151
|
Ladwig F, Stahl M, Ludewig U, Hirner AA, Hammes UZ, Stadler R, Harter K, Koch W. Siliques are Red1 from Arabidopsis acts as a bidirectional amino acid transporter that is crucial for the amino acid homeostasis of siliques. PLANT PHYSIOLOGY 2012; 158:1643-55. [PMID: 22312005 PMCID: PMC3320175 DOI: 10.1104/pp.111.192583] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many membrane proteins are involved in the transport of nutrients in plants. While the import of amino acids into plant cells is, in principle, well understood, their export has been insufficiently described. Here, we present the identification and characterization of the membrane protein Siliques Are Red1 (SIAR1) from Arabidopsis (Arabidopsis thaliana) that is able to translocate amino acids bidirectionally into as well as out of the cell. Analyses in yeast and oocytes suggest a SIAR1-mediated export of amino acids. In Arabidopsis, SIAR1 localizes to the plasma membrane and is expressed in the vascular tissue, in the pericycle, in stamen, and in the chalazal seed coat of ovules and developing seeds. Mutant alleles of SIAR1 accumulate anthocyanins as a symptom of reduced amino acid content in the early stages of silique development. Our data demonstrate that the SIAR1-mediated export of amino acids plays an important role in organic nitrogen allocation and particularly in amino acid homeostasis in developing siliques.
Collapse
Affiliation(s)
- Friederike Ladwig
- Zentrum für Molekularbiologie der Pflanzen, Plant Physiology, D-72076 Tuebingen, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
152
|
Angeles-Núñez JG, Tiessen A. Regulation of AtSUS2 and AtSUS3 by glucose and the transcription factor LEC2 in different tissues and at different stages of Arabidopsis seed development. PLANT MOLECULAR BIOLOGY 2012; 78:377-92. [PMID: 22228409 DOI: 10.1007/s11103-011-9871-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/14/2011] [Indexed: 05/25/2023]
Abstract
Sucrose synthase (SUS) is a key enzyme of carbon metabolism in heterotrophic tissues of plants. The Arabidopsis genome contains six SUS genes. Two members of this family, namely AtSUS2 (At5g49190) and AtSUS3 (At4g02280) are strongly and differentially expressed in Arabidopsis seed. Expression analysis was carried out using SUS:promoter-GUS fusion lines in a wild-type genetic background or in a mutant carrying a lesion in the transcription factor LEAFY COTYLEDON 2 (LEC2; At1g28300). The accumulation patterns of mRNA, protein, and SUS activity were altered in the lec2 mutant during seed development 9-18 days after flowering. This indicates that LEC2 acts epistatically on the expression of AtSUS2 and AtSUS3. It appears that LEC2 is required for cotyledon-specific expression of both SUS genes but it is not responsible for expression in the radicle tip during embryo development. The AtSUS2 promoter was induced in planta by feeding of glucose but less so by sucrose and trehalose. Non-phosphorylable glucose analogs such as 3-O-methyl-glucose and 2-deoxyglucose also caused an induction, suggesting that sugar signaling proceeds by a hexokinase-independent pathway, possibly involving hexose sensing. Analysis of transgenic lines carrying of truncated versions of the AtSUS2:promoter fused to Beta-glucuronidase activity revealed an internal 421 bp region that was responsible for expression in seeds. Bioinformatic sequence analysis revealed regulatory cis-elements putatively responsible for the spatio-temporal pattern of AtSUS2 expression such as the SEF3 (aaccca) and W-box (ttgact) motifs. These findings are discussed in relation to the roles played by AtSUS2, AtSUS3 and LEC2 in the biosynthesis of seed storage products in Arabidopsis.
Collapse
Affiliation(s)
- Juan Gabriel Angeles-Núñez
- Departamento de Ingeniería Genética, CINVESTAV, Unidad Irapuato, Km 9.8 Libramiento Norte, CP 36821 Irapuato, Guanajuato, Mexico
| | | |
Collapse
|
153
|
|
154
|
|
155
|
Wipf D, Loqué D, Lalonde S, Frommer WB. Amino Acid transporter inventory of the selaginella genome. FRONTIERS IN PLANT SCIENCE 2012; 3:36. [PMID: 22639646 PMCID: PMC3355638 DOI: 10.3389/fpls.2012.00036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 02/10/2012] [Indexed: 05/05/2023]
Abstract
Amino acids play fundamental roles in a multitude of functions including protein synthesis, hormone metabolism, nerve transmission, cell growth, production of metabolic energy, nucleobase synthesis, nitrogen metabolism, and urea biosynthesis. Selaginella as a member of the lycophytes is part of an ancient lineage of vascular plants that had arisen ∼400 million years ago. In angiosperms, which have attracted most of the attention for nutrient transport so far, we have been able to identify many of the key transporters for nitrogen. Their role is not always fully clear, thus an analysis of Selaginella as a representative of an ancient vascular plant may help shed light on the evolution and function of these diverse transporters. Here we annotated and analyzed the genes encoding putative transporters involved in cellular uptake of amino acids present in the Selaginella genome.
Collapse
Affiliation(s)
- Daniel Wipf
- UMR INRA 1088, CNRS 5184, Université de Bourgogne Plante-Microbe-EnvironnementDijon, France
- *Correspondence: Daniel Wipf, UMR INRA 1088, CNRS 5184, Université de Bourgogne Plante-Microbe-Environnement, BP 86510, 21065 Dijon Cedex, France. e-mail:
| | | | - Sylvie Lalonde
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
| | - Wolf B. Frommer
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
| |
Collapse
|
156
|
Herschbach C, Gessler A, Rennenberg H. Long-Distance Transport and Plant Internal Cycling of N- and S-Compounds. PROGRESS IN BOTANY 2012. [DOI: 10.1007/978-3-642-22746-2_6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
|
157
|
Ainsworth EA, Yendrek CR, Skoneczka JA, Long SP. Accelerating yield potential in soybean: potential targets for biotechnological improvement. PLANT, CELL & ENVIRONMENT 2012; 35:38-52. [PMID: 21689112 DOI: 10.1111/j.1365-3040.2011.02378.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Soybean (Glycine max Merr.) is the world's most widely grown legume and provides an important source of protein and oil. Global soybean production and yield per hectare increased steadily over the past century with improved agronomy and development of cultivars suited to a wide range of latitudes. In order to meet the needs of a growing world population without unsustainable expansion of the land area devoted to this crop, yield must increase at a faster rate than at present. Here, the historical basis for the yield gains realized in the past 90 years are examined together with potential metabolic targets for achieving further improvements in yield potential. These targets include improving photosynthetic efficiency, optimizing delivery and utilization of carbon, more efficient nitrogen fixation and altering flower initiation and abortion. Optimization of investment in photosynthetic enzymes, bypassing photorespiratory metabolism, engineering the electron transport chain and engineering a faster recovery from the photoprotected state are different strategies to improve photosynthesis in soybean. These potential improvements in photosynthetic carbon gain will need to be matched by increased carbon and nitrogen transport to developing soybean pods and seeds in order to maximize the benefit. Better understanding of control of carbon and nitrogen transport along with improved knowledge of the regulation of flower initiation and abortion will be needed to optimize sink capacity in soybean. Although few single targets are likely to deliver a quantum leap in yields, biotechnological advances in molecular breeding techniques that allow for alteration of the soybean genome and transcriptome promise significant yield gains.
Collapse
Affiliation(s)
- Elizabeth A Ainsworth
- USDA ARS Global Change and Photosynthesis Research Unit, 1201 W. Gregory Drive, Urbana, IL 61801, USA.
| | | | | | | |
Collapse
|
158
|
Lalonde S, Frommer WB. SUT Sucrose and MST Monosaccharide Transporter Inventory of the Selaginella Genome. FRONTIERS IN PLANT SCIENCE 2012; 3:24. [PMID: 22645575 PMCID: PMC3355790 DOI: 10.3389/fpls.2012.00024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 01/20/2012] [Indexed: 05/05/2023]
Abstract
Most metazoa use hexose transporters to acquire hexoses from their diet and as a transport form for distributing carbon and energy within their bodies; insects use trehalose, and plants use sucrose as their major form for translocation. Plant genomes contain at least three families of mono- and disaccharide transporters: monosaccharide/polyol transporters that are evolutionary closely related to the yeast and human glucose transporters, sucrose transporters of the SUT family, which similar to the hexose transporters belong to the major facilitator superfamily, but share only minimal amino acid sequence homology with the hexose transporters, and the family of SWEET sugar transporters conserved between animals and plants. Recently, the genome sequence of the spikemoss Selaginella has been determined. In order to study the evolution of sugar transport in plants, we carefully annotated of the complement of sugar transporters in Selaginella. We review the current knowledge regarding sugar transport in spikemoss and provide phylogenetic analyses of the complement of MST and SUT homologs in Selaginella (and Physcomitrella).
Collapse
Affiliation(s)
- Sylvie Lalonde
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
| | - Wolf B. Frommer
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
- *Correspondence: Wolf B. Frommer, Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA. e-mail:
| |
Collapse
|
159
|
Chen LQ, Qu XQ, Hou BH, Sosso D, Osorio S, Fernie AR, Frommer WB. Sucrose efflux mediated by SWEET proteins as a key step for phloem transport. Science 2011; 335:207-11. [PMID: 22157085 DOI: 10.1126/science.1213351] [Citation(s) in RCA: 773] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Plants transport fixed carbon predominantly as sucrose, which is produced in mesophyll cells and imported into phloem cells for translocation throughout the plant. It is not known how sucrose migrates from sites of synthesis in the mesophyll to the phloem, or which cells mediate efflux into the apoplasm as a prerequisite for phloem loading by the SUT sucrose-H(+) (proton) cotransporters. Using optical sucrose sensors, we identified a subfamily of SWEET sucrose efflux transporters. AtSWEET11 and 12 localize to the plasma membrane of the phloem. Mutant plants carrying insertions in AtSWEET11 and 12 are defective in phloem loading, thus revealing a two-step mechanism of SWEET-mediated export from parenchyma cells feeding H(+)-coupled import into the sieve element-companion cell complex. We discuss how restriction of intercellular transport to the interface of adjacent phloem cells may be an effective mechanism to limit the availability of photosynthetic carbon in the leaf apoplasm in order to prevent pathogen infections.
