI-anchored form of PMEI1 as well as a form (PMEI1-GFP) that was unable to bind membranes failed to reach the cell wall, and accumulated in the Golgi stacks. In contrast, PGIP2-GFP moved as a soluble cargo protein along the secretory pathway, but was not stably retained in the cell wall, due to internalization to an endosomal compartment and eventually the vacuole. Stable localization of PGIP2 in the wall was observed only in the presence of a specific fungal endopolygalacturonase ligand in the cell wall. Both secGFP-PMEI1 and PGIP2-GFP sorting were distinguishable from that of a secreted GFP, suggesting that rigorous and more complex controls than the simple mechanism of bulk flow are the basis of cell-wall growth and differentiation.
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Affiliation(s)
- Monica De Caroli
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, 73100 Lecce, Italy
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183
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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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184
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Kasai K, Takano J, Miwa K, Toyoda A, Fujiwara T. High boron-induced ubiquitination regulates vacuolar sorting of the BOR1 borate transporter in Arabidopsis thaliana. J Biol Chem 2010; 286:6175-83. [PMID: 21148314 DOI: 10.1074/jbc.m110.184929] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Boron homeostasis is important for plants, as boron is essential but is toxic in excess. Under high boron conditions, the Arabidopsis thaliana borate transporter BOR1 is trafficked from the plasma membrane (PM) to the vacuole via the endocytic pathway for degradation to avoid excess boron transport. Here, we show that boron-induced ubiquitination is required for vacuolar sorting of BOR1. We found that a substitution of lysine 590 with alanine (K590A) in BOR1 blocked degradation. BOR1 was mono- or diubiquitinated within several minutes after applying a high concentration of boron, whereas the K590A mutant was not. The K590A mutation abolished vacuolar transport of BOR1 but did not apparently affect polar localization to the inner PM domains. Furthermore, brefeldin A and wortmannin treatment suggested that Lys-590 is required for BOR1 translocation from an early endosomal compartment to multivesicular bodies. Our results show that boron-induced ubiquitination of BOR1 is not required for endocytosis from the PM but is crucial for the sorting of internalized BOR1 to multivesicular bodies for subsequent degradation in vacuoles.
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Affiliation(s)
- Koji Kasai
- Biotechnology Research Center, University of Tokyo, Tokyo 113-8657, Japan
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185
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Paciorek T, Bergmann DC. The secret to life is being different: asymmetric divisions in plant development. CURRENT OPINION IN PLANT BIOLOGY 2010; 13:661-669. [PMID: 20970370 DOI: 10.1016/j.pbi.2010.09.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/02/2010] [Accepted: 09/23/2010] [Indexed: 05/30/2023]
Abstract
Asymmetric cell divisions (ACDs) are used to create organismal form and cellular diversity during plant development. In several embryonic and postembryonic contexts, genes that specify cell fates and networks that provide positional information have been identified. The cellular mechanisms that translate this information into a physically ACD, however, are still obscure. In this review we examine the cell polarization events that precede asymmetric divisions in plants. Using principles derived from studies of other organisms and from postmitotic polarity generation in plants, we endeavor to provide a framework of what is known, what is on the horizon and what is critically needed to develop a rigorous mechanistic understanding of ACDs in plants.
