1
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Schreier TB, Müller KH, Eicke S, Faulkner C, Zeeman SC, Hibberd JM. Plasmodesmal connectivity in C 4 Gynandropsis gynandra is induced by light and dependent on photosynthesis. THE NEW PHYTOLOGIST 2024; 241:298-313. [PMID: 37882365 PMCID: PMC10952754 DOI: 10.1111/nph.19343] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Accepted: 09/28/2023] [Indexed: 10/27/2023]
Abstract
In leaves of C4 plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C4 acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C4 grasses, proliferation of plasmodesmata between these cell types is thought to increase cell-to-cell connectivity to allow efficient metabolite movement. However, it is not known whether C4 dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C4 photosynthesis is not clear. How M and BS cells in C4 leaves become highly connected is also not known. We investigated these questions using 3D- and 2D-electron microscopy on the C4 dicotyledon Gynandropsis gynandra as well as phylogenetically close C3 relatives. The M-BS interface of C4 G. gynandra showed higher plasmodesmal frequency compared with closely related C3 species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose. We conclude that enhanced formation of plasmodesmata between M and BS cells is wired to the induction of photosynthesis in C4 G. gynandra.
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Affiliation(s)
- Tina B. Schreier
- Department of Plant SciencesUniversity of CambridgeDowning StreetCambridgeCB1 3EAUK
- Present address:
Department of BiologyUniversity of OxfordSouth Parks RoadOxfordOX1 3RBUK
| | - Karin H. Müller
- Cambridge Advanced Imaging Centre (CAIC)University of CambridgeDowning StreetCambridgeCB2 3DYUK
| | - Simona Eicke
- Institute of Molecular Plant BiologyETH ZurichZurichCH‐8092Switzerland
| | - Christine Faulkner
- Cell and Developmental BiologyJohn Innes CentreNorwich Research ParkNorwichNR4 7UHUK
| | - Samuel C. Zeeman
- Institute of Molecular Plant BiologyETH ZurichZurichCH‐8092Switzerland
| | - Julian M. Hibberd
- Department of Plant SciencesUniversity of CambridgeDowning StreetCambridgeCB1 3EAUK
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Sanyal R, Kumar S, Pattanayak A, Kar A, Bishi SK. Optimizing raffinose family oligosaccharides content in plants: A tightrope walk. FRONTIERS IN PLANT SCIENCE 2023; 14:1134754. [PMID: 37056499 PMCID: PMC10088399 DOI: 10.3389/fpls.2023.1134754] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 03/08/2023] [Indexed: 06/19/2023]
Abstract
Plants synthesize various compounds for their growth, metabolism, and stress mitigation, and one such group of compounds is the raffinose family of oligosaccharides (RFOs). RFOs are non-reducing oligosaccharides having galactose residues attached to a sucrose moiety. They act as carbohydrate reserves in plants, assisting in seed germination, desiccation tolerance, and biotic/abiotic stress tolerance. Although legumes are among the richest sources of dietary proteins, the direct consumption of legumes is hindered by an excess of RFOs in the edible parts of the plant, which causes flatulence in humans and monogastric animals. These opposing characteristics make RFOs manipulation a complicated tradeoff. An in-depth knowledge of the chemical composition, distribution pattern, tissue mobilization, and metabolism is required to optimize the levels of RFOs. The most recent developments in our understanding of RFOs distribution, physiological function, genetic regulation of their biosynthesis, transport, and degradation in food crops have been covered in this review. Additionally, we have suggested a few strategies that can sustainably reduce RFOs in order to solve the flatulence issue in animals. The comprehensive information in this review can be a tool for researchers to precisely control the level of RFOs in crops and create low antinutrient, nutritious food with wider consumer acceptability.
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Affiliation(s)
- Rajarshi Sanyal
- School of Genomics and Molecular Breeding, ICAR-Indian Institute of Agricultural Biotechnology, Ranchi, Jharkhand, India
- Division of Biochemistry, ICAR-Indian Agricultural Research Institute, Pusa, New Delhi, India
| | - Sandeep Kumar
- Automation & Plant Engineering Division, ICAR-National Institute of Secondary Agriculture, Ranchi, Jharkhand, India
| | - Arunava Pattanayak
- School of Genomics and Molecular Breeding, ICAR-Indian Institute of Agricultural Biotechnology, Ranchi, Jharkhand, India
| | - Abhijit Kar
- Automation & Plant Engineering Division, ICAR-National Institute of Secondary Agriculture, Ranchi, Jharkhand, India
| | - Sujit K. Bishi
- School of Genomics and Molecular Breeding, ICAR-Indian Institute of Agricultural Biotechnology, Ranchi, Jharkhand, India
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3
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Halder NK, Fuentes D, Possell M, Bradshaw B, Ingram L, Merchant A. Phloem sap metabolites vary according to the interactive effects of nutrient supply and seasonal conditions in Eucalyptus globulus (Labill). TREE PHYSIOLOGY 2021; 41:1439-1449. [PMID: 33517450 DOI: 10.1093/treephys/tpab009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 01/18/2021] [Indexed: 06/12/2023]
Abstract
Improving the efficiency of fertilizer application is paramount to both the sustainability and profitability of forest plantations. Therefore, developing reliable, cost-effective tools to assess tree nutritional status is of great interest. This investigation sought to assess the use of phloem sap-derived metabolites as an indicator of nutritional status on a background of seasonal water availability of Eucalyptus globulus (Labill) trees grown under field conditions. Phloem is a central conduit for long-distance transport and signaling in plants and offers great promise in reflecting plant-scale resource limitations. Changes in the abundance of solutes and isotopes in phloem sap are sensitive to environmental cues. With a focus on both water and nutrient availability, we characterize patterns in phloem sugars, amino acids and the abundance of carbon isotopes in phloem sap obtained from E. globulus among different seasons and fertilizer treatments. Phloem-derived total amino acid concentration was found to increase with an increasing nitrogen (N) supply; however, this response was lost with the concurrent addition of phosphorus and at the highest level of N supply. Significant seasonal variation in all measured parameters was also detected, highlighting the need for caution in making quantitative relationships with growth. Broader implications of the interactive effects of both water supply and multi-nutrient additions and relationships with growth are discussed.
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Affiliation(s)
- Nirmol Kumar Halder
- Faculty of Science, Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia
- Ministry of Planning. Government of the People Republic of Bangladesh, Dhakar, Dhakar District, 1207 Bangladesh
| | - David Fuentes
- Sydney Mass Spectrometry, Charles Perkins Centre, University of Sydney, NSW 2006, Australia
| | - Malcolm Possell
- Faculty of Science, Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia
| | - Ben Bradshaw
- Australian Blue Gum Plantations, 3/191 Chesterpass Road, Albany, WA 6330, Australia
| | - Lachlan Ingram
- Faculty of Science, Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia
| | - Andrew Merchant
- Faculty of Science, Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia
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Voitsekhovskaja OV, Melnikova AN, Demchenko KN, Ivanova AN, Dmitrieva VA, Maksimova AI, Lohaus G, Tomos AD, Tyutereva EV, Koroleva OA. Leaf Epidermis: The Ambiguous Symplastic Domain. FRONTIERS IN PLANT SCIENCE 2021; 12:695415. [PMID: 34394148 PMCID: PMC8358407 DOI: 10.3389/fpls.2021.695415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/24/2021] [Indexed: 06/13/2023]
Abstract
The ability to develop secondary (post-cytokinetic) plasmodesmata (PD) is an important evolutionary advantage that helps in creating symplastic domains within the plant body. Developmental regulation of secondary PD formation is not completely understood. In flowering plants, secondary PD occur exclusively between cells from different lineages, e.g., at the L1/L2 interface within shoot apices, or between leaf epidermis (L1-derivative), and mesophyll (L2-derivative). However, the highest numbers of secondary PD occur in the minor veins of leaf between bundle sheath cells and phloem companion cells in a group of plant species designated "symplastic" phloem loaders, as opposed to "apoplastic" loaders. This poses a question of whether secondary PD formation is upregulated in general in symplastic loaders. Distribution of PD in leaves and in shoot apices of two symplastic phloem loaders, Alonsoa meridionalis and Asarina barclaiana, was compared with that in two apoplastic loaders, Solanum tuberosum (potato) and Hordeum vulgare (barley), using immunolabeling of the PD-specific proteins and transmission electron microscopy (TEM), respectively. Single-cell sampling was performed to correlate sugar allocation between leaf epidermis and mesophyll to PD abundance. Although the distribution of PD in the leaf lamina (except within the vascular tissues) and in the meristem layers was similar in all species examined, far fewer PD were found at the epidermis/epidermis and mesophyll/epidermis boundaries in apoplastic loaders compared to symplastic loaders. In the latter, the leaf epidermis accumulated sugar, suggesting sugar import from the mesophyll via PD. Thus, leaf epidermis and mesophyll might represent a single symplastic domain in Alonsoa meridionalis and Asarina barclaiana.
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Affiliation(s)
- Olga V. Voitsekhovskaja
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Department of Plant Biochemistry, Albrecht von Haller Institute for Plant Sciences, Göttingen, Germany
| | - Anna N. Melnikova
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Saint Petersburg State University, Saint Petersburg, Russia
| | - Kirill N. Demchenko
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Alexandra N. Ivanova
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Saint Petersburg State University, Saint Petersburg, Russia
| | - Valeria A. Dmitrieva
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | | | - Gertrud Lohaus
- Department of Plant Biochemistry, Albrecht von Haller Institute for Plant Sciences, Göttingen, Germany
- Molecular Plant Research/Plant Biochemistry, School of Mathematics and Natural Sciences, University of Wuppertal, Wuppertal, Germany
| | - A. Deri Tomos
- School of Biological Sciences, Bangor University, Bangor, United Kingdom
| | - Elena V. Tyutereva
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Olga A. Koroleva
- School of Biological Sciences, Bangor University, Bangor, United Kingdom
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Aliche EB, Theeuwen TPJM, Oortwijn M, Visser RGF, van der Linden CG. Carbon partitioning mechanisms in POTATO under drought stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2020; 146:211-219. [PMID: 31756607 DOI: 10.1016/j.plaphy.2019.11.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/11/2019] [Accepted: 11/11/2019] [Indexed: 05/23/2023]
Abstract
Potato (Solanum tuberosum) is an important food crop consumed all over the world, but it is generally sensitive to drought conditions. One of the major physiological processes affected by drought stress is carbon partitioning: the plant's choice of where to allocate its photoassimilates. Our aim was to investigate the molecular factors and possible bottlenecks affecting carbon partitioning during drought. We studied potato cultivars with contrasting drought responses in the greenhouse in the years 2013-2015, and further investigated the expression of genes involved in carbon partitioning and metabolite levels. Our results indicate that one of the most severe effects of drought stress on potato is the arrest of stolon differentiation and formation of tubers. We also identified some physiological traits like stomatal conductance and chlorophyll content as affecting carbon assimilation, partitioning and eventual tuber yield. The gene expressions and biochemical analyses highlight the various tissues prioritized by the plant for assimilate transport during drought stress, and give indications of what distinguishes drought tolerance and sensitivity of cultivated potato. Some of the key genes studied (like Sucrose synthase and Sucrose transporters) may be inclusive breeding targets for drought tolerance in potato.
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Affiliation(s)
- Ernest B Aliche
- Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands; Graduate School Experimental Plant Sciences, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Tom P J M Theeuwen
- Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Marian Oortwijn
- Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Richard G F Visser
- Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - C Gerard van der Linden
- Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.
