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Chen L, Ghannoum O, Furbank RT. Sugar sensing in C4 source leaves: a gap that needs to be filled. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:3818-3834. [PMID: 38642398 PMCID: PMC11233418 DOI: 10.1093/jxb/erae166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 04/18/2024] [Indexed: 04/22/2024]
Abstract
Plant growth depends on sugar production and export by photosynthesizing source leaves and sugar allocation and import by sink tissues (grains, roots, stems, and young leaves). Photosynthesis and sink demand are tightly coordinated through metabolic (substrate, allosteric) feedback and signalling (sugar, hormones) mechanisms. Sugar signalling integrates sugar production with plant development and environmental cues. In C3 plants (e.g. wheat and rice), it is well documented that sugar accumulation in source leaves, due to source-sink imbalance, negatively feeds back on photosynthesis and plant productivity. However, we have a limited understanding about the molecular mechanisms underlying those feedback regulations, especially in C4 plants (e.g. maize, sorghum, and sugarcane). Recent work with the C4 model plant Setaria viridis suggested that C4 leaves have different sugar sensing thresholds and behaviours relative to C3 counterparts. Addressing this research priority is critical because improving crop yield requires a better understanding of how plants coordinate source activity with sink demand. Here we review the literature, present a model of action for sugar sensing in C4 source leaves, and suggest ways forward.
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Affiliation(s)
- Lily Chen
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, NSW, 2753, Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, NSW, 2753, Australia
| | - Robert T Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
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2
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Gao H, Li D, Hu H, Zhou F, Yu Y, Wei Q, Liu Q, Liu M, Hu P, Chen E, Song P, Su X, Guan Y, Qiao M, Ru Z, Li C. Regulation of carbohydrate metabolism during anther development in a thermo-sensitive genic male-sterile wheat line. PLANT, CELL & ENVIRONMENT 2024; 47:2410-2425. [PMID: 38517937 DOI: 10.1111/pce.14888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 03/03/2024] [Accepted: 03/05/2024] [Indexed: 03/24/2024]
Abstract
Bainong sterility (BNS) is a thermo-sensitive genic male sterile wheat line, characterised by anther fertility transformation in response to low temperature (LT) stress during meiosis, the failure of vacuole decomposition and the absence of starch accumulation in sterile bicellular pollen. Our study demonstrates that the late microspore (LM) stage marks the transition from the anther growth to anther maturation phase, characterised by the changes in anther structure, carbohydrate metabolism and the main transport pathway of sucrose (Suc). Fructan is a main storage polysaccharide in wheat anther, and its synthesis and remobilisation are crucial for anther development. Moreover, the process of pollen amylogenesis and the fate of the large vacuole in pollen are closely intertwined with fructan synthesis and remobilisation. LT disrupts the normal physiological metabolism of BNS anthers during meiosis, particularly affecting carbohydrate metabolism, thus determining the fate of male gametophytes and pollen abortion. Disruption of fructan synthesis and remobilisation regulation serves as a decisive event that results in anther abortion. Sterile pollen exhibits common traits of pollen starvation and impaired starch accumulation due to the inhibition of apoplastic transport starting from the LM stage, which is regulated by cell wall invertase TaIVR1 and Suc transporter TaSUT1.
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Affiliation(s)
- Huanting Gao
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Dongxiao Li
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Haiyan Hu
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Feng Zhou
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Yongang Yu
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Qichao Wei
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Qili Liu
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Mingjiu Liu
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Ping Hu
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Eryong Chen
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Puwen Song
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Xiaojia Su
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Yuanyuan Guan
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Mei Qiao
- College of Science and Engineering, Hebei Agricultural University, Baoding, Hebei, China
| | - Zhengang Ru
- Henan Collaborative Innovation Centre of Modern Biological Breeding, Henan Institute of Science and Technology, Xinxiang, Henan, China
- Henan Provincial Key Laboratory of Hybrid Wheat, Henan Institute of Science and Technology, Xinxiang, Henan, China
| | - Chengwei Li
- Henan Engineering Research Centre of Crop Genome Editing, Henan Institute of Science and Technology, Xinxiang, Henan, China
- College of Life Science, Henan Agricultural University, Zhengzhou, Henan, China
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3
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Zhang S, Ghatak A, Mohammadi Bazargani M, Kramml H, Zang F, Gao S, Ramšak Ž, Gruden K, Varshney RK, Jiang D, Chaturvedi P, Weckwerth W. Cell-type proteomic and metabolomic resolution of early and late grain filling stages of wheat endosperm. PLANT BIOTECHNOLOGY JOURNAL 2024; 22:555-571. [PMID: 38050335 DOI: 10.1111/pbi.14203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 08/21/2023] [Accepted: 10/03/2023] [Indexed: 12/06/2023]
Abstract
The nutritional value of wheat grains, particularly their protein and metabolite composition, is a result of the grain-filling process, especially in the endosperm. Here, we employ laser microdissection (LMD) combined with shotgun proteomics and metabolomics to generate a cell type-specific proteome and metabolome inventory of developing wheat endosperm at the early (15 DAA) and late (26 DAA) grain-filling stages. We identified 1803 proteins and 41 metabolites from four different cell types (aleurone (AL), sub-aleurone (SA), starchy endosperm (SE) and endosperm transfer cells (ETCs). Differentially expressed proteins were detected, 67 in the AL, 31 in the SA, 27 in the SE and 50 in the ETCs between these two-time points. Cell-type accumulation of specific SUT and GLUT transporters, sucrose converting and starch biosynthesis enzymes correlate well with the respective sugar metabolites, suggesting sugar upload and starch accumulation via nucellar projection and ETC at 15 DAA in contrast to the later stage at 26 DAA. Changes in various protein levels between AL, SA and ETC support this metabolic switch from 15 to 26 DAA. The distinct spatial and temporal abundances of proteins and metabolites revealed a contrasting activity of nitrogen assimilation pathways, e.g. for GOGAT, GDH and glutamic acid, in the different cell types from 15 to 26 DAA, which can be correlated with specific protein accumulation in the endosperm. The integration of cell-type specific proteome and metabolome data revealed a complex metabolic interplay of the different cell types and a functional switch during grain development and grain-filling processes.
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Affiliation(s)
- Shuang Zhang
- Molecular Systems Biology Lab (MOSYS), Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
- National Technique Innovation Center for Regional Wheat Production/Key Laboratory of Crop Ecophysiology, Ministry of Agriculture/Nanjing Agricultural University, Nanjing, China
| | - Arindam Ghatak
- Molecular Systems Biology Lab (MOSYS), Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
- Vienna Metabolomics Center (VIME), University of Vienna, Vienna, Austria
| | | | - Hannes Kramml
- Molecular Systems Biology Lab (MOSYS), Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Fujuan Zang
- National Technique Innovation Center for Regional Wheat Production/Key Laboratory of Crop Ecophysiology, Ministry of Agriculture/Nanjing Agricultural University, Nanjing, China
| | - Shuang Gao
- National Technique Innovation Center for Regional Wheat Production/Key Laboratory of Crop Ecophysiology, Ministry of Agriculture/Nanjing Agricultural University, Nanjing, China
| | - Živa Ramšak
- Department of Systems Biology and Biotechnology, National Institute of Biology, Ljubljana, Slovenia
| | - Kristina Gruden
- Department of Systems Biology and Biotechnology, National Institute of Biology, Ljubljana, Slovenia
| | - Rajeev K Varshney
- State Agricultural Biotechnology Centre, Centre for Crop and Food Innovation, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
| | - Dong Jiang
- National Technique Innovation Center for Regional Wheat Production/Key Laboratory of Crop Ecophysiology, Ministry of Agriculture/Nanjing Agricultural University, Nanjing, China
| | - Palak Chaturvedi
- Molecular Systems Biology Lab (MOSYS), Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Wolfram Weckwerth
- Molecular Systems Biology Lab (MOSYS), Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
- Vienna Metabolomics Center (VIME), University of Vienna, Vienna, Austria
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4
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Pfrieme AK, Will T, Pillen K, Stahl A. The Past, Present, and Future of Wheat Dwarf Virus Management-A Review. PLANTS (BASEL, SWITZERLAND) 2023; 12:3633. [PMID: 37896096 PMCID: PMC10609771 DOI: 10.3390/plants12203633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 09/29/2023] [Accepted: 10/04/2023] [Indexed: 10/29/2023]
Abstract
Wheat dwarf disease (WDD) is an important disease of monocotyledonous species, including economically important cereals. The causative pathogen, wheat dwarf virus (WDV), is persistently transmitted mainly by the leafhopper Psammotettix alienus and can lead to high yield losses. Due to climate change, the periods of vector activity increased, and the vectors have spread to new habitats, leading to an increased importance of WDV in large parts of Europe. In the light of integrated pest management, cultivation practices and the use of resistant/tolerant host plants are currently the only effective methods to control WDV. However, knowledge of the pathosystem and epidemiology of WDD is limited, and the few known sources of genetic tolerance indicate that further research is needed. Considering the economic importance of WDD and its likely increasing relevance in the coming decades, this study provides a comprehensive compilation of knowledge on the most important aspects with information on the causal virus, its vector, symptoms, host range, and control strategies. In addition, the current status of genetic and breeding efforts to control and manage this disease in wheat will be discussed, as this is crucial to effectively manage the disease under changing environmental conditions and minimize impending yield losses.