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Affiliation(s)
- Tomasz Paciorek
- Biology Department, 371 Serra Mall, Stanford University, Stanford, CA 94305-5020, USA
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186
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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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187
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Kinoshita A, Betsuyaku S, Osakabe Y, Mizuno S, Nagawa S, Stahl Y, Simon R, Yamaguchi-Shinozaki K, Fukuda H, Sawa S. RPK2 is an essential receptor-like kinase that transmits the CLV3 signal in Arabidopsis. Development 2010; 137:3911-20. [PMID: 20978082 DOI: 10.1242/dev.048199] [Citation(s) in RCA: 235] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The shoot apical meristem (SAM) is the fundamental structure that is located at the growing tip and gives rise to all aerial parts of plant tissues and organs, such as leaves, stems and flowers. In Arabidopsis thaliana, the CLAVATA3 (CLV3) pathway regulates the stem cell pool in the SAM, in which a small peptide ligand derived from CLV3 is perceived by two major receptor complexes, CLV1 and CLV2-CORYNE (CRN)/SUPPRESSOR OF LLP1 2 (SOL2), to restrict WUSCHEL (WUS) expression. In this study, we used the functional, synthetic CLV3 peptide (MCLV3) to isolate CLV3-insensitive mutants and revealed that a receptor-like kinase, RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2), also known as TOADSTOOL 2 (TOAD2), is another key regulator of meristem maintenance. Mutations in the RPK2 gene result in stem cell expansion and increased number of floral organs, as seen in the other clv mutants. These phenotypes are additive with both clv1 and clv2 mutations. Moreover, our biochemical analyses using Nicotiana benthamiana revealed that RPK2 forms homo-oligomers but does not associate with CLV1 or CLV2. These genetic and biochemical findings suggest that three major receptor complexes, RPK2 homomers, CLV1 homomers and CLV2-CRN/SOL2 heteromers, are likely to mediate three signalling pathways, mainly in parallel but with potential crosstalk, to regulate the SAM homeostasis.
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Affiliation(s)
- Atsuko Kinoshita
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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188
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Liesche J, He HX, Grimm B, Schulz A, Kühn C. Recycling of Solanum sucrose transporters expressed in yeast, tobacco, and in mature phloem sieve elements. MOLECULAR PLANT 2010; 3:1064-74. [PMID: 20924029 DOI: 10.1093/mp/ssq059] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The plant sucrose transporter SUT1 (from Solanum tuberosum, S. lycopersicum, or Zea mays) exhibits redox-dependent dimerization and targeting if heterologously expressed in S. cerevisiae (Krügel et al., 2008). It was also shown that SUT1 is present in motile vesicles when expressed in tobacco cells and that its targeting to the plasma membrane is reversible. StSUT1 is internalized in the presence of brefeldin A (BFA) in yeast, plant cells, and in mature sieve elements as confirmed by immunolocalization. These results were confirmed here and the dynamics of intracellular SUT1 localization were further elucidated. Inhibitor studies revealed that vesicle movement of SUT1 is actin-dependent. BFA-mediated effects might indicate that anterograde vesicle movement is possible even in mature sieve elements, and could involve components of the cytoskeleton that were previously thought to be absent in SEs. Our results are in contradiction to this old dogma of plant physiology and the potential of mature sieve elements should therefore be re-evaluated. In addition, SUT1 internalization was found to be dependent on the plasma membrane lipid composition. SUT1 belongs to the detergent-resistant membrane (DRM) fraction in planta and is targeted to membrane raft-like microdomains when expressed in yeast (Krügel et al., 2008). Here, SUT1-GFP expression in different yeast mutants, which were unable to perform endocytosis and/or raft formation, revealed a strong link between SUT1 raft localization, the sterol composition and membrane potential of the yeast plasma membrane, and the capacity of the SUT1 protein to be internalized by endocytosis. The results provide new insight into the regulation of sucrose transport and the mechanism of endocytosis in plant cells.