Collapse
Affiliation(s)
- Li-Qing Chen
- Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA
| | | | | | | | | | | | | |
Collapse
|
160
|
Melkus G, Rolletschek H, Fuchs J, Radchuk V, Grafahrend-Belau E, Sreenivasulu N, Rutten T, Weier D, Heinzel N, Schreiber F, Altmann T, Jakob PM, Borisjuk L. Dynamic ¹³C/¹ H NMR imaging uncovers sugar allocation in the living seed. PLANT BIOTECHNOLOGY JOURNAL 2011; 9:1022-37. [PMID: 21535356 DOI: 10.1111/j.1467-7652.2011.00618.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Seed growth and accumulation of storage products relies on the delivery of sucrose from the maternal to the filial tissues. The transport route is hidden inside the seed and has never been visualized in vivo. Our approach, based on high-field nuclear magnetic resonance and a custom made (13)C/(1) H double resonant coil, allows the non-invasive imaging and monitoring of sucrose allocation within the seed. The new technique visualizes the main stream of sucrose and determines its velocity during the grain filling in barley (Hordeum vulgare L.). Quantifiable dynamic images are provided, which allow observing movement of (13)C-sucrose at a sub-millimetre level of resolution. The analysis of genetically modified barley grains (Jekyll transgenic lines, seg8 and Risø13 mutants) demonstrated that sucrose release via the nucellar projection towards the endosperm provides an essential mean for the control of seed growth by maternal organism. The sucrose allocation was further determined by structural and metabolic features of endosperm. Sucrose monitoring was integrated with an in silico flux balance analysis, representing a powerful platform for non-invasive study of seed filling in crops.
Collapse
Affiliation(s)
- Gerd Melkus
- Institute of Experimental Physics, University of Würzburg, Am Hubland, Würzburg, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
161
|
Yamada K, Kanai M, Osakabe Y, Ohiraki H, Shinozaki K, Yamaguchi-Shinozaki K. Monosaccharide absorption activity of Arabidopsis roots depends on expression profiles of transporter genes under high salinity conditions. J Biol Chem 2011; 286:43577-86. [PMID: 22041897 DOI: 10.1074/jbc.m111.269712] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plant roots are able to absorb sugars from the rhizosphere but also release sugars and other metabolites that are critical for growth and environmental signaling. Reabsorption of released sugar molecules could help reduce the loss of photosynthetically fixed carbon through the roots. Although biochemical analyses have revealed monosaccharide uptake mechanisms in roots, the transporters that are involved in this process have not yet been fully characterized. In the present study we demonstrate that Arabidopsis STP1 and STP13 play important roles in roots during the absorption of monosaccharides from the rhizosphere. Among 14 STP transporter genes, we found that STP1 had the highest transcript level and that STP1 was a major contributor for monosaccharide uptake under normal conditions. In contrast, STP13 was found to be induced by abiotic stress, with low expression under normal conditions. We analyzed the role of STP13 in roots under high salinity conditions where membranes of the epidermal cells were damaged, and we detected an increase in the amount of STP13-dependent glucose uptake. Furthermore, the amount of glucose efflux from stp13 mutants was higher than that from wild type plants under high salinity conditions. These results indicate that STP13 can reabsorb the monosaccharides that are released by damaged cells under high salinity conditions. Overall, our data indicate that sugar uptake capacity in Arabidopsis roots changes in response to environmental stresses and that this activity is dependent on the expression pattern of sugar transporters.
Collapse
Affiliation(s)
- Kohji Yamada
- Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | | | | | | | | | | |
Collapse
|
162
|
Eom JS, Cho JI, Reinders A, Lee SW, Yoo Y, Tuan PQ, Choi SB, Bang G, Park YI, Cho MH, Bhoo SH, An G, Hahn TR, Ward JM, Jeon JS. Impaired function of the tonoplast-localized sucrose transporter in rice, OsSUT2, limits the transport of vacuolar reserve sucrose and affects plant growth. PLANT PHYSIOLOGY 2011; 157:109-19. [PMID: 21771914 PMCID: PMC3165862 DOI: 10.1104/pp.111.176982] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Accepted: 07/18/2011] [Indexed: 05/18/2023]
Abstract
Physiological functions of sucrose (Suc) transporters (SUTs) localized to the tonoplast in higher plants are poorly understood. We here report the isolation and characterization of a mutation in the rice (Oryza sativa) OsSUT2 gene. Expression of OsSUT2-green fluorescent protein in rice revealed that OsSUT2 localizes to the tonoplast. Analysis of the OsSUT2 promoter::β-glucuronidase transgenic rice indicated that this gene is highly expressed in leaf mesophyll cells, emerging lateral roots, pedicels of fertilized spikelets, and cross cell layers of seed coats. Results of Suc transport assays in yeast were consistent with a H(+)-Suc symport mechanism, suggesting that OsSUT2 functions in Suc uptake from the vacuole. The ossut2 mutant exhibited a growth retardation phenotype with a significant reduction in tiller number, plant height, 1,000-grain weight, and root dry weight compared with the controls, the wild type, and complemented transgenic lines. Analysis of primary carbon metabolites revealed that ossut2 accumulated more Suc, glucose, and fructose in the leaves than the controls. Further sugar export analysis of detached leaves indicated that ossut2 had a significantly decreased sugar export ability compared with the controls. These results suggest that OsSUT2 is involved in Suc transport across the tonoplast from the vacuole lumen to the cytosol in rice, playing an essential role in sugar export from the source leaves to sink organs.
Collapse
|
163
|
Chen T, Ye R, Fan X, Li X, Lin Y. Identification of C4 photosynthesis metabolism and regulatory-associated genes in Eleocharis vivipara by SSH. PHOTOSYNTHESIS RESEARCH 2011; 108:157-170. [PMID: 21739352 DOI: 10.1007/s11120-011-9668-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Accepted: 06/27/2011] [Indexed: 05/31/2023]
Abstract
This is the first effort to investigate the candidate genes involved in kranz developmental regulation and C(4) metabolic fluxes in Eleocharis vivipara, which is a leafless freshwater amphibious plant and possesses a distinct culms anatomy structure and photosynthetic pattern in contrasting environments. A terrestrial specific SSH library was constructed to investigate the genes involved in kranz anatomy developmental regulation and C(4) metabolic fluxes. A total of 73 ESTs and 56 unigenes in 384 clones were identified by array hybridization and sequencing. In total, 50 unigenes had homologous genes in the databases of rice and Arabidopsis. The real-time quantitative PCR results showed that most of the genes were accumulated in terrestrial culms and ABA-induced culms. The C(4) marker genes were stably accumulated during the culms development process in terrestrial culms. With respect to C(3) culms, C(4) photosynthesis metabolism consumed much more transporters and translocators related to ion metabolism, organic acids and carbohydrate metabolism, phosphate metabolism, amino acids metabolism, and lipids metabolism. Additionally, ten regulatory genes including five transcription factors, four receptor-like proteins, and one BURP protein were identified. These regulatory genes, which co-accumulated with the culms developmental stages, may play important roles in culms structure developmental regulation, bundle sheath chloroplast maturation, and environmental response. These results shed new light on the C(4) metabolic fluxes, environmental response, and anatomy structure developmental regulation in E. vivipara.
Collapse
Affiliation(s)
- Taiyu Chen
- National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | | | | | | | | |
Collapse
|
164
|
Sun A, Dai Y, Zhang X, Li C, Meng K, Xu H, Wei X, Xiao G, Ouwerkerk PBF, Wang M, Zhu Z. A transgenic study on affecting potato tuber yield by expressing the rice sucrose transporter genes OsSUT5Z and OsSUT2M. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2011; 53:586-595. [PMID: 21676173 DOI: 10.1111/j.1744-7909.2011.01063.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In many plants, sucrose transporters are essential for both sucrose exports from sources and imports into sinks, indicating a function in assimilate partitioning. To investigate whether sucrose transporters can improve the yield of starch plant, potato plants (Solanum tuberosum L. cv. Désirée) were transformed with cDNAs of the rice sucrose transporter genes OsSUT5Z and OsSUT2M under the control of a tuber-specific, class-I patatin promoter. Compared to the controls, the average fructose content of OsSUT5Z transgenic tubers significantly increased. However, the content of the sugars and starch in the OsSUT2M transgenic potato tubers showed no obvious difference. Correspondingly, the average tuber yield, average number of tubers per plant and average weight of single tuber showed no significant difference in OsSUT2M transgenic tubers with controls. In the OsSUT5Z transgenic lines, the average tuber yield per plant was 1.9-fold higher than the controls, and the average number of tubers per plant increased by more than 10 tubers on average, whereas the average weight of a single tuber did not increase significantly. These results suggested that the average number of tubers per plant showed more contribution than the average weight of a single tuber to the tuber yield per plant.
Collapse
Affiliation(s)
- Aijun Sun
- National Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
165
|
Ayre BG. Membrane-transport systems for sucrose in relation to whole-plant carbon partitioning. MOLECULAR PLANT 2011; 4:377-94. [PMID: 21502663 DOI: 10.1093/mp/ssr014] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition and contribute to plant vigor by controlling source/sink relationships and biomass partitioning. Sucrose is synthesized in the cytoplasm and may move cell to cell through plasmodesmata or may cross membranes to be compartmentalized or exported to the apoplasm for uptake into adjacent cells. As a relatively large polar compound, sucrose requires proteins to facilitate efficient membrane transport. Transport across the tonoplast by facilitated diffusion, antiport with protons, and symport with protons have been proposed; for transport across plasma membranes, symport with protons and a mechanism resembling facilitated diffusion are evident. Despite decades of research, only symport with protons is well established at the molecular level. This review aims to integrate recent and older studies on sucrose flux across membranes with principles of whole-plant carbon partitioning.