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Affiliation(s)
- Anne-Kathrin Pfrieme
- Institute for Resistance Research and Stress Tolerance, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, 06484 Quedlinburg, Germany; (T.W.); (A.S.)
| | - Torsten Will
- Institute for Resistance Research and Stress Tolerance, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, 06484 Quedlinburg, Germany; (T.W.); (A.S.)
| | - Klaus Pillen
- Institute of Agricultural and Nutritional Science, Plant Breeding, Martin-Luther-University Halle-Wittenberg, 06108 Halle (Saale), Germany;
| | - Andreas Stahl
- Institute for Resistance Research and Stress Tolerance, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, 06484 Quedlinburg, Germany; (T.W.); (A.S.)
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5
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Chen J, Sun M, Xiao G, Shi R, Zhao C, Zhang Q, Yang S, Xuan Y. Starving the enemy: how plant and microbe compete for sugar on the border. FRONTIERS IN PLANT SCIENCE 2023; 14:1230254. [PMID: 37600180 PMCID: PMC10433384 DOI: 10.3389/fpls.2023.1230254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Accepted: 07/20/2023] [Indexed: 08/22/2023]
Abstract
As the primary energy source for a plant host and microbe to sustain life, sugar is generally exported by Sugars Will Eventually be Exported Transporters (SWEETs) to the host extracellular spaces or the apoplast. There, the host and microbes compete for hexose, sucrose, and other important nutrients. The host and microbial monosaccharide transporters (MSTs) and sucrose transporters (SUTs) play a key role in the "evolutionary arms race". The result of this competition hinges on the proportion of sugar distribution between the host and microbes. In some plants (such as Arabidopsis, corn, and rice) and their interacting pathogens, the key transporters responsible for sugar competition have been identified. However, the regulatory mechanisms of sugar transporters, especially in the microbes require further investigation. Here, the key transporters that are responsible for the sugar competition in the host and pathogen have been identified and the regulatory mechanisms of the sugar transport have been briefly analyzed. These data are of great significance to the increase of the sugar distribution in plants for improvement in the yield.
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Affiliation(s)
- Jingsheng Chen
- College of Biology and Food Engineering, Chongqing Three Gorges University, Wanzhou, China
| | - Miao Sun
- College of Biology and Food Engineering, Chongqing Three Gorges University, Wanzhou, China
| | - Guosheng Xiao
- College of Biology and Food Engineering, Chongqing Three Gorges University, Wanzhou, China
| | - Rujie Shi
- College of Biology and Food Engineering, Chongqing Three Gorges University, Wanzhou, China
| | - Chanjuan Zhao
- Chongqing Three Gorges Vocational College, Wanzhou, China
| | - Qianqian Zhang
- College of Biology and Food Engineering, Chongqing Three Gorges University, Wanzhou, China
| | - Shuo Yang
- College of Plant Protection, Shenyang Agricultural University, Shenyang, China
| | - Yuanhu Xuan
- College of Plant Protection, Shenyang Agricultural University, Shenyang, China
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6
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Liang Y, Bai J, Xie Z, Lian Z, Guo J, Zhao F, Liang Y, Huo H, Gong H. Tomato sucrose transporter SlSUT4 participates in flowering regulation by modulating gibberellin biosynthesis. PLANT PHYSIOLOGY 2023; 192:1080-1098. [PMID: 36943245 PMCID: PMC10231472 DOI: 10.1093/plphys/kiad162] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 02/14/2023] [Accepted: 02/26/2023] [Indexed: 06/01/2023]
Abstract
The functions of sucrose transporters (SUTs) differ among family members. The physiological function of SUT1 has been studied intensively, while that of SUT4 in various plant species including tomato (Solanum lycopersicum) is less well-understood. In this study, we characterized the function of tomato SlSUT4 in the regulation of flowering using a combination of molecular and physiological analyses. SlSUT4 displayed transport activity for sucrose when expressed in yeast (Saccharomyces cerevisiae), and it localized at both the plasma membrane and tonoplast. SlSUT4 interacted with SlSUT1, causing partial internalization of the latter, the main phloem loader of sucrose in tomato. Silencing of SlSUT4 promoted SlSUT1 localization to the plasma membrane, contributing to increased sucrose export and thus increased sucrose level in the shoot apex, which promoted flowering. Both silencing of SlSUT4 and spraying with sucrose suppressed gibberellin biosynthesis through repression of ent-kaurene oxidase and gibberellin 20-oxidase-1 (2 genes encoding key enzymes in gibberellin biosynthesis) expression by SlMYB76, which directly bound to their promoters. Silencing of SlMYB76 promoted gibberellin biosynthesis. Our results suggest that SlSUT4 is a functional SUT in tomato; downregulation of SlSUT4 expression enhances sucrose transport to the shoot apex, which promotes flowering by inhibiting gibberellin biosynthesis.
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Affiliation(s)
- Yufei Liang
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Jiayu Bai
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Zhilong Xie
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Zhaoyuan Lian
- Mid-Florida Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, 2725 South Binion Road, Apopka, FL 32703, USA
| | - Jia Guo
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Feiyang Zhao
- College of Life Sciences, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Yan Liang
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
| | - Heqiang Huo
- Mid-Florida Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, 2725 South Binion Road, Apopka, FL 32703, USA
| | - Haijun Gong
- Shaanxi Engineering Research Center for Vegetables/College of Horticulture, Northwest A&F University,Yangling, Shaanxi 712100, China
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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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8
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Ma WF, Li YB, Nai GJ, Liang GP, Ma ZH, Chen BH, Mao J. Changes and response mechanism of sugar and organic acids in fruits under water deficit stress. PeerJ 2022; 10:e13691. [PMID: 36039369 PMCID: PMC9419716 DOI: 10.7717/peerj.13691] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 06/16/2022] [Indexed: 01/19/2023] Open
Abstract
The content and the ratio of soluble sugars and organic acids in fruits are significant indicators for fruit quality. They are affected by multiple environmental factors, in which water-deficient is the most concern. Previous studies found that the content of soluble sugars and organic acids in fruit displayed great differences under varied water stress. It is important to clarify the mechanism of such difference and to provide researchers with systematic knowledge about the response to drought stress and the mechanism of sugar and acid changes in fruits, so that they can better carry out the study of fruit quality under drought stress. Therefore, the researchers studied dozens of research articles about the content of soluble sugar and organic acid, the activity of related metabolic enzymes, and the expression of related metabolic genes in fruits under water stress, and the stress response of plants to water stress. We found that after plants perceived and transmitted the signal of water deficit, the expression of genes related to the metabolism of soluble sugars and organic acids changed. It was then affected the synthesis of metabolic enzymes and changed their metabolic rate, ultimately leading to changes in soluble sugar and organic acid content. Based on the literature review, we described the pathway diagrams of sugar metabolism, organic acid metabolism, mainly malic acid, tartaric acid, and citric acid metabolism, and of the response to drought stress. From many aspects including plants' perception of water stress signal, signal conversion and transmission, induced gene expression, the changes in soluble sugar and the enzyme activities of organic acids, as well as the final sugar and acid content in fruits, this thesis summarized previous studies on the influence of water stress on soluble sugars and the metabolism of organic acids in fruits.