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Affiliation(s)
- Johannes Liesche
- Humboldt University, Institute of Biology, Plant Physiology, Philippstrasse 13, Building 12, 10115 Berlin, Germany
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189
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Wang Z, Wang Z, Shi L, Wang L, Xu F. Proteomic alterations of Brassica napus root in response to boron deficiency. PLANT MOLECULAR BIOLOGY 2010; 74:265-78. [PMID: 20694506 DOI: 10.1007/s11103-010-9671-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 07/26/2010] [Indexed: 05/02/2023]
Abstract
Boron (B) deficiency is a worldwide problem, and Brassica napus is one of the most sensitive crops to B deficiency. To better understand the B starvation response of Brassica napus, we conducted a comparative proteomic analysis of seedling stage Brassica napus root between B-sufficient and B-limited conditions: 45 differentially expressed proteins were successfully identified by 2-DE coupled with MALDI-TOF/TOF-MS and LTQ-ESI-MS/MS analysis. Among these proteins, 10 were down-regulated and 35 were up-regulated under B-limited condition. Combining GO and KEGG analyses with data from previous reports, proteins were categorized into several functional groups, including antioxidant and detoxification, defense-related proteins, signaling and regulation, carbohydrate and energy metabolism, amino acid and fatty acid metabolism, protein translation and degradation, cell wall structure, and transporter. The genes of selected proteins were analyzed by quantitative RT-PCR. Our results provide novel information for better understanding the physiological and biochemical responses to B deficiency in plants.
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Affiliation(s)
- Zhifang Wang
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
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190
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Grunewald W, Friml J. The march of the PINs: developmental plasticity by dynamic polar targeting in plant cells. EMBO J 2010; 29:2700-14. [PMID: 20717140 DOI: 10.1038/emboj.2010.181] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 07/09/2010] [Indexed: 11/09/2022] Open
Abstract
Development of plants and their adaptive capacity towards ever-changing environmental conditions largely depend on the spatial distribution of the plant hormone auxin. At the cellular level, various internal and external signals are translated into specific changes in the polar, subcellular localization of auxin transporters from the PIN family thereby directing and redirecting the intercellular fluxes of auxin. The current model of polar targeting of PIN proteins towards different plasma membrane domains encompasses apolar secretion of newly synthesized PINs followed by endocytosis and recycling back to the plasma membrane in a polarized manner. In this review, we follow the subcellular march of the PINs and highlight the cellular and molecular mechanisms behind polar foraging and subcellular trafficking pathways. Also, the entry points for different signals and regulations including by auxin itself will be discussed within the context of morphological and developmental consequences of polar targeting and subcellular trafficking.
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Affiliation(s)
- Wim Grunewald
- Department of Plant Systems Biology, VIB, Technologiepark, Gent, Belgium
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191
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Miwa K, Fujiwara T. Boron transport in plants: co-ordinated regulation of transporters. ANNALS OF BOTANY 2010; 105:1103-8. [PMID: 20228086 PMCID: PMC2887066 DOI: 10.1093/aob/mcq044] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
BACKGROUND The essentiality of boron (B) for plant growth was established > 85 years ago. In the last decade, it has been revealed that one of the physiological roles of B is cross-linking the pectic polysaccharide rhamnogalacturonan II in primary cell walls. Borate cross-linking of pectic networks serves both for physical strength of cell walls and for cell adhesion. On the other hand, high concentrations of B are toxic to plant growth. To avoid deficiency and toxicity problems, it is important for plants to maintain their tissue B concentrations within an optimum range by regulating transport processes. Boron transport was long believed to be a passive, unregulated process, but the identification of B transporters has suggested that plants sense and respond to the B conditions and regulate transporters to maintain B homeostasis. SCOPE Transporters responsible for efficient B uptake by roots, xylem loading and B distribution among leaves have been described. These transporters are required under B limitation for efficient acquisition and utilization of B. Transporters important for tolerating high B levels in the environment have also been identified, and these transporters export B from roots back to the soil. Two types of transporters are involved in these processes: NIPs (nodulin-26-like intrinsic proteins), boric acid channels, and BORs, B exporters. It is demonstrated that the expression of genes encoding these transporters is finely regulated in response to B availability in the environment to ensure tissue B homeostasis. Furthermore, plants tolerant to stress produced by low B or high B in the environment can be generated through altered expression of these transporters. CONCLUSIONS The identification of the first B transporter led to the discovery that B transport was a process mediated not only by passive diffusion but also by transporters whose activity was regulated in response to B conditions. Now it is evident that plants sense internal and external B conditions and regulate B transport by modulating the expression and/or accumulation of these transporters. Results obtained in model plants are applicable to other plant species, and such knowledge may be useful in designing plants or crops tolerant to soils containing low or high B.