Collapse
Affiliation(s)
- Brian G Ayre
- University of North Texas, Department of Biological Sciences, Denton, Texas, USA.
| |
Collapse
|
166
|
Okumoto S, Pilot G. Amino acid export in plants: a missing link in nitrogen cycling. MOLECULAR PLANT 2011; 4:453-63. [PMID: 21324969 PMCID: PMC3143828 DOI: 10.1093/mp/ssr003] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 12/24/2010] [Indexed: 05/17/2023]
Abstract
The export of nutrients from source organs to parts of the body where they are required (e.g. sink organs) is a fundamental biological process. Export of amino acids, one of the most abundant nitrogen species in plant long-distance transport tissues (i.e. xylem and phloem), is an essential process for the proper distribution of nitrogen in the plant. Physiological studies have detected the presence of multiple amino acid export systems in plant cell membranes. Yet, surprisingly little is known about the molecular identity of amino acid exporters, partially due to the technical difficulties hampering the identification of exporter proteins. In this short review, we will summarize our current knowledge about amino acid export systems in plants. Several studies have described plant amino acid transporters capable of bi-directional, facilitative transport, reminiscent of activities identified by earlier physiological studies. Moreover, recent expansion in the number of available amino acid transporter sequences have revealed evolutionary relationships between amino acid exporters from other organisms with a number of uncharacterized plant proteins, some of which might also function as amino acid exporters. In addition, genes that may regulate export of amino acids have been discovered. Studies of these putative transporter and regulator proteins may help in understanding the elusive molecular mechanisms of amino acid export in plants.
Collapse
Affiliation(s)
- Sakiko Okumoto
- 549 Latham Hall, Virginia Tech, Blacksburg, VA 24061, USA.
| | | |
Collapse
|
167
|
Functional Classification of Plant Plasma Membrane Transporters. THE PLANT PLASMA MEMBRANE 2011. [DOI: 10.1007/978-3-642-13431-9_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
168
|
Palmgren MG, Bækgaard L, López-Marqués RL, Fuglsang AT. Plasma Membrane ATPases. THE PLANT PLASMA MEMBRANE 2011. [DOI: 10.1007/978-3-642-13431-9_7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
169
|
|
170
|
Sugar transporters for intercellular exchange and nutrition of pathogens. Nature 2010; 468:527-32. [PMID: 21107422 DOI: 10.1038/nature09606] [Citation(s) in RCA: 930] [Impact Index Per Article: 66.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 10/19/2010] [Indexed: 02/07/2023]
Abstract
Sugar efflux transporters are essential for the maintenance of animal blood glucose levels, plant nectar production, and plant seed and pollen development. Despite broad biological importance, the identity of sugar efflux transporters has remained elusive. Using optical glucose sensors, we identified a new class of sugar transporters, named SWEETs, and show that at least six out of seventeen Arabidopsis, two out of over twenty rice and two out of seven homologues in Caenorhabditis elegans, and the single copy human protein, mediate glucose transport. Arabidopsis SWEET8 is essential for pollen viability, and the rice homologues SWEET11 and SWEET14 are specifically exploited by bacterial pathogens for virulence by means of direct binding of a bacterial effector to the SWEET promoter. Bacterial symbionts and fungal and bacterial pathogens induce the expression of different SWEET genes, indicating that the sugar efflux function of SWEET transporters is probably targeted by pathogens and symbionts for nutritional gain. The metazoan homologues may be involved in sugar efflux from intestinal, liver, epididymis and mammary cells.
Collapse
|
171
|
Dusotoit-Coucaud A, Kongsawadworakul P, Maurousset L, Viboonjun U, Brunel N, Pujade-Renaud V, Chrestin H, Sakr S. Ethylene stimulation of latex yield depends on the expression of a sucrose transporter (HbSUT1B) in rubber tree (Hevea brasiliensis). TREE PHYSIOLOGY 2010; 30:1586-1598. [PMID: 20980289 DOI: 10.1093/treephys/tpq088] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Hevea brasiliensis is an important industrial crop for natural rubber production. Latex biosynthesis occurs in the cytoplasm of highly specialized latex cells and requires sucrose as the unique precursor. Ethylene stimulation of latex production results in high sugar flow from the surrounding cells of inner bark towards the latex cells. The aim of this work was to understand the role of seven sucrose transporters (HbSUTs) and one hexose transporter (HbHXT1) in this process. Two Hevea clones were used: PB217 and PB260, respectively described as high and low yielding clones. The expression pattern of these sugar transporters (HbSUTs and HbHXT1) was monitored under different physiological conditions and found to be maximal in latex cells. HbSUT1, one of the most abundant isoforms, displayed the greatest response to ethylene treatment. In clone PB217, ethylene treatment led to a higher accumulation of HbSUT1B in latex cells than in the inner bark tissues. Conversely, stronger expression of HbSUT1B was observed in inner bark tissues than in latex cells of PB260. A positive correlation with HbSUT1B transcript accumulation and increased latex production was further supported by its lower expression in latex cells of the virgin clone PB217.
Collapse
|
172
|
Jeong SW, Das PK, Jeoung SC, Song JY, Lee HK, Kim YK, Kim WJ, Park YI, Yoo SD, Choi SB, Choi G, Park YI. Ethylene suppression of sugar-induced anthocyanin pigmentation in Arabidopsis. PLANT PHYSIOLOGY 2010; 154:1514-31. [PMID: 20876338 PMCID: PMC2971625 DOI: 10.1104/pp.110.161869] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Accepted: 09/25/2010] [Indexed: 05/18/2023]
Abstract
Anthocyanin accumulation is regulated negatively by ethylene signaling and positively by sugar and light signaling. However, the antagonistic interactions underlying these signalings remain to be elucidated fully. We show that ethylene inhibits anthocyanin accumulation induced by sucrose (Suc) and light by suppressing the expression of transcription factors that positively regulate anthocyanin biosynthesis, including GLABRA3, TRANSPARENT TESTA8, and PRODUCTION OF ANTHOCYANIN PIGMENT1, while stimulating the concomitant expression of the negative R3-MYB regulator MYBL2. Genetic analyses show that the ethylene-mediated suppression of anthocyanin accumulation is dependent upon ethylene signaling components responsible for the triple response. Furthermore, these positive and negative signaling pathways appear to be under photosynthetic control. Suc and light induction of anthocyanin accumulation was almost fully inhibited in wild-type Arabidopsis (Arabidopsis thaliana) ecotype Columbia and ethylene (ethylene response1 [etr1-1]) and light (long hypocotyl1 [hy1], cryptochrome1/2, and hy5) signaling mutants treated with the photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The transcript level of the sugar transporter gene SUC1 was enhanced in ecotype Columbia treated with the ethylene-binding inhibitor silver and in etr1-1, ethylene insensitive2 (ein2-1), and ein3 ein3-like1 mutants. In contrast, 3-(3,4-dichlorophenyl)-1,1-dimethylurea treatment reduced SUC1 expression, which indicates strongly that SUC1 represents an integrator for signals provided by sugar, light, and ethylene. SUC1 mutations lowered accumulations of anthocyanin pigment, soluble sugar content, and ethylene production in response to Suc and light signals. These data demonstrate that the suppression of SUC1 expression by ethylene inhibits Suc-induced anthocyanin accumulation in the presence of light and, hence, fine-tunes anthocyanin homeostasis.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Youn-Il Park
- Department of Biological Science and Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 305–764, Korea (S.-W.J., P.K.D., J.-Y.S., H.K.L., Y.-I.P.); Division of Advanced Technology, Korea Research Institute of Standards and Science, Daejeon 305–340, Korea (S.-W.J., S.C.J.); GreenGene Biotech (Y.-K.K.) and Division of Bioscience and Bioinformatics (S.-B.C.), Myongji University, Yongin 449–728, Korea; Division of Biotechnology, Catholic University, Bucheon 420–743, Korea (W.J.K., Y.I.P.); Department of Biological Science, Sungkyunkwan University, Suwon 440–764, Korea (S.-D.Y.); Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305–701, Korea (G.C.)
| |
Collapse
|
173
|
Zhang L, Tan Q, Lee R, Trethewy A, Lee YH, Tegeder M. Altered xylem-phloem transfer of amino acids affects metabolism and leads to increased seed yield and oil content in Arabidopsis. THE PLANT CELL 2010; 22:3603-20. [PMID: 21075769 PMCID: PMC3015121 DOI: 10.1105/tpc.110.073833] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2010] [Revised: 10/20/2010] [Accepted: 10/29/2010] [Indexed: 05/17/2023]
Abstract
Seed development and nitrogen (N) storage depend on delivery of amino acids to seed sinks. For efficient translocation to seeds, amino acids are loaded into the phloem in source leaves and along the long distance transport pathway through xylem-phloem transfer. We demonstrate that Arabidopsis thaliana AMINO ACID PERMEASE2 (AAP2) localizes to the phloem throughout the plant. AAP2 T-DNA insertion lines showed changes in source-sink translocation of amino acids and a decrease in the amount of seed total N and storage proteins, supporting AAP2 function in phloem loading and amino acid distribution to the embryo. Interestingly, in aap2 seeds, total carbon (C) levels were unchanged, while fatty acid levels were elevated. Moreover, branch and silique numbers per plant and seed yield were strongly increased. This suggests changes in N and C delivery to sinks and subsequent modulations of sink development and seed metabolism. This is supported by tracer experiments, expression studies of genes of N/C transport and metabolism in source and sink, and by phenotypic and metabolite analyses of aap2 plants. Thus, AAP2 is key for xylem to phloem transfer and sink N and C supply; moreover, modifications of N allocation can positively affect C assimilation and source-sink transport and benefit sink development and oil yield.