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9
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Li G, Zhou C, Yang Z, Zhang C, Dai Q, Huo Z, Xu K. Low Nitrogen Enhances Apoplastic Phloem Loading and Improves the Translocation of Photoassimilates in Rice Leaves and Stems. PLANT & CELL PHYSIOLOGY 2022; 63:991-1007. [PMID: 35579477 DOI: 10.1093/pcp/pcac066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/07/2022] [Accepted: 05/17/2022] [Indexed: 06/15/2023]
Abstract
The grain filling of rice depends on photoassimilates from leaves and stems. Phloem loading is the first crucial step for the transportation of sucrose to grains. However, phloem loading mechanisms in rice leaves and stems and their response to nitrogen (N) remain unclear. Here, using a combination of electron microscopy, transportation of a phloem tracer and 13C labeling, phloem loading was studied in rice leaves and stems. The results showed that the sieve element-companion cell complex lacked a symplastic connection with surrounding parenchyma cells in leaves and stems. The genes expression and protein levels of sucrose transporter (SUTs) and sugars will eventually be exported transporters (SWEETs) were detected in the vascular bundle of leaves and stems. A decrease in the 13C isotope remobilization from leaves to stems and panicles following treatment with p-chloromercuribenzenesulfonic acid indicated that rice leaves and stems actively transport sucrose into the phloem. Under low-N (LN) treatment, the activities of α-amylase, β-amylase and sucrose phosphate synthase (SPS) in stems and activity of SPS in leaves increased; genes expression and protein levels of SUTs and SWEETs in leaves and stems increased; the 13C isotope reallocation in panicles increased. These indicated that LN enhanced apoplastic phloem loading in stems and leaves. This improved the translocation of photoassimilates and consequently increased grain filling percentage, grain weight and harvest index. This study provides evidence that rice leaves and stems utilize an apoplastic loading strategy and respond to N stimuli by regulating the genes expression and protein levels of SUTs and SWEETs.
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Affiliation(s)
- Guohui Li
- Agricultural College, Yangzhou University, Yangzhou 225009, China
- Innovation Center of Rice Cultivation Technology in Yangtze River Valley of Ministry of Agriculture, Yangzhou 225009, China
- Jiangsu Key Laboratory of Crop Cultivation and Physiology, Yangzhou 225009, China
- Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou 225009, China
| | - Chiyan Zhou
- Agricultural College, Yangzhou University, Yangzhou 225009, China
| | - Zijun Yang
- Agricultural College, Yangzhou University, Yangzhou 225009, China
| | - Chenhui Zhang
- Agricultural College, Yangzhou University, Yangzhou 225009, China
| | - Qigen Dai
- Agricultural College, Yangzhou University, Yangzhou 225009, China
- Innovation Center of Rice Cultivation Technology in Yangtze River Valley of Ministry of Agriculture, Yangzhou 225009, China
- Jiangsu Key Laboratory of Crop Cultivation and Physiology, Yangzhou 225009, China
- Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou 225009, China
| | - Zhongyang Huo
- Agricultural College, Yangzhou University, Yangzhou 225009, China
- Innovation Center of Rice Cultivation Technology in Yangtze River Valley of Ministry of Agriculture, Yangzhou 225009, China
- Jiangsu Key Laboratory of Crop Cultivation and Physiology, Yangzhou 225009, China
- Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou 225009, China
| | - Ke Xu
- Agricultural College, Yangzhou University, Yangzhou 225009, China
- Innovation Center of Rice Cultivation Technology in Yangtze River Valley of Ministry of Agriculture, Yangzhou 225009, China
- Jiangsu Key Laboratory of Crop Cultivation and Physiology, Yangzhou 225009, China
- Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou 225009, China
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10
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Li R, Zheng W, Jiang M, Zhang H. A review of starch biosynthesis in cereal crops and its potential breeding applications in rice ( Oryza Sativa L.). PeerJ 2022; 9:e12678. [PMID: 35036154 PMCID: PMC8710062 DOI: 10.7717/peerj.12678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 12/02/2021] [Indexed: 11/20/2022] Open
Abstract
Starch provides primary storage of carbohydrates, accounting for approximately 85% of the dry weight of cereal endosperm. Cereal seeds contribute to maximum annual starch production and provide the primary food for humans and livestock worldwide. However, the growing demand for starch in food and industry and the increasing loss of arable land with urbanization emphasizes the urgency to understand starch biosynthesis and its regulation. Here, we first summarized the regulatory signaling pathways about leaf starch biosynthesis. Subsequently, we paid more attention to how transcriptional factors (TFs) systematically respond to various stimulants via the regulation of the enzymes during starch biosynthesis. Finally, some strategies to improve cereal yield and quality were put forward based on the previous reports. This review would collectively help to design future studies on starch biosynthesis in cereal crops.
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Affiliation(s)
- Ruiqing Li
- State Key Laboratory of Rice Biology and Chinese National Center for Rice Improvement, China National Rice Research Institute, Hangzhou, China.,College of Agronomy, Anhui Agricultural University, Hefei, China
| | - Wenyin Zheng
- College of Agronomy, Anhui Agricultural University, Hefei, China
| | - Meng Jiang
- State Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou, China
| | - Huali Zhang
- State Key Laboratory of Rice Biology and Chinese National Center for Rice Improvement, China National Rice Research Institute, Hangzhou, China
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11
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Hetero/Homo-Complexes of Sucrose Transporters May Be a Subtle Mode to Regulate Sucrose Transportation in Grape Berries. Int J Mol Sci 2021; 22:ijms222112062. [PMID: 34769493 PMCID: PMC8584533 DOI: 10.3390/ijms222112062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/02/2021] [Accepted: 11/04/2021] [Indexed: 11/17/2022] Open
Abstract
The sugar distribution mechanism in fruits has been the focus of research worldwide; however, it remains unclear. In order to elucidate the relevant mechanisms in grape berries, the expression, localization, function, and regulation of three sucrose transporters were studied in three representative Vitis varieties. Both SUC11 and SUC12 expression levels were positively correlated with sugar accumulation in grape berries, whereas SUC27 showed a negative relationship. The alignment analysis and sucrose transport ability of isolated SUCs were determined to reflect coding region variations among V. vinifera, V. amurensis Ruper, and V. riparia, indicating that functional variation existed in one SUT from different varieties. Furthermore, potentially oligomerized abilities of VvSUCs colocalized in the sieve elements of the phloem as plasma membrane proteins were verified. The effects of oligomerization on transport properties were characterized in yeast. VvSUC11 and VvSUC12 are high-affinity/low-capacity types of SUTs that stimulate each other by upregulating Vmax and Km, inhibiting sucrose transport, and downregulating the Km of VvSUC27. Thus, changes in the distribution of different SUTs in the same cell govern functional regulation. The activation and inhibition of sucrose transport could be achieved in different stages and tissues of grape development to achieve an effective distribution of sugar.
