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Ham BK, Wang X, Toscano-Morales R, Lin J, Lucas WJ. Plasmodesmal endoplasmic reticulum proteins regulate intercellular trafficking of cucumber mosaic virus in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:4401-4414. [PMID: 37210666 PMCID: PMC10838158 DOI: 10.1093/jxb/erad190] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
Plasmodesmata (PD) are plasma membrane-lined cytoplasmic nanochannels that mediate cell-to-cell communication across the cell wall. A range of proteins are embedded in the PD plasma membrane and endoplasmic reticulum (ER), and function in regulating PD-mediated symplasmic trafficking. However, knowledge of the nature and function of the ER-embedded proteins in the intercellular movement of non-cell-autonomous proteins is limited. Here, we report the functional characterization of two ER luminal proteins, AtBiP1/2, and two ER integral membrane proteins, AtERdj2A/B, which are located within the PD. These PD proteins were identified as interacting proteins with cucumber mosaic virus (CMV) movement protein (MP) in co-immunoprecipitation studies using an Arabidopsis-derived plasmodesmal-enriched cell wall protein preparation (PECP). The AtBiP1/2 PD location was confirmed by TEM-based immunolocalization, and their AtBiP1/2 signal peptides (SPs) function in PD targeting. In vitro/in vivo pull-down assays revealed the association between AtBiP1/2 and CMV MP, mediated by AtERdj2A, through the formation of an AtBiP1/2-AtERdj2-CMV MP complex within PD. The role of this complex in CMV infection was established, as systemic infection was retarded in bip1/bip2w and erdj2b mutants. Our findings provide a model for a mechanism by which the CMV MP mediates cell-to-cell trafficking of its viral ribonucleoprotein complex.
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Affiliation(s)
- Byung-Kook Ham
- Global Institute for Food Security (GIFS), University of Saskatchewan, 421 Downey Rd, Saskatoon, SK S7N 4L8, Canada
- Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
| | - Xiaohua Wang
- Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Roberto Toscano-Morales
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
| | - Jinxing Lin
- Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - William J Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
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2
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Castellano MM, Merchante C. Peculiarities of the regulation of translation initiation in plants. CURRENT OPINION IN PLANT BIOLOGY 2021; 63:102073. [PMID: 34186463 DOI: 10.1016/j.pbi.2021.102073] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/21/2021] [Accepted: 05/27/2021] [Indexed: 06/13/2023]
Abstract
Protein synthesis is a fundamental process for life and, as such, plays a crucial role in the adaptation to energy, developmentaland environmental conditions. For these reasons, and despite the general conservation of the eukaryotic translational machinery, it is not surprising that organisms with different lifestyles have evolved distinct mechanisms of regulation to adapt translation initiation to their intrinsic growth and development. Plants have clear peculiarities compared with other eukaryotes that have also extended to translation control. This review describes the plant-specific mechanisms for regulation of translation initiation, with a focus on those that modulate the eIF4F complexes, central translational regulatory hubs in all eukaryotes, and highlights the latest discoveries on the signaling pathways that regulate their constituents and activity.
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Affiliation(s)
- M Mar Castellano
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA, CSIC), Campus Montegancedo UPM, Pozuelo de Alarcón, Madrid, 28223, Spain.
| | - Catharina Merchante
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" (IHSM-UMA-CSIC), Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Campus de Teatinos, Universidad de Málaga, Málaga, 29071, Spain.
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3
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Pálfi P, Bakacsy L, Kovács H, Szepesi Á. Hypusination, a Metabolic Posttranslational Modification of eIF5A in Plants during Development and Environmental Stress Responses. PLANTS 2021; 10:plants10071261. [PMID: 34206171 PMCID: PMC8309165 DOI: 10.3390/plants10071261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/15/2021] [Accepted: 06/21/2021] [Indexed: 12/25/2022]
Abstract
Hypusination is a unique posttranslational modification of eIF5A, a eukaryotic translation factor. Hypusine is a rare amino acid synthesized in this process and is mediated by two enzymes, deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH). Despite the essential participation of this conserved eIF5A protein in plant development and stress responses, our knowledge of its proper function is limited. In this review, we demonstrate the main findings regarding how eIF5A and hypusination could contribute to plant-specific responses in growth and stress-related processes. Our aim is to briefly discuss the plant-specific details of hypusination and decipher those signal pathways which can be effectively modified by this process. The diverse functions of eIF5A isoforms are also discussed in this review.
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Yan Y, Ham BK, Chong YH, Yeh SD, Lucas WJ. A Plant SMALL RNA-BINDING PROTEIN 1 Family Mediates Cell-to-Cell Trafficking of RNAi Signals. MOLECULAR PLANT 2020; 13:321-335. [PMID: 31812689 DOI: 10.1016/j.molp.2019.12.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/30/2019] [Accepted: 12/02/2019] [Indexed: 05/20/2023]
Abstract
In plants, RNA interference (RNAi) plays a pivotal role in growth and development, and responses to environmental inputs, including pathogen attack. The intercellular and systemic trafficking of small interfering RNA (siRNA)/microRNA (miRNA) is a central component in this regulatory pathway. Currently, little is known with regards to the molecular agents involved in the movement of these si/miRNAs. To address this situation, we employed a biochemical approach to identify and characterize a conserved SMALL RNA-BINDING PROTEIN 1 (SRBP1) family that mediates non-cell-autonomous small RNA (sRNA) trafficking. In Arabidopsis, AtSRBP1 is a glycine-rich (GR) RNA-binding protein, also known as AtGRP7, which we show binds single-stranded siRNA. A viral vector, Zucchini yellow mosaic virus (ZYMV), was employed to functionally characterized the AtSRBP1-4 (AtGRP7/2/4/8) RNA recognition motif and GR domains. Cellular-based studies revealed the GR domain as being necessary and sufficient for SRBP1 cell-to-cell movement. Taken together, our findings provide a foundation for future research into the mechanism and function of mobile sRNA signaling agents in plants.