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6
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Zhang J, Wu S, Boehlein SK, McCarty DR, Song G, Walley JW, Myers A, Settles AM. Maize defective kernel5 is a bacterial TamB homologue required for chloroplast envelope biogenesis. J Cell Biol 2019; 218:2638-2658. [PMID: 31235479 PMCID: PMC6683743 DOI: 10.1083/jcb.201807166] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 05/07/2019] [Accepted: 06/04/2019] [Indexed: 01/10/2023] Open
Abstract
Zhang et al. show that the maize dek5 locus is required for chloroplast envelope biogenesis and encodes a TamB-like protein. Bacterial TamB proteins facilitate insertion of β-barrel outer membrane proteins, indicating plastids have a conserved mechanism for envelope membrane biogenesis. Chloroplasts are of prokaryotic origin with a double-membrane envelope separating plastid metabolism from the cytosol. Envelope membrane proteins integrate chloroplasts with the cell, but envelope biogenesis mechanisms remain elusive. We show that maize defective kernel5 (dek5) is critical for envelope biogenesis. Amyloplasts and chloroplasts are larger and reduced in number in dek5 with multiple ultrastructural defects. The DEK5 protein is homologous to rice SSG4, Arabidopsis thaliana EMB2410/TIC236, and Escherichia coli tamB. TamB functions in bacterial outer membrane biogenesis. DEK5 is localized to the envelope with a topology analogous to TamB. Increased levels of soluble sugars in dek5 developing endosperm and elevated osmotic pressure in mutant leaf cells suggest defective intracellular solute transport. Proteomics and antibody-based analyses show dek5 reduces levels of Toc75 and chloroplast envelope transporters. Moreover, dek5 chloroplasts reduce inorganic phosphate uptake with at least an 80% reduction relative to normal chloroplasts. These data suggest that DEK5 functions in plastid envelope biogenesis to enable transport of metabolites and proteins.
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Affiliation(s)
- Junya Zhang
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL
| | - Shan Wu
- Horticultural Sciences Department, University of Florida, Gainesville, FL
| | - Susan K Boehlein
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL.,Horticultural Sciences Department, University of Florida, Gainesville, FL
| | - Donald R McCarty
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL.,Horticultural Sciences Department, University of Florida, Gainesville, FL
| | - Gaoyuan Song
- Plant Pathology and Microbiology, Iowa State University, Ames, IA
| | - Justin W Walley
- Plant Pathology and Microbiology, Iowa State University, Ames, IA
| | - Alan Myers
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA
| | - A Mark Settles
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL .,Horticultural Sciences Department, University of Florida, Gainesville, FL
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7
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Liesche J, Gao C, Binczycki P, Andersen SR, Rademaker H, Schulz A, Martens HJ. Direct Comparison of Leaf Plasmodesma Structure and Function in Relation to Phloem-Loading Type. PLANT PHYSIOLOGY 2019; 179:1768-1778. [PMID: 30723179 PMCID: PMC6446768 DOI: 10.1104/pp.18.01353] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/28/2019] [Indexed: 05/09/2023]
Abstract
The export of photosynthetically produced sugars from leaves depends on plasmodesmatal transport of sugar molecules from mesophyll to phloem. Traditionally, the density of plasmodesmata (PD) along this phloem-loading pathway has been used as a defining feature of different phloem-loading types, with species proposed to have either many or few PD between the phloem and surrounding cells of the leaf. However, quantitative determination of PD density has rarely been performed. Moreover, the structure of PD has not been considered, even though it could impact permeability, and functional data are only available for very few species. Here, a comparison of PD density, structure, and function using data from transmission electron microscopy and live-cell microscopy was conducted for all relevant cell-cell interfaces in leaves of nine species. These species represent the three principal phloem-loading types currently discussed in literature. Results show that relative PD density among the different cell-cell interfaces in one species, but not absolute PD density, is indicative of phloem-loading type. PD density data of single interfaces, even combined with PD diameter and length data, did not correlate with the intercellular diffusion capacity measured by the fluorescence loss in photobleaching method. This means that PD substructure not visible on standard transmission electron micrographs may have a strong influence on permeability. Furthermore, the results support a proposed passive symplasmic loading mechanism in the tree species horse chestnut (Aesculus hippocastanum), white birch (Betula pubescens), orchard apple (Malus domestica), and gray poplar (Populus x canescens) as functional cell coupling and PD structure differed from active symplasmic and apoplasmic phloem-loading species.
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Affiliation(s)
- Johannes Liesche
- College of Life Sciences, Northwest A&F University, Yangling 712100, China
- Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Yangling 712100, China
| | - Chen Gao
- College of Life Sciences, Northwest A&F University, Yangling 712100, China
- Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Yangling 712100, China
| | - Piotr Binczycki
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg, Denmark
| | - Signe R Andersen
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg, Denmark
| | - Hanna Rademaker
- Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg, Denmark
| | - Helle Juel Martens
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg, Denmark
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8
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Ganusova EE, Burch-Smith TM. Review: Plant-pathogen interactions through the plasmodesma prism. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2019; 279:70-80. [PMID: 30709495 DOI: 10.1016/j.plantsci.2018.05.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/18/2018] [Accepted: 05/23/2018] [Indexed: 06/09/2023]
Abstract
Plasmodesmata (PD) allow membrane and cytoplasmic continuity between plant cells, and they are essential for intercellular communication and signaling in addition to metabolite partitioning. Plant pathogens have evolved a variety of mechanisms to subvert PD to facilitate their infection of plant hosts. PD are implicated not only in local spread around infection sites but also in the systemic spread of pathogens and pathogen-derived molecules. In turn, plants have developed strategies to limit pathogen spread via PD, and there is increasing evidence that PD may also be active players in plant defense responses. The last few years have seen important advances in understanding the roles of PD in plant-pathogen infection. Nonetheless, several critical areas remain to be addressed. Here we highlight some of these, focusing on the need to consider the effects of pathogen-PD interaction on the trafficking of endogenous molecules, and the involvement of chloroplasts in regulating PD during pathogen defense. By their very nature, PD are recalcitrant to most currently used investigative techniques, therefore answering these questions will require creative imaging and novel quantification approaches.
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Affiliation(s)
- Elena E Ganusova
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, United States
| | - Tessa M Burch-Smith
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, United States.
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Roscher C, Karlowsky S, Milcu A, Gessler A, Bachmann D, Jesch A, Lange M, Mellado-Vázquez P, Strecker T, Landais D, Ravel O, Buchmann N, Roy J, Gleixner G. Functional composition has stronger impact than species richness on carbon gain and allocation in experimental grasslands. PLoS One 2019; 14:e0204715. [PMID: 30703101 PMCID: PMC6354960 DOI: 10.1371/journal.pone.0204715] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/07/2019] [Indexed: 11/18/2022] Open
Abstract
Numerous experiments have shown positive diversity effects on plant productivity, but little is known about related processes of carbon gain and allocation. We investigated these processes in a controlled environment (Montpellier European Ecotron) applying a continuous 13CO2 label for three weeks to 12 soil-vegetation monoliths originating from a grassland biodiversity experiment (Jena Experiment) and representing two diversity levels (4 and 16 sown species). Plant species richness did not affect community- and species-level 13C abundances neither in total biomass nor in non-structural carbohydrates (NSC). Community-level 13C excess tended to be higher in the 16-species than in the 4-species mixtures. Community-level 13C excess was positively related to canopy leaf nitrogen (N), i.e. leaf N per unit soil surface. At the species level, shoot 13C abundances varied among plant functional groups and were larger in legumes and tall herbs than in grasses and small herbs, and correlated positively with traits as leaf N concentrations, stomatal conductance and shoot height. The 13C abundances in NSC were larger in transport sugars (sucrose, raffinose-family oligosaccharides) than in free glucose, fructose and compounds of the storage pool (starch) suggesting that newly assimilated carbon is to a small portion allocated to storage. Our results emphasize that the functional composition of communities is key in explaining carbon assimilation in grasslands.
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Affiliation(s)
- Christiane Roscher
- Department of Physiological Diversity, UFZ, Helmholtz Centre for Environmental Research, Leipzig, Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
| | | | - Alexandru Milcu
- Montpellier European Ecotron (UPS 3248), National Center for Scientific Research (CNRS), Montferrier sur-Lez, France
- Centre d’Ecologie Fonctionnelle et Evolutive (UMR 5175), CNRS, Université de Montpellier, Université Paul-Valéry, EPHE, IRD, Montpellier, France
| | - Arthur Gessler
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Zürich, Switzerland
| | - Dörte Bachmann
- Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - Annette Jesch
- Department of Geobotany, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Markus Lange
- Max Planck Institute for Biogeochemistry, Jena, Germany
| | | | - Tanja Strecker
- J.F. Blumbach Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany
| | - Damien Landais
- Montpellier European Ecotron (UPS 3248), National Center for Scientific Research (CNRS), Montferrier sur-Lez, France
| | - Olivier Ravel
- Montpellier European Ecotron (UPS 3248), National Center for Scientific Research (CNRS), Montferrier sur-Lez, France
| | - Nina Buchmann
- Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - Jacques Roy
- Montpellier European Ecotron (UPS 3248), National Center for Scientific Research (CNRS), Montferrier sur-Lez, France
| | - Gerd Gleixner
- Max Planck Institute for Biogeochemistry, Jena, Germany
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10
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Fink D, Dobbelstein E, Barbian A, Lohaus G. Ratio of sugar concentrations in the phloem sap and the cytosol of mesophyll cells in different tree species as an indicator of the phloem loading mechanism. PLANTA 2018; 248:661-673. [PMID: 29882156 DOI: 10.1007/s00425-018-2933-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 06/01/2018] [Indexed: 05/28/2023]
Abstract
Sucrose concentration in phloem sap was several times higher than in the cytosol of mesophyll cells. The results suggest that phloem loading involves active steps in the analyzed tree species. Phloem loading in source leaves is a key step for carbon partitioning and passive symplastic loading has been proposed for several tree species. However, experimental evidence to prove the potential for sucrose diffusion from mesophyll to phloem is rare. Here, we analyzed three tree species (two angiosperms, Fagus sylvatica, Magnolia kobus, and one gymnosperm, Gnetum gnemon) to investigate the proposed phloem loading mechanism. For this purpose, the minor vein structure and the sugar concentrations in phloem sap as well as in the subcellular compartments of mesophyll cells were investigated. The analyzed tree species belong to the open type minor vein subcategory. The sucrose concentration in the cytosol of mesophyll cells ranged between 75 and 165 mM and was almost equal to the vacuolar concentration. Phloem sap could be collected from F. sylvatica and M. kobus and the concentration of sucrose in phloem sap was about five- and 11-fold higher, respectively, than in the cytosol of mesophyll cells. Sugar exudation of cut leaves was decreased by p-chloromercuribenzenesulfonic acid, an inhibitor of sucrose-proton transporter. The results suggest that phloem loading of sucrose in the analyzed tree species involves active steps, and apoplastic phloem loading seems more likely.
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Affiliation(s)
- Daniel Fink
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany
| | - Elena Dobbelstein
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany
| | - Andreas Barbian
- Core Facility Electron Microscopy, UKD, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Gertrud Lohaus
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany.