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12
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Sanden NC, Schulz A. Stationary sieve element proteins. JOURNAL OF PLANT PHYSIOLOGY 2021; 266:153511. [PMID: 34537466 DOI: 10.1016/j.jplph.2021.153511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/13/2021] [Accepted: 09/01/2021] [Indexed: 06/13/2023]
Abstract
Vascular plants use the phloem to move sugars and other molecules from source leaves to sink organs such as roots and fruits. Within the phloem, enucleate sieve elements provide the low-resistance pipe system that enable bulk flow of sap. In this review, we provide an overview of the highly specific protein machinery that localize to mature sieve elements without entering the phloem translocation stream. Generally, the proteins either maintain the flow, protect the sieve element against pathogens or transmit system wide signals. A notable exception is found in poppy, where part of the opium biosynthesis is compartmentalized in sieve elements. Biosynthesis of sieve element proteins happens either continuously in companion cell or transiently in immature sieve elements before nuclear disintegration. The latter population is translated during differentiation and stays functional without turnover during the entire lifespan of sieve elements. We discuss how protein longevity imposes some interesting restrictions on plants, especially in arborescent monocots with long living sieve elements.
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Affiliation(s)
- Niels Christian Sanden
- DynaMo Center, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark; Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark
| | - Alexander Schulz
- DynaMo Center, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark; Section for Transport Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark.
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13
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Wang Y, Chen Y, Wei Q, Wan H, Sun C. Phylogenetic relationships of sucrose transporters (SUTs) in plants and genome-wide characterization of SUT genes in Orchidaceae reveal roles in floral organ development. PeerJ 2021; 9:e11961. [PMID: 34603845 PMCID: PMC8445082 DOI: 10.7717/peerj.11961] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 07/21/2021] [Indexed: 11/20/2022] Open
Abstract
Sucrose is the primary form of photosynthetically produced carbohydrates transported long distance in many plant species and substantially affects plant growth, development and physiology. Sucrose transporters (SUTs or SUCs) are a group of membrane proteins that play vital roles in mediating sucrose allocation within cells and at the whole-plant level. In this study, we investigated the relationships among SUTs in 24 representative plant species and performed an analysis of SUT genes in three sequenced Orchidaceae species: Dendrobium officinale, Phalaenopsis equestris, and Apostasia shenzhenica. All the SUTs from the 24 plant species were classified into three groups and five subgroups, subgroups A, B1, B2.1, B2.2, and C, based on their evolutionary relationships. A total of 22 SUT genes were identified among Orchidaceae species, among which D. officinale had 8 genes (DoSUT01-08), P. equestris had eight genes (PeqSUT01-08) and A. shenzhenica had 6 genes (AsSUT01-06). For the 22 OrchidaceaeSUTs, subgroups A, B2.2 and C contained three genes, whereas the SUT genes were found to have significantly expanded in the monocot-specific subgroup B2.1, which contained 12 genes. To understand sucrose partitioning and the functions of sucrose transporters in Orchidaceae species, we analyzed the water-soluble sugar content and performed RNA sequencing of different tissues of D. officinale, including leaves, stems, flowers and roots. The results showed that although the total content of water-soluble polysaccharides was highest in the stems of D. officinale, the sucrose content was highest in the flowers. Moreover, gene expression analysis showed that most of the DoSUTs were expressed in the flowers, among which DoSUT01,DoSUT07 and DoSUT06 had significantly increased expression levels. These results indicated that stems are used as the main storage sinks for photosynthetically produced sugar in D. officinale and that DoSUTs mainly function in the cellular machinery and development of floral organs. Our findings provide valuable information on sucrose partitioning and the evolution and functions of SUT genes in Orchidaceae and other species.
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Affiliation(s)
- Yunzhu Wang
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Yue Chen
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Qingzhen Wei
- Institute of Vegetable Research, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Hongjian Wan
- Institute of Vegetable Research, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Chongbo Sun
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
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14
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van Bel AJE. The plant axis as the command centre for (re)distribution of sucrose and amino acids. JOURNAL OF PLANT PHYSIOLOGY 2021; 265:153488. [PMID: 34416599 DOI: 10.1016/j.jplph.2021.153488] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 07/13/2021] [Accepted: 08/01/2021] [Indexed: 06/13/2023]
Abstract
Along with the increase in size required for optimal colonization of terrestrial niches, channels for bidirectional bulk transport of materials in land plants evolved during a period of about 100 million years. These transport systems are essentially still in operation - though perfected over the following 400 million years - and make use of hydrostatic differentials. Substances are accumulated or released at the loading and unloading ends, respectively, of the transport channels. The intermediate stretch between the channel termini is bifunctional and executes orchestrated release and retrieval of solutes. Analyses of anatomical and physiological data demonstrate that the release/retrieval zone extends deeper into sources and sinks than is commonly thought and covers usually much more than 99% of the translocation stretch. This review sketches the significance of events in the intermediate stretch for distribution of organic materials over the plant body. Net leakage from the channels does not only serve maintenance and growth of tissues along the pathway, but also diurnal, short-term or seasonal storage of reserve materials, and balanced distribution of organic C- and N-compounds over axial and terminal sinks. Release and retrieval are controlled by plasma-membrane transporters at the vessel/parenchyma interface in the contact pits along xylem vessels and by plasma-membrane transporters at the interface between companion cells and phloem parenchyma along sieve tubes. The xylem-to-phloem pathway vice versa is a bifacial, radially oriented system comprising a symplasmic pathway, of which entrance and exit are controlled at specific membrane checkpoints, and a parallel apoplasmic pathway. A broad range of specific sucrose and amino-acid transporters are deployed at the checkpoint plasma membranes. SUCs, SUTs, STPs, SWEETs, and AAPs, LTHs, CATs are localized to the plasma membranes in question, both in monocots and eudicots. Presence of Umamits in monocots is uncertain. There is some evidence for endo- and exocytosis at the vessel/parenchyma interface supplementary to the transporter-mediated uptake and release. Actions of transporters at the checkpoints are equally decisive for storage and distribution of amino acids and sucrose in monocots and eudicots, but storage and distribution patterns may differ between both taxa. While the majority of reserves is sequestered in vascular parenchyma cells in dicots, lack of space in monocot vasculature urges "outsourcing" of storage in ground parenchyma around the translocation path. In perennial dicots, specialized radial pathways (rays) include the sites for seasonal alternation of storage and mobilization. In dicots, apoplasmic phloem loading and a correlated low rate of release along the path would favour supply with photoassimilates of terminal sinks, while symplasmic phloem loading and a correlated higher rate of release along the path favours supply of axial sinks and transfer to the xylem. The balance between the resource acquisition by terminal and axial sinks is an important determinant of relative growth rate and, hence, for the fitness of plants in various habitats. Body enlargement as the evolutionary drive for emergence of vascular systems and mass transport propelled by hydrostatic differentials.
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Affiliation(s)
- Aart J E van Bel
- Institute of Phythopathology, Centre for BioSystems, Land Use and Nutrition, Justus-Liebig University, Heinrich-Buff-Ring 26-32, D-35392, Giessen, Germany.
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15
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Regmi KC, Yogendra K, Farias JG, Li L, Kandel R, Yadav UP, Sha S, Trittermann C, Short L, George J, Evers J, Plett D, Ayre BG, Roy SJ, Gaxiola RA. Improved Yield and Photosynthate Partitioning in AVP1 Expressing Wheat ( Triticum aestivum) Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:273. [PMID: 32256508 PMCID: PMC7090233 DOI: 10.3389/fpls.2020.00273] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 02/21/2020] [Indexed: 05/28/2023]
Abstract
A fundamental factor to improve crop productivity involves the optimization of reduced carbon translocation from source to sink tissues. Here, we present data consistent with the positive effect that the expression of the Arabidopsis thaliana H+-PPase (AVP1) has on reduced carbon partitioning and yield increases in wheat. Immunohistochemical localization of H+-PPases (TaVP) in spring wheat Bobwhite L. revealed the presence of this conserved enzyme in wheat vasculature and sink tissues. Of note, immunogold imaging showed a plasma membrane localization of TaVP in sieve element- companion cell complexes of Bobwhite source leaves. These data together with the distribution patterns of a fluorescent tracer and [U14C]-sucrose are consistent with an apoplasmic phloem-loading model in wheat. Interestingly, 14C-labeling experiments provided evidence for enhanced carbon partitioning between shoots and roots, and between flag leaves and milk stage kernels in AVP1 expressing Bobwhite lines. In keeping, there is a significant yield improvement triggered by the expression of AVP1 in these lines. Green house and field grown transgenic wheat expressing AVP1 also produced higher grain yield and number of seeds per plant, and exhibited an increase in root biomass when compared to null segregants. Another agriculturally desirable phenotype showed by AVP1 Bobwhite plants is a robust establishment of seedlings.