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Affiliation(s)
- Yan Yan
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
| | - Byung-Kook Ham
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
| | - Yee Hang Chong
- Department of Plant Pathology, National Chung-Hsing University, Taichung
| | - Shyi-Dong Yeh
- Department of Plant Pathology, National Chung-Hsing University, Taichung
| | - William J Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
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5
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Zhang Z, Zheng Y, Ham BK, Zhang S, Fei Z, Lucas WJ. Plant lncRNAs are enriched in and move systemically through the phloem in response to phosphate deficiency. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2019; 61:492-508. [PMID: 30171742 DOI: 10.1111/jipb.12715] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 08/29/2018] [Indexed: 05/08/2023]
Abstract
In response to phosphate (Pi) deficiency, it has been shown that micro-RNAs (miRNAs) and mRNAs are transported through the phloem for delivery to sink tissues. Growing evidence also indicates that long non-coding RNAs (lncRNAs) are critical regulators of Pi homeostasis in plants. However, whether lncRNAs are present in and move through the phloem, in response to Pi deficiency, remains to be established. Here, using cucumber as a model plant, we show that lncRNAs are enriched in the phloem translocation stream and respond, systemically, to an imposed Pi-stress. A well-known lncRNA, IPS1, the target mimic (TM) of miRNA399, accumulates to a high level in the phloem, but is not responsive to early Pi deficiency. An additional 24 miRNA TMs were also detected in the phloem translocation stream; among them miRNA171 TMs and miR166 TMs were induced in response to an imposed Pi stress. Grafting studies identified 22 lncRNAs which move systemically into developing leaves and root tips. A CU-rich PTB motif was further identified in these mobile lncRNAs. Our findings revealed that lncRNAs respond to Pi deficiency, non-cell-autonomously, and may act as systemic signaling agents to coordinate early Pi deficiency signaling, at the whole-plant level.
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Affiliation(s)
- Zhaoliang Zhang
- State Key Laboratory of Tea Biology and Utilization, Anhui Agricultural University, Hefei 230036, China
| | - Yi Zheng
- Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York, USA
| | - Byung-Kook Ham
- Global Institute for Food Security, Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Shupei Zhang
- State Key Laboratory of Tea Biology and Utilization, Anhui Agricultural University, Hefei 230036, China
| | - Zhangjun Fei
- Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York, USA
| | - William J Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California, USA
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De Marco F, Le Hir R, Dinant S. The rendez-vous of mobile sieve-element and abundant companion-cell proteins. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:108-112. [PMID: 29704830 DOI: 10.1016/j.pbi.2018.04.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 03/19/2018] [Accepted: 04/09/2018] [Indexed: 06/08/2023]
Abstract
Thousands of sieve tube exudate proteins (STEP) have now been identified and predicted to fulfill a diversity of functions. However, most STEPs should be considered putative, since methods to collect sieve tube exudates have many technical drawbacks, and advanced functional characterization will be required to distinguish contaminant from bonafide proteins, and determine the latter's location and activity in sieve elements (SE). One major challenge is to develop new approaches to elucidate the function of these SE proteins, which in turn, is expected to shed light on intriguing aspects of SE cell biology.
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Affiliation(s)
- Federica De Marco
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000 Versailles, France
| | - Rozenn Le Hir
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000 Versailles, France
| | - Sylvie Dinant
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000 Versailles, France.
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7
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Xia C, Zheng Y, Huang J, Zhou X, Li R, Zha M, Wang S, Huang Z, Lan H, Turgeon R, Fei Z, Zhang C. Elucidation of the Mechanisms of Long-Distance mRNA Movement in a Nicotiana benthamiana/Tomato Heterograft System. PLANT PHYSIOLOGY 2018; 177:745-758. [PMID: 29720554 PMCID: PMC6001325 DOI: 10.1104/pp.17.01836] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/23/2018] [Indexed: 05/19/2023]
Abstract
Recent heterograft analyses showed that large-scale messenger RNA (mRNA) movement takes place in the phloem, but the number of mobile transcripts reported varies widely. However, our knowledge of the mechanisms underlying large-scale mRNA movement remains limited. In this study, using a Nicotiana benthamiana/tomato (Solanum lycopersicum) heterograft system and a transgenic approach involving potato (Solanum tuberosum), we found that: (1) the overall mRNA abundance in the leaf is not a good indicator of transcript mobility to the root; (2) increasing the expression levels of nonmobile mRNAs in the companion cells does not promote their mobility; (3) mobile mRNAs undergo degradation during their movement; and (4) some mRNAs arriving in roots move back to shoots. These results indicate that mRNA movement has both regulated and unregulated components. The cellular origins of mobile mRNAs may differ between herbaceous and woody species. Taken together, these findings suggest that the long-distance movement of mRNAs is a complex process and that elucidating the physiological roles associated with this movement is challenging but remains an important task for future research.
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Affiliation(s)
- Chao Xia
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
- Maize Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
- Key Laboratory of Biology and Genetic Improvement of Maize in Southwest Region, Ministry of Agriculture, Chengdu, Sichuan 611130, China
| | - Yi Zheng
- Boyce Thompson Institute, Cornell University, Ithaca, New York 14853
| | - Jing Huang
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | - Xiangjun Zhou
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | - Rui Li
- College of Agronomy, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - Manrong Zha
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | - Shujuan Wang
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | | | - Hai Lan
- Maize Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
- Key Laboratory of Biology and Genetic Improvement of Maize in Southwest Region, Ministry of Agriculture, Chengdu, Sichuan 611130, China
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853
| | - Zhangjun Fei
- Boyce Thompson Institute, Cornell University, Ithaca, New York 14853
- United States Department of Agriculture-Agricultural Research Service Robert W. Holley Center for Agriculture and Health, Ithaca, New York 14853
| | - Cankui Zhang
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
- Purdue Center for Plant Biology, Purdue University, West Lafayette, Indiana 47907
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8
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Kehr J, Kragler F. Long distance RNA movement. THE NEW PHYTOLOGIST 2018; 218:29-40. [PMID: 29418002 DOI: 10.1111/nph.15025] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 12/28/2017] [Indexed: 05/06/2023]
Abstract
Contents Summary 29 I. Introduction 29 II. Phloem as a conduit for macromolecules 30 III. Classes of phloem transported RNAs and their function 32 IV. Mode of RNA transport 35 V. Conclusions 37 Acknowledgements 37 References 37 SUMMARY: In higher plants, small noncoding RNAs and large messenger RNA (mRNA) molecules are transported between cells and over long distances via the phloem. These large macromolecules are thought to get access to the sugar-conducting phloem vessels via specialized plasmodesmata (PD). Analyses of the phloem exudate suggest that all classes of RNA molecules, including silencing-induced RNAs (siRNAs), micro RNAs (miRNAs), transfer RNAs (tRNAs), ribosomal RNA (rRNAs) and mRNAs, are transported via the vasculature to distant tissues. Although the functions of mobile siRNAs and miRNAs as signalling molecules are well established, we lack a profound understanding of mobile mRNA function(s) in recipient cells and tissues, and how they are selected for transport. A surprisingly high number of up to thousands of mRNAs were described in diverse plant species such as cucumber, pumpkin, Arabidopsis and grapevine to move long distances over graft junctions to distinct body parts. In this review, we present an overview of the classes of mobile RNAs, the potential mechanisms facilitating RNA long-distance transport, and the roles of mobile RNAs in regulating transcription and translation. Furthermore, we address potential function(s) of mobile protein-encoding mRNAs with respect to their characteristics and evolutionary constraints.
