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Chen L, Ganguly DR, Shafik SH, Danila F, Grof CPL, Sharwood RE, Furbank RT. The role of SWEET4 proteins in the post-phloem sugar transport pathway of Setaria viridis sink tissues. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:2968-2986. [PMID: 36883216 PMCID: PMC10560085 DOI: 10.1093/jxb/erad076] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 03/06/2023] [Indexed: 05/21/2023]
Abstract
In the developing seeds of all higher plants, filial cells are symplastically isolated from the maternal tissue supplying photosynthate to the reproductive structure. Photoassimilates must be transported apoplastically, crossing several membrane barriers, a process facilitated by sugar transporters. Sugars Will Eventually be Exported Transporters (SWEETs) have been proposed to play a crucial role in apoplastic sugar transport during phloem unloading and the post-phloem pathway in sink tissues. Evidence for this is presented here for developing seeds of the C4 model grass Setaria viridis. Using immunolocalization, SvSWEET4 was detected in various maternal and filial tissues within the seed along the sugar transport pathway, in the vascular parenchyma of the pedicel, and in the xylem parenchyma of the stem. Expression of SvSWEET4a in Xenopus laevis oocytes indicated that it functions as a high-capacity glucose and sucrose transporter. Carbohydrate and transcriptional profiling of Setaria seed heads showed that there were some developmental shifts in hexose and sucrose content and consistent expression of SvSWEET4 homologues. Collectively, these results provide evidence for the involvement of SWEETs in the apoplastic transport pathway of sink tissues and allow a pathway for post-phloem sugar transport into the seed to be proposed.
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Affiliation(s)
- Lily Chen
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Diep R Ganguly
- Research School of Biology, ARC Centre of Excellence in Plant Energy Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- CSIRO Synthetic Biology Future Science Platform, Canberra, Australian Capital Territory 2601, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Florence Danila
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Christopher P L Grof
- Centre for Plant Science, School of Environmental and Life Sciences, College of Engineering Science and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Robert E Sharwood
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Robert T Furbank
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Chen L, Ganguly DR, Shafik SH, Ermakova M, Pogson BJ, Grof CPL, Sharwood RE, Furbank RT. Elucidating the role of SWEET13 in phloem loading of the C 4 grass Setaria viridis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:615-632. [PMID: 34780111 DOI: 10.1111/tpj.15581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/11/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
Photosynthetic efficiency and sink demand are tightly correlated with rates of phloem loading, where maintaining low cytosolic sugar concentrations is paramount to prevent the downregulation of photosynthesis. Sugars Will Eventually be Exported Transporters (SWEETs) are thought to have a pivotal role in the apoplastic phloem loading of C4 grasses. SWEETs have not been well studied in C4 species, and their investigation is complicated by photosynthesis taking place across two cell types and, therefore, photoassimilate export can occur from either one. SWEET13 homologues in C4 grasses have been proposed to facilitate apoplastic phloem loading. Here, we provide evidence for this hypothesis using the C4 grass Setaria viridis. Expression analyses on the leaf gradient of C4 species Setaria and Sorghum bicolor show abundant transcript levels for SWEET13 homologues. Carbohydrate profiling along the Setaria leaf shows total sugar content to be significantly higher in the mature leaf tip compared with the younger tissue at the base. We present the first known immunolocalization results for SvSWEET13a and SvSWEET13b using novel isoform-specific antisera. These results show localization to the bundle sheath and phloem parenchyma cells of both minor and major veins. We further present the first transport kinetics study of C4 monocot SWEETs by using a Xenopus laevis oocyte heterologous expression system. We demonstrate that SvSWEET13a and SvSWEET13b are high-capacity transporters of glucose and sucrose, with a higher apparent Vmax for sucrose, compared with glucose, typical of clade III SWEETs. Collectively, these results provide evidence for an apoplastic phloem loading pathway in Setaria and possibly other C4 species.