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Affiliation(s)
- Kamesh C. Regmi
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Kalenahalli Yogendra
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - Júlia Gomes Farias
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Lin Li
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Raju Kandel
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Umesh P. Yadav
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, TX, United States
| | - Shengbo Sha
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - Christine Trittermann
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - Laura Short
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - Jessey George
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - John Evers
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, TX, United States
| | - Darren Plett
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
| | - Brian G. Ayre
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, TX, United States
| | - Stuart John Roy
- Australian Centre for Plant Functional Genomics, The University of Adelaide, Adelaide, SA, Australia
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16
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Deng L, Li P, Chu C, Ding Y, Wang S. Symplasmic phloem unloading and post-phloem transport during bamboo internode elongation. TREE PHYSIOLOGY 2020; 40:391-412. [PMID: 31976532 DOI: 10.1093/treephys/tpz140] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 12/04/2019] [Accepted: 12/18/2019] [Indexed: 05/16/2023]
Abstract
In traditional opinions, no radial transportation was considered to occur in the bamboo internodes but was usually considered to occur in the nodes. Few studies have involved the phloem unloading and post-phloem transport pathways in the rapid elongating bamboo shoots. Our observations indicated a symplastic pathway in phloem unloading and post-unloading pathways in the culms of Fargesiayunnanensis Hsueh et Yi, based on a 5,6-carboxyfluorescein diacetate tracing experiment. Significant lignification and suberinization in fiber and parenchyma cell walls in maturing internodes blocked the apoplastic transport. Assimilates were transported out of the vascular bundles in four directions in the inner zones but in two directions in the outer zones via the continuum of parenchyma cells. In transverse sections, assimilates were outward transported from the inner zones to the outer zones. Assimilates transport velocities varied with time, with the highest values at 0):00 h, which were affected by water transport. The assimilate transport from the adult culms to the young shoots also varied with the developmental degree of bamboo shoots, with the highest transport velocities in the rapidly elongating internodes. The localization of sucrose, glucose, starch grains and the related enzymes reconfirmed that the parenchyma cells in and around the vascular bundles constituted a symplastic pathway for the radial transport of sugars and were the main sites for sugar metabolism. The parenchyma cells functioned as the 'rays' for the radial transport in and between vascular bundles in bamboo internodes. These results systematically revealed the transport mechanism of assimilate and water in the elongating bamboo shoots.
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Affiliation(s)
- Lin Deng
- Key Laboratory for Sympodial Bamboo Research, Southwest Forestry University, Bailong Road, Panlong District, Kunming, Yunnan 650224, P. R. China
| | - Pengcheng Li
- Key Laboratory for Sympodial Bamboo Research, Southwest Forestry University, Bailong Road, Panlong District, Kunming, Yunnan 650224, P. R. China
| | - Caihua Chu
- Key Laboratory for Sympodial Bamboo Research, Southwest Forestry University, Bailong Road, Panlong District, Kunming, Yunnan 650224, P. R. China
| | - Yulong Ding
- Bamboo Research Institute, Nanjing Forestry University, Longpan Road, Xuanwu District, Nanjing, Jiangsu 210037, P.R. China
| | - Shuguang Wang
- Key Laboratory for Sympodial Bamboo Research, Southwest Forestry University, Bailong Road, Panlong District, Kunming, Yunnan 650224, P. R. China
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17
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Kumar R, Bishop E, Bridges WC, Tharayil N, Sekhon RS. Sugar partitioning and source-sink interaction are key determinants of leaf senescence in maize. PLANT, CELL & ENVIRONMENT 2019; 42:2597-2611. [PMID: 31158300 DOI: 10.1111/pce.13599] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 05/28/2019] [Accepted: 05/31/2019] [Indexed: 05/09/2023]
Abstract
Source-sink communication is one of the key regulators of senescence; however, the mechanisms underlying such regulation are largely unknown. We analysed senescence induced by the lack of grain sink in maize, termed source-sink regulated senescence (SSRS), and compared the associated physiological and metabolic changes with those accompanying natural senescence. Phenotypic characterization of 31 diverse field-grown inbreds revealed substantial variation for both SSRS and natural senescence. Partitioning of excess carbohydrates to alternative sinks, mainly internodes and husks, emerged as a critical mechanism underlying both SSRS and stay-green. Time-course analyses of SSRS sensitive (B73) and resistant (PHG35) inbreds confirmed the role of sugar partitioning in SSRS and stay-green. Elevated hemicellulose content in PHG35 internodes highlighted the role of the cell wall as a significant alternative sink. Sugar signalling emerged as an important regulator of SSRS as evident from an increased accumulation of trehalose-6-phosphate and decreased transcript levels of snf1-related protein kinase1, two signalling components associated with senescence, in B73. These findings demonstrate a crucial role of sugar partitioning, signalling, and utilization in SSRS. Available genetic variation for SSRS and a better understanding of the underlying mechanisms would help modify sugar partitioning and senescence to enhance the productivity of maize and related grasses.
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Affiliation(s)
- Rohit Kumar
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, 29634
| | - Eugene Bishop
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, 29634
| | - William C Bridges
- Department of Mathematical Sciences, Clemson University, Clemson, SC, 29634
| | - Nishanth Tharayil
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, 29634
| | - Rajandeep S Sekhon
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, 29634
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18
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Éva C, Oszvald M, Tamás L. Current and possible approaches for improving photosynthetic efficiency. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2019; 280:433-440. [PMID: 30824023 DOI: 10.1016/j.plantsci.2018.11.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 10/09/2018] [Accepted: 11/19/2018] [Indexed: 06/09/2023]
Abstract
One of the most important tasks laying ahead today's biotechnology is to improve crop productivity with the aim of meeting increased food and energy demands of humankind. Plant productivity depends on many genetic factors, including life cycle, harvest index, stress tolerance and photosynthetic activity. Many approaches were already tested or suggested to improve either. Limitations of photosynthesis have also been uncovered and efforts been taken to increase its efficiency. Examples include decreasing photosynthetic antennae size, increasing the photosynthetically available light spectrum, countering oxygenase activity of Rubisco by implementing C4 photosynthesis to C3 plants and altering source to sink transport of metabolites. A natural and effective photosynthetic adaptation, the sugar alcohol metabolism got however remarkably little attention in the last years, despite being comparably efficient as C4, and can be considered easier to introduce to new species. We also propose root to shoot carbon-dioxide transport as a means to improve photosynthetic performance and drought tolerance at the same time. Different suggestions and successful examples are covered here for improving plant photosynthesis as well as novel perspectives are presented for future research.