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Affiliation(s)
- Julia Kehr
- Biocenter Klein Flottbek, Molekulare Pflanzengenetik, University Hamburg, Ohnhorststr. 18, Hamburg 22609, Germany
| | - Friedrich Kragler
- Department II, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, Potsdam-Golm 14476, Germany
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9
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Ostendorp A, Pahlow S, Krüßel L, Hanhart P, Garbe MY, Deke J, Giavalisco P, Kehr J. Functional analysis of Brassica napus phloem protein and ribonucleoprotein complexes. THE NEW PHYTOLOGIST 2017; 214:1188-1197. [PMID: 28052459 PMCID: PMC6079638 DOI: 10.1111/nph.14405] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/26/2016] [Indexed: 05/18/2023]
Abstract
Phloem sap contains a large number of macromolecules, including proteins and RNAs from different classes. Proteome analyses of phloem samples from different plant species under denaturing conditions identified hundreds of proteins potentially involved in diverse processes. Surprisingly, these studies also found a significant number of ribosomal and proteasomal proteins. This led to the suggestion that active ribosome and proteasome complexes might be present in the phloem, challenging the paradigm that protein synthesis and turnover are absent from the enucleate sieve elements of angiosperms. However, the existence of such complexes has as yet not been demonstrated. In this study we used three-dimensional gel electrophoresis to separate several protein complexes from native phloem sap from Brassica napus. Matrix-assisted laser desorption ionization-time of flight MS analyses identified more than 100 proteins in the three major protein-containing complexes. All three complexes contained proteins belonging to different ribosomal fragments and blue native northern blot confirmed the existence of ribonucleoprotein complexes. In addition, one complex contained proteasome components and further functional analyses confirmed activity of a proteasomal degradation pathway and showed a large number of ubiquitinated phloem proteins. Our results suggest specialized roles for ubiquitin modification and proteasome-mediated degradation in the phloem.
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Affiliation(s)
- Anna Ostendorp
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Steffen Pahlow
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Lena Krüßel
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Patrizia Hanhart
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Marcel Y. Garbe
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Jennifer Deke
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
| | - Patrick Giavalisco
- Max Planck Institute of Molecular Plant Physiologyam Mühlenberg 1Potsdam14476Germany
| | - Julia Kehr
- Molecular Plant GeneticsUniversity HamburgBiocenter Klein Flottbek, Ohnhorststr. 18Hamburg22609Germany
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Abstract
The plant vascular system plays a central role in coordinating physiological and developmental events through delivery of both essential nutrients and long-distance signaling agents. The enucleate phloem sieve tube system of the angiosperms contains a broad spectrum of RNA species. Grafting and transcriptomics studies have indicated that several thousand mRNAs move long distances from source organs to meristematic sink tissues. Ribonucleoprotein complexes play a pivotal role as stable RNA-delivery systems for systemic translocation of cargo RNA. In this review, we assess recent progress in the characterization of phloem and plasmodesmal transport as an integrated local and systemic communication network. We discuss the roles of phloem-mobile small RNAs in epigenetic events, including meristem development and genome stability, and the delivery of mRNAs to specific tissues in response to environmental inputs. A large body of evidence now supports a model in which phloem-mobile RNAs act as critical components of gene regulatory networks involved in plant growth, defense, and crop yield at the whole-plant level.
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Affiliation(s)
- Byung-Kook Ham
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616; ,
| | - William J Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616; ,
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Wang L, Huang GQ, Sun Y, Li Y, Yao WJ, Jiang TB. Cloning and expression analysis of eIF-5A gene in Apocynum venetum. BIOTECHNOL BIOTEC EQ 2016. [DOI: 10.1080/13102818.2016.1172944] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Lei Wang
- Department of Biotechnology, Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin, PR China
- Department of Plant Science, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, PR China
| | - Guo-Qing Huang
- Department of Biotechnology, Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin, PR China
| | - Yao Sun
- Department of Biotechnology, Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin, PR China
| | - Yao Li
- Department of Biotechnology, Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin, PR China
| | - Wen-Jing Yao
- State Key Laboratory of Tree Genetics and Breeding, College of Forestry, Northeast Forestry University, Harbin, PR China
| | - Ting-Bo Jiang
- State Key Laboratory of Tree Genetics and Breeding, College of Forestry, Northeast Forestry University, Harbin, PR China
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12
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Xu XY, Ding ZJ, Chen L, Yan JY, Li GX, Zheng SJ. An eukaryotic translation initiation factor, AteIF5A-2, affects cadmium accumulation and sensitivity in Arabidopsis. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:848-58. [PMID: 25559189 DOI: 10.1111/jipb.12329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 12/31/2014] [Indexed: 05/22/2023]
Abstract
Cadmium (Cd) is one of the most toxic elements and can be accumulated in plants easily; meanwhile, eIF5A is a highly conserved protein in all eukaryotic organisms. The present work tried to investigate whether eIF5A is involved in Cd accumulation and sensitivity in Arabidopsis (Arabidopsis thaliana L.) by comparing the wild-type Columbia-0 (Col-0) with a knockdown mutant of AteIF5A-2, fbr12-3 under Cd stress conditions. The results showed that the mutant fbr12-3 accumulated more Cd in roots and shoots and had significantly lower chlorophyll content, shorter root length, and smaller biomass, suggesting that downregulation of AteIF5A-2 makes the mutant more Cd sensitive. Real-time polymerase chain reaction revealed that the expressions of metal transporters involved in Cd uptake and translocation including IRT1, ZIP1, AtNramp3, and AtHMA4 were significantly increased but the expressions of PCS1 and PCS2 related to Cd detoxification were decreased notably in fbr12-3 compared with Col-0. As a result, an increase in MDA and H2 O2 content but decrease in root trolox, glutathione and proline content under Cd stress was observed, indicating that a severer oxidative stress occurs in the mutant. All these results demonstrated for the first time that AteIF5A influences Cd sensitivity by affecting Cd uptake, accumulation, and detoxification in Arabidopsis.