Collapse
Affiliation(s)
| | | | | | | | | | - Mechthild Tegeder
- School of Biological Sciences, Center for Reproductive Biology, Washington State University, Pullman, Washington 99164-4236
| |
Collapse
|
174
|
Majeran W, Friso G, Ponnala L, Connolly B, Huang M, Reidel E, Zhang C, Asakura Y, Bhuiyan NH, Sun Q, Turgeon R, van Wijk KJ. Structural and metabolic transitions of C4 leaf development and differentiation defined by microscopy and quantitative proteomics in maize. THE PLANT CELL 2010; 22:3509-42. [PMID: 21081695 PMCID: PMC3015116 DOI: 10.1105/tpc.110.079764] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 10/22/2010] [Accepted: 10/29/2010] [Indexed: 05/17/2023]
Abstract
C(4) grasses, such as maize (Zea mays), have high photosynthetic efficiency through combined biochemical and structural adaptations. C(4) photosynthesis is established along the developmental axis of the leaf blade, leading from an undifferentiated leaf base just above the ligule into highly specialized mesophyll cells (MCs) and bundle sheath cells (BSCs) at the tip. To resolve the kinetics of maize leaf development and C(4) differentiation and to obtain a systems-level understanding of maize leaf formation, the accumulation profiles of proteomes of the leaf and the isolated BSCs with their vascular bundle along the developmental gradient were determined using large-scale mass spectrometry. This was complemented by extensive qualitative and quantitative microscopy analysis of structural features (e.g., Kranz anatomy, plasmodesmata, cell wall, and organelles). More than 4300 proteins were identified and functionally annotated. Developmental protein accumulation profiles and hierarchical cluster analysis then determined the kinetics of organelle biogenesis, formation of cellular structures, metabolism, and coexpression patterns. Two main expression clusters were observed, each divided in subclusters, suggesting that a limited number of developmental regulatory networks organize concerted protein accumulation along the leaf gradient. The coexpression with BSC and MC markers provided strong candidates for further analysis of C(4) specialization, in particular transporters and biogenesis factors. Based on the integrated information, we describe five developmental transitions that provide a conceptual and practical template for further analysis. An online protein expression viewer is provided through the Plant Proteome Database.
Collapse
Affiliation(s)
- Wojciech Majeran
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Giulia Friso
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Lalit Ponnala
- Computational Biology Service Unit, Cornell University, Ithaca, New York 14853
| | - Brian Connolly
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Mingshu Huang
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Edwin Reidel
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Cankui Zhang
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Yukari Asakura
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Nazmul H. Bhuiyan
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Qi Sun
- Computational Biology Service Unit, Cornell University, Ithaca, New York 14853
| | - Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| | - Klaas J. van Wijk
- Department of Plant Biology, Cornell University, Ithaca, New York 14853
| |
Collapse
|
175
|
Wingenter K, Schulz A, Wormit A, Wic S, Trentmann O, Hoermiller II, Heyer AG, Marten I, Hedrich R, Neuhaus HE. Increased activity of the vacuolar monosaccharide transporter TMT1 alters cellular sugar partitioning, sugar signaling, and seed yield in Arabidopsis. PLANT PHYSIOLOGY 2010; 154:665-77. [PMID: 20709831 PMCID: PMC2949046 DOI: 10.1104/pp.110.162040] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 08/10/2010] [Indexed: 05/18/2023]
Abstract
The extent to which vacuolar sugar transport activity affects molecular, cellular, and developmental processes in Arabidopsis (Arabidopsis thaliana) is unknown. Electrophysiological analysis revealed that overexpression of the tonoplast monosaccharide transporter TMT1 in a tmt1-2::tDNA mutant led to increased proton-coupled monosaccharide import into isolated mesophyll vacuoles in comparison with wild-type vacuoles. TMT1 overexpressor mutants grew faster than wild-type plants on soil and in high-glucose (Glc)-containing liquid medium. These effects were correlated with increased vacuolar monosaccharide compartmentation, as revealed by nonaqueous fractionation and by chlorophyll(ab)-binding protein1 and nitrate reductase1 gene expression studies. Soil-grown TMT1 overexpressor plants respired less Glc than wild-type plants and only about half the amount of Glc respired by tmt1-2::tDNA mutants. In sum, these data show that TMT activity in wild-type plants limits vacuolar monosaccharide loading. Remarkably, TMT1 overexpressor mutants produced larger seeds and greater total seed yield, which was associated with increased lipid and protein content. These changes in seed properties were correlated with slightly decreased nocturnal CO(2) release and increased sugar export rates from detached source leaves. The SUC2 gene, which codes for a sucrose transporter that may be critical for phloem loading in leaves, has been identified as Glc repressed. Thus, the observation that SUC2 mRNA increased slightly in TMT1 overexpressor leaves, characterized by lowered cytosolic Glc levels than wild-type leaves, provided further evidence of a stimulated source capacity. In summary, increased TMT activity in Arabidopsis induced modified subcellular sugar compartmentation, altered cellular sugar sensing, affected assimilate allocation, increased the biomass of Arabidopsis seeds, and accelerated early plant development.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | - H. Ekkehard Neuhaus
- Pflanzenphysiologie, Technische Universität Kaiserslautern, D–67653 Kaiserslautern, Germany (K.W., A.W., S.W., O.T., H.E.N.); Botanik, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Institut, Julius-Maximilians-Universität Würzburg, D–97082 Wuerzburg, Germany (A.S., I.M., R.H.); Botanik, Institut für Biologie, Universität Stuttgart, D–70569 Stuttgart, Germany (I.I.H., A.G.H.)
| |
Collapse
|
176
|
Angeles-Núñez JG, Tiessen A. Arabidopsis sucrose synthase 2 and 3 modulate metabolic homeostasis and direct carbon towards starch synthesis in developing seeds. PLANTA 2010; 232:701-18. [PMID: 20559653 DOI: 10.1007/s00425-010-1207-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 06/01/2010] [Indexed: 05/20/2023]
Abstract
Two genes encoding sucrose synthase (SUS), namely SUS2 (At5g49190) and SUS3 (At4g02280), are strongly and differentially expressed in Arabidopsis seed. Detailed biochemical analysis was carried out in developing seeds 9-21 days after flowering (DAF) of wild type and two knockouts. SUS2 and SUS3 are not redundant genes since single knockouts show a phenotype in developing seeds. The mutants had 30-50% less SUS activity and therefore accumulated 40% more sucrose and 50% less fructose at 15 DAF. This did not affect the hexose-P pool, but led to 30-70% less starch in embryo and seed coat. Lipids were 55% higher in both mutants at 9-15 DAF. It seems that sucrolysis via SUS is not required for oil or protein synthesis but rather for channeling carbon toward ADP-glucose and starch in seeds. Metabolite profiling with GC-TOF revealed specific downstream changes in primary metabolism as a consequence of signaling or regulatory fine-tuning. While sucrose increased, hexoses and specific amino acids decreased reciprocally. There was a developmental shift regarding an earlier timing of dry weight accumulation, germinative maturity, oil deposition, sugar levels, transient starch buildup, and protein storage. Nevertheless, final seed size and composition were unaltered due to an earlier cessation of growth, thus giving rise to an apparent silent phenotype of mature mutant seeds. We conclude that SUS is important for metabolite homeostasis and timing of seed development, and propose that an altered sucrose/hexose ratio can modify carbon partitioning and the pattern of storage compounds in Arabidopsis.
Collapse
|
177
|
Coll A, Nadal A, Collado R, Capellades G, Kubista M, Messeguer J, Pla M. Natural variation explains most transcriptomic changes among maize plants of MON810 and comparable non-GM varieties subjected to two N-fertilization farming practices. PLANT MOLECULAR BIOLOGY 2010; 73:349-62. [PMID: 20349115 DOI: 10.1007/s11103-010-9624-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 03/07/2010] [Indexed: 05/12/2023]
Abstract
The introduction of genetically modified organisms (GMO) in many countries follows strict regulations to ensure that only safety-tested products are marketed. Over the last few years, targeted approaches have been complemented by profiling methods to assess possible unintended effects of transformation. Here we used a commercial (Affymertix) microarray platform (i.e. allowing assessing the expression of approximately 1/3 of the genes of maize) to evaluate transcriptional differences between commercial MON810 GM maize and non-transgenic crops in real agricultural conditions, in a region where about 70% of the maize grown was MON810. To consider natural variation in gene expression in relation to biotech plants we took two common MON810/non-GM variety pairs as examples, and two farming practices (conventional and low-nitrogen fertilization). MON810 and comparable non-GM varieties grown in the field have very low numbers of sequences with differential expression, and their identity differs among varieties. Furthermore, we show that the differences between a given MON810 variety and the non-GM counterpart do not appear to depend to any major extent on the assayed cultural conditions, even though these differences may slightly vary between the conditions. In our study, natural variation explained most of the variability in gene expression among the samples. Up to 37.4% was dependent upon the variety (obtained by conventional breeding) and 31.9% a result of the fertilization treatment. In contrast, the MON810 GM character had a very minor effect (9.7%) on gene expression in the analyzed varieties and conditions, even though similar cryIA(b) expression levels were detected in the two MON810 varieties and nitrogen treatments. This indicates that transcriptional differences of conventionally-bred varieties and under different environmental conditions should be taken into account in safety assessment studies of GM plants.
Collapse
Affiliation(s)
- Anna Coll
- Institut de Tecnologia Agroalimentària (INTEA), Universitat de Girona, Campus Montilivi, EPS-I, Girona, Spain
| | | | | | | | | | | | | |
Collapse
|
178
|
Slewinski TL, Garg A, Johal GS, Braun DM. Maize SUT1 functions in phloem loading. PLANT SIGNALING & BEHAVIOR 2010; 5:687-90. [PMID: 20404497 PMCID: PMC3001560 DOI: 10.4161/psb.5.6.11575] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 02/16/2010] [Indexed: 05/18/2023]
Abstract
The functions of dicot sucrose transporters (SUTs) in apoplastic phloem loading of sucrose are well established; however, whether SUTs similarly function in monocots was unresolved. To address this question, we recently provided genetic evidence that ZmSUT1 from maize (Zea mays) is required for efficient phloem loading. sut1-m1 mutant plants hyperaccumulate carbohydrates in leaves, are defective in loading sucrose into the phloem, and have altered biomass partitioning. Presumably due to the hyperaccumulation of soluble sugars in leaves, mutations in ZmSUT1 lead to downregulation of chlorophyll accumulation, photosynthesis and stomatal conductance. However, because we had identified only a single mutant allele, we were not able to exclude the possibility that the mutant phenotypes were instead caused by a closely linked mutation. Based on a novel aspect of the sut1 mutant phenotype, secretion of a concentrated sugar solution from leaf hydathodes, we identified an additional mutant allele, sut1-m4. This confirms that the mutation of SUT1 is responsible for the impairment in phloem loading. In addition, the sut1-m4 mutant does not accumulate transcripts, supporting the findings reported previously that the original mutant allele is also a null mutation. Collectively, these data demonstrate that ZmSUT1 functions to phloem load sucrose in maize leaves.