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11
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Zhang C, Turgeon R. Mechanisms of phloem loading. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:71-75. [PMID: 29448176 DOI: 10.1016/j.pbi.2018.01.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 01/15/2018] [Accepted: 01/24/2018] [Indexed: 05/02/2023]
Abstract
The complex form of higher plants requires continuous, balanced transport of nutrients in the phloem. The initial step of transferring sugars, amino acids, and other materials from photosynthetic cells to the conducting sieve tubes is known as phloem loading. Three phloem loading mechanisms have been described. The first involves release of sucrose into the apoplast and subsequent retrieval by the phloem. The initial release step in this process is now known to be mediated by a new class of transporters, the SWEET proteins. In the other two loading mechanisms, polymer trapping and diffusion, sucrose passes into the phloem through cytoplasmic channels, the plasmodesmata. Recent models have shed additional light on these mechanisms and their ability to sustain the growth of even the tallest trees.
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Affiliation(s)
- Cankui Zhang
- Department of Agronomy and Purdue Center for Plant Biology, Purdue University, West Lafayette, IN 49707, USA
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA.
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Wu H, Marhadour S, Lei ZW, Dugaro É, Gaillard C, Porcheron B, Marivingt-Mounir C, Lemoine R, Chollet JF, Bonnemain JL. Use of D-glucose-fenpiclonil conjugate as a potent and specific inhibitor of sucrose carriers. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:5599-5613. [PMID: 29088431 PMCID: PMC5853465 DOI: 10.1093/jxb/erx354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 09/25/2017] [Indexed: 05/12/2023]
Abstract
Until now, specific inhibitors of sucrose carriers were not available. This led us to study the properties of the recently synthesized D-glucose-fenpiclonil conjugate (D-GFC). This large amphiphilic glucoside exhibited an extremely low phloem systemicity in contrast to L-amino acid-fenpiclonil conjugates. Using Ricinus seedlings, the effect of D-GFC on 0.5 mM [14C]sucrose (Suc), 3-O-[3H]methylglucose, and [3H]glutamine uptake by cotyledon tissues was compared with that of p-chloromercuribenzenesulfonic acid (PCMBS). D-GFC dramatically inhibited H+-Suc symport at the same concentrations as PCMBS (0.5 and 1 mM), but in contrast to the thiol reagent, it did not affect 3-O-methylglucose and glutamine transport, nor the acidification of the incubation medium by cotyledon tissues. Similarly, 0.5 mM D-GFC inhibited active Suc uptake by Vicia faba leaf tissues and by Saccharomyces cerevisiae cells transformed with AtSUC2, a gene involved in Suc phloem loading in Arabidopsis, by approximately 80%. The data indicated that D-GFC was a potent inhibitor of Suc uptake from the endosperm and of Suc phloem loading. It is the first chemical known to exhibit such specificity, at least in Ricinus, and this property permitted the quantification of the two routes involved in phloem loading of endogenous sugars after endosperm removal.
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Affiliation(s)
- Hanxiang Wu
- Laboratoire EBI (Écologie et Biologie des Interactions), UMR CNRS 7267, Équipe SEVE (Sucres, Échanges Végétaux, Environnement), Université de Poitiers, 3 rue Jacques Fort, Poitiers cedex, France
- IC2MP (Institut de Chimie des Milieux et des Matériaux de Poitiers), UMR CNRS 7285, Université de Poitiers, 4 rue Michel Brunet, TSA, Poitiers cedex, France
| | - Sophie Marhadour
- IC2MP (Institut de Chimie des Milieux et des Matériaux de Poitiers), UMR CNRS 7285, Université de Poitiers, 4 rue Michel Brunet, TSA, Poitiers cedex, France
| | - Zhi-Wei Lei
- Guizhou Tea Reasearch Institute, Guizhou Academy of Agricultural Science, Guiyang, Guizhou, China
| | - Émilie Dugaro
- IC2MP (Institut de Chimie des Milieux et des Matériaux de Poitiers), UMR CNRS 7285, Université de Poitiers, 4 rue Michel Brunet, TSA, Poitiers cedex, France
| | - Cécile Gaillard
- Laboratoire EBI (Écologie et Biologie des Interactions), UMR CNRS 7267, Équipe SEVE (Sucres, Échanges Végétaux, Environnement), Université de Poitiers, 3 rue Jacques Fort, Poitiers cedex, France
| | - Benoit Porcheron
- Laboratoire EBI (Écologie et Biologie des Interactions), UMR CNRS 7267, Équipe SEVE (Sucres, Échanges Végétaux, Environnement), Université de Poitiers, 3 rue Jacques Fort, Poitiers cedex, France
| | - Cécile Marivingt-Mounir
- IC2MP (Institut de Chimie des Milieux et des Matériaux de Poitiers), UMR CNRS 7285, Université de Poitiers, 4 rue Michel Brunet, TSA, Poitiers cedex, France
| | - Rémi Lemoine
- Laboratoire EBI (Écologie et Biologie des Interactions), UMR CNRS 7267, Équipe SEVE (Sucres, Échanges Végétaux, Environnement), Université de Poitiers, 3 rue Jacques Fort, Poitiers cedex, France
| | - Jean-François Chollet
- IC2MP (Institut de Chimie des Milieux et des Matériaux de Poitiers), UMR CNRS 7285, Université de Poitiers, 4 rue Michel Brunet, TSA, Poitiers cedex, France
| | - Jean-Louis Bonnemain
- Laboratoire EBI (Écologie et Biologie des Interactions), UMR CNRS 7267, Équipe SEVE (Sucres, Échanges Végétaux, Environnement), Université de Poitiers, 3 rue Jacques Fort, Poitiers cedex, France
- Correspondence:
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13
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Liesche J. Sucrose transporters and plasmodesmal regulation in passive phloem loading. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:311-321. [PMID: 28429873 DOI: 10.1111/jipb.12548] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 04/21/2017] [Indexed: 06/07/2023]
Abstract
An essential step for the distribution of carbon throughout the whole plant is the loading of sugars into the phloem in source organs. In many plants, accumulation of sugars in the sieve element-companion cell (SE-CC) complex is mediated and regulated by active processes. However, for poplar and many other tree species, a passive symplasmic mechanism of phloem loading has been proposed, characterized by symplasmic continuity along the pre-phloem pathway and the absence of active sugar accumulation in the SE-CC complex. A high overall leaf sugar concentration is thought to enable diffusion of sucrose into the phloem. In this review, we critically evaluate current evidence regarding the mechanism of passive symplasmic phloem loading, with a focus on the potential influence of active sugar transport and plasmodesmal regulation. The limited experimental data, combined with theoretical considerations, suggest that a concomitant operation of passive symplasmic and active phloem loading in the same minor vein is unlikely. However, active sugar transport could well play an important role in how passively loading plants might modulate the rate of sugar export from leaves. Insights into the operation of this mechanism has direct implications for our understanding of how these plants utilize assimilated carbon.
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Affiliation(s)
- Johannes Liesche
- College of Life Science, Northwest A&F University, No 3 Taicheng Road, Yangling 712100, China
- Biomass Energy Center for Arid and Semi-arid lands, Northwest A&F University, Yangling 712100, China
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14
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Spokevicius AV, Tibbits J, Rigault P, Nolin MA, Müller C, Merchant A. Medium term water deficit elicits distinct transcriptome responses in Eucalyptus species of contrasting environmental origin. BMC Genomics 2017; 18:284. [PMID: 28388878 PMCID: PMC5383985 DOI: 10.1186/s12864-017-3664-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 03/25/2017] [Indexed: 12/21/2022] Open
Abstract
Background Climatic and edaphic conditions over geological timescales have generated enormous diversity of adaptive traits and high speciation within the genus Eucalyptus (L. Hér.). Eucalypt species occur from high rainfall to semi-arid zones and from the tropics to latitudes as high as 43°S. Despite several morphological and metabolomic characterizations, little is known regarding gene expression differences that underpin differences in tolerance to environmental change. Using species of contrasting taxonomy, morphology and physiology (E. globulus and E. cladocalyx), this study combines physiological characterizations with ‘second-generation’ sequencing to identify key genes involved in eucalypt responses to medium-term water limitation. Results One hundred twenty Million high-quality HiSeq reads were created from 14 tissue samples in plants that had been successfully subjected to a water deficit treatment or a well-watered control. Alignment to the E. grandis genome saw 23,623 genes of which 468 exhibited differential expression (FDR < 0.01) in one or both ecotypes in response to the treatment. Further analysis identified 80 genes that demonstrated a significant species-specific response of which 74 were linked to the ‘dry’ species E. cladocalyx where 23 of these genes were uncharacterised. The majority (approximately 80%) of these differentially expressed genes, were expressed in stem tissue. Key genes that differentiated species responses were linked to photoprotection/redox balance, phytohormone/signalling, primary photosynthesis/cellular metabolism and secondary metabolism based on plant metabolic pathway network analysis. Conclusion These results highlight a more definitive response to water deficit by a ‘dry’ climate eucalypt, particularly in stem tissue, identifying key pathways and associated genes that are responsible for the differences between ‘wet’ and ‘dry’ climate eucalypts. This knowledge provides the opportunity to further investigate and understand the mechanisms and genetic variation linked to this important environmental response that will assist with genomic efforts in managing native populations as well as in tree improvement programs under future climate scenarios. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3664-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Antanas V Spokevicius
- School of Ecosystem and Forest Sciences, University of Melbourne, Creswick, Victoria, 3363, Australia.
| | - Josquin Tibbits
- Victorian AgriBiosciences Centre, La Trobe University R&D Park, 1 Park Drive, Bundoora, Victoria, 3083, Australia
| | | | | | - Caroline Müller
- Faculty of Agriculture and the Environment, The University of Sydney, Sydney, 2006, Australia
| | - Andrew Merchant
- Faculty of Agriculture and the Environment, The University of Sydney, Sydney, 2006, Australia
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Błażejewska K, Kapusta M, Zielińska E, Tukaj Z, Chincinska IA. Mature Luffa Leaves ( Luffa cylindrica L.) as a Tool for Gene Expression Analysis by Agroinfiltration. FRONTIERS IN PLANT SCIENCE 2017; 8:228. [PMID: 28270826 PMCID: PMC5318407 DOI: 10.3389/fpls.2017.00228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 02/06/2017] [Indexed: 05/23/2023]
Abstract
We exploited the potential of cucurbits for ectopic gene expression. Agroinfiltration is a simple and commonly used method to obtain transient expression of foreign genes in plants. In contrast to in vitro transformation techniques, agroinfiltration can be used for genetic modification of mature plant tissues. Although the cucurbits are commonly used as model plants for molecular biology and biotechnology studies, to date there are no literature sources on the possibility of transient gene expression in mature cucurbit tissues. Our research has shown that mature leaves of Luffa cylindrica L. (luffa), in contrast to other cucurbit species, can be successfully transiently transformed with Agrobacterium tumefaciens. We efficiently transformed luffa leaves with a reporter gene encoding β-glucuronidase (GUS). The GUS activity in transiently transformed leaf tissues was detected within 24 h after the infiltration with bacteria. Additionally, we have shown that the activity of a transiently expressed the GUS gene can be monitored directly in the EDTA-exudates collected from the cut petioles of the agroinfiltrated leaves. The results suggest that luffa leaves can be useful as a plant expression system for studies of physiological and biochemical processes in cucurbits.