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Affiliation(s)
- Kyoko Miwa
- Creative Research Initiative Sousei, Hokkaido University, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.
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Viotti C, Bubeck J, Stierhof YD, Krebs M, Langhans M, van den Berg W, van Dongen W, Richter S, Geldner N, Takano J, Jürgens G, de Vries SC, Robinson DG, Schumacher K. Endocytic and secretory traffic in Arabidopsis merge in the trans-Golgi network/early endosome, an independent and highly dynamic organelle. THE PLANT CELL 2010; 22:1344-57. [PMID: 20435907 PMCID: PMC2879741 DOI: 10.1105/tpc.109.072637] [Citation(s) in RCA: 352] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 03/22/2010] [Accepted: 04/09/2010] [Indexed: 05/17/2023]
Abstract
Plants constantly adjust their repertoire of plasma membrane proteins that mediates transduction of environmental and developmental signals as well as transport of ions, nutrients, and hormones. The importance of regulated secretory and endocytic trafficking is becoming increasingly clear; however, our knowledge of the compartments and molecular machinery involved is still fragmentary. We used immunogold electron microscopy and confocal laser scanning microscopy to trace the route of cargo molecules, including the BRASSINOSTEROID INSENSITIVE1 receptor and the REQUIRES HIGH BORON1 boron exporter, throughout the plant endomembrane system. Our results provide evidence that both endocytic and secretory cargo pass through the trans-Golgi network/early endosome (TGN/EE) and demonstrate that cargo in late endosomes/multivesicular bodies is destined for vacuolar degradation. Moreover, using spinning disc microscopy, we show that TGN/EEs move independently and are only transiently associated with an individual Golgi stack.
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Affiliation(s)
- Corrado Viotti
- Department of Cell Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
| | - Julia Bubeck
- Department of Developmental Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
| | - York-Dieter Stierhof
- Microscopy Unit, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Melanie Krebs
- Department of Developmental Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
| | - Markus Langhans
- Department of Cell Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
| | - Willy van den Berg
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands
| | - Walter van Dongen
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands
| | - Sandra Richter
- Developmental Genetics, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Niko Geldner
- Department of Plant Molecular Biology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Junpei Takano
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Gerd Jürgens
- Developmental Genetics, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
| | - Sacco C. de Vries
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands
| | - David G. Robinson
- Department of Cell Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
| | - Karin Schumacher
- Department of Developmental Biology, Heidelberg Institute for Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany
- Address correspondence to
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Polar localization and degradation of Arabidopsis boron transporters through distinct trafficking pathways. Proc Natl Acad Sci U S A 2010; 107:5220-5. [PMID: 20194745 DOI: 10.1073/pnas.0910744107] [Citation(s) in RCA: 245] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Boron (B) is essential for plant growth but is toxic when present in excess. In the roots of Arabidopsis thaliana under B limitation, a boric acid channel, NIP5;1, and a boric acid/borate exporter, BOR1, are required for efficient B uptake and subsequent translocation into the xylem, respectively. However, under high-B conditions, BOR1 activity is repressed through endocytic degradation, presumably to avoid B toxicity. In this study, we investigated the localization of GFP-tagged NIP5;1 and BOR1 expressed under the control of their native promoters. Under B limitation, GFP-NIP5;1 and BOR1-GFP localized preferentially in outer (distal) and inner (proximal) plasma membrane domains, respectively, of various root cells. The polar localization of the boric acid channel and boric acid/borate exporter indicates the radial transport route of B toward the stele. Furthermore, mutational analysis revealed a requirement of tyrosine residues, in a probable cytoplasmic loop region of BOR1, for polar localization in various cells of the meristem and elongation zone. The same tyrosine residues were also required for vacuolar targeting upon high B supply. The present study of BOR1 and NIP5;1 demonstrates the importance of selective endocytic trafficking in polar localization and degradation of plant nutrient transporters for radial transport and homeostasis of plant mineral nutrients.