Collapse
Affiliation(s)
- Thomas L Slewinski
- Department of Biology, Pennsylvania State University, University Park, PA, USA
| | | | | | | |
Collapse
|
179
|
Slewinski TL, Braun DM. The psychedelic genes of maize redundantly promote carbohydrate export from leaves. Genetics 2010; 185:221-32. [PMID: 20142436 PMCID: PMC2870957 DOI: 10.1534/genetics.109.113357] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Accepted: 02/06/2010] [Indexed: 11/18/2022] Open
Abstract
Whole-plant carbohydrate partitioning involves the assimilation of carbon in leaves and its translocation to nonphotosynthetic tissues. This process is fundamental to plant growth and development, but its regulation is poorly understood. To identify genes controlling carbohydrate partitioning, we isolated mutants that are defective in exporting fixed carbon from leaves. Here we describe psychedelic (psc), a new mutant of maize (Zea mays) that is perturbed in carbohydrate partitioning. psc mutants exhibit stable, discrete chlorotic and green regions within their leaves. psc chlorotic tissues hyperaccumulate starch and soluble sugars, while psc green tissues appear comparable to wild-type leaves. The psc chlorotic and green tissue boundaries are usually delineated by larger veins, suggesting that translocation of a mobile compound through the veins may influence the tissue phenotype. psc mutants display altered biomass partitioning, which is consistent with reduced carbohydrate export from leaves to developing tissues. We determined that the psc mutation is unlinked to previously characterized maize leaf carbohydrate hyperaccumulation mutants. Additionally, we found that the psc mutant phenotype is inherited as a recessive, duplicate-factor trait in some inbred lines. Genetic analyses with other maize mutants with variegated leaves and impaired carbohydrate partitioning suggest that Psc defines an independent pathway. Therefore, investigations into the psc mutation have uncovered two previously unknown genes that redundantly function to regulate carbohydrate partitioning in maize.
Collapse
Affiliation(s)
| | - David M. Braun
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802
| |
Collapse
|
180
|
Cho JI, Burla B, Lee DW, Ryoo N, Hong SK, Kim HB, Eom JS, Choi SB, Cho MH, Bhoo SH, Hahn TR, Neuhaus HE, Martinoia E, Jeon JS. Expression analysis and functional characterization of the monosaccharide transporters, OsTMTs, involving vacuolar sugar transport in rice (Oryza sativa). THE NEW PHYTOLOGIST 2010; 186:657-68. [PMID: 20202129 DOI: 10.1111/j.1469-8137.2010.03194.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In Arabidopsis, the compartmentation of sugars into vacuoles is known to be facilitated by sugar transporters. However, vacuolar sugar transporters have not been studied in detail in other plant species. To characterize the rice (Oryza sativa) tonoplast monosaccharide transporters, OsTMT1 and OsTMT2, we analysed their subcellular localization using green fluorescent protein (GFP) and expression patterns using reverse-transcription polymerase chain reaction (RT-PCR), performed histochemical beta-glucuronidase (GUS) assay and in situ hybridization analysis, and assessed sugar transport ability using isolated vacuoles. Expression of OsTMT-GFP fusion protein in rice and Arabidopsis revealed that the OsTMTs localize at the tonoplast. Analyses of OsTMT promoter-GUS transgenic rice indicated that OsTMT1 and OsTMT2 are highly expressed in bundle sheath cells, and in vascular parenchyma and companion cells in leaves, respectively. Both genes were found to be preferentially expressed in the vascular tissues of roots, the palea/lemma of spikelets, and in the main vascular tissues and nucellar projections on the dorsal side of the seed coats. Glucose uptake studies using vacuoles isolated from transgenic mutant Arabidopsis (tmt1-2-3) expressing OsTMT1 demonstrated that OsTMTs are capable of transporting glucose into vacuoles. Based on expression analysis and functional characterization, our present findings suggest that the OsTMTs play a role in vacuolar glucose storage in rice.
Collapse
Affiliation(s)
- Jung-Il Cho
- Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 446-701, Korea
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
181
|
Padilla-Chacón D, Cordoba E, Olivera T, Sánchez S, Coello P, León P, Tiessen A, Martínez-Barajas E. Heterologous expression of yeast Hxt2 in Arabidopsis thaliana alters sugar uptake, carbon metabolism and gene expression leading to glucose tolerance of germinating seedlings. PLANT MOLECULAR BIOLOGY 2010; 72:631-41. [PMID: 20101436 DOI: 10.1007/s11103-010-9602-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 01/13/2010] [Indexed: 05/25/2023]
Abstract
The hexose transporter 2 gene (Hxt2) from Saccharomyces cerevisiae was expressed in Arabidopsis thaliana under control of the 35S promoter. Several independent transgenic lines were selected after confirming single gene insertion by southern blot analysis in the T4 generation. Northern blots revealed the presence of heterologous transcript. Radiolabeling experiments revealed an increased rate of incorporation of the non-metabolizable analog 3-O-methyl-[U-14C]-glucose. This confirmed that the yeast Hxt2 transporter was functional in Arabidopsis. No phenotypic changes at the vegetative and reproductive stages could be detected in the transgenic lines when compared to wild type plants. Shortly after germination some differences in development and glucose signaling were observed. Transgenic seedlings cultivated in liquid medium or on solid agar plates were able to grow with 3% glucose (producing bigger plants and longer roots), while development of wild type plants was delayed under those conditions. Metabolite analysis revealed that the Hxt2 transgenic lines had higher rates of sugar utilization. Transcriptional profiling showed that particular genes were significantly up- or down-regulated. Some transcription factors like At1g27000 were repressed, while others, such as At3g58780, were induced. The mRNA from classical sugar signaling genes such as STP1, Hxk1, and ApL3 behaved similarly in transgenic lines and wild type lines. Results suggest that the Hxt2 transgene altered some developmental processes related to the perception of high carbon availability after the germination stage. We conclude that the developmental arrest of wild type plants at 3% glucose not only depends on Hxk1 as the only sugar sensor but might also be influenced by the route of hexose transport across the plasma membrane.
Collapse
Affiliation(s)
- Daniel Padilla-Chacón
- Facultad de Química, Departamento de Bioquímica, Universidad Nacional Autónoma de México, 04510, México D.F., México
| | | | | | | | | | | | | | | |
Collapse
|
182
|
Peuke AD. Correlations in concentrations, xylem and phloem flows, and partitioning of elements and ions in intact plants. A summary and statistical re-evaluation of modelling experiments in Ricinus communis. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:635-55. [PMID: 20032109 DOI: 10.1093/jxb/erp352] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Within the last two decades, a series of papers have dealt with the effects of nutrition and nutrient deficiency, as well as salt stress, on the long-distance transport and partitioning of nutrients in castor bean. Flows in xylem and phloem were modelled according to an empirically-based modelling technique that permits additional quantification of the uptake and incorporation into plant organs. In the present paper these data were statistically re-evaluated, and new correlations are presented. Numerous relationships between different compartments and transport processes for single elements, but also between elements, were detected. These correlations revealed different selectivities for ions in bulk net transport. Generally, increasing chemical concentration gradients for mineral nutrients from the rhizosphere to the root and from the xylem to leaf tissue were observed, while such gradients decreased from root tissue to the xylem and from leaves to the phloem. These studies showed that, for the partitioning of nutrients within a plant, the correlated interactions of uptake, xylem and phloem flow, as well as loading and unloading of solutes from transport systems, are of central importance. For essential nutrients, tight correlations between uptake, xylem and phloem flow, and the resulting partitioning of elements, were observed, which allows the stating of general models. For non-essential ions like Na(+) or Cl(-), a statistically significant dependence of xylem transport on uptake was not detected. The central role of the phloem for adjusting, but also signalling, of nutrition status is discussed, since strong correlations between leaf nutrient concentrations and those in phloem saps were observed. In addition, negative correlations between phloem sap sugar concentration and net-photosynthesis, growth, and uptake of nutrients were demonstrated. The question remains whether this is only a consequence of an insufficient use of carbohydrates in plants or a ubiquitous signal for stress in plants. In general, high sugar concentrations in phloem saps indicate (nutritional) stress, and high nutrient concentrations in phloem saps indicate nutritional sufficiency of leaf tissues.
Collapse
Affiliation(s)
- Andreas D Peuke
- ADP International Plant Science Consulting, Talstrasse 8, D-79194 Gundelfingen-Wildtal, Germany.
| |
Collapse
|
183
|
Zhang H, Liang W, Yang X, Luo X, Jiang N, Ma H, Zhang D. Carbon starved anther encodes a MYB domain protein that regulates sugar partitioning required for rice pollen development. THE PLANT CELL 2010; 22:672-89. [PMID: 20305120 PMCID: PMC2861464 DOI: 10.1105/tpc.109.073668] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 02/14/2010] [Accepted: 03/02/2010] [Indexed: 05/18/2023]
Abstract
In flowering plants, sink tissues rely on transport of carbohydrates from photosynthetic tissues (sources) for nutrition and energy. However, how sugar partitioning in plants is regulated at the molecular level during development remains unknown. We have isolated and characterized a rice (Oryza sativa) mutant, carbon starved anther (csa), that showed increased sugar contents in leaves and stems and reduced levels of sugars and starch in floral organs. In particular, the csa mutant had reduced levels of carbohydrates in later anthers and was male sterile. The csa mutant had reduced accumulation of (14)C-labeled sugars in anther sink tissue. CSA was isolated by map-based cloning and was shown to encode an R2R3 MYB transcription factor that was expressed preferentially in the anther tapetal cells and in the sugar-transporting vascular tissues. In addition, the expression of MST8, encoding a monosaccharide transporter, was greatly reduced in csa anthers. Furthermore, CSA was found to be associated in vivo and in vitro with the promoter of MST8. Our findings suggest that CSA is a key transcriptional regulator for sugar partitioning in rice during male reproductive development. This study also establishes a molecular model system for further elucidation of the genetic control of carbon partitioning in plants.