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Affiliation(s)
- Kamila Błażejewska
- Department of Plant Physiology and Biotechnology, Faculty of Biology, University of GdańskGdańsk, Poland
| | - Małgorzata Kapusta
- Department of Plant Cytology and Embryology, Faculty of Biology, University of GdańskGdańsk, Poland
| | - Elżbieta Zielińska
- Department of Plant Physiology and Biotechnology, Faculty of Biology, University of GdańskGdańsk, Poland
| | - Zbigniew Tukaj
- Department of Plant Physiology and Biotechnology, Faculty of Biology, University of GdańskGdańsk, Poland
| | - Izabela A. Chincinska
- Department of Plant Physiology and Biotechnology, Faculty of Biology, University of GdańskGdańsk, Poland
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16
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Kraner ME, Link K, Melzer M, Ekici AB, Uebe S, Tarazona P, Feussner I, Hofmann J, Sonnewald U. Choline transporter-like1 (CHER1) is crucial for plasmodesmata maturation in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:394-406. [PMID: 27743414 DOI: 10.1111/tpj.13393] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 09/30/2016] [Accepted: 10/03/2016] [Indexed: 05/05/2023]
Abstract
Plasmodesmata (PD) are microscopic pores connecting plant cells and enable cell-to-cell transport. Currently, little information is known about the molecular mechanisms regulating PD formation and development. To uncover components of PD development we made use of the 17 kDa movement protein (MP17) encoded by the Potato leafroll virus (PLRV). The protein is required for cell-to-cell movement of the virus and localises to complex PD. Forward genetic screening for Arabidopsis mutants with altered PD binding of MP17 revealed several mutant lines, while molecular genetics, biochemical and microscopic studies allowed further characterisation. Map-based cloning of one mutant revealed a point mutation in the choline transporter-like 1 (CHER1) protein, changing glycine247 into glutamate. Mutation in CHER1 resulted in a starch excess phenotype and stunted growth. Ultrastructure analysis of shoot apical meristems, developing and fully developed leaves showed reduced PD numbers and the absence of complex PD in fully developed leaves. This indicates that cher1 mutants are impaired in PD formation and development. Global lipid profiling revealed only slight modifications in the overall lipid composition, however, altered composition of PD-associated lipids cannot be ruled out. Thus, cher1 is devoid of complex PD in developed leaves and provides insights into the formation of complex PD at the molecular level.
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Affiliation(s)
- Max E Kraner
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Katrin Link
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Michael Melzer
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466, Seeland, Gatersleben, OT, Germany
| | - Arif B Ekici
- Institute of Human Genetics, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, D-91054, Erlangen, Germany
| | - Steffen Uebe
- Institute of Human Genetics, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, D-91054, Erlangen, Germany
| | - Pablo Tarazona
- Department of Plant Biochemistry, Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
| | - Ivo Feussner
- Department of Plant Biochemistry, Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
- Department of Plant Biochemistry, Georg-August-University Goettingen, Goettingen Center for Molecular Biosciences (GZMB), Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
| | - Jörg Hofmann
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Uwe Sonnewald
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
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17
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Savage JA, Clearwater MJ, Haines DF, Klein T, Mencuccini M, Sevanto S, Turgeon R, Zhang C. Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology? PLANT, CELL & ENVIRONMENT 2016; 39:709-25. [PMID: 26147312 DOI: 10.1111/pce.12602] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 05/30/2015] [Accepted: 06/19/2015] [Indexed: 05/02/2023]
Abstract
Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.
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Affiliation(s)
- Jessica A Savage
- Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA, 02131, USA
| | | | - Dustin F Haines
- Department of Environmental Conservation, University of Massachusetts, 160 Holdsworth Way, Amherst, MA, 01003, USA
| | - Tamir Klein
- Institute of Botany, University of Basel, Schoenbeinstrasse 6, 4056, Basel, Switzerland
| | - Maurizio Mencuccini
- School of GeoSciences, University of Edinburgh, Crew Building, West Mains Road, EH9 3JN, Edinburgh, UK
- ICREA at CREAF, Campus de UAB, Cerdanyola del Valles, Barcelona, 08023, Spain
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA
| | - Cankui Zhang
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
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18
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Öner-Sieben S, Rappl C, Sauer N, Stadler R, Lohaus G. Characterization, localization, and seasonal changes of the sucrose transporter FeSUT1 in the phloem of Fraxinus excelsior. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4807-19. [PMID: 26022258 PMCID: PMC4507781 DOI: 10.1093/jxb/erv255] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Trees are generally assumed to be symplastic phloem loaders. A typical feature for most wooden species is an open minor vein structure with symplastic connections between mesophyll cells and phloem cells, which allow sucrose to move cell-to-cell through the plasmodesmata into the phloem. Fraxinus excelsior (Oleaceae) also translocates raffinose family oligosaccharides in addition to sucrose. Sucrose concentration was recently shown to be higher in the phloem sap than in the mesophyll cells. This suggests the involvement of apoplastic steps and the activity of sucrose transporters in addition to symplastic phloem-loading processes. In this study, the sucrose transporter FeSUT1 from F. excelsior was analysed. Heterologous expression in baker's yeast showed that FeSUT1 mediates the uptake of sucrose. Immunohistochemical analyses revealed that FeSUT1 was exclusively located in phloem cells of minor veins and in the transport phloem of F. excelsior. Further characterization identified these cells as sieve elements and possibly ordinary companion cells but not as intermediary cells. The localization and expression pattern point towards functions of FeSUT1 in phloem loading of sucrose as well as in sucrose retrieval. FeSUT1 is most likely responsible for the observed sucrose gradient between mesophyll and phloem. The elevated expression level of FeSUT1 indicated an increased apoplastic carbon export activity from the leaves during spring and late autumn. It is hypothesized that the importance of apoplastic loading is high under low-sucrose conditions and that the availability of two different phloem-loading mechanisms confers advantages for temperate woody species like F. excelsior.
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Affiliation(s)
- Soner Öner-Sieben
- Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany
| | - Christine Rappl
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Norbert Sauer
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Ruth Stadler
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Gertrud Lohaus
- Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany
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19
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Zhang P, Howell K, Krstic M, Herderich M, Barlow EWR, Fuentes S. Environmental Factors and Seasonality Affect the Concentration of Rotundone in Vitis vinifera L. cv. Shiraz Wine. PLoS One 2015; 10:e0133137. [PMID: 26176692 PMCID: PMC4503395 DOI: 10.1371/journal.pone.0133137] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/23/2015] [Indexed: 11/18/2022] Open
Abstract
Rotundone is a sesquiterpene that gives grapes and wine a desirable ‘peppery’ aroma. Previous research has reported that growing grapevines in a cool climate is an important factor that drives rotundone accumulation in grape berries and wine. This study used historical data sets to investigate which weather parameters are mostly influencing rotundone concentration in grape berries and wine. For this purpose, wines produced from 15 vintages from the same Shiraz vineyard (The Old Block, Mount Langi Ghiran, Victoria, Australia) were analysed for rotundone concentration and compared to comprehensive weather data and minimal temperature information. Degree hours were obtained by interpolating available temperature information from the vineyard site using a simple piecewise cubic hermite interpolating polynomial method (PCHIP). Results showed that the highest concentrations of rotundone were consistently found in wines from cool and wet seasons. The Principal Component Analysis (PCA) showed that the concentration of rotundone in wine was negatively correlated with daily solar exposure and grape bunch zone temperature, and positively correlated with vineyard water balance. Finally, models were constructed based on the Gompertz function to describe the dynamics of rotundone concentration in berries through the ripening process according to phenological and thermal times. This characterisation is an important step forward to potentially predict the final quality of the resultant wines based on the evolution of specific compounds in berries according to critical environmental and micrometeorological variables. The modelling techniques described in this paper were able to describe the behaviour of rotundone concentration based on seasonal weather conditions and grapevine phenological stages, and could be potentially used to predict the final rotundone concentration early in future growing seasons. This could enable the adoption of precision irrigation and canopy management strategies to effectively mitigate adverse impacts related to climate change and microclimatic variability, such as heat waves, within a vineyard on wine quality.
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Affiliation(s)
- Pangzhen Zhang
- Department of Agriculture & Food Systems, The University of Melbourne, Parkville, Vic, Australia
| | - Kate Howell
- Department of Agriculture & Food Systems, The University of Melbourne, Parkville, Vic, Australia
| | - Mark Krstic
- Australian Wine Research Institute, Port Melbourne, Vic, Australia
| | | | - Edward William R. Barlow
- Department of Agriculture & Food Systems, The University of Melbourne, Parkville, Vic, Australia
| | - Sigfredo Fuentes
- Department of Agriculture & Food Systems, The University of Melbourne, Parkville, Vic, Australia
- * E-mail:
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20
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Zhang P, Barlow S, Krstic M, Herderich M, Fuentes S, Howell K. Within-Vineyard, Within-Vine, and Within-Bunch Variability of the Rotundone Concentration in Berries of Vitis vinifera L. cv. Shiraz. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:4276-4283. [PMID: 25891266 DOI: 10.1021/acs.jafc.5b00590] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study characterizes the environmental factors driving rotundone concentrations in grape berries by quantifying rotundone variability and correlating it with viticultural parameters. Dissection of the vineyard into distinct zones (on the basis of vigor, electrical soil conductivity, and slope), vine into orientations to sun (shaded/unshaded), and grape bunches into sectors (upper and lower and front and back) shows the influence of vine vigor, sunlight, and temperature. Occurrence of the highest rotundone concentration was observed in shaded bunch sectors and vines and from higher vigor vines in the southern-facing areas of the vineyard. The highest concentration of rotundone is consistently found at the top and in shaded sectors of bunches, and this correlates to lower grape surface temperatures. Modeling showed that berry temperature exceeding 25 °C negatively affects the rotundone concentration in Shiraz. Both natural and artificial shading modulated the grape surface and air temperature at the bunch zone and increased the rotundone concentration, without affecting other grape berry quality parameters. Thus, temperature and possibly sunlight interception are the main determinants of rotundone in grape berries. Vineyard topography, vine vigor, vine row, and grape bunch orientation influence the level of berry shading and can, therefore, adjust bunch surface and zone temperatures and influence the berry rotundone concentration.
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Affiliation(s)
- Pangzhen Zhang
- †Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Snow Barlow
- †Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Mark Krstic
- ‡Australian Wine Research Institute, Port Melbourne, Victoria 3207, Australia
| | - Markus Herderich
- §Australian Wine Research Institute, Urrbrae, South Australia 5064, Australia
| | - Sigfredo Fuentes
- †Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Kate Howell
- †Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria 3010, Australia
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21
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Yadav UP, Ayre BG, Bush DR. Transgenic approaches to altering carbon and nitrogen partitioning in whole plants: assessing the potential to improve crop yields and nutritional quality. FRONTIERS IN PLANT SCIENCE 2015; 6:275. [PMID: 25954297 PMCID: PMC4405696 DOI: 10.3389/fpls.2015.00275] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/06/2015] [Indexed: 05/18/2023]
Abstract
The principal components of plant productivity and nutritional value, from the standpoint of modern agriculture, are the acquisition and partitioning of organic carbon (C) and nitrogen (N) compounds among the various organs of the plant. The flow of essential organic nutrients among the plant organ systems is mediated by its complex vascular system, and is driven by a series of transport steps including export from sites of primary assimilation, transport into and out of the phloem and xylem, and transport into the various import-dependent organs. Manipulating C and N partitioning to enhance yield of harvested organs is evident in the earliest crop domestication events and continues to be a goal for modern plant biology. Research on the biochemistry, molecular and cellular biology, and physiology of C and N partitioning has now matured to an extent that strategic manipulation of these transport systems through biotechnology are being attempted to improve movement from source to sink tissues in general, but also to target partitioning to specific organs. These nascent efforts are demonstrating the potential of applied biomass targeting but are also identifying interactions between essential nutrients that require further basic research. In this review, we summarize the key transport steps involved in C and N partitioning, and discuss various transgenic approaches for directly manipulating key C and N transporters involved. In addition, we propose several experiments that could enhance biomass accumulation in targeted organs while simultaneously testing current partitioning models.