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Affiliation(s)
- Csaba Éva
- Applied Genomics Department, Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Martonvásár 2462, Hungary.
| | - Mária Oszvald
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
| | - László Tamás
- Department of Plant Physiology and Molecular Plant Biology, Eötvös Loránd University, Budapest 1117, Hungary
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19
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Al-Sheikh Ahmed S, Zhang J, Ma W, Dell B. Contributions of TaSUTs to grain weight in wheat under drought. PLANT MOLECULAR BIOLOGY 2018; 98:333-347. [PMID: 30288667 DOI: 10.1007/s11103-018-0782-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Accepted: 09/19/2018] [Indexed: 06/08/2023]
Abstract
The homologous genes to OsSUT1-5 in wheat were identified and detailed analysed. TaSUT1 was the predominant sucrose transporter group and it illustrated the genotypic variations towards drought during grain filling. Sucrose transporters (SUT) play crucial roles in wheat stem water soluble carbohydrate (WSC) remobilization to grain. To determine the major functional SUT gene groups in shoot parts of wheat during grain development, drought tolerant varieties, Westonia and Kauz, were investigated in field drought experiments. Fourteen homologous genes to OsSUT1-5 were identified on five homeologous groups, namely TaSUT1_4A, TaSUT1_4B, TaSUT1_4D; TaSUT2_5A, TaSUT2_5B, TaSUT2_5D; TaSUT3_1A, TaSUT3_1D; TaSUT4_6A, TaSUT4_6B, TaSUT4_6D; TaSUT5_2A, TaSUT5_2B, and TaSUT5_2D, and their gene structures were analysed. Wheat plants above the ground were harvested from pre-anthesis to grain maturity and the stem, leaf sheath, rachis, lemma and developing grain were used for analysing TaSUT gene expression. Grain weight, thousand grain weight, kernel number per spike, biomass and stem WSC were characterized. The study showed that among the five TaSUT groups, TaSUT1 was the predominant sucrose transporting group in all organs sampled, and the expression was particularly high in the developing grain. In contrast to TaSUT1, the gene expression levels of TaSUT2, TaSUT3 and TaSUT4 were lower, except for TaSUT3 which showed preferential expression in the lemma before anthesis. The TaSUT5 gene group was very weakly expressed in all tissues. The upregulated gene expression of TaSUT1 Westonia type in stem and grain reveal a crucial role in stem WSC remobilization to grain under drought. The high TaSUT1 gene expression and the significant correlations with thousand grain weight (TGW) and kernel number per spike demonstrated the contribution in Kauz's high grain yield in an irrigated environment and high TGW in Westonia under drought stress. Further molecular level identification is required for gene marker development.
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Affiliation(s)
- Sarah Al-Sheikh Ahmed
- School of Veterinary and Life Sciences, Murdoch University, South Street, Murdoch, WA, 6150, Australia
| | - Jingjuan Zhang
- School of Veterinary and Life Sciences, Murdoch University, South Street, Murdoch, WA, 6150, Australia.
| | - Wujun Ma
- School of Veterinary and Life Sciences, Murdoch University, South Street, Murdoch, WA, 6150, Australia
| | - Bernard Dell
- School of Veterinary and Life Sciences, Murdoch University, South Street, Murdoch, WA, 6150, Australia
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20
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Daba SD, Tyagi P, Brown-Guedira G, Mohammadi M. Genome-Wide Association Studies to Identify Loci and Candidate Genes Controlling Kernel Weight and Length in a Historical United States Wheat Population. FRONTIERS IN PLANT SCIENCE 2018; 9:1045. [PMID: 30123226 PMCID: PMC6086202 DOI: 10.3389/fpls.2018.01045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 06/27/2018] [Indexed: 05/26/2023]
Abstract
Although kernel weight (KW) is a major component of grain yield, its contribution to yield genetic gain during breeding history has been minimal. This highlights an untapped potential for further increases in yield via improving KW. We investigated variation and genetics of KW and kernel length (KL) via genome-wide association studies (GWAS) using a historical and contemporary soft red winter wheat population representing 200 years of selection and breeding history in the United States. The observed changes of KW and KL over time did not show any conclusive trend. The population showed a structure, which was mainly explained by the time and location of germplasm development. Cluster sharing by germplasm from more than one breeding population was suggestive of episodes of germplasm exchange. Using 2 years of field-based phenotyping, we detected 26 quantitative trait loci (QTL) for KW and 27 QTL for KL with -log10(p) > 3.5. The search for candidate genes near the QTL on the wheat genome version IWGSCv1.0 has resulted in over 500 genes. The predicted functions of several of these genes are related to kernel development, photosynthesis, sucrose and starch synthesis, and assimilate remobilization and transport. We also evaluated the effect of allelic polymorphism of genes previously reported for KW and KL by using Kompetitive Allele Specific PCR (KASP) markers. Only TaGW2 showed significant association with KW. Two genes, i.e., TaSus2-2B and TaGS-D1 showed significant association with KL. Further physiological studies are needed to decipher the involvement of these genes in KW and KL development.
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Affiliation(s)
- Sintayehu D. Daba
- Department of Agronomy, Purdue University, West Lafayette, IN, United States
| | - Priyanka Tyagi
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| | - Gina Brown-Guedira
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
- Small Grains Genotyping Laboratory, United States Department of Agriculture, Agricultural Research Services, Raleigh, NC, United States
| | - Mohsen Mohammadi
- Department of Agronomy, Purdue University, West Lafayette, IN, United States
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21
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Kumar R, Mukherjee S, Ayele BT. Molecular aspects of sucrose transport and its metabolism to starch during seed development in wheat: A comprehensive review. Biotechnol Adv 2018; 36:954-967. [PMID: 29499342 DOI: 10.1016/j.biotechadv.2018.02.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 01/27/2018] [Accepted: 02/24/2018] [Indexed: 10/17/2022]
Abstract
Wheat is one of the most important crops globally, and its grain is mainly used for human food, accounting for 20% of the total dietary calories. It is also used as animal feed and as a raw material for a variety of non-food and non-feed industrial products such as a feedstock for the production of bioethanol. Starch is the major constituent of a wheat grain, as a result, it is considered as a critical determinant of wheat yield and quality. The amount and composition of starch deposited in wheat grains is controlled primarily by sucrose transport from source tissues to the grain and its conversion to starch. Therefore, elucidation of the molecular mechanisms regulating these physiological processes provides important opportunities to improve wheat starch yield and quality through biotechnological approaches. This review comprehensively discusses the current understanding of the molecular aspects of sucrose transport and sucrose-to-starch metabolism in wheat grains. It also highlights the advances and prospects of starch biotechnology in wheat.
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Affiliation(s)
- Rohit Kumar
- Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, Manitoba R3T 2N2, Canada
| | - Shalini Mukherjee
- Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, Manitoba R3T 2N2, Canada
| | - Belay T Ayele
- Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, Manitoba R3T 2N2, Canada.
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Julius BT, Leach KA, Tran TM, Mertz RA, Braun DM. Sugar Transporters in Plants: New Insights and Discoveries. PLANT & CELL PHYSIOLOGY 2017; 58:1442-1460. [PMID: 28922744 DOI: 10.1093/pcp/pcx090] [Citation(s) in RCA: 187] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 06/19/2017] [Indexed: 05/24/2023]
Abstract
Carbohydrate partitioning is the process of carbon assimilation and distribution from source tissues, such as leaves, to sink tissues, such as stems, roots and seeds. Sucrose, the primary carbohydrate transported long distance in many plant species, is loaded into the phloem and unloaded into distal sink tissues. However, many factors, both genetic and environmental, influence sucrose metabolism and transport. Therefore, understanding the function and regulation of sugar transporters and sucrose metabolic enzymes is key to improving agriculture. In this review, we highlight recent findings that (i) address the path of phloem loading of sucrose in rice and maize leaves; (ii) discuss the phloem unloading pathways in stems and roots and the sugar transporters putatively involved; (iii) describe how heat and drought stress impact carbohydrate partitioning and phloem transport; (iv) shed light on how plant pathogens hijack sugar transporters to obtain carbohydrates for pathogen survival, and how the plant employs sugar transporters to defend against pathogens; and (v) discuss novel roles for sugar transporters in plant biology. These exciting discoveries and insights provide valuable knowledge that will ultimately help mitigate the impending societal challenges due to global climate change and a growing population by improving crop yield and enhancing renewable energy production.