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Affiliation(s)
- Lily Chen
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- School of Science, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales, 2753, Australia
| | - Diep R Ganguly
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- CSIRO Synthetic Biology Future Science Platform, Canberra, Australian Capital Territory, 2601, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Maria Ermakova
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Barry J Pogson
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Christopher P L Grof
- Centre for Plant Science, School of Environmental and Life Sciences, College of Engineering Science and Environment, University of Newcastle, Callaghan, New South Wales, 2308, Australia
| | - Robert E Sharwood
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- School of Science, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales, 2753, Australia
| | - Robert T Furbank
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
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Franceus J, Desmet T. Sucrose Phosphorylase and Related Enzymes in Glycoside Hydrolase Family 13: Discovery, Application and Engineering. Int J Mol Sci 2020; 21:E2526. [PMID: 32260541 PMCID: PMC7178133 DOI: 10.3390/ijms21072526] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 04/01/2020] [Accepted: 04/01/2020] [Indexed: 02/07/2023] Open
Abstract
Sucrose phosphorylases are carbohydrate-active enzymes with outstanding potential for the biocatalytic conversion of common table sugar into products with attractive properties. They belong to the glycoside hydrolase family GH13, where they are found in subfamily 18. In bacteria, these enzymes catalyse the phosphorolysis of sucrose to yield α-glucose 1-phosphate and fructose. However, sucrose phosphorylases can also be applied as versatile transglucosylases for the synthesis of valuable glycosides and sugars because their broad promiscuity allows them to transfer the glucosyl group of sucrose to a diverse collection of compounds other than phosphate. Numerous process and enzyme engineering studies have expanded the range of possible applications of sucrose phosphorylases ever further. Moreover, it has recently been discovered that family GH13 also contains a few novel phosphorylases that are specialised in the phosphorolysis of sucrose 6F-phosphate, glucosylglycerol or glucosylglycerate. In this review, we provide an overview of the progress that has been made in our understanding and exploitation of sucrose phosphorylases and related enzymes over the past ten years.
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Affiliation(s)
| | - Tom Desmet
- Centre for Synthetic Biology (CSB), Department of Biotechnology, Ghent University, Coupure Links 653, 9000 Ghent, Belgium;
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Yuan H, Wu Y, Liu W, Liu Y, Gao X, Lin J, Zhao Y. Mass spectrometry-based method to investigate the natural selectivity of sucrose as the sugar transport form for plants. Carbohydr Res 2015; 407:5-9. [DOI: 10.1016/j.carres.2015.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 11/28/2022]
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Liu DD, Chao WM, Turgeon R. Transport of sucrose, not hexose, in the phloem. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:4315-20. [PMID: 22553289 PMCID: PMC3398456 DOI: 10.1093/jxb/ers127] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 02/28/2012] [Accepted: 04/02/2012] [Indexed: 05/17/2023]
Abstract
Several lines of evidence indicate that glucose and fructose are essentially absent in mobile phloem sap. However, this paradigm has been called into question, especially but not entirely, with respect to species in the Ranunculaceae and Papaveraceae. In the experiments in question, phloem sap was obtained by detaching leaves and placing the cut ends of the petioles in an EDTA solution. More hexose than sucrose was detected. In the present study, these results were confirmed for four species. However, almost identical results were obtained when the leaf blades were removed and only petiole stubs were immersed. This suggests that the sugars in the EDTA solution represent compounds extracted from the petioles, rather than sugars in transit in the phloem. In further experiments, the leaf blades were exposed to (14)CO(2) and, following a chase period, radiolabelled sugars in the petioles and EDTA exudate were identified. Almost all the radiolabel was in the form of [(14)C]sucrose, with little radiolabelled hexose. The data support the long-held contention that sucrose is a ubiquitous transport sugar, but hexoses are essentially absent in the phloem stream.
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van Bel AJE, Hess PH. Hexoses as phloem transport sugars: the end of a dogma? JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:261-272. [PMID: 18332226 DOI: 10.1093/jxb/erm294] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
According to most textbooks, only non-reducing carbohydrate species such as sucrose, sugar alcohols, and raffinose-family sugars function as phloem translocates. Occasional abundance of reducing sugar species (such as hexoses) in sieve-tube sap has been discarded as an experimental artefact. This study, however, discloses a widespread occurrence of hexoses in the sieve-tube sap. Phloem exudation facilitated by EDTA provided evidence that many of the members of two plant families (Ranunculaceae and Papaveraceae) investigated translocate >80% of carbohydrates in the form of hexoses. Representatives of other families also appear to translocate appreciable amounts of hexoses in the sieve tubes. Promoting effects of EDTA, activities of sucrose-degrading enzymes, and sugar uptake by micro-organisms on hexose contents of phloem exudates were checked. The rate of sucrose degradation is far too low to explain the large proportions of hexoses measured in phloem exudates; nor did other factors tested seem to stimulate the occurrence of hexoses. The validity of the approach is further supported by the virtual absence of hexoses in exudates from species that were known as exclusive sucrose transporters. This study urges a rethink of the existing views on carbohydrate transport species in the phloem stream. Hexose translocation is to be regarded as a normal mode of carbohydrate transfer by the phloem equivalent to that of sucrose, raffinose-family sugars, or sugar alcohols.
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Affiliation(s)
- Aart J E van Bel
- Plant Cell Biology Research Group, Institute of General Botany, Justus-Liebig-University, Senckenbergstrasse 17, D-35390 Giessen, Germany.