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Affiliation(s)
- Umesh P. Yadav
- Department of Biological Sciences, University of North Texas, Denton, TX, USA
| | - Brian G. Ayre
- Department of Biological Sciences, University of North Texas, Denton, TX, USA
| | - Daniel R. Bush
- Department of Biology, Colorado State University, Fort Collins, CO, USA
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22
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Öner-Sieben S, Lohaus G. Apoplastic and symplastic phloem loading in Quercus robur and Fraxinus excelsior. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1905-16. [PMID: 24591056 PMCID: PMC3978624 DOI: 10.1093/jxb/eru066] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Whereas most of the research on phloem loading is performed on herbaceous plants, less is known about phloem loading strategies in trees. In this study, the phloem loading mechanisms of Quercus robur and Fraxinus excelsior were analysed. The following features were examined: the minor vein structure, the sugar concentrations in phloem sap by the laser-aphid-stylet technique, the distribution of photoassimilates in the mesophyll cells by non-aqueous fractionation, gradients of sugar concentrations and osmotic pressure, and the expression of sucrose transporters. The minor vein configurations of Q. robur and F. excelsior belong to the open type. Quercus robur contained companion cells in the minor veins whereas F. excelsior showed intermediary cells in addition to ordinary companion cells. The main carbon transport form in Q. robur was sucrose (~1M). In F. excelsior high amounts of raffinose and stachyose were also transported. However, in both tree species, the osmolality of phloem sap was higher than the osmolality of the mesophyll cells. The concentration gradients between phloem sap and the cytoplasm of mesophyll cells for sucrose were 16-fold and 14-fold for Q. robur and F. excelsior, respectively. Independent of the type of translocated sugars, sucrose transporter cDNAs were cloned from both species. The results indicate that phloem loading of sucrose and other metabolites must involve active loading steps in both tree species. Quercus robur seems to be an apoplastic phloem loader while F. excelsior shows indications of being a symplastic or mixed symplastic-apoplastic phloem loader.
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Liesche J, Schulz A. Modeling the parameters for plasmodesmal sugar filtering in active symplasmic phloem loaders. FRONTIERS IN PLANT SCIENCE 2013; 4:207. [PMID: 23802006 PMCID: PMC3685819 DOI: 10.3389/fpls.2013.00207] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 05/31/2013] [Indexed: 05/05/2023]
Abstract
Plasmodesmata (PD) play a key role in loading of sugars into the phloem. In plant species that employ the so-called active symplasmic loading strategy, sucrose that diffuses into their unique intermediary cells (ICs) is converted into sugar oligomers. According to the prevalent hypothesis, the oligomers are too large to pass back through PD on the bundle sheath side, but can pass on into the sieve element to be transported in the phloem. Here, we investigate if the PD at the bundle sheath-IC interface can indeed fulfill the function of blocking transport of sugar oligomers while still enabling efficient diffusion of sucrose. Hindrance factors are derived via theoretical modeling for different PD substructure configurations: sub-nano channels, slit, and hydrogel. The results suggest that a strong discrimination could only be realized when the PD opening is almost as small as the sugar oligomers. In order to find model parameters that match the in vivo situation, we measured the effective diffusion coefficient across the interface in question in Cucurbita pepo with 3D-photoactivation microscopy. Calculations indicate that a PD substructure of several sub-nano channels with a radius around 7 Å, a 10.4 Å-wide slit or a hydrogel with 49% polymer fraction would be compatible with the effective diffusion coefficient. If these configurations can accommodate sufficient flux of sucrose into the IC, while blocking raffinose and stachyose movement was assessed using literature data. While the slit-configuration would efficiently prevent the sugar oligomers from "leaking" from the IC, none of the configurations could enable a diffusion-driven sucrose flux that matches the reported rates at a physiologically relevant concentration potential. The presented data provides a first insight on how the substructure of PD could enable selective transport, but indicates that additional factors are involved in efficient phloem loading in active symplasmic loading species.
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Affiliation(s)
- Johannes Liesche
- Department of Plant and Environmental Sciences, University of CopenhagenCopenhagen, Denmark
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Turnbull CGN, Lopez-Cobollo RM. Heavy traffic in the fast lane: long-distance signalling by macromolecules. THE NEW PHYTOLOGIST 2013; 198:33-51. [PMID: 23398598 DOI: 10.1111/nph.12167] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 12/21/2012] [Indexed: 05/05/2023]
Abstract
The two major vascular conduits in plants, the xylem and phloem, theoretically provide opportunities for the long-distance translocation of almost any type of water-borne molecule. This review focuses on the signalling functions conveyed by the movement of macromolecules. Here, a signal is defined as the communication of information from source to destination, where it modifies development, physiology or defence through altered gene expression or by direct influences on other cellular processes. Xylem and phloem sap both contain diverse classes of proteins; in addition, phloem contains many full-length and small RNA species. Only a few of these mobile molecules have proven functions in signalling. The transduction of signals typically depends on connection to appropriate signalling pathways. Incoming protein signals require specific detection systems, generally via receptors. Mobile RNAs require either the translation or presence of a homologous target. Given that phloem sieve elements are enucleate and lack translation machinery, RNA function requires subsequent unloading at least into adjacent companion cells. The binding of RNA by proteins in ribonucleoprotein complexes enables the translocation of some signals, with evidence for both sequence-specific and size-specific binding. Several examples of long-distance macromolecular signalling are highlighted, including the FT protein signal which regulates flowering time and other developmental switches.
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Affiliation(s)
- Colin G N Turnbull
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
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Slewinski TL, Zhang C, Turgeon R. Structural and functional heterogeneity in phloem loading and transport. FRONTIERS IN PLANT SCIENCE 2013; 4:244. [PMID: 23847646 PMCID: PMC3701861 DOI: 10.3389/fpls.2013.00244] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 06/18/2013] [Indexed: 05/05/2023]
Abstract
The phloem is often regarded as a relatively straightforward transport system composed of loading (collection), long-distance (transport), and unloading (release) zones. While this simple view is necessary and useful in many contexts, it belies the reality, which is that the phloem is inherently complex. At least three types of sieve element-companion cell complexes are found in minor veins of leaves. Individual species may have more than one type, indicating that they employ multiple loading strategies, even in the same vein. Gene expression data in particular point to heterogeneity in sieve element-companion cell complexes of minor veins, perhaps in all flowering plants. Phloem heterogeneity in the transport phloem is also evident in many species based on anatomical, biochemical and gene expression data. In this regard, members of the Cucurbitaceae are especially complex and interesting. We conclude that a hidden world of specialized phloem function awaits discovery.
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Affiliation(s)
- Thomas L. Slewinski
- *Correspondence: Thomas L. Slewinski and Robert Turgeon, Department of Plant Biology, 262 Plant Science, Cornell University, Ithaca, NY, USA e-mail: ;
| | | | - Robert Turgeon
- *Correspondence: Thomas L. Slewinski and Robert Turgeon, Department of Plant Biology, 262 Plant Science, Cornell University, Ithaca, NY, USA e-mail: ;
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26
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Batashev DR, Pakhomova MV, Razumovskaya AV, Voitsekhovskaja OV, Gamalei YV. Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes. FRONTIERS IN PLANT SCIENCE 2013; 4:312. [PMID: 23970890 PMCID: PMC3748319 DOI: 10.3389/fpls.2013.00312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 07/24/2013] [Indexed: 05/05/2023]
Abstract
The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of "open" and "closed" types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, 1990). These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on companion cell types and their combinations which have not been reported previously. The percentage of Asteridae species with "open" minor vein cytology which also contain sieve-element-companion cell complexes with "closed" cytology, i.e., that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009), these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading.
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Affiliation(s)
| | | | | | - Olga V. Voitsekhovskaja
- *Correspondence: Olga V. Voitsekhovskaja, Laboratory of Plant Ecological Physiology, Komarov Botanical Institute, Russian Academy of Sciences, ul. Professora Popova, 2, 197376 St. Petersburg, Russia e-mail:
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Cao T, Lahiri I, Singh V, Louis J, Shah J, Ayre BG. Metabolic engineering of raffinose-family oligosaccharides in the phloem reveals alterations in carbon partitioning and enhances resistance to green peach aphid. FRONTIERS IN PLANT SCIENCE 2013; 4:263. [PMID: 23882277 PMCID: PMC3715723 DOI: 10.3389/fpls.2013.00263] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 06/29/2013] [Indexed: 05/18/2023]
Abstract
Many plants employ energized loading strategies to accumulate osmotically-active solutes into the phloem of source organs to accentuate the hydrostatic pressure gradients that drive the flow of water, nutrients and signals from source to sinks. Proton-coupled symport of sugars from the apoplasm into the phloem symplasm is the best studied phloem-loading mechanism. As an alternative, numerous species use a polymer trapping mechanism to load through symplasm: sucrose enters the phloem through specialized plasmodesmata and is converted to raffinose-family oligosaccharides (RFOs) which accumulate because of their larger size. In this study, metabolic engineering was used to generate RFOs at the inception of the translocation stream of Arabidopsis thaliana, which loads from the apoplasm and transports predominantly sucrose, and the fate of the sugars throughout the plant determined. Three genes, GALACTINOL SYNTHASE, RAFFINOSE SYNTHASE and STACHYOSE SYNTHASE, were expressed from promoters specific to the companion cells of minor veins. Two transgenic lines homozygous for all three genes (GRS63 and GRS47) were selected for further analysis. Three-week-old plants of both lines had RFO levels approaching 50% of total soluble sugar. RFOs were also identified in exudates from excised leaves of transgenic plants whereas levels were negligible in exudates from wild type (WT) leaves. Differences in starch accumulation between WT and GRS63 and GRS47 lines were not observed. Similarly, there were no differences in vegetative growth between WT and engineered plants, but the latter flowered slightly earlier. Finally, since the sugar composition of the translocation stream appeared altered, we tested for an impact on green peach aphid (Myzus persicae Sulzer) feeding. When given a choice between WT and transgenic plants, green peach aphids preferred settling on the WT plants. Furthermore, green peach aphid fecundity was lower on the transgenic plants compared to the WT plants. When added to an artificial diet, RFOs did not have a negative effect on aphid fecundity, suggesting that although aphid resistance in the transgenic plants is enhanced, it is not due to direct toxicity of RFO toward the insect.