Collapse
Affiliation(s)
- Hui Zhang
- School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Bio-X Research Center, Key Laboratory of Genetics and Development and Neuropsychiatric Diseases, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Wanqi Liang
- School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xijia Yang
- School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xue Luo
- School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ning Jiang
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824
| | - Hong Ma
- State Key Laboratory of Genetic Engineering, Institute of Plant Biology, Center for Evolutionary Biology, School of Life Sciences, Fudan University, Shanghai 200433, China
- Department of Biology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16082
| | - Dabing Zhang
- School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
- Bio-X Research Center, Key Laboratory of Genetics and Development and Neuropsychiatric Diseases, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
- Address correspondence to
| |
Collapse
|
184
|
Yamada K, Osakabe Y, Mizoi J, Nakashima K, Fujita Y, Shinozaki K, Yamaguchi-Shinozaki K. Functional analysis of an Arabidopsis thaliana abiotic stress-inducible facilitated diffusion transporter for monosaccharides. J Biol Chem 2010; 285:1138-46. [PMID: 19901034 PMCID: PMC2801242 DOI: 10.1074/jbc.m109.054288] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 11/06/2009] [Indexed: 11/06/2022] Open
Abstract
Sugars play indispensable roles in biological reactions and are distributed into various tissues or organelles via transporters in plants. Under abiotic stress conditions, plants accumulate sugars as a means to increase stress tolerance. Here, we report an abiotic stress-inducible transporter for monosaccharides from Arabidopsis thaliana that is termed ESL1 (ERD six-like 1). Expression of ESL1 was induced under drought and high salinity conditions and with exogenous application of abscisic acid. Promoter analyses using beta-glucuronidase and green fluorescent protein reporters revealed that ESL1 is mainly expressed in pericycle and xylem parenchyma cells. The fluorescence of ESL1-green fluorescent protein-fused protein was detected at tonoplast in transgenic Arabidopsis plants and tobacco BY-2 cells. Furthermore, alanine-scanning mutagenesis revealed that an N-terminal LXXXLL motif in ESL1 was essential for its localization at the tonoplast. Transgenic BY-2 cells expressing mutated ESL1, which was localized at the plasma membrane, showed an uptake ability for monosaccharides. Moreover, the value of K(m) for glucose uptake activity of mutated ESL1 in the transgenic BY-2 cells was extraordinarily high, and the transport activity was independent from a proton gradient. These results indicate that ESL1 is a low affinity facilitated diffusion transporter. Finally, we detected that vacuolar invertase activity was increased under abiotic stress conditions, and the expression patterns of vacuolar invertase genes were similar to that of ESL1. Under abiotic stress conditions, ESL1 might function coordinately with the vacuolar invertase to regulate osmotic pressure by affecting the accumulation of sugar in plant cells.
Collapse
Affiliation(s)
- Kohji Yamada
- From the Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
- the Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan, and
| | - Yuriko Osakabe
- From the Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Junya Mizoi
- the Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan, and
| | - Kazuo Nakashima
- the Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan, and
| | - Yasunari Fujita
- the Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan, and
| | - Kazuo Shinozaki
- the RIKEN Plant Science Center, Yokohama, Kanagawa 203-0045, Japan
| | - Kazuko Yamaguchi-Shinozaki
- From the Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
- the Biological Resources Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan, and
| |
Collapse
|
185
|
Zavaliev R, Sagi G, Gera A, Epel BL. The constitutive expression of Arabidopsis plasmodesmal-associated class 1 reversibly glycosylated polypeptide impairs plant development and virus spread. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:131-42. [PMID: 19887501 PMCID: PMC2791124 DOI: 10.1093/jxb/erp301] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 09/03/2009] [Indexed: 05/17/2023]
Abstract
Arabidopsis class 1 reversibly glycosylated polypeptides (C1RGPs) were shown to be plasmodesmal-associated proteins. Transgenic tobacco (Nicotiana tabacum) plants constitutively expressing GFP tagged AtRGP2 under the control of the CaMV 35S promoter are stunted, have a rosette-like growth pattern, and in source leaves exhibit strong chlorosis, increased photoassimilate retention and starch accumulation that results in elevated leaf specific fresh and dry weights. Basal callose levels around plasmodesmata (Pd) of leaf epidermal cells in transgenic plants are higher than in WT. Such a phenotype is characteristic of virus-infected plants and some transgenic plants expressing Pd-associated viral movement proteins (MP). The local spread of Tobacco mosaic virus (TMV) is inhibited in AtRGP2:GFP transgenics compared to WT. Taken together these observations suggest that overexpression of the AtRGP2:GFP leads to a reduction in Pd permeability to photoassimilate, thus lowering the normal rate of translocation from source leaves to sink organs. Such a reduction may also inhibit the local cell-to-cell spread of viruses in transgenic plants. The observed reduction in Pd permeability could be due to a partial Pd occlusion caused either by the accumulation of AtRGP2:GFP fusion in Pd, and/or by constriction of Pd by the excessive callose accumulation.
Collapse
Affiliation(s)
- Raul Zavaliev
- Department of Plant Sciences, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Guy Sagi
- Department of Plant Sciences, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Abed Gera
- Department of Plant Pathology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
| | - Bernard L. Epel
- Department of Plant Sciences, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| |
Collapse
|
186
|
Zhang C, Turgeon R. Downregulating the sucrose transporter VpSUT1 in Verbascum phoeniceum does not inhibit phloem loading. Proc Natl Acad Sci U S A 2009; 106:18849-54. [PMID: 19846784 PMCID: PMC2774004 DOI: 10.1073/pnas.0904189106] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Indexed: 11/18/2022] Open
Abstract
Sucrose is loaded into the phloem in the minor veins of leaves before export. Two active, species-specific loading mechanisms have been proposed. One involves transporter-mediated sucrose transfer from the apoplast into the sieve element-companion cell complex, so-called apoplastic loading. In the putative second mechanism, sucrose follows an entirely symplastic pathway, and the solute concentration is elevated by the synthesis of raffinose and stachyose in the phloem, not by transporter activity. Several sucrose-transporting plants have been shown to be apoplastic loaders by downregulating sucrose transporter 1 (SUT1), leading to accumulation of sugars and leaf chlorosis. In this study we compared the effect of downregulating SUT1 in Nicotiana tabacum, a sucrose transporter, and Verbascum phoeniceum, a species that transports raffinose and stachyose. To test the effectiveness of RNAi downregulation, we measured SUT1 mRNA levels and sucrose-H(+) symport in leaf discs. Mild NtSUT1 downregulation in N. tabacum resulted in the pronounced phenotype associated with loading inhibition. In contrast, no such phenotype developed when VpSUT1 was downregulated in V. phoeniceum, leaving minimal sucrose transport activity. Only those plants with the most severe VpSUT1 downregulation accumulated more carbohydrate than usual and these plants were normal by other criteria: growth rate, photosynthesis, and ability to clear starch during the night. The results provide direct evidence that the mechanism of phloem loading in V. phoeniceum does not require active sucrose uptake from the apoplast and strongly supports the conclusion that the loading pathway is symplastic in this species.
Collapse
Affiliation(s)
- Cankui Zhang
- Department of Plant Biology, Cornell University, Ithaca, NY 14853
| | - Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, NY 14853
| |
Collapse
|
187
|
Srivastava AC, Dasgupta K, Ajieren E, Costilla G, McGarry RC, Ayre BG. Arabidopsis plants harbouring a mutation in AtSUC2, encoding the predominant sucrose/proton symporter necessary for efficient phloem transport, are able to complete their life cycle and produce viable seed. ANNALS OF BOTANY 2009; 104:1121-8. [PMID: 19789176 PMCID: PMC2766205 DOI: 10.1093/aob/mcp215] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Revised: 07/21/2009] [Accepted: 07/23/2009] [Indexed: 05/18/2023]
Abstract
BACKGROUND AND AIMS AtSUC2 encodes a sucrose/proton symporter that localizes throughout the collection and transport phloem and is necessary for efficient transport of sucrose from source to sink tissues in Arabidopsis thaliana. Plants harbouring homozygous AtSUC2 null alleles accumulate sugar, starch, and anthocyanin in mature leaves, have severely delayed development and stunted growth and, in previous studies, failed to complete their life cycle by producing viable seed. METHODS An AtSUC2 allele with a T-DNA insertion in the second intron was analysed. Full-length transcript from this allele is not produced, and a truncated protein translated from sequences upstream of the insertion site did not catalyse sucrose uptake into yeast, supporting the contention that this is a null allele. Mutant plants were grown in a growth chamber with a diurnal light/dark cycle, and growth patterns recorded. KEY RESULTS This allele (SALK_038124, designated AtSUC2-4) has the hallmarks of previously described null alleles but, despite compromised carbon partitioning and growth, produces viable seeds. The onset of flowering was chronologically delayed but occurred at the same point in the plastochron index as wild type. CONCLUSIONS AtSUC2 is important for phloem loading and is therefore fundamental to phloem transport and plant productivity, but plants can complete their life cycle and produce viable seed in its absence. Arabidopsis appears to have mechanisms for mobilizing reduced carbon from the phloem into developing seeds independent of AtSUC2.