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195
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Sasaki T, Mori IC, Furuichi T, Munemasa S, Toyooka K, Matsuoka K, Murata Y, Yamamoto Y. Closing plant stomata requires a homolog of an aluminum-activated malate transporter. PLANT & CELL PHYSIOLOGY 2010; 51:354-65. [PMID: 20154005 PMCID: PMC2835873 DOI: 10.1093/pcp/pcq016] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 02/09/2010] [Indexed: 05/18/2023]
Abstract
Plant stomata limit both carbon dioxide uptake and water loss; hence, stomatal aperture is carefully set as the environment fluctuates. Aperture area is known to be regulated in part by ion transport, but few of the transporters have been characterized. Here we report that AtALMT12 (At4g17970), a homolog of the aluminum-activated malate transporter (ALMT) of wheat, is expressed in guard cells of Arabidopsis thaliana. Loss-of-function mutations in AtALMT12 impair stomatal closure induced by ABA, calcium and darkness, but do not abolish either the rapidly activated or the slowly activated anion currents previously identified as being important for stomatal closure. Expressed in Xenopus oocytes, AtALMT12 facilitates chloride and nitrate currents, but not those of organic solutes. Therefore, we conclude that AtALMT12 is a novel class of anion transporter involved in stomatal closure.
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Affiliation(s)
- Takayuki Sasaki
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
- These authors contributed equally to this work
- *Corresponding author: E-mail, ; Fax, +81-86-434-1236
| | - Izumi C. Mori
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
- These authors contributed equally to this work
| | - Takuya Furuichi
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
- These authors contributed equally to this work
| | - Shintaro Munemasa
- Graduate School of Natural Science and Technology, Okayama University, Tsushima-Naka, Okayama, 700-8530 Japan
| | - Kiminori Toyooka
- RIKEN Plant Science Center, Tsurumi-ku, Yokohama, 230-0045 Japan
| | - Ken Matsuoka
- Laboratory of Plant Nutrition, Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka, 812-8581 Japan
| | - Yoshiyuki Murata
- Graduate School of Natural Science and Technology, Okayama University, Tsushima-Naka, Okayama, 700-8530 Japan
| | - Yoko Yamamoto
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
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196
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A developmental framework for endodermal differentiation and polarity. Proc Natl Acad Sci U S A 2010; 107:5214-9. [PMID: 20142472 DOI: 10.1073/pnas.0910772107] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The endodermis is a root cell layer common to higher plants and of fundamental importance for root function and nutrient uptake. The endodermis separates outer (peripheral) from inner (central) cell layers by virtue of its Casparian strips, precisely aligned bands of specialized wall material. Here we reveal that the membrane at the Casparian strip is a diffusional barrier between the central and peripheral regions of the plasma membrane and that it mediates attachment to the extracellular matrix. This membrane region thus functions like a tight junction in animal epithelia, although plants lack the molecular modules that establish tight junction in animals. We have also identified a pair of influx and efflux transporters that mark both central and peripheral domains of the plasma membrane. These transporters show opposite polar distributions already in meristems, but their localization becomes refined and restricted upon differentiation. This "central-peripheral" polarity coexists with the apical-basal polarity defined by PIN proteins within the same cells, but utilizes different polarity determinants. Central-peripheral polarity can be already observed in early embryogenesis, where it reveals a cellular polarity within the quiescent center precursor cell. A strict diffusion block between polar domains is common in animals, but had never been described in plants. Yet, its relevance to endodermal function is evident, as central and peripheral membranes of the endodermis face fundamentally different root compartments. Further analysis of endodermal transporter polarity and manipulation of its barrier function will greatly promote our understanding of plant nutrition and stress tolerance in roots.