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Affiliation(s)
| | | | | | | | | | - Brian G. Ayre
- *Correspondence: Brian G. Ayre, Department of Biological Sciences, University of North Texas, 1155 Union Circle, 305220, Denton, TX 76203, USA e-mail:
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Frost CJ, Nyamdari B, Tsai CJ, Harding SA. The tonoplast-localized sucrose transporter in Populus (PtaSUT4) regulates whole-plant water relations, responses to water stress, and photosynthesis. PLoS One 2012; 7:e44467. [PMID: 22952983 PMCID: PMC3432113 DOI: 10.1371/journal.pone.0044467] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 08/02/2012] [Indexed: 12/24/2022] Open
Abstract
The Populus sucrose (Suc) transporter 4 (PtaSUT4), like its orthologs in other plant taxa, is tonoplast localized and thought to mediate Suc export from the vacuole into the cytosol. In source leaves of Populus, SUT4 is the predominantly expressed gene family member, with transcript levels several times higher than those of plasma membrane SUTs. A hypothesis is advanced that SUT4-mediated tonoplast sucrose fluxes contribute to the regulation of osmotic gradients between cellular compartments, with the potential to mediate both sink provisioning and drought tolerance in Populus. Here, we describe the effects of PtaSUT4-RNA interference (RNAi) on sucrose levels and raffinose family oligosaccharides (RFO) induction, photosynthesis, and water uptake, retention and loss during acute and chronic drought stresses. Under normal water-replete growing conditions, SUT4-RNAi plants had generally higher shoot water contents than wild-type plants. In response to soil drying during a short-term, acute drought, RNAi plants exhibited reduced rates of water uptake and delayed wilting relative to wild-type plants. SUT4-RNAi plants had larger leaf areas and lower photosynthesis rates than wild-type plants under well-watered, but not under chronic water-limiting conditions. Moreover, the magnitude of shoot water content, height growth, and photosynthesis responses to contrasting soil moisture regimes was greater in RNAi than wild-type plants. The concentrations of stress-responsive RFOs increased in wild-type plants but were unaffected in SUT4-RNAi plants under chronically dry conditions. We discuss a model in which the subcellular compartmentalization of sucrose mediated by PtaSUT4 is regulated in response to both sink demand and plant water status in Populus.
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Affiliation(s)
- Christopher J Frost
- Warnell School of Forestry and Natural Resources and Department of Genetics, University of Georgia, Athens, Georgia, USA
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29
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Liesche J, Schulz A. In vivo quantification of cell coupling in plants with different phloem-loading strategies. PLANT PHYSIOLOGY 2012; 159:355-65. [PMID: 22422939 PMCID: PMC3375970 DOI: 10.1104/pp.112.195115] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Accepted: 03/09/2012] [Indexed: 05/18/2023]
Abstract
Uptake of photoassimilates into the leaf phloem is the key step in carbon partitioning and phloem transport. Symplasmic and apoplasmic loading strategies have been defined in different plant taxa based on the abundance of plasmodesmata between mesophyll and phloem. For apoplasmic loading to occur, an absence of plasmodesmata is a sufficient but not a necessary criterion, as passage of molecules through plasmodesmata might well be blocked or restricted. Here, we present a noninvasive, whole-plant approach to test symplasmic coupling and quantify the intercellular flux of small molecules using photoactivation microscopy. Quantification of coupling between all cells along the prephloem pathways of the apoplasmic loader Vicia faba and Nicotiana tabacum showed, to our knowledge for the first time in vivo, that small solutes like sucrose can diffuse through plasmodesmata up to the phloem sieve element companion cell complex (SECCC). As expected, the SECCC was found to be symplasmically isolated for small solutes. In contrast, the prephloem pathway of the symplasmic loader Cucurbita maxima was found to be well coupled with the SECCC. Phloem loading in gymnosperms is not well understood, due to a profoundly different leaf anatomy and a scarcity of molecular data compared with angiosperms. A cell-coupling analysis for Pinus sylvestris showed high symplasmic coupling along the entire prephloem pathway, comprising at least seven cell border interfaces between mesophyll and sieve elements. Cell coupling together with measurements of leaf sap osmolality indicate a passive symplasmic loading type. Similarities and differences of this loading type with that of angiosperm trees are discussed.
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Affiliation(s)
- Johannes Liesche
- Department of Plant Biology and Biotechnology, University of Copenhagen, DK–1871 Frederiksberg C, Denmark
| | - Alexander Schulz
- Department of Plant Biology and Biotechnology, University of Copenhagen, DK–1871 Frederiksberg C, Denmark
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30
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31
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32
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Cao H, Guo S, Xu Y, Jiang K, Jones AM, Chong K. Reduced expression of a gene encoding a Golgi localized monosaccharide transporter (OsGMST1) confers hypersensitivity to salt in rice (Oryza sativa). JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4595-604. [PMID: 21613379 PMCID: PMC3170556 DOI: 10.1093/jxb/err178] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 05/01/2011] [Accepted: 05/03/2011] [Indexed: 05/18/2023]
Abstract
Sugar transport is critical for normal plant development and stress responses. However, functional evidence for the roles of monosaccharide transporters in rice (Oryza sativa) has not previously been presented. In this study, reversed genetics was used to identify OsGMST1 as a member of the monosaccharide transporter family in rice. The predicted 481 amino acid protein has the typical features of a sugar transporter in the plastid glucose transporter subfamily consistent with reduced monosaccharide accumulation in plants with reduced OsGMST1 expression. OsGMST1-green fluorescent protein is localized to the Golgi apparatus. OsGMST1 expression is induced by salt treatment and reduced expression confers hypersensitivity to salt stress in rice. OsGMST1 may play a direct or an indirect role in tolerance to salt stress in rice.
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Affiliation(s)
- Hong Cao
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Siyi Guo
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yunyuan Xu
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Kun Jiang
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
| | - Alan M. Jones
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
| | - Kang Chong
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- National Research Center for Plant Gene, Beijing 100093, China
- To whom correspondence should be addressed. E-mail:
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Payyavula RS, Tay KHC, Tsai CJ, Harding SA. The sucrose transporter family in Populus: the importance of a tonoplast PtaSUT4 to biomass and carbon partitioning. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 65:757-70. [PMID: 21261761 DOI: 10.1111/j.1365-313x.2010.04463.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Plasma membrane, proton-coupled Group II sucrose symporters (SUT) mediate apoplastic phloem loading and sucrose efflux from source leaves in Arabidopsis and agricultural crop species that have been studied to date. We now report that the most abundantly expressed SUT isoform in Populus tremula×alba, PtaSUT4, is a tonoplast (Group IV) symporter. PtaSUT4 transcripts were readily detected in conducting as well as mesophyll cells in stems and source leaves. In comparison, Group II orthologs PtaSUT1 and PtaSUT3 were very weakly expressed in leaves. Both Group II and Group IV SUT genes were expressed in secondary stem xylem of Populus. Transgenic poplars with RNAi-suppressed PtaSUT4 exhibited increased leaf-to-stem biomass ratios, elevated sucrose content in source leaves and stems, and altered phenylpropanoid metabolism. Transcript abundance of several carbohydrate-active enzymes and phenylalanine ammonia-lyases was also altered in transgenic source leaves. Nitrogen-limitation led to a down-regulation of vacuolar invertases in all plants, which resulted in an augmentation of sucrose pooling and hexose depletion in source leaves and secondary xylem of the transgenic plants. These results are consistent with a major role for PtaSUT4 in orchestrating the intracellular partitioning, and consequently, the efflux of sucrose from source leaves and the utilization of sucrose by lateral and terminal sinks. Our findings also support the idea that PtaSUT4 modulates sucrose efflux and utilization in concert with plant N-status.
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Affiliation(s)
- Raja S Payyavula
- School of Forest Resources and Environmental Sciences, Michigan Technological University, Houghton, MI 49931, USA
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34
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Davidson A, Keller F, Turgeon R. Phloem loading, plant growth form, and climate. PROTOPLASMA 2011; 248:153-63. [PMID: 21125302 DOI: 10.1007/s00709-010-0240-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 11/01/2010] [Indexed: 05/08/2023]
Abstract
Plasmodesmatal frequencies in the phloem of leaf minor veins vary considerably, suggesting that photoassimilate is loaded into the phloem by different strategies. The ecophysiological basis for multiple loading types is unknown. We updated the analysis of van Bel and Gamalei (Plant Cell Environ 15: 265-270, 1992) with more current phylogenetic data and by treating separately two symplastic loading types, those that load actively by polymer trapping (synthesis of raffinose family oligosaccharides--RFOs), and those that load passively, by diffusion. The results indicate a stronger association between passive, symplastic loading and the tree growth form than previously recognized. Apoplastic loading is highly correlated with the herbaceous habit. There is no correlation between RFO families and growth form. At the family level, there are no correlations between minor vein types and climate that cannot be explained by the dearth of woody plants in the arctic for reasons unassociated with phloem loading. However, at the species level, a floristic analysis uncovered a correlation between the RFO trait and species frequency in tropical and subtropical regions of the world. The correlations between loading types and both growth form and climate are subtle, probably indirect, and poorly understood.
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Affiliation(s)
- Anna Davidson
- Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA
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35
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Turgeon R, Medville R. Amborella trichopoda, plasmodesmata, and the evolution of phloem loading. PROTOPLASMA 2011; 248:173-80. [PMID: 21080011 DOI: 10.1007/s00709-010-0237-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 10/26/2010] [Indexed: 05/09/2023]
Abstract
Phloem loading is the process by which photoassimilates synthesized in the mesophyll cells of leaves enter the sieve elements and companion cells of minor veins in preparation for long distance transport to sink organs. Three loading strategies have been described: active loading from the apoplast, passive loading via the symplast, and passive symplastic transfer followed by polymer trapping of raffinose and stachyose. We studied phloem loading in Amborella trichopoda, a premontane shrub that may be sister to all other flowering plants. The minor veins of A. trichopoda contain intermediary cells, indicative of the polymer trap mechanism, forming an arc on the abaxial side and subtending a cluster of ordinary companion cells in the interior of the veins. Intermediary cells are linked to bundle sheath cells by highly abundant plasmodesmata whereas ordinary companion cells have few plasmodesmata, characteristic of phloem that loads from the apoplast. Intermediary cells, ordinary companion cells, and sieve elements form symplastically connected complexes. Leaves provided with (14)CO(2) translocate radiolabeled sucrose, raffinose, and stachyose. Therefore, structural and physiological evidence suggests that both apoplastic and polymer trapping mechanisms of phloem loading operate in A. trichopoda. The evolution of phloem loading strategies is complex and may be difficult to resolve.
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Affiliation(s)
- Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
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36
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Werner D, Gerlitz N, Stadler R. A dual switch in phloem unloading during ovule development in Arabidopsis. PROTOPLASMA 2011; 248:225-35. [PMID: 21153670 DOI: 10.1007/s00709-010-0223-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 10/12/2010] [Indexed: 05/18/2023]
Abstract
Developing flowers are important sinks in Arabidopsis thaliana. Their energy demand is covered by assimilates which are synthesized in source leaves and transported via the vasculature. Assimilates are unloaded either symplastically through plasmodesmata or apoplastically by specific transport proteins. Here we studied the pathway of phloem unloading and post-phloem transport in developing gynoecia. Using phloem-mobile fluorescent tracers, we show that phloem unloading into cells of ovule primordia followed a symplastic pathway. Subsequently, the same tracers could not move out of phloem cells into mature ovules anymore. A further change in the mode of phloem unloading occurred after anthesis. In open flowers as well as in outgrowing siliques, the phloem was again unloaded via the symplast. This observed onset of symplastic phloem unloading was accompanied by a change in frequency of MP17-GFP-labeled plasmodesmata. We could also show that the change in cell-cell connectivity was independent of fertilization and increasing sink demand. The presented results indicate that symplastic connectivity is highly regulated and varies not only between different sink tissues but also between different developmental stages.