Collapse
Affiliation(s)
| | | | | | | | | | - Brian G. Ayre
- University of North Texas, Department of Biological Sciences, 1155 Union Circle #305220, Denton TX 76203-5017, USA
| |
Collapse
|
188
|
Parrent JL, Vilgalys R. Expression of genes involved in symbiotic carbon and nitrogen transport in Pinus taeda mycorrhizal roots exposed to CO2 enrichment and nitrogen fertilization. MYCORRHIZA 2009; 19:469-479. [PMID: 19415342 DOI: 10.1007/s00572-009-0250-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 04/16/2009] [Indexed: 05/27/2023]
Abstract
As atmospheric carbon dioxide (CO(2)) concentrations rise, one important mechanism by which plants can gain greater access to necessary soil nutrients is through greater investment in their mycorrhizal symbionts. In this study, we tested the hypotheses that (1) plants increase C allocation to ectomycorrhizal fungi (EMF) under elevated CO(2) conditions, (2) N fertilization decreases C allocation to EMF, and (3) EMF activity at the site of symbiotic C and nutrient exchange is enhanced with CO(2) enrichment. To test these hypotheses, we examined expression levels of Pinus taeda genes encoding monosaccharide transport (MST) and ammonium transport (AMT) proteins thought to be involved in symbiotic C and N movement, respectively, from mycorrhizal root tips exposed to CO(2) and N fertilization. We also examined EMF ribosomal RNA expression (18S rRNA) to determine EMF activity. There was a trend toward lower relative MST expression with increased CO(2). AMT expression levels showed no significant differences between control and treatment plots. EMF 18S rRNA expression was increased in CO(2)-enriched plots and there was a marginally significant positive interactive effect of CO(2) and N fertilization on expression (p = 0.09 and 0.10, respectively). These results are consistent with greater C allocation to EMF and greater EMF metabolic activity under elevated CO(2) conditions, although selective allocation of C to particular EMF species and greater fungal biomass on roots are plausible alternative hypotheses.
Collapse
Affiliation(s)
- Jeri Lynn Parrent
- Biology Department, Duke University, P.O. Box 90338, Durham, NC, 27708-0338, USA.
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, 48109-1048, USA.
| | - Rytas Vilgalys
- Biology Department, Duke University, P.O. Box 90338, Durham, NC, 27708-0338, USA
| |
Collapse
|
189
|
Fan RC, Peng CC, Xu YH, Wang XF, Li Y, Shang Y, Du SY, Zhao R, Zhang XY, Zhang LY, Zhang DP. Apple sucrose transporter SUT1 and sorbitol transporter SOT6 interact with cytochrome b5 to regulate their affinity for substrate sugars. PLANT PHYSIOLOGY 2009; 150:1880-901. [PMID: 19502355 PMCID: PMC2719124 DOI: 10.1104/pp.109.141374] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 06/03/2009] [Indexed: 05/18/2023]
Abstract
Sugar transporters are central machineries to mediate cross-membrane transport of sugars into the cells, and sugar availability may serve as a signal to regulate the sugar transporters. However, the mechanisms of sugar transport regulation by signal sugar availability remain unclear in plant and animal cells. Here, we report that a sucrose transporter, MdSUT1, and a sorbitol transporter, MdSOT6, both localized to plasma membrane, were identified from apple (Malus domestica) fruit. Using a combination of the split-ubiquitin yeast two-hybrid, immunocoprecipitation, and bimolecular fluorescence complementation assays, the two distinct sugar transporters were shown to interact physically with an apple endoplasmic reticulum-anchored cytochrome b5 MdCYB5 in vitro and in vivo. In the yeast systems, the two different interaction complexes function to up-regulate the affinity of the sugar transporters, allowing cells to adapt to sugar starvation. An Arabidopsis (Arabidopsis thaliana) homolog of MdCYB5, AtCYB5-A, also interacts with the two sugar transporters and functions similarly. The point mutations leucine-73 --> proline in MdSUT1 and leucine-117 --> proline in MdSOT6, disrupting the bimolecular interactions but without significantly affecting the transporter activities, abolish the stimulating effects of the sugar transporter-cytochrome b5 complex on the affinity of the sugar transporters. However, the yeast (Saccharomyces cerevisiae) cytochrome b5 ScCYB5, an additional interacting partner of the two plant sugar transporters, has no function in the regulation of the sugar transporters, indicating that the observed biological functions in the yeast systems are specific to plant cytochrome b5s. These findings suggest a novel mechanism by which the plant cells tailor sugar uptake to the surrounding sugar availability.
Collapse
Affiliation(s)
- Ren-Chun Fan
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100094, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
190
|
Gharbi I, Ricard B, Smiti S, Bizid E, Brouquisse R. Increased hexose transport in the roots of tomato plants submitted to prolonged hypoxia. PLANTA 2009; 230:441-448. [PMID: 19437034 DOI: 10.1007/s00425-009-0941-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 04/24/2009] [Indexed: 05/27/2023]
Abstract
We investigated the effects of prolonged hypoxia on the sugar uptake in tomato (Solanum lycopersicum L. var. MP-1) roots. Hydroponic cultures of whole tomato plants were submitted to hypoxic treatment for 1 week, and the roots were analyzed for sugar concentrations, hexose uptake and hexose transporter expression level. Contrary to what has been observed after anoxic shock or short-term hypoxic treatment, we show that sugar concentrations increase and hexose uptake is up-regulated in the roots after 1 week of hypoxic treatment. Increased hexose transport is concomitant with the induction of the hexose transporter gene LeHT2. These responses may be due either to a direct effect of low O(2) supply, or to a secondary effect associated with the increase in sugar concentrations, which, typically, develops in most hypoxic plants.
Collapse
Affiliation(s)
- Imène Gharbi
- Unité d'Ecologie Végétale, Département des Sciences Biologiques, Faculté des Sciences de Tunis, 2092, El Manar II, Tunisia.
| | | | | | | | | |
Collapse
|
191
|
Slewinski TL, Meeley R, Braun DM. Sucrose transporter1 functions in phloem loading in maize leaves. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:881-92. [PMID: 19181865 PMCID: PMC2652052 DOI: 10.1093/jxb/ern335] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 11/26/2008] [Accepted: 11/27/2008] [Indexed: 05/18/2023]
Abstract
In most plants, sucrose is exported from source leaves to carbon-importing sink tissues to sustain their growth and metabolism. Apoplastic phloem-loading species require sucrose transporters (SUTs) to transport sucrose into the phloem. In many dicot plants, genetic and biochemical evidence has established that SUT1-type proteins function in phloem loading. However, the role of SUT1 in phloem loading in monocot plants is not clear since the rice (Oryza sativa) and sugarcane (Saccharum hybrid) SUT1 orthologues do not appear to function in phloem loading of sucrose. A SUT1 gene was previously cloned from maize (Zea mays) and shown to have expression and biochemical activity consistent with a hypothesized role in phloem loading. To determine the biological function of SUT1 in maize, a sut1 mutant was isolated and characterized. sut1 mutant plants hyperaccumulate carbohydrates in mature leaves and display leaf chlorosis with premature senescence. In addition, sut1 mutants have greatly reduced stature, altered biomass partitioning, delayed flowering, and stunted tassel development. Cold-girdling wild-type leaves to block phloem transport phenocopied the sut1 mutants, supporting a role for maize SUT1 in sucrose export. Furthermore, application of (14)C-sucrose to abraded sut1 mutant and wild-type leaves showed that sucrose export was greatly diminished in sut1 mutants compared with wild type. Collectively, these data demonstrate that SUT1 is crucial for efficient phloem loading of sucrose in maize leaves.
Collapse
Affiliation(s)
- Thomas L. Slewinski
- Department of Biology, Pennsylvania State University, 208 Mueller Lab, University Park, PA 16802, USA
| | - Robert Meeley
- Pioneer Hi-Bred International, Incorporated, Johnston, IA 50131 USA
| | - David M. Braun
- Department of Biology, Pennsylvania State University, 208 Mueller Lab, University Park, PA 16802, USA
| |
Collapse
|
192
|
Braun DM, Slewinski TL. Genetic control of carbon partitioning in grasses: roles of sucrose transporters and tie-dyed loci in phloem loading. PLANT PHYSIOLOGY 2009; 149:71-81. [PMID: 19126697 PMCID: PMC2613709 DOI: 10.1104/pp.108.129049] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 10/19/2008] [Indexed: 05/18/2023]
Affiliation(s)
- David M Braun
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
| | | |
Collapse
|
193
|
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.
Collapse
Affiliation(s)
- Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA.
| | | |
Collapse
|
194
|
Ma Y, Slewinski TL, Baker RF, Braun DM. Tie-dyed1 encodes a novel, phloem-expressed transmembrane protein that functions in carbohydrate partitioning. PLANT PHYSIOLOGY 2009; 149:181-94. [PMID: 18923021 PMCID: PMC2613742 DOI: 10.1104/pp.108.130971] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 10/10/2008] [Indexed: 05/18/2023]
Abstract
Carbon is partitioned between export from the leaf and retention within the leaf, and this process is essential for all aspects of plant growth and development. In most plants, sucrose is loaded into the phloem of carbon-exporting leaves (sources), transported through the veins, and unloaded into carbon-importing tissues (sinks). We have taken a genetic approach to identify genes regulating carbon partitioning in maize (Zea mays). We identified a collection of mutants, called the tie-dyed (tdy) loci, that hyperaccumulate carbohydrates in regions of their leaves. To understand the molecular function of Tdy1, we cloned the gene. Tdy1 encodes a novel transmembrane protein present only in grasses, although two protein domains are conserved across angiosperms. We found that Tdy1 is expressed exclusively in phloem cells of both source and sink tissues, suggesting that Tdy1 may play a role in phloem loading and unloading processes. In addition, Tdy1 RNA accumulates in protophloem cells upon differentiation, suggesting that Tdy1 may function as soon as phloem cells become competent to transport assimilates. Monitoring the movement of a fluorescent, soluble dye showed that tdy1 leaves have retarded phloem loading. However, once the dye entered into the phloem, solute transport appeared equal in wild-type and tdy1 mutant plants, suggesting that tdy1 plants are not defective in phloem unloading. Therefore, even though Tdy1 RNA accumulates in source and sink tissues, we propose that TDY1 functions in carbon partitioning by promoting phloem loading. Possible roles for TDY1 are discussed.