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Affiliation(s)
- Xiao-Yan Xu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Zhong-Jie Ding
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Lei Chen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Jin-Ying Yan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Gui-Xin Li
- College of Agronomy and Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Shao-Jian Zheng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
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Browning KS, Bailey-Serres J. Mechanism of cytoplasmic mRNA translation. THE ARABIDOPSIS BOOK 2015; 13:e0176. [PMID: 26019692 PMCID: PMC4441251 DOI: 10.1199/tab.0176] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Protein synthesis is a fundamental process in gene expression that depends upon the abundance and accessibility of the mRNA transcript as well as the activity of many protein and RNA-protein complexes. Here we focus on the intricate mechanics of mRNA translation in the cytoplasm of higher plants. This chapter includes an inventory of the plant translational apparatus and a detailed review of the translational processes of initiation, elongation, and termination. The majority of mechanistic studies of cytoplasmic translation have been carried out in yeast and mammalian systems. The factors and mechanisms of translation are for the most part conserved across eukaryotes; however, some distinctions are known to exist in plants. A comprehensive understanding of the complex translational apparatus and its regulation in plants is warranted, as the modulation of protein production is critical to development, environmental plasticity and biomass yield in diverse ecosystems and agricultural settings.
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Affiliation(s)
- Karen S. Browning
- Department of Molecular Biosciences and Institute for Cell and Molecular Biology, University of Texas at Austin, Austin TX 78712-0165
- Both authors contributed equally to this work
| | - Julia Bailey-Serres
- Department of Botany and Plant Sciences and Center for Plant Cell Biology, University of California, Riverside, CA, 92521 USA
- Both authors contributed equally to this work
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14
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Notaguchi M, Higashiyama T, Suzuki T. Identification of mRNAs that move over long distances using an RNA-Seq analysis of Arabidopsis/Nicotiana benthamiana heterografts. PLANT & CELL PHYSIOLOGY 2015; 56:311-21. [PMID: 25527829 DOI: 10.1093/pcp/pcu210] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Phloem is a conductive tissue that allocates nutrients from mature source leaves to sinks such as young developing tissues. Phloem also delivers proteins and RNA species, such as small RNAs and mRNAs. Intensive studies on plant systemic signaling revealed the essential roles of proteins and RNA species. However, many of their functions are still largely unknown, with the roles of transported mRNAs being particularly poorly understood. A major difficulty is the absence of an accurate and comprehensive list of mobile transcripts. In this study, we used a hetero-graft system with Nicotiana benthamiana as the recipient scion and Arabidopsis as the donor stock, to identify transcripts that moved long distances across the graft union. We identified 138 Arabidopsis transcripts as mobile mRNAs, which we collectively termed the mRNA mobilome. Reverse transcription-PCR, quantitative real-time PCR and droplet digital PCR analyses confirmed the mobility. The transcripts included potential signaling factors and, unexpectedly, more general factors. In our investigations, we found no preferred transcript length, no previously known sequence motifs in promoter or transcript sequences and no similarities between the level of the transcripts and that in the source leaves. Grafting experiments regarding the function of ERECTA, an identified transcript, showed that no function of the transcript mobilized. To our knowledge, this is the first report identifying transcripts that move over long distances using a hetero-graft system between different plant taxa.
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Affiliation(s)
- Michitaka Notaguchi
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan ERATO Higashiyama Live-holonics Project, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
| | - Tetsuya Higashiyama
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan ERATO Higashiyama Live-holonics Project, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan Institute of Transformative Bio-Molecules, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
| | - Takamasa Suzuki
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan ERATO Higashiyama Live-holonics Project, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan Present address: College of Bioscience and Biotechnology, Matsumoto-cho, Kasugai, 478-8501 Japan
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15
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Notaguchi M. Identification of phloem-mobile mRNA. JOURNAL OF PLANT RESEARCH 2015; 128:27-35. [PMID: 25516498 DOI: 10.1007/s10265-014-0675-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 10/06/2014] [Indexed: 05/07/2023]
Abstract
Signaling between cells, tissues and organs is essential for multicellular organisms to coordinate and adapt their development and growth to internal and environmental changes. Plants have evolved a plant-specific symplasmic pathway, called plasmodesmata, for efficient intercellular communication, in addition to the receptor-ligand-based apoplasmic pathway. Long-distance signaling between distant organs is enabled via the phloem tube system, where plasmodesmata contribute to phloem loading and unloading for photosynthate allocation. In addition to signaling by small molecules such as metabolites and phytohormones, the transport of proteins, small RNAs and mRNAs is also considered an important mechanism to achieve long-distance signaling in plants. Recent studies on phloem-mobile proteins and small RNAs have revealed their role in crucial physiological processes including flowering, systemic silencing and nutrient allocation. However, the biological role of mRNAs found in the phloem tube is not yet clear, though their mobility over long-distances has been well evidenced. To gain this knowledge, it is important to collect further information on mRNA profiles in the phloem translocation stream. In this review, I summarize the current approaches to identifying the mRNA population in the phloem translocation system, and discuss the possible role of short- and long-distance mRNA transport.
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Affiliation(s)
- Michitaka Notaguchi
- Graduate School of Science, Nagoya University, B-105, Bldg B, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan,
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16
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Ham BK, Li G, Jia W, Leary JA, Lucas WJ. Systemic delivery of siRNA in pumpkin by a plant PHLOEM SMALL RNA-BINDING PROTEIN 1-ribonucleoprotein complex. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 80:683-94. [PMID: 25227635 DOI: 10.1111/tpj.12662] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 08/21/2014] [Accepted: 08/29/2014] [Indexed: 05/20/2023]
Abstract
In plants, the vascular system, specifically the phloem, functions in delivery of small RNA (sRNA) to exert epigenetic control over developmental and defense-related processes. Although the importance of systemic sRNA delivery has been established, information is currently lacking concerning the nature of the protein machinery involved in this process. Here, we show that a PHLOEM SMALL-RNA BINDING PROTEIN 1 (PSRP1) serves as the basis for formation of an sRNA ribonucleoprotein complex (sRNPC) that delivers sRNA (primarily 24 nt) to sink organs. Assembly of this complex is facilitated through PSRP1 phosphorylation by a phloem-localized protein kinase, PSRPK1. During long-distance transport, PSRP1-sRNPC is stable against phloem phosphatase activity. Within target tissues, phosphatase activity results in disassembly of PSRP1-sRNPC, a process that is probably required for unloading cargo sRNA into surrounding cells. These findings provide an insight into the mechanism involved in delivery of sRNA associated with systemic gene silencing in plants.