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Affiliation(s)
- Dagmar Werner
- Lehrstuhl Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
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Ali A, Roossinck MJ. Genetic bottlenecks during systemic movement of Cucumber mosaic virus vary in different host plants. Virology 2010; 404:279-83. [PMID: 20542533 DOI: 10.1016/j.virol.2010.05.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 03/25/2010] [Accepted: 05/16/2010] [Indexed: 10/19/2022]
Abstract
Genetic bottlenecks are stochastic events that narrow variation in a population. We compared bottlenecks during the systemic infection of Cucumber mosaic virus (CMV) in four host plants. We mechanically inoculated an artificial population of twelve CMV mutants to young leaves of tomato, pepper, Nicotiana benthamiana, and squash. The inoculated leaves and primary and secondary systemically infected leaves were sampled at 2, 10, and 15 days post-inoculation. All twelve mutants were detected in all of the inoculated leaves. The number of mutants recovered from the systemically infected leaves of all host species was reduced significantly, indicating bottlenecks in systemic movement. The recovery frequencies of a few of the mutants were significantly different in each host probably due to host-specific selective forces. These results have implications for the differences in virus population variation that is seen in different host plants.
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Affiliation(s)
- Akhtar Ali
- Plant Biology Division, The Samuel Roberts Noble Foundation, P.O. Box 2180, Ardmore, OK 73401, USA
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38
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Merchant A, Peuke AD, Keitel C, Macfarlane C, Warren CR, Adams MA. Phloem sap and leaf delta13C, carbohydrates, and amino acid concentrations in Eucalyptus globulus change systematically according to flooding and water deficit treatment. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1785-93. [PMID: 20211969 PMCID: PMC2852667 DOI: 10.1093/jxb/erq045] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 01/28/2010] [Accepted: 02/12/2010] [Indexed: 05/18/2023]
Abstract
Phloem is a central conduit for the distribution of photoassimilate, nutrients, and signals among plant organs. A revised technique was used to collect phloem sap from small woody plants in order to assess changes in composition induced by water deficit and flooding. Bled phloem sap delta(13)C and sugar concentrations were compared to delta(13)C of bulk material, soluble carbon extracts, and the neutral sugar fraction from leaves. Amino acid composition and inorganic ions of the phloem sap was also analysed. Quantitative, systematic changes were detected in phloem sap composition and delta(13)C in response to altered water availability. Phloem sap delta(13)C was more sensitive to changes of water availability than the delta(13)C of bulk leaf, the soluble carbon fraction, and the neutral soluble fraction of leaves. Changes in water availability also resulted in significant changes in phloem sugar (sucrose and raffinose), inorganic nutrient (potassium), and amino acid (phenylalanine) concentrations with important implications for the maintenance of phloem function and biomass partitioning. The differences in carbohydrate and amino acid composition as well as the delta(13)C in the phloem, along with a new model system for phloem research, offer an improved understanding of the phloem-mediated signal, nutrient, and photoassimilate transduction in relation to water availability.
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Affiliation(s)
- Andrew Merchant
- School of Biological, Earth and Environmental Science University of New South Wales, Sydney NSW, Australia 2052.
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Khodorova NV, Miroslavov EA, Shavarda AL, Laberche JC, Boitel-Conti M. Bud development in corydalis (Corydalis bracteata) requires low temperature: a study of developmental and carbohydrate changes. ANNALS OF BOTANY 2010; 105:891-903. [PMID: 20382640 PMCID: PMC2876016 DOI: 10.1093/aob/mcq076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS Spring geophytes require a period of low temperature for proper flower development but the mechanism that underlies the relationship between cold treatment and flowering remains unknown. The present study aims to compare the developmental anatomy and carbohydrate content of the tuberous geophyte Corydalis bracteata growing under natural winter conditions from 10 to -10 degrees C (field-grown) and under a mild temperature regime of 18 degrees C (indoor-grown plants). METHODS Samples were studied under light and electron microscopy. A histochemical test (periodic acid--Schiff's) was employed to identify starch in sectioned material. Sugars were analysed by capillary gas chromatography. Apoplastic wash fluid was prepared. KEY RESULTS Under natural conditions, shoots were elongated, and buds gained in dry mass and developed normally. For indoor-grown plants, these parameters were lower in value and, from December, a progressive necrosis of flower buds was observed. The tuber consisted of the new developing one, which was connected to the bud, and the old tuber with its starch reserve. Due to the absence of plasmodesmata between new and old tuber cells, sugar transport cannot be through the symplast. Thus, a potential apoplastic route is proposed from old tuber phloem parenchyma cells to the adjacent new tuber cells. Sugar content in buds during the autumn months (September-November) was lower for indoor-grown plants than control plants, whereas the sugar content in tubers during the same period was similar for plants from both temperature treatments. However, the amount of apoplastic sugars in tubers of field-grown plants was almost 15-fold higher than in indoor-grown tubers. CONCLUSIONS The results suggest that low temperature activates the apoplastic route of sugar transport in C. bracteata tubers and a consequent carbohydrate delivery to the bud. In the absence of cold treatment, the carbohydrate reserve is locked in old tuber cells so the nutrient supply to the buds is suppressed, possibly leading to bud abortion.
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Affiliation(s)
- Nadejda V. Khodorova
- Laboratory of Anatomy and Morphology
- Laboratory of Phytochemistry, Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street, 2, 197376, St-Petersburg, Russia
| | | | - Alexey L. Shavarda
- Unité de Recherche EA 3900 BioPI ‘Biologie des Plantes et contrôle des Insectes ravageurs’, UFR des Sciences, Ilot des Poulies, Jules Verne University of Picardie, 33 rue St-Leu, 80039, Amiens, France
| | - Jean-Claude Laberche
- Laboratory of Phytochemistry, Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street, 2, 197376, St-Petersburg, Russia
| | - Michèle Boitel-Conti
- Laboratory of Phytochemistry, Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street, 2, 197376, St-Petersburg, Russia
- For correspondence. E-mail
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Dinant S, Bonnemain JL, Girousse C, Kehr J. Phloem sap intricacy and interplay with aphid feeding. C R Biol 2010; 333:504-15. [PMID: 20541162 DOI: 10.1016/j.crvi.2010.03.008] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Aphididae feed upon the plant sieve elements (SE), where they ingest sugars, nitrogen compounds and other nutrients. For ingestion, aphid stylets penetrate SE, and because of the high hydrostatic pressure in SE, phloem sap exudes out into the stylets. Severing stylets to sample phloem exudates (i.e. stylectomy) has been used extensively for the study of phloem contents. Alternative sampling techniques are spontaneous exudation upon wounding that only works in a few plant species, and the popular EDTA-facilitated exudation technique. These approaches have allowed fundamental advances on the understanding of phloem sap composition and sieve tube physiology, which are surveyed in this review. A more complete picture of metabolites, ions, proteins and RNAs present in phloem sap is now available, which has provided large evidence for the phloem role as a signalling network in addition to its primary role in partitioning of photo-assimilates. Thus, phloem sap sampling methods can have remarkable applications to analyse plant nutrition, physiology and defence responses. Since aphid behaviour is suspected to be affected by phloem sap quality, attempts to manipulate phloem sap content were recently undertaken based on deregulation in mutant plants of genes controlling amino acid or sugar content of phloem sap. This opens up new strategies to control aphid settlement on a plant host.
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Affiliation(s)
- Sylvie Dinant
- UMR 1318 INRA-AgroParisTech, institut Jean-Pierre-Bourgin, bâtiment 2, route de Saint-Cyr, Versailles, France.
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Abstract
Mechanisms of phloem loading in the minor veins of leaves are known for only a few species. We propose that there are a limited number of loading strategies for the primary photoassimilates, sucrose and sugar alcohols. These strategies can be predicted based on thermodynamic and anatomical considerations and identified by autoradiography of veins following uptake of (14)C-labeled compounds, analysis of leaf solute composition and concentrations, and plasmodesmatal counting. Experiments on 45 dicotyledonous species identified the predicted loading patterns. Over 50-fold differences in concentrations of sucrose and sugar alcohols in leaves were measured. The cumulative concentrations of transport compounds in leaves correlated with loading mechanisms, a previously unrecognized association. Comparisons of solute concentrations and osmotic potentials of whole leaves suggest that sucrose and sugar alcohols are more concentrated in the cytosol than in the vacuoles of mesophyll cells, thus increasing the driving force for passive loading in species that employ this strategy. Passive loading is more widespread than previously thought, especially in trees. The results indicate that plants have exploited all thermodynamically feasible and structurally compatible loading strategies and that these strategies can be identified with straightforward protocols.
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Park JY, Canam T, Kang KY, Unda F, Mansfield SD. Sucrose phosphate synthase expression influences poplar phenology. TREE PHYSIOLOGY 2009; 29:937-46. [PMID: 19429901 DOI: 10.1093/treephys/tpp028] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The objective of this study was to manipulate the intracellular pools of sucrose, and investigate its role in regulating plant growth, phenology (leaf senescence and bud break) and fibre development. This objective was achieved by differentially expressing an Arabidopsis (Arabidopsis thaliana L. Heynh.) sucrose phosphate synthase (SPS) gene in hybrid poplar (Populus alba L.xPopulus grandidentata Michx.), a model system for tree biology with substantial industrial relevance in the context of short rotation forestry and a target bioenergy crop. Phenotypic differences were evident in the transgenic trees, as both the timing of bud flush and leaf senescence were altered compared to wild-type (WT) trees. Tree height and stem diameter were similar in WT and in the AtSPS transgenic trees, however, there were differences in the length of xylem fibres. Elevated concentrations of intracellular sucrose in both leaf and stem tissue of the transgenic trees are associated with a prolonged onset of senescence and an advancement in bud flush in the following spring. The association among sucrose content, tree phenology and elevated SPS gene expression implicates both enzyme and product in regulating poplar developmental processes.
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Affiliation(s)
- Ji-Young Park
- Department of Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
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Abbes Z, Kharrat M, Delavault P, Chaïbi W, Simier P. Nitrogen and carbon relationships between the parasitic weed Orobanche foetida and susceptible and tolerant faba bean lines. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2009; 47:153-159. [PMID: 19036596 DOI: 10.1016/j.plaphy.2008.10.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 10/15/2008] [Accepted: 10/18/2008] [Indexed: 05/26/2023]
Abstract
The parasitic weed Orobanche foetida (Poiret) is an emergent agronomical problem on faba bean in Tunisia. The Tunisian breeding programs for faba bean resistance to O. foetida have produced several tolerant lines including the line XBJ90.03-16-1-1-1, which limits both parasite attachments to the host roots and growth of the attached parasites. The present study aims to provide a better understanding of the nutritional relationships between the parasite and this tolerant line in comparison with the susceptible Bachaar genotype. Phloem saps of faba bean were harvested using phloem exudation experiments. The major organic compounds potentially transferred from both faba bean genotypes to the parasite were identified as sucrose, raffinose, stachyose, citrate, malate, asparagine (ASN), aspartate (ASP), glutamine, glutamate, serine, alanine and GABA. However, the phloem exudates of the tolerant line were highly deficient in nitrogen when compared to that of the susceptible line. When attached to roots of the tolerant line, the parasite displayed limited activities of soluble invertases in tubercles, and especially in shoots, suggesting that the low performance of the broomrapes attached to the tolerant line resulted from a reduced capacity to utilize the host-derived carbohydrates. On the other hand, the mechanisms involved in the osmotic adjustment and primary metabolism of the parasite did not differ significantly according to the host genotype: mineral cations, especially potassium and calcium, predominated as the major osmotically-active compounds in both tubercles and shoots; shoots accumulated preferentially hexoses as organic solutes although tubercles accumulated preferentially starch and soluble amino acids, especially ASP and ASN. This suggests an important role for a glutamine-dependent asparagine synthetase (EC 6.3.5.4) in the N metabolism of the parasite.