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Lemaire K, Van de Velde S, Van Dijck P, Thevelein JM. Glucose and sucrose act as agonist and mannose as antagonist ligands of the G protein-coupled receptor Gpr1 in the yeast Saccharomyces cerevisiae. Mol Cell 2004; 16:293-9. [PMID: 15494315 DOI: 10.1016/j.molcel.2004.10.004] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 08/03/2004] [Accepted: 08/10/2004] [Indexed: 11/26/2022]
Abstract
Several examples of G protein-coupled receptors have recently been suggested to respond to common sugars in millimolar concentrations. This low affinity has made it difficult to demonstrate direct receptor-ligand interaction. In the yeast Saccharomyces cerevisiae, rapid activation of the cAMP pathway by glucose and sucrose requires the GPCR Gpr1. Our results obtained by cysteine scanning mutagenesis and SCAM (substituted cysteine accessibility method) of residues in TMD VI provide strong evidence that glucose and sucrose directly interact as ligands with Gpr1. The affinity for sucrose is much higher. Structurally similar sugars such as galactose, mannose, and fructose do not act as agonists, but mannose acts as an antagonist for both sucrose and glucose. These results support the idea that Gpr1 directly senses sugars and that sugars can effectively bind GPCRs with a low affinity in a binding pocket formed by the transmembrane domains. The ligand repertoire of GPCRs can thus be extended to common sugars in millimolar concentrations.
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Affiliation(s)
- Katleen Lemaire
- Laboratorium voor Moleculaire Celbiologie, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, B-3001 Leuven-Heverlee, Flanders, Belgium
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Soluble carbohydrates of red pine (Pinus resinosa) mycorrhizas and mycorrhizal fungi. ACTA ACUST UNITED AC 2000. [DOI: 10.1017/s0953756299002166] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Lemoine R. Sucrose transporters in plants: update on function and structure. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1465:246-62. [PMID: 10748258 DOI: 10.1016/s0005-2736(00)00142-5] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In plants, sucrose is the major transport form for photoassimilated carbon and is both a source of carbon skeletons and energy for plant organs unable to perform photosynthesis (sink organs). As a molecule translocated over distance, sucrose has to pass through a number of membranes. Membrane transport of sucrose has therefore been considered for a long time as a major determinant of plant productivity. After several decades of physiological and biochemical experiments measuring the activity of sucrose carriers, unequivocal evidence came from the first identification of a cDNA coding a sucrose carrier (SoSUT1, Riesmeier et al. (1992) EMBO J. 11, 4705-4713). At present 20 different cDNAs encoding sucrose carriers have been identified in different plant species, in both dicots and monocots (one case). The total number is increasing rapidly and most importantly, it can be guessed from the results obtained for Arabidopsis, that in each species, sucrose transporters represent a gene family. The sequences are highly conserved and those carriers display the typical 12 transmembrane alpha-helices of members of the Major Facilitator superfamily. Yeast expression of those carriers indicate that they are all influx carriers, all cotransport sucrose and proton and that their affinity for sucrose is surprisingly similar (0.2-2 mM). All their characteristics are in agreement with those demonstrated at the physiological level in plants. These characteristics are discussed in relation to the function in plants and the few data available on the structure of those transporters in relation to their function are presented.
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Affiliation(s)
- R Lemoine
- Laboratoire de Biochimie et Physiologie Végétales, ESA CNRS 6161, Bâtiment Botanique, 40 Avenue du Recteur Pineau, F-86022, Poitiers, France.
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Bates RB, Byrne DN, Kane VV, Miller WB, Taylor SR. N.m.r. characterization of trehalulose from the excrement of the sweet potato whitefly, Bemisia tabaci. Carbohydr Res 1990. [DOI: 10.1016/0008-6215(90)84250-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Jakinovich W, Sugarman D, Vlahopoulos V. Gustatory responses of the cockroach, house fly, and gerbils to methyl glycosides. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 1981. [DOI: 10.1007/bf00609931] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
The gustatory responses of the Mongolian gerbil were tested with a large number of monosaccharides. Electrophysiological methods were used to record from the chorda tympani nerve. Methyl glycosides which have structural features in common with sucrose are the most effective monosaccharides for eliciting a neural response. Among the monosaccharides tested, efficacy appears to be highest in D-pyranosides having equatorial substituents at the C-2 and C-4 positions and axial substituents at the C-1 position. A C-5 hydroxymethyl group is not required. Similarities in the structural requirements for taste response in the fly and gerbil are discussed.
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Broughton WJ, Hellmuth EO, Yeung D. Role of glucose in development of the gibberellin response in peas. BIOCHIMICA ET BIOPHYSICA ACTA 1970; 222:491-500. [PMID: 5491226 DOI: 10.1016/0304-4165(70)90140-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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