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Affiliation(s)
- Byung-Kook Ham
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA
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17
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Mulekar JJ, Huq E. Expanding roles of protein kinase CK2 in regulating plant growth and development. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:2883-93. [PMID: 24307718 DOI: 10.1093/jxb/ert401] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Protein kinase CK2 (formerly known as casein kinase II) is a ubiquitious Ser/Thr kinase present in all eukaryotes. The α (catalytic) and β (regulatory) subunits of CK2 exist both as a tetrameric holoenzyme and as monomers in eukaryotic cells. CK2 has been implicated in multiple developmental and stress-responsive pathways including light signalling and circadian clock in plants. Recent studies using CK2 knockout and dominant negative mutants in Arabidopsis have uncovered new roles for this enzyme. CK2 substrates that have been identified so far are primarily transcription factors or regulatory proteins. CK2-mediated phosphorylation of these factors often results in alteration of the protein function including changes in the DNA-binding affinity, dimerization, stability, protein-protein interactions, and subcellular localization. CK2 has evolved as an essential housekeeping kinase in plants that modifies protein function in a dynamic way. This review summarizes the current knowledge of the role of CK2 in plant development.
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Affiliation(s)
- Jidnyasa Jayant Mulekar
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Enamul Huq
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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18
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Ham BK, Lucas WJ. The angiosperm phloem sieve tube system: a role in mediating traits important to modern agriculture. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1799-1816. [PMID: 24368503 DOI: 10.1093/jxb/ert417] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The plant vascular system serves a vital function by distributing water, nutrients and hormones essential for growth and development to the various organs of the plant. In this review, attention is focused on the role played by the phloem as the conduit for delivery of both photosynthate and information macromolecules, especially from the context of its mediation in traits that are important to modern agriculture. Resource allocation of sugars and amino acids, by the phloem, to specific sink tissues is of importance to crop yield and global food security. Current findings are discussed in the context of a hierarchical control network that operates to integrate resource allocation to competing sinks. The role of plasmodesmata that connect companion cells to neighbouring sieve elements and phloem parenchyma cells is evaluated in terms of their function as valves, connecting the sieve tube pressure manifold system to the various plant tissues. Recent studies have also revealed that plasmodesmata and the phloem sieve tube system function cooperatively to mediate the long-distance delivery of proteins and a diverse array of RNA species. Delivery of these information macromolecules is discussed in terms of their roles in control over the vegetative-to-floral transition, tuberization in potato, stress-related signalling involving miRNAs, and genetic reprogramming through the delivery of 24-nucleotide small RNAs that function in transcriptional gene silencing in recipient sink organs. Finally, we discuss important future research areas that could contribute to developing agricultural crops with engineered performance characteristics for enhance yield potential.
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Affiliation(s)
- Byung-Kook Ham
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
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19
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Rossi D, Kuroshu R, Zanelli CF, Valentini SR. eIF5A and EF-P: two unique translation factors are now traveling the same road. WILEY INTERDISCIPLINARY REVIEWS. RNA 2014; 5:209-22. [PMID: 24402910 DOI: 10.1002/wrna.1211] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 11/01/2013] [Accepted: 11/06/2013] [Indexed: 11/09/2022]
Abstract
Translational control is extremely important in all organisms, and some of its aspects are highly conserved among all primary kingdoms, such as those related to the translation elongation step. The previously classified translation initiation factor 5A (eIF5A) and its bacterial homologue elongation factor P (EF-P) were discovered in the late 70's and have recently been the object of many studies. eIF5A and EF-P are the only cellular proteins that undergo hypusination and lysinylation, respectively, both of which are unique posttranslational modifications. Herein, we review all the important discoveries related to the biochemical and functional characterization of these factors, highlighting the implication of eIF5A in translation elongation instead of initiation. The findings that eIF5A and EF-P are important for specific cellular processes and play a role in the relief of ribosome stalling caused by specific amino acid sequences, such as those containing prolines reinforce the hypothesis that these factors are involved in specialized translation. Although there are some divergences between these unique factors, recent studies have clarified that they act similarly during protein synthesis. Further studies may reveal their precise mechanism of ribosome activity modulation as well as the mRNA targets that require eIF5A and EF-P for their proper translation.
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Affiliation(s)
- Danuza Rossi
- Department of Biological Sciences, School of Pharmaceutical Sciences, Univ Estadual Paulista (UNESP), Araraquara, SP, Brazil
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20
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Ren B, Chen Q, Hong S, Zhao W, Feng J, Feng H, Zuo J. The Arabidopsis eukaryotic translation initiation factor eIF5A-2 regulates root protoxylem development by modulating cytokinin signaling. THE PLANT CELL 2013; 25:3841-57. [PMID: 24163315 PMCID: PMC3877783 DOI: 10.1105/tpc.113.116236] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/04/2013] [Accepted: 10/06/2013] [Indexed: 05/07/2023]
Abstract
The phytohormone cytokinin regulates various aspects of plant growth and development, including root vascular development. In Arabidopsis thaliana, mutations in the cytokinin signaling components cause misspecification of protoxylem cell files. Auxin antagonizes cytokinin-regulated root protoxylem differentiation by inducing expression of Arabidopsis phosphotransfer protein6 (AHP6), a negative regulator of cytokinin signaling. However, the molecular mechanism of cytokinin-regulated protoxylem differentiation is not fully understood. Here, we show that a mutation in Arabidopsis fumonisin B1-resistant12 (FBR12), which encodes a eukaryotic translation initiation factor 5A, causes defective protoxylem development and reduced sensitivity to cytokinin. FBR12 genetically interacts with the cytokinin receptor cytokinin response1 (CRE1) and downstream AHP genes, as double mutants show enhanced phenotypes. FBR12 forms a protein complex with CRE1 and AHP1, and cytokinin regulates formation of this protein complex. Intriguingly, ahp6 partially suppresses the fbr12 mutant phenotype, and the fbr12 mutation causes increased expression of AHP6, indicating that FBR12 negatively regulates AHP6. Consistent with this, ectopic expression of FBR12 in the CRE1-expressing domain partially rescues defective protoxylem development in fbr12, and overexpression of AHP6 causes an fbr12-like phenotype. These results define a regulatory role of the highly conserved FBR12 in cytokinin-mediated root protoxylem specification.