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Affiliation(s)
- Zouhaier Abbes
- Institut National de la Recherche Agronomique de Tunisie (INRAT), Laboratoire des Grandes Cultures, Rue Hédi Karray, 2080 Ariana, Tunisia.
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Turgeon R, Wolf S. Phloem transport: cellular pathways and molecular trafficking. ANNUAL REVIEW OF PLANT BIOLOGY 2009; 60:207-21. [PMID: 19025382 DOI: 10.1146/annurev.arplant.043008.092045] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The phloem transports nutrients, defensive compounds, and informational signals throughout vascular plants. Sampling the complex components of mobile phloem sap is difficult because of the damage incurred when the pressurized sieve tubes are breached. In this review we discuss sampling methods, the artifacts that can be introduced by different sampling procedures, the intricate pathways by which materials enter and exit the phloem, and the major types of compounds transported. Loading and unloading patterns are largely determined by the conductivity and number of plasmodesmata and the position-dependent function of solute-specific, plasma membrane transport proteins. Recent evidence indicates that mobile proteins and RNA are part of the plant's long-distance communication signaling system. Evidence also exists for the directed transport and sorting of macromolecules as they pass through plasmodesmata. A future challenge is to dissect the molecular and cellular aspects of long-distance macromolecular trafficking in the signal transduction pathways of the whole plant.
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Affiliation(s)
- Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA.
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Canam T, Unda F, Mansfield SD. Heterologous expression and functional characterization of two hybrid poplar cell-wall invertases. PLANTA 2008; 228:1011-1019. [PMID: 18704491 DOI: 10.1007/s00425-008-0801-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2008] [Accepted: 07/28/2008] [Indexed: 05/26/2023]
Abstract
The expression of two hybrid poplar cell-wall invertases (EC 3.2.1.26; PaxgINV1 and PaxgINV2) were previously shown to be spatially and temporally regulated in the vegetative tissues. The expression of PaxgINV1 was linked to processes relating to dormancy, while PaxgINV2 expression was prominent in tissues undergoing growth and expansion. In an effort to further elucidate the physiological roles of these key cell wall enzymes, PaxgINV1 and PaxgINV2 were heterologously expressed in the methylotrophic yeast Pichia pastoris. Three-dimensional predictive models of the poplar invertases revealed a structural channel containing both the conserved beta-fructofuranosidase and cell-wall invertase motifs, suggesting that this channel is the putative active site of these enzymes. Recombinant PaxgINV1 and PaxgINV2 had pH optima of 4.8 and 5.6 and temperature optima of 45 and 40 degrees C, respectively. Functional characterization revealed the ability for both enzymes to hydrolyze the fructose residue of sucrose, raffinose, stachyose and verbascose, with PaxgINV2 having higher specific activity for each of the substrates tested. The K(m) values of sucrose/raffinose/stachyose were 1.7/1.8/5.0 mM for PaxgINV1 and 1.6/1.7/1.9 mM for PaxgINV2, respectively. Activity analyses in the presence of various metal cations showed that PaxgINV2 was strongly inhibited by Cu(2+), Zn(2+) and Hg(2+), while PaxgINV1 was only weakly inhibited by these cations. The results from this study, coupled with previous expression data, suggest that PaxgINV1 and PaxgINV2 have distinct roles with respect to the physiology and development of hybrid poplar, specifically phloem unloading and processes related to dormancy and bud break.
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Affiliation(s)
- Thomas Canam
- Department of Wood Science, University of British Columbia, Vancouver, BC, Canada
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Bayer E, Thomas C, Maule A. Symplastic domains in the Arabidopsis shoot apical meristem correlate with PDLP1 expression patterns. PLANT SIGNALING & BEHAVIOR 2008; 3:853-5. [PMID: 19704520 PMCID: PMC2634395 DOI: 10.4161/psb.3.10.6020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 04/01/2008] [Indexed: 05/18/2023]
Abstract
Symplastic domains in plants are defined by spatial limitations on cell-to-cell communication through plasmodesmata (Pds) and establish tissue boundaries necessary for metabolic and developmental programming. With the exception of the physical closure of Pds by callose, the cues and the processes for creating symplastic domains remain poorly understood. Recently, we identified a novel family of eight proteins, called Pd-located protein 1 (PDLP1). These proteins span the plasma membrane within Pds and likely form part of a signal transduction system that perceives external signals to regulate molecular trafficking between cells. For two members of this family that have high expression in the shoot apex we show that they have defined and partially overlapping tissue-specific expression patterns that correlate in part with previously defined symplastic domains. The importance of non-cell-autonomous proteins in shoot development and of the spatial rules that govern leaf and floral development highlight the need to have a clearer understanding of symplastic domains.
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Affiliation(s)
- Emmanuelle Bayer
- John Innes Centre; Norwich Research Park; Colney, Norwich United Kingdom
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Srivastava AC, Ganesan S, Ismail IO, Ayre BG. Functional characterization of the Arabidopsis AtSUC2 Sucrose/H+ symporter by tissue-specific complementation reveals an essential role in phloem loading but not in long-distance transport. PLANT PHYSIOLOGY 2008; 148:200-11. [PMID: 18650401 PMCID: PMC2528097 DOI: 10.1104/pp.108.124776] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2008] [Accepted: 07/17/2008] [Indexed: 05/18/2023]
Abstract
AtSUC2 (At1g22710) encodes a phloem-localized sucrose (Suc)/H(+) symporter necessary for efficient Suc transport from source tissues to sink tissues in Arabidopsis (Arabidopsis thaliana). AtSUC2 is highly expressed in the collection phloem of mature leaves, and its function in phloem loading is well established. AtSUC2, however, is also expressed strongly in the transport phloem, where its role is more ambiguous, and it has been implicated in mediating both efflux and retrieval to and from flanking tissues via the apoplast. To characterize the role of AtSUC2 in controlling carbon partitioning along the phloem path, AtSUC2 cDNA was expressed from tissue-specific promoters in an Atsuc2 mutant background. Suc transport in this mutant is highly compromised, as indicated by stunted growth and the accumulation of large quantities of sugar and starch in vegetative tissues. Expression of AtSUC2 cDNA from the 2-kb AtSUC2 promoter was sufficient to restore growth and carbon partitioning to nearly wild-type levels. The GALACTINOL SYNTHASE promoter of Cucumis melo (CmGAS1p) confers expression only in the minor veins of mature leaves, not in the transport phloem of larger leaf veins and stems. Mutant plants expressing AtSUC2 cDNA from CmGAS1p had intermediate growth and accumulated sugar and starch, but otherwise they had normal morphology. These characteristics support a role for AtSUC2 in retrieval but not efflux along the transport phloem and show that the only vital function of AtSUC2 in photoassimilate distribution is phloem loading. In addition, Atsuc2 mutant plants, although debilitated, do grow, and AtSUC2-independent modes of phloem transport are discussed, including an entirely symplastic pathway from mesophyll cells to sink tissues.
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Affiliation(s)
- Avinash C Srivastava
- Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5220, USA
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Sowiński P, Szczepanik J, Minchin PEH. On the mechanism of C4 photosynthesis intermediate exchange between Kranz mesophyll and bundle sheath cells in grasses. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:1137-1147. [PMID: 18375930 DOI: 10.1093/jxb/ern054] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
C(4) photosynthesis involves cell-to-cell exchange of photosynthetic intermediates between the Kranz mesophyll (KMS) and bundle sheath (BS) cells. This was believed to occur by simple diffusion through plentiful plasmodesmatal (PD) connections between these cell types. The model of C(4) intermediates' transport was elaborated over 30 years ago and was based on experimental data derived from measurements at the time. The model assumed that plasmodesmata occupied about 3% of the interface between the KMS and BS cells and that the plasmodesmata structure did not restrict metabolite movement. Recent advances in the knowledge of plasmodesmatal structure put these assumptions into doubt, so a new model is presented here taking the new anatomical details into account. If one assumes simple diffusion as the sole driving force, then calculations based on the experimental data obtained for C(4) grasses show that the gradients expected of C(4) intermediates between KMS and BS cells are about three orders of magnitude higher than experimentally estimated. In addition, if one takes into account that the plasmodesmata microchannel diameter might constrict the movement of C(4) intermediates of comparable Stokes' radii, the differences in concentration of photosynthetic intermediates between KMS and BS cells should be further increased. We believe that simple diffusion-driven transport of C(4) intermediates between KMS and BS cells through the plasmodesmatal microchannels is not adequate to explain the C(4) metabolite exchange during C(4) photosynthesis. Alternative mechanisms are proposed, involving the participation of desmotubule and/or active mechanisms as either apoplasmic or vesicular transport.
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Affiliation(s)
- Paweł Sowiński
- University of Warsaw, Institute of Plant Experimental Biology, Department of Plant Growth and Development, Miecznikowa 1, 02-096 Warszawa, Poland.
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Voitsekhovskaja OV, Koroleva OA, Batashev DR, Knop C, Tomos AD, Gamalei YV, Heldt HW, Lohaus G. Phloem loading in two Scrophulariaceae species. What can drive symplastic flow via plasmodesmata? PLANT PHYSIOLOGY 2006. [PMID: 16377750 DOI: 10.?1104/?pp.?105.?068312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
To determine the driving forces for symplastic sugar flux between mesophyll and phloem, gradients of sugar concentrations and osmotic pressure were studied in leaf tissues of two Scrophulariaceae species, Alonsoa meridionalis and Asarina barclaiana. A. meridionalis has a typical symplastic configuration of minor-vein phloem, i.e. intermediary companion cells with highly developed plasmodesmal connections to bundle-sheath cells. In A. barclaiana, two types of companion cells, modified intermediary cells and transfer cells, were found in minor-vein phloem, giving this species the potential to have a complex phloem-loading mode. We identified all phloem-transported carbohydrates in both species and analyzed the levels of carbohydrates in chloroplasts, vacuoles, and cytoplasm of mesophyll cells by nonaqueous fractionation. Osmotic pressure was measured in single epidermal and mesophyll cells and in whole leaves and compared with calculated values for phloem sap. In A. meridionalis, a 2-fold concentration gradient for sucrose between mesophyll and phloem was found. In A. barclaiana, the major transported carbohydrates, sucrose and antirrhinoside, were present in the phloem in 22- and 6-fold higher concentrations, respectively, than in the cytoplasm of mesophyll cells. The data show that diffusion of sugars along their concentration gradients is unlikely to be the major mechanism for symplastic phloem loading if this were to occur in these species. We conclude that in both A. meridionalis and A. barclaiana, apoplastic phloem loading is an indispensable mechanism and that symplastic entrance of solutes into the phloem may occur by mass flow. The conditions favoring symplastic mass flow into the phloem are discussed.
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Affiliation(s)
- Olga V Voitsekhovskaja
- Albrecht-von-Haller-Institute for Plant Sciences, Plant Biochemistry, 37077 Goettingen, Germany.
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