Collapse
Affiliation(s)
- Yi Ma
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | | | | | | |
Collapse
|
195
|
Antony E, Borland AM. The Role and Regulation of Sugar Transporters in Plants with Crassulacean Acid Metabolism. PROGRESS IN BOTANY 2008. [DOI: 10.1007/978-3-540-68421-3_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
196
|
Chaudhuri B, Hörmann F, Lalonde S, Brady SM, Orlando DA, Benfey P, Frommer WB. Protonophore- and pH-insensitive glucose and sucrose accumulation detected by FRET nanosensors in Arabidopsis root tips. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 56:948-62. [PMID: 18702670 PMCID: PMC2752219 DOI: 10.1111/j.1365-313x.2008.03652.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Although soil contains only traces of soluble carbohydrates, plant roots take up glucose and sucrose efficiently when supplied in artificial media. Soluble carbohydrates and other small metabolites found in soil are in part products from exudation from plant roots. The molecular nature of the transporters for uptake and exudation is unknown. Here, fluorescence resonance energy transfer (FRET) glucose and sucrose sensors were used to characterize accumulation and elimination of glucose and sucrose in Arabidopsis roots tips. Using an improved image acquisition set-up, FRET responses to perfusion with carbohydrates were detectable in roots within less than 10 sec and over a wide concentration range. Accumulation was fully reversible within 10-180 sec after glucose or sucrose had been withdrawn; elimination may be caused by metabolism and/or efflux. The rate of elimination was unaffected by pre-incubation with high concentrations of glucose, suggesting that elimination is not due to accumulation in a short-term buffer such as the vacuole. Glucose and sucrose accumulation was insensitive to protonophores, was comparable in media differing in potassium levels, and was similar at pH 5.8, 6.8 and 7.8, suggesting that both influx and efflux may be mediated by proton-independent transport systems. High-resolution expression mapping in root tips showed that only a few proton-dependent transport of the STP (Sugar Transport Protein) and SUT/SUC (Sucrose Transporter/Carrier) families are expressed in the external cell layers of root tips. The root expression maps may help to pinpoint candidate genes for uptake and release of carbohydrates from roots.
Collapse
Affiliation(s)
- Bhavna Chaudhuri
- Carnegie Institution for Science, Department of Plant Biology, 260 Panama Street, Stanford, CA 94305, USA
| | | | | | | | | | | | | |
Collapse
|
197
|
Zhou Y, Chan K, Wang TL, Hedley CL, Offler CE, Patrick JW. Intracellular sucrose communicates metabolic demand to sucrose transporters in developing pea cotyledons. JOURNAL OF EXPERIMENTAL BOTANY 2008; 60:71-85. [PMID: 18931350 PMCID: PMC3071760 DOI: 10.1093/jxb/ern254] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 09/05/2008] [Accepted: 09/09/2008] [Indexed: 05/18/2023]
Abstract
Mechanistic inter-relationships in sinks between sucrose compartmentation/metabolism and phloem unloading/translocation are poorly understood. Developing grain legume seeds provide tractable experimental systems to explore this question. Metabolic demand by cotyledons is communicated to phloem unloading and ultimately import by sucrose withdrawal from the seed apoplasmic space via a turgor-homeostat mechanism. What is unknown is how metabolic demand is communicated to cotyledon sucrose transporters responsible for withdrawing sucrose from the apoplasmic space. This question was explored here using a pea rugosus mutant (rrRbRb) compromised in starch biosynthesis compared with its wild-type counterpart (RRRbRb). Sucrose influx into cotyledons was found to account for 90% of developmental variations in their absolute growth and hence starch biosynthetic rates. Furthermore, rr and RR cotyledons shared identical response surfaces, indicating that control of transporter activity was likely to be similar for both lines. In this context, sucrose influx was correlated positively with expression of a sucrose/H(+) symporter (PsSUT1) and negatively with two sucrose facilitators (PsSUF1 and PsSUF4). Sucrose influx exhibited a negative curvilinear relationship with cotyledon concentrations of sucrose and hexoses. In contrast, the impact of intracellular sugars on transporter expression was transporter dependent, with expression of PsSUT1 inhibited, PsSUF1 unaffected, and PsSUF4 enhanced by sugars. Sugar supply to, and sugar concentrations of, RR cotyledons were manipulated using in vitro pod and cotyledon culture. Collectively the results obtained showed that intracellular sucrose was the physiologically active sugar signal that communicated metabolic demand to sucrose influx and this transport function was primarily determined by PsSUT1 regulated at the transcriptional level.
Collapse
Affiliation(s)
- Yuchan Zhou
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Katie Chan
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Trevor L. Wang
- Metabolic Biology, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK
| | - Cliff L. Hedley
- Metabolic Biology, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK
| | - Christina E. Offler
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - John W. Patrick
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| |
Collapse
|
198
|
Szarka A, Horemans N, Passarella S, Tarcsay A, Orsi F, Salgó A, Bánhegyi G. Demonstration of an intramitochondrial invertase activity and the corresponding sugar transporters of the inner mitochondrial membrane in Jerusalem artichoke (Helianthus tuberosus L.) tubers. PLANTA 2008; 228:765-75. [PMID: 18600345 DOI: 10.1007/s00425-008-0778-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 06/20/2008] [Indexed: 05/24/2023]
Abstract
Genetic evidences indicate that alkaline/neutral invertases are present in plant cell organelles, and they might have a novel physiological function in mitochondria. The present study demonstrates an invertase activity in the mitochondrial matrix of Helianthus tuberosus tubers. The pH optimum, the kinetic parameters and the inhibitor profile of the invertase activity indicated that it belongs to the neutral invertases. In accordance with this topology, transport activities responsible for the mediation of influx/efflux of substrate/products were studied in the inner mitochondrial membrane. The transport of sucrose, glucose and fructose was shown to be bidirectional, saturable and independent of the mitochondrial respiration and membrane potential. Sucrose transport was insensitive to the inhibitors of the proton-sucrose symporters. The different kinetic parameters and inhibitors as well as the absence of cross-inhibition suggest that sucrose, glucose and fructose transport are mediated by separate transporters in the inner mitochondrial membrane. The mitochondrial invertase system composed by an enzyme activity in the matrix and the corresponding sugar transporters might have a role in both osmoregulation and intermediary metabolism.
Collapse
Affiliation(s)
- András Szarka
- Department of Applied Biotechnology and Food Science, Laboratory of Biochemistry and Molecular Biology, Budapest University of Technology and Economics, Muegyetem rakpart 3, 1111, Budapest, Hungary.
| | | | | | | | | | | | | |
Collapse
|
199
|
McGarry RC, Ayre BG. A DNA element between At4g28630 and At4g28640 confers companion-cell specific expression following the sink-to-source transition in mature minor vein phloem. PLANTA 2008; 228:839-49. [PMID: 18682980 DOI: 10.1007/s00425-008-0786-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2008] [Accepted: 07/04/2008] [Indexed: 05/05/2023]
Abstract
The collection phloem in minor veins is distinct from other vein classes in that the minor veins mature during the sink to source transition and are the primary sites of phloem loading. After maturation, minor vein phloem maintains its character in part through minor-vein specific regulatory cascades; however despite its physiological significance, little of these developmental programs is understood. From an Arabidopsis enhancer trap screen, we identified MATURE MINOR VEIN ELEMENT1 (MMVE1) in the intergenic region between two oppositely oriented genes, the ABC transporter ATM1 (At4g28630) and IAA11 (At4g28640). MMVE1 promotes reporter gene activity in minor vein phloem in a pattern resembling the sink to source transition. Promoter truncation experiments and phylogenetic footprinting demonstrate sequences proximal to ATM1 promote minor vein expression whereas sequences closer to IAA11 repress it. Both orientations of the promoter were used to drive expression of CONSTANS to generate a phloem mobile signal conferring early flowering under non-inductive conditions. Tandem copies of MMVE1 increase minor vein expression strength and specificity. MMVE1 is the first minor vein enhancer characterized from a species that loads from the apoplast, and supports the presence of unique regulatory cascades operating in minor vein phloem.
Collapse
Affiliation(s)
- Roisin C McGarry
- Department of Biological Sciences, University of North Texas, 1504 W. Mulberry, SRB Rm 120, P.O. Box 305220, Denton, TX 76203 5220, USA.
| | | |
Collapse
|
200
|
Macgregor DR, Deak KI, Ingram PA, Malamy JE. Root system architecture in Arabidopsis grown in culture is regulated by sucrose uptake in the aerial tissues. THE PLANT CELL 2008; 20:2643-60. [PMID: 18952782 PMCID: PMC2590740 DOI: 10.1105/tpc.107.055475] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 08/08/2008] [Accepted: 09/30/2008] [Indexed: 05/20/2023]
Abstract
This article presents a detailed model for the regulation of lateral root formation in Arabidopsis thaliana seedlings grown in culture. We demonstrate that direct contact between the aerial tissues and sucrose in the growth media is necessary and sufficient to promote emergence of lateral root primordia from the parent root. Mild osmotic stress is perceived by the root, which then sends an abscisic acid-dependent signal that causes a decrease in the permeability of aerial tissues; this reduces uptake of sucrose from the culture media, which leads to a repression of lateral root formation. Osmotic repression of lateral root formation in culture can be overcome by mutations that cause the cuticle of a plant's aerial tissues to become more permeable. Indeed, we report here that the previously described lateral root development2 mutant overcomes osmotic repression of lateral root formation because of a point mutation in Long Chain Acyl-CoA Synthetase2, a gene essential for cutin biosynthesis. Together, our findings (1) impact the interpretation of experiments that use Arabidopsis grown in culture to study root system architecture; (2) identify sucrose as an unexpected regulator of lateral root formation; (3) demonstrate mechanisms by which roots communicate information to aerial tissues and receive information in turn; and (4) provide insights into the regulatory pathways that allow plants to be developmentally plastic while preserving the essential balance between aboveground and belowground organs.
Collapse
Affiliation(s)
- Dana R Macgregor
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA
| | | | | | | |
Collapse
|