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Affiliation(s)
- Bo Ren
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qingguo Chen
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Sulei Hong
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenming Zhao
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jian Feng
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haizhong Feng
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Jianru Zuo
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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21
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Yoo SC, Chen C, Rojas M, Daimon Y, Ham BK, Araki T, Lucas WJ. Phloem long-distance delivery of FLOWERING LOCUS T (FT) to the apex. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:456-68. [PMID: 23607279 DOI: 10.1111/tpj.12213] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 04/05/2013] [Accepted: 04/16/2013] [Indexed: 05/05/2023]
Abstract
Cucurbita moschata FLOWERING LOCUS T-LIKE 2 (hereafter FTL2) and Arabidopsis thaliana (Arabidopsis) FLOWERING LOCUS T (FT), components of the plant florigenic signaling system, move long-distance through the phloem from source leaves to the vegetative apex where they mediate floral induction. The mechanisms involved in long-distance trafficking of FT/FTL2 remain to be elucidated. In this study, we identified the critical motifs on both FT and FTL2 required for cell-to-cell trafficking through mutant analyses using a zucchini yellow mosaic virus expression vector. Western blot analysis, performed on phloem sap collected from just beneath the vegetative apex of C. moschata plants, established that all mutant proteins tested retained the ability to enter the phloem translocation stream. However, immunolocalization studies revealed that a number of these FTL2/FT mutants were defective in the post-phloem zone, suggesting that a regulation mechanism for FT trafficking exists in the post-phloem unloading step. The selective movements of FT/FTL2 were further observed by microinjection and trichome rescue studies, which revealed that FT/FTL2 has the ability to dilate plasmodesmata microchannels during the process of cell-to-cell trafficking, and various mutants were compromised in their capacity to traffic through plasmodesmata. Based on these findings, a model is presented to account for the mechanism by which FT/FTL2 enters the phloem translocation stream and subsequently exits the phloem and enters the apical tissue, where it initiates the vegetative to floral transition.
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Affiliation(s)
- Soo-Cheul Yoo
- Department of Plant Biology, University of California, Davis, CA 95616, USA
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22
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Gepstein S, Glick BR. Strategies to ameliorate abiotic stress-induced plant senescence. PLANT MOLECULAR BIOLOGY 2013; 82:623-33. [PMID: 23595200 DOI: 10.1007/s11103-013-0038-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 02/26/2013] [Indexed: 05/05/2023]
Abstract
The plant senescence syndrome resembles, in many molecular and phenotypic aspects, plant responses to abiotic stresses. Both processes have an enormous negative global agro-economic impact and endanger food security worldwide. Premature plant senescence is the main cause of losses in grain filling and biomass yield due to leaf yellowing and deteriorated photosynthesis, and is also responsible for the losses resulting from the short shelf life of many vegetables and fruits. Under abiotic stress conditions the yield losses are often even greater. The primary challenge in agricultural sciences today is to develop technologies that will increase food production and sustainability of agriculture especially under environmentally limiting conditions. In this chapter, some of the mechanisms involved in abiotic stress-induced plant senescence are discussed. Recent studies have shown that crop yield and nutritional values can be altered as well as plant stress tolerance through manipulating the timing of senescence. It is often difficult to separate the effects of age-dependent senescence from stress-induced senescence since both share many biochemical processes and ultimately result in plant death. The focus of this review is on abiotic stress-induced senescence. Here, a number of the major approaches that have been developed to ameliorate some of the effects of abiotic stress-induced plant senescence are considered and discussed. Some approaches mimic the mechanisms already used by some plants and soil bacteria whereas others are based on development of new improved transgenic plants. While there may not be one simple strategy that can effectively decrease all losses of crop yield that accrue as a consequence of abiotic stress-induced plant senescence, some of the strategies that are discussed already show great promise.
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Affiliation(s)
- Shimon Gepstein
- Faculty of Biology, The Technion, Israel Institute of Technology, Haifa, Israel.
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23
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Lucas WJ, Groover A, Lichtenberger R, Furuta K, Yadav SR, Helariutta Y, He XQ, Fukuda H, Kang J, Brady SM, Patrick JW, Sperry J, Yoshida A, López-Millán AF, Grusak MA, Kachroo P. The plant vascular system: evolution, development and functions. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2013; 55:294-388. [PMID: 23462277 DOI: 10.1111/jipb.12041] [Citation(s) in RCA: 381] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The emergence of the tracheophyte-based vascular system of land plants had major impacts on the evolution of terrestrial biology, in general, through its role in facilitating the development of plants with increased stature, photosynthetic output, and ability to colonize a greatly expanded range of environmental habitats. Recently, considerable progress has been made in terms of our understanding of the developmental and physiological programs involved in the formation and function of the plant vascular system. In this review, we first examine the evolutionary events that gave rise to the tracheophytes, followed by analysis of the genetic and hormonal networks that cooperate to orchestrate vascular development in the gymnosperms and angiosperms. The two essential functions performed by the vascular system, namely the delivery of resources (water, essential mineral nutrients, sugars and amino acids) to the various plant organs and provision of mechanical support are next discussed. Here, we focus on critical questions relating to structural and physiological properties controlling the delivery of material through the xylem and phloem. Recent discoveries into the role of the vascular system as an effective long-distance communication system are next assessed in terms of the coordination of developmental, physiological and defense-related processes, at the whole-plant level. A concerted effort has been made to integrate all these new findings into a comprehensive picture of the state-of-the-art in the area of plant vascular biology. Finally, areas important for future research are highlighted in terms of their likely contribution both to basic knowledge and applications to primary industry.
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Affiliation(s)
- William J Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
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24
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Notaguchi M, Wolf S, Lucas WJ. Phloem-mobile Aux/IAA transcripts target to the root tip and modify root architecture. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2012; 54:760-72. [PMID: 22925478 DOI: 10.1111/j.1744-7909.2012.01155.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In plants, the phloem is the component of the vascular system that delivers nutrients and transmits signals from mature leaves to developing sink tissues. Recent studies have identified proteins, mRNA, and small RNA within the phloem sap of several plant species. It is now of considerable interest to elucidate the biological functions of these potential long-distance signal agents, to further our understanding of how plants coordinate their developmental programs at the whole-plant level. In this study, we developed a strategy for the functional analysis of phloem-mobile mRNA by focusing on IAA transcripts, whose mobility has previously been reported in melon (Cucumis melo cv. Hale's Best Jumbo). Indoleacetic acid (IAA) proteins are key transcriptional regulators of auxin signaling, and are involved in a broad range of developmental processes including root development. We used a combination of vasculature-enriched sampling and hetero-grafting techniques to identify IAA18 and IAA28 as phloem-mobile transcripts in the model plant Arabidopsis thaliana. Micro-grafting experiments were used to confirm that these IAA transcripts, which are generated in vascular tissues of mature leaves, are then transported into the root system where they negatively regulate lateral root formation. Based on these findings, we present a model in which auxin distribution, in combination with phloem-mobile Aux/IAA transcripts, can determine the sites of auxin action.