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Affiliation(s)
- Benjamin T Julius
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 116 Tucker Hall, Columbia, MO 65211, USA
| | - Kristen A Leach
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 116 Tucker Hall, Columbia, MO 65211, USA
| | - Thu M Tran
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 116 Tucker Hall, Columbia, MO 65211, USA
- Plant Imaging Consortium, USA
| | - Rachel A Mertz
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 116 Tucker Hall, Columbia, MO 65211, USA
| | - David M Braun
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 116 Tucker Hall, Columbia, MO 65211, USA
- Plant Imaging Consortium, USA
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Glassop D, Stiller J, Bonnett GD, Grof CPL, Rae AL. An analysis of the role of the ShSUT1 sucrose transporter in sugarcane using RNAi suppression. FUNCTIONAL PLANT BIOLOGY : FPB 2017; 44:795-808. [PMID: 32480608 DOI: 10.1071/fp17073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 05/11/2017] [Indexed: 06/11/2023]
Abstract
The role of ShSUT1 in sucrose mobilisation and storage in sugarcane was investigated by employing RNAi technology to reduce the expression of this gene. Transcript profiling in non-transformed plants showed an alignment between expression and sucrose concentration, with strongest expression in source leaves and increasing expression through the daylight period of a diurnal cycle. Five transgenic plant lines were produced with reduced ShSUT1 expression ranging from 52 to 92% lower than control plants. Differential suppression of ShSUT1 sequence variants in the highly polyploid sugarcane genome were also investigated. Amplicon sequencing of the ShSUT1 variants within the transgenic lines and controls showed no preferential suppression with only minor differences in the proportional expression of the variants. A range of altered sugar, fibre and moisture contents were measured in mature leaf and internode samples, but no phenotype was consistently exhibited by all five transgenic lines. Phenotypes observed indicate that ShSUT1 does not play a direct role in phloem loading. ShSUT1 is likely involved with retrieving sucrose from intercellular spaces for transport and storage.
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Affiliation(s)
- Donna Glassop
- CSIRO Agriculture and Food, 306 Carmody Road, St Lucia, Qld 4067, Australia
| | - Jiri Stiller
- CSIRO Agriculture and Food, 306 Carmody Road, St Lucia, Qld 4067, Australia
| | - Graham D Bonnett
- CSIRO Agriculture and Food, 306 Carmody Road, St Lucia, Qld 4067, Australia
| | - Christopher P L Grof
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Anne L Rae
- CSIRO Agriculture and Food, 306 Carmody Road, St Lucia, Qld 4067, Australia
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24
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Milne RJ, Reinders A, Ward JM, Offler CE, Patrick JW, Grof CPL. Contribution of sucrose transporters to phloem unloading within Sorghum bicolor stem internodes. PLANT SIGNALING & BEHAVIOR 2017; 12:e1319030. [PMID: 28426383 PMCID: PMC5501222 DOI: 10.1080/15592324.2017.1319030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 04/09/2017] [Indexed: 05/14/2023]
Abstract
Sucrose produced in source leaves is loaded into collection phloem, transported to sinks and unloaded for utilization or storage. In the context of long distance transport, sucrose transporters (SUTs) can function to load sucrose into collection phloem, retrieve leaked sucrose during long distance transport, and load sucrose into sink cells. SUTs have also been proposed to efflux sucrose under conditions of low proton motive force and low extracellular sucrose. The involvement of sucrose transporters in phloem unloading in a representative monocot stem, Sorghum bicolor, was evaluated during different stages of internode development. Transcript levels and functional properties of selected key transporters were measured, with both cellular and subcellular localization determined.
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Affiliation(s)
- Ricky J Milne
- a School of Environmental and Life Sciences , The University of Newcastle , NSW , Australia
- b CSIRO Agriculture and Food , Canberra , ACT , Australia
| | - Anke Reinders
- c Department of Plant and Microbial Biology , University of Minnesota , St. Paul , MN , USA
| | - John M Ward
- c Department of Plant and Microbial Biology , University of Minnesota , St. Paul , MN , USA
| | - Christina E Offler
- a School of Environmental and Life Sciences , The University of Newcastle , NSW , Australia
| | - John W Patrick
- a School of Environmental and Life Sciences , The University of Newcastle , NSW , Australia
| | - Christopher P L Grof
- a School of Environmental and Life Sciences , The University of Newcastle , NSW , Australia
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Jian H, Lu K, Yang B, Wang T, Zhang L, Zhang A, Wang J, Liu L, Qu C, Li J. Genome-Wide Analysis and Expression Profiling of the SUC and SWEET Gene Families of Sucrose Transporters in Oilseed Rape ( Brassica napus L.). FRONTIERS IN PLANT SCIENCE 2016; 7:1464. [PMID: 0 PMCID: PMC5039336 DOI: 10.3389/fpls.2016.01464] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 09/14/2016] [Indexed: 05/18/2023]
Abstract
Sucrose is the principal transported product of photosynthesis from source leaves to sink organs. SUTs/SUCs (sucrose transporters or sucrose carriers) and SWEETs (Sugars Will Eventually be Exported Transporters) play significant central roles in phloem loading and unloading. SUTs/SUCs and SWEETs are key players in sucrose translocation and are associated with crop yields. The SUT/SUC and SWEET genes have been characterized in several plant species, but a comprehensive analysis of these two gene families in oilseed rape has not yet been reported. In our study, 22 and 68 members of the SUT/SUCs and SWEET gene families, respectively, were identified in the oilseed rape (Brassica napus) genome through homology searches. An analysis of the chromosomal distribution, phylogenetic relationships, gene structures, motifs and the cis-acting regulatory elements in the promoters of BnSUC and BnSWEET genes were analyzed. Furthermore, we examined the expression of the 18 BnSUC and 16 BnSWEET genes in different tissues of "ZS11" and the expression of 9 BnSUC and 7 BnSWEET genes in "ZS11" under various conditions, including biotic stress (Sclerotinia sclerotiorum), abiotic stresses (drought, salt and heat), and hormone treatments (abscisic acid, auxin, cytokinin, brassinolide, gibberellin, and salicylic acid). In conclusion, our study provides the first comprehensive analysis of the oilseed rape SUC and SWEET gene families. Information regarding the phylogenetic relationships, gene structure and expression profiles of the SUC and SWEET genes in the different tissues of oilseed rape helps to identify candidates with potential roles in specific developmental processes. Our study advances our understanding of the important roles of sucrose transport in oilseed rape.
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Milne RJ, Offler CE, Patrick JW, Grof CPL. Cellular pathways of source leaf phloem loading and phloem unloading in developing stems of Sorghum bicolor in relation to stem sucrose storage. FUNCTIONAL PLANT BIOLOGY : FPB 2015; 42:957-970. [PMID: 32480736 DOI: 10.1071/fp15133] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 06/25/2015] [Indexed: 06/11/2023]
Abstract
Cellular pathways of phloem loading in source leaves and phloem unloading in stems of sweet Sorghum bicolor (L.) Moench were deduced from histochemical determinations of cell wall composition and from the relative radial mobilities of fluorescent tracer dyes exiting vascular pipelines. The cell walls of small vascular bundles in source leaves, the predicted site of phloem loading, contained minimal quantities of lignin and suberin. A phloem-loaded symplasmic tracer, carboxyfluorescein, was retained within the collection phloem, indicating symplasmic isolation. Together, these findings suggested that phloem loading in source leaves occurs apoplasmically. Lignin was restricted to the walls of protoxylem elements located in meristematic, elongating and recently elongated regions of the stem. The apoplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moved radially from the transpiration stream, consistent with phloem and storage parenchyma cells being interconnected by an apoplasmic pathway. The major phase of sucrose accumulation in mature stems coincided with heavy lignification and suberisation of sclerenchyma sheath cell walls restricting apoplasmic tracer movement from the phloem to storage parenchyma apoplasms. Phloem unloading at this stage of stem development followed a symplasmic route linking sieve elements and storage parenchyma cells, as confirmed by the phloem-delivered symplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moving radially from the stem phloem.