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197
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Zhao H, Liu J, Shi L, Xu F, Wang Y. Development of boron-efficient near isogenic lines of Brassica napus and their response to low boron stress at seedling stage. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410010096] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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198
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Miwa K, Tanaka M, Kamiya T, Fujiwara T. Molecular Mechanisms of Boron Transport in Plants: Involvement of Arabidopsis NIP5;1 and NIP6;1. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 679:83-96. [DOI: 10.1007/978-1-4419-6315-4_7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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199
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Reid RJ, Fitzpatrick KL. Redistribution of boron in leaves reduces boron toxicity. PLANT SIGNALING & BEHAVIOR 2009; 4:1091-1093. [PMID: 20009556 PMCID: PMC2819523 DOI: 10.4161/psb.4.11.9798] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 08/12/2009] [Indexed: 05/28/2023]
Abstract
High soil boron (B) concentrations lead to the accumulation of B in leaves, causing the development of necrotic regions in leaf tips and margins, gradually extending back along the leaf. Plants vary considerably in their tolerance to B toxicity, and it was recently discovered that one of the tolerance mechanisms involved extrusion of B from the root. Expression of a gene encoding a root B efflux transporter was shown to be much higher in tolerant cultivars. In our current research we have shown that the same gene is also upregulated in leaves. However, unlike in the root, the increased activity of the B efflux transporter in the leaves cannot reduce the tissue B concentration. Instead, we have shown that in tolerant cultivars, these transporters redistribute B from the intracellular phase where it is toxic, into the apoplast which is much less sensitive to B. These results provide an explanation of why different cultivars with the same leaf B concentrations can show markedly different toxicity symptoms. We have also shown that rain can remove a large proportion of leaf B, leading to significant improvements of growth of both leaves and roots.
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Affiliation(s)
- Robert J Reid
- School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, Australia.
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Honsbein A, Sokolovski S, Grefen C, Campanoni P, Pratelli R, Paneque M, Chen Z, Johansson I, Blatt MR. A tripartite SNARE-K+ channel complex mediates in channel-dependent K+ nutrition in Arabidopsis. THE PLANT CELL 2009; 21:2859-77. [PMID: 19794113 PMCID: PMC2768940 DOI: 10.1105/tpc.109.066118] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 07/28/2009] [Accepted: 09/03/2009] [Indexed: 05/17/2023]
Abstract
A few membrane vesicle trafficking (SNARE) proteins in plants are associated with signaling and transmembrane ion transport, including control of plasma membrane ion channels. Vesicle traffic contributes to the population of ion channels at the plasma membrane. Nonetheless, it is unclear whether these SNAREs also interact directly to affect channel gating and, if so, what functional impact this might have on the plant. Here, we report that the Arabidopsis thaliana SNARE SYP121 binds to KC1, a regulatory K(+) channel subunit that assembles with different inward-rectifying K(+) channels to affect their activities. We demonstrate that SYP121 interacts preferentially with KC1 over other Kv-like K(+) channel subunits and that KC1 interacts specifically with SYP121 but not with its closest structural and functional homolog SYP122 nor with another related SNARE SYP111. SYP121 promoted gating of the inward-rectifying K(+) channel AKT1 but only when heterologously coexpressed with KC1. Mutation in any one of the three genes, SYP121, KC1, and AKT1, selectively suppressed the inward-rectifying K(+) current in Arabidopsis root epidermal protoplasts as well as K(+) acquisition and growth in seedlings when channel-mediated K(+) uptake was limiting. That SYP121 should be important for gating of a K(+) channel and its role in inorganic mineral nutrition demonstrates an unexpected role for SNARE-ion channel interactions, apparently divorced from signaling and vesicle traffic. Instead, it suggests a role in regulating K(+) uptake coordinately with membrane expansion for cell growth.
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