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Affiliation(s)
- Michitaka Notaguchi
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
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25
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Ham BK, Li G, Kang BH, Zeng F, Lucas WJ. Overexpression of Arabidopsis plasmodesmata germin-like proteins disrupts root growth and development. THE PLANT CELL 2012; 24:3630-48. [PMID: 22960910 PMCID: PMC3480292 DOI: 10.1105/tpc.112.101063] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 08/13/2012] [Accepted: 08/18/2012] [Indexed: 05/18/2023]
Abstract
In plants, a population of non-cell-autonomous proteins (NCAPs), including numerous transcription factors, move cell to cell through plasmodesmata (PD). In many cases, the intercellular trafficking of these NCAPs is regulated by their interaction with specific PD components. To gain further insight into the functions of this NCAP pathway, coimmunoprecipitation experiments were performed on a tobacco (Nicotiana tabacum) plasmodesmal-enriched cell wall protein preparation using as bait the NCAP, pumpkin (Cucurbita maxima) PHLOEM PROTEIN16 (Cm-PP16). A Cm-PP16 interaction partner, Nt-PLASMODESMAL GERMIN-LIKE PROTEIN1 (Nt-PDGLP1) was identified and shown to be a PD-located component. Arabidopsis thaliana putative orthologs, PDGLP1 and PDGLP2, were identified; expression studies indicated that, postgermination, these proteins were preferentially expressed in the root system. The PDGLP1 signal peptide was shown to function in localization to the PD by a novel mechanism involving the endoplasmic reticulum-Golgi secretory pathway. Overexpression of various tagged versions altered root meristem function, leading to reduced primary root but enhanced lateral root growth. This effect on root growth was corrected with an inability of these chimeric proteins to form stable PD-localized complexes. PDGLP1 and PDGLP2 appear to be involved in regulating primary root growth by controlling phloem-mediated allocation of resources between the primary and lateral root meristems.
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Affiliation(s)
- Byung-Kook Ham
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - Gang Li
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - Byung-Ho Kang
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611
| | - Fanchang Zeng
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
| | - William J. Lucas
- Department of Plant Biology, College of Biological Sciences, University of California, Davis, California 95616
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26
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Wang L, Xu C, Wang C, Wang Y. Characterization of a eukaryotic translation initiation factor 5A homolog from Tamarix androssowii involved in plant abiotic stress tolerance. BMC PLANT BIOLOGY 2012; 12:118. [PMID: 22834699 PMCID: PMC3479025 DOI: 10.1186/1471-2229-12-118] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/09/2012] [Indexed: 05/18/2023]
Abstract
BACKGROUND The eukaryotic translation initiation factor 5A (eIF5A) promotes formation of the first peptide bond at the onset of protein synthesis. However, the function of eIF5A in plants is not well understood. RESULTS In this study, we characterized the function of eIF5A (TaeIF5A1) from Tamarix androssowii. The promoter of TaeIF5A1 with 1,486 bp in length was isolated, and the cis-elements in the promoter were identified. A WRKY (TaWRKY) and RAV (TaRAV) protein can specifically bind to a W-box motif in the promoter of TaeIF5A1 and activate the expression of TaeIF5A1. Furthermore, TaeIF5A1, TaWRKY and TaRAV share very similar expression pattern and are all stress-responsive gene that functions in the abscisic acid (ABA) signaling pathway, indicating that they are components of a single regulatory pathway. Transgenic yeast and poplar expressing TaeIF5A1 showed elevated protein levels combined with improved abiotic stresses tolerance. Furthermore, TaeIF5A1-transformed plants exhibited enhanced superoxide dismutase (SOD) and peroxidase (POD) activities, lower electrolyte leakage and higher chlorophyll content under salt stress. CONCLUSIONS These results suggested that TaeIF5A1 is involved in abiotic stress tolerance, and is likely regulated by transcription factors TaWRKY and TaRAV both of which can bind to the W-box motif. In addition, TaeIF5A1 may mediate stress tolerance by increasing protein synthesis, enhancing ROS scavenging by improving SOD and POD activities, and preventing chlorophyll loss and membrane damage. Therefore, eIF5A may play an important role in plant adaptation to changing environmental conditions.
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MESH Headings
- Abscisic Acid/metabolism
- Abscisic Acid/pharmacology
- Adaptation, Physiological
- Cell Membrane/genetics
- Cell Membrane/metabolism
- Chlorophyll/genetics
- Chlorophyll/metabolism
- Cloning, Molecular
- Gene Expression Regulation, Plant
- Genetic Vectors
- Peptide Initiation Factors/genetics
- Peptide Initiation Factors/metabolism
- Peroxidase/genetics
- Peroxidase/metabolism
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/metabolism
- Plants, Genetically Modified/physiology
- Promoter Regions, Genetic
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Regulatory Sequences, Nucleic Acid
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Salt-Tolerant Plants/genetics
- Salt-Tolerant Plants/metabolism
- Salt-Tolerant Plants/physiology
- Signal Transduction
- Sodium Chloride/pharmacology
- Solubility
- Stress, Physiological
- Superoxide Dismutase/genetics
- Superoxide Dismutase/metabolism
- Tamaricaceae/genetics
- Tamaricaceae/metabolism
- Tamaricaceae/physiology
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transformation, Genetic
- Eukaryotic Translation Initiation Factor 5A
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Affiliation(s)
- Liuqiang Wang
- State Key Laboratory of Tree Genetics and Breeding (Northeast Forestry University), 26 Hexing Road, Harbin, China
| | - Chenxi Xu
- State Key Laboratory of Tree Genetics and Breeding (Northeast Forestry University), 26 Hexing Road, Harbin, China
| | - Chao Wang
- State Key Laboratory of Tree Genetics and Breeding (Northeast Forestry University), 26 Hexing Road, Harbin, China
| | - Yucheng Wang
- State Key Laboratory of Tree Genetics and Breeding (Northeast Forestry University), 26 Hexing Road, Harbin, China
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27
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Waduwara-Jayabahu I, Oppermann Y, Wirtz M, Hull ZT, Schoor S, Plotnikov AN, Hell R, Sauter M, Moffatt BA. Recycling of methylthioadenosine is essential for normal vascular development and reproduction in Arabidopsis. PLANT PHYSIOLOGY 2012; 158:1728-44. [PMID: 22345506 PMCID: PMC3320181 DOI: 10.1104/pp.111.191072] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
5'-Methylthioadenosine (MTA) is the common by-product of polyamine (PA), nicotianamine (NA), and ethylene biosynthesis in Arabidopsis (Arabidopsis thaliana). The methylthiol moiety of MTA is salvaged by 5'-methylthioadenosine nucleosidase (MTN) in a reaction producing methylthioribose (MTR) and adenine. The MTN double mutant, mtn1-1mtn2-1, retains approximately 14% of the MTN enzyme activity present in the wild type and displays a pleiotropic phenotype that includes altered vasculature and impaired fertility. These abnormal traits were associated with increased MTA levels, altered PA profiles, and reduced NA content. Exogenous feeding of PAs partially recovered fertility, whereas NA supplementation improved fertility and also reversed interveinal chlorosis. The analysis of PA synthase crystal structures containing bound MTA suggests that the corresponding enzyme activities are sensitive to available MTA. Mutant plants that expressed either MTN or human methylthioadenosine phosphorylase (which metabolizes MTA without producing MTR) appeared wild type, proving that the abnormal traits of the mutant are due to MTA accumulation rather than reduced MTR. Based on our results, we propose that the key targets affected by increased MTA content are thermospermine synthase activity and spermidine-dependent posttranslational modification of eukaryotic initiation factor 5A.
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Muench DG, Zhang C, Dahodwala M. Control of cytoplasmic translation in plants. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:178-94. [DOI: 10.1002/wrna.1104] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Cho SK, Kang IH, Carr T, Hannapel DJ. Using the Yeast Three-Hybrid System to Identify Proteins that Interact with a Phloem-Mobile mRNA. FRONTIERS IN PLANT SCIENCE 2012; 3:189. [PMID: 22969782 PMCID: PMC3427875 DOI: 10.3389/fpls.2012.00189] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 08/02/2012] [Indexed: 05/02/2023]
Abstract
Heterografting and RNA transport experiments have demonstrated the long-distance mobility of StBEL5 RNA, its role in controlling tuber formation, and the function of the 503-nt 3' untranslated region (UTR) of the RNA in mediating transport. Because the 3' UTR of StBEL5 is a key element in regulating several aspects of RNA metabolism, a potato leaf cDNA library was screened using the 3' UTR of StBEL5 as bait in the yeast three-hybrid (Y3H) system to identify putative partner RNA-binding proteins (RBPs). From this screen, 116 positive cDNA clones were isolated based on nutrient selection, HIS3 activation, and lacZ induction and were sequenced and classified. Thirty-five proteins that were predicted to function in either RNA- or DNA-binding were selected from this pool. Seven were monitored for their expression profiles and further evaluated for their capacity to bind to the 3' UTR of StBEL5 using β-galactosidase assays in the Y3H system and RNA gel-shift assays. Among the final selections were two RBPs, a zinc finger protein, and one protein, StLSH10, from a family involved in light signaling. In this study, the Y3H system is presented as a valuable tool to screen and verify interactions between target RNAs and putative RBPs. These results can shed light on the dynamics and composition of plant RNA-protein complexes that function to regulate RNA metabolism.
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Affiliation(s)
- Sung Ki Cho
- Plant Biology Major, Iowa State University Ames, IA, USA
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Li P, Ham BK, Lucas WJ. CmRBP50 protein phosphorylation is essential for assembly of a stable phloem-mobile high-affinity ribonucleoprotein complex. J Biol Chem 2011; 286:23142-9. [PMID: 21572046 PMCID: PMC3123081 DOI: 10.1074/jbc.m111.244129] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 04/29/2011] [Indexed: 01/30/2023] Open
Abstract
RNA-binding proteins (RBPs) form ribonucleoprotein (RNP) complexes that play crucial roles in RNA processing for gene regulation. The angiosperm sieve tube system contains a unique population of transcripts, some of which function as long-distance signaling agents involved in regulating organ development. These phloem-mobile mRNAs are translocated as RNP complexes. One such complex is based on a phloem RBP named Cucurbita maxima RNA-binding protein 50 (CmRBP50), a member of the polypyrimidine track binding protein family. The core of this RNP complex contains six additional phloem proteins. Here, requirements for assembly of this CmRBP50 RNP complex are reported. Phosphorylation sites on CmRBP50 were mapped, and then coimmunoprecipitation and protein overlay studies established that the phosphoserine residues, located at the C terminus of CmRBP50, are critical for RNP complex assembly. In vitro pull-down experiments revealed that three phloem proteins, C. maxima phloem protein 16, C. maxima GTP-binding protein, and C. maxima phosphoinositide-specific phospholipase-like protein, bind directly with CmRBP50. This interaction required CmRBP50 phosphorylation. Gel mobility-shift assays demonstrated that assembly of the CmRBP50-based protein complex results in a system having enhanced binding affinity for phloem-mobile mRNAs carrying polypyrimidine track binding motifs. This property would be essential for effective long-distance translocation of bound mRNA to the target tissues.
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Affiliation(s)
- Pingfang Li
- From the Department of Plant Biology, College of Biological Sciences, University of California, Davis, California, 95616 and
- the Department of Horticulture, Huajiachi Campus, Zhejiang University, Kaixuan Road 268, Hangzhou, 310029, China
| | - Byung-Kook Ham
- From the Department of Plant Biology, College of Biological Sciences, University of California, Davis, California, 95616 and
| | - William J. Lucas
- From the Department of Plant Biology, College of Biological Sciences, University of California, Davis, California, 95616 and
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Lan P, Schmidt W. The enigma of eIF5A in the iron deficiency response of Arabidopsis. PLANT SIGNALING & BEHAVIOR 2011; 6:528-30. [PMID: 21383540 PMCID: PMC3142383 DOI: 10.4161/psb.6.4.14747] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 01/06/2011] [Indexed: 05/08/2023]
Abstract
Iron (Fe) deficiency is a nutritional disorder that poses severe problems in agriculture and health due to decreased yield of crop plants and poor quality of edible plant parts. Plants respond to suboptimal Fe availability with a suite of responses, aimed at improving Fe acquisition and re-establishing cellular Fe homeostasis. In a recent study, we reported a comprehensive analysis of Fe deficiency-induced changes in the Arabidopsis root proteome using iTRAQ (Isobaric Tag for Relative and Absolute Quantification) differential LC/MS/MS. Proteins that differentially accumulate upon Fe deficiency were quantitatively identified from a total of 4,454 proteins that were detected in root cells. The abundance of several RNA-binding proteins without defined functions in the Fe deficiency response was increased by Fe deficiency. Among these were two members of the conserved eukaryotic elongation factor 5A (eIF5A) family. Due to a lack of responsiveness of the corresponding genes at the transcriptional level, these proteins have not been identified in transcriptional profiling studies. eIF5A plays an important role in regulating translation under stress conditions in eukaryotic cells and may be critical in adapting plants to prevailing environmental conditions.
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Affiliation(s)
- Ping Lan
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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