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Affiliation(s)
- Ricky J Milne
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Christina E Offler
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - John W Patrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Christopher P L Grof
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
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Öner-Sieben S, Rappl C, Sauer N, Stadler R, Lohaus G. Characterization, localization, and seasonal changes of the sucrose transporter FeSUT1 in the phloem of Fraxinus excelsior. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4807-19. [PMID: 26022258 PMCID: PMC4507781 DOI: 10.1093/jxb/erv255] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Trees are generally assumed to be symplastic phloem loaders. A typical feature for most wooden species is an open minor vein structure with symplastic connections between mesophyll cells and phloem cells, which allow sucrose to move cell-to-cell through the plasmodesmata into the phloem. Fraxinus excelsior (Oleaceae) also translocates raffinose family oligosaccharides in addition to sucrose. Sucrose concentration was recently shown to be higher in the phloem sap than in the mesophyll cells. This suggests the involvement of apoplastic steps and the activity of sucrose transporters in addition to symplastic phloem-loading processes. In this study, the sucrose transporter FeSUT1 from F. excelsior was analysed. Heterologous expression in baker's yeast showed that FeSUT1 mediates the uptake of sucrose. Immunohistochemical analyses revealed that FeSUT1 was exclusively located in phloem cells of minor veins and in the transport phloem of F. excelsior. Further characterization identified these cells as sieve elements and possibly ordinary companion cells but not as intermediary cells. The localization and expression pattern point towards functions of FeSUT1 in phloem loading of sucrose as well as in sucrose retrieval. FeSUT1 is most likely responsible for the observed sucrose gradient between mesophyll and phloem. The elevated expression level of FeSUT1 indicated an increased apoplastic carbon export activity from the leaves during spring and late autumn. It is hypothesized that the importance of apoplastic loading is high under low-sucrose conditions and that the availability of two different phloem-loading mechanisms confers advantages for temperate woody species like F. excelsior.
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Affiliation(s)
- Soner Öner-Sieben
- Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany
| | - Christine Rappl
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Norbert Sauer
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Ruth Stadler
- Lehrstuhl Molekulare Pflanzenphysiologie Department Biologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Gertrud Lohaus
- Molekulare Pflanzenforschung/Pflanzenbiochemie (Botanik), Bergische Universität Wuppertal, Gaußstraße 20, D-42119 Wuppertal, Germany
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Bihmidine S, Baker RF, Hoffner C, Braun DM. Sucrose accumulation in sweet sorghum stems occurs by apoplasmic phloem unloading and does not involve differential Sucrose transporter expression. BMC PLANT BIOLOGY 2015; 15:186. [PMID: 26223524 PMCID: PMC4518677 DOI: 10.1186/s12870-015-0572-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/16/2015] [Indexed: 05/19/2023]
Abstract
BACKGROUND Sorghum (Sorghum bicolor L. Moench) cultivars store non-structural carbohydrates predominantly as either starch in seeds (grain sorghums) or sugars in stems (sweet sorghums). Previous research determined that sucrose accumulation in sweet sorghum stems was not correlated with the activities of enzymes functioning in sucrose metabolism, and that an apoplasmic transport step may be involved in stem sucrose accumulation. However, the sucrose unloading pathway from stem phloem to storage parenchyma cells remains unelucidated. Sucrose transporters (SUTs) transport sucrose across membranes, and have been proposed to function in sucrose partitioning differences between sweet and grain sorghums. The purpose of this study was to characterize the key differences in carbohydrate accumulation between a sweet and a grain sorghum, to define the path sucrose may follow for accumulation in sorghum stems, and to determine the roles played by sorghum SUTs in stem sucrose accumulation. RESULTS Dye tracer studies to determine the sucrose transport route revealed that, for both the sweet sorghum cultivar Wray and grain sorghum cultivar Macia, the phloem in the stem veins was symplasmically isolated from surrounding cells, suggesting sucrose was apoplasmically unloaded. Once in the phloem apoplasm, a soluble tracer diffused from the vein to stem parenchyma cell walls, indicating the lignified mestome sheath encompassing the vein did not prevent apoplasmic flux outside of the vein. To characterize carbohydrate partitioning differences between Wray and Macia, we compared the growth, stem juice volume, solute contents, SbSUTs gene expression, and additional traits. Contrary to previous findings, we detected no significant differences in SbSUTs gene expression within stem tissues. CONCLUSIONS Phloem sieve tubes within sweet and grain sorghum stems are symplasmically isolated from surrounding cells; hence, unloading from the phloem likely occurs apoplasmically, thereby defining the location of the previously postulated step for sucrose transport. Additionally, no changes in SbSUTs gene expression were detected in sweet vs. grain sorghum stems, suggesting alterations in SbSUT transcript levels do not account for the carbohydrate partitioning differences between cultivars. A model illustrating sucrose phloem unloading and movement to stem storage parenchyma, and highlighting roles for sucrose transport proteins in sorghum stems is discussed.
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Affiliation(s)
- Saadia Bihmidine
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO, 65211, USA.
| | - R Frank Baker
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO, 65211, USA.
- University of Missouri Molecular Cytology Core, 120 Bond Life Sciences Center, 1201 Rollins Street, Columbia, MO, 65211-7310, USA.
| | - Cassandra Hoffner
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO, 65211, USA.
- Sigma-Aldrich Biotech, 545 S. Ewing, Saint Louis, MO, 63103, USA.
| | - David M Braun
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO, 65211, USA.
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Buchner P, Tausz M, Ford R, Leo A, Fitzgerald GJ, Hawkesford MJ, Tausz-Posch S. Expression patterns of C- and N-metabolism related genes in wheat are changed during senescence under elevated CO2 in dry-land agriculture. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 236:239-249. [PMID: 26025537 DOI: 10.1016/j.plantsci.2015.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 04/09/2015] [Accepted: 04/10/2015] [Indexed: 06/04/2023]
Abstract
Projected climatic impacts on crop yield and quality, and increased demands for production, require targeted research to optimise nutrition of crop plants. For wheat, post-anthesis carbon and nitrogen remobilisation from vegetative plant parts and translocation to grains directly affects grain carbon (C), nitrogen (N) and protein levels. We analysed the influence of increased atmospheric CO2 on the expression of genes involved in senescence, leaf carbohydrate and nitrogen metabolism and assimilate transport in wheat under field conditions (Australian Grains Free Air CO2 Enrichment; AGFACE) over a time course from anthesis to maturity, the key period for grain filling. Wheat grown under CO2 enrichment had lower N concentrations and a tendency towards greater C/N ratios. A general acceleration of the senescence process by elevated CO2 was not confirmed. The expression patterns of genes involved in carbohydrate metabolism, nitrate reduction and metabolite transport differed between CO2 treatments, and this CO2 effect was different between pre-senescence and during senescence. The results suggest up-regulation of N remobilisation and down-regulation of C remobilisation during senescence under elevated CO2, which is consistent with greater grain N-sink strength of developing grains.
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Affiliation(s)
- Peter Buchner
- Plant Biology and Crop Science Department, Rothamsted Research, Harpenden AL5 4TX, UK.
| | - Michael Tausz
- School of Ecosystem and Forest Sciences, The University of Melbourne, 4 Water Street, Creswick, VIC 3363, Australia.
| | - Rebecca Ford
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville Campus, Melbourne, VIC 3010, Australia.
| | - Audrey Leo
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville Campus, Melbourne, VIC 3010, Australia.
| | - Glenn J Fitzgerald
- Department of Economic Development, Jobs, Transport and Resources, 110 Natimuk Road, Horsham, VIC 3400, Australia.
| | - Malcolm J Hawkesford
- Plant Biology and Crop Science Department, Rothamsted Research, Harpenden AL5 4TX, UK.
| | - Sabine Tausz-Posch
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville Campus, Melbourne, VIC 3010, Australia.
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Berthier A, Meuriot F, Dédaldéchamp F, Lemoine R, Prud'homme MP, Noiraud-Romy N. Identification of a new sucrose transporter in rye-grass (LpSUT2): effect of defoliation and putative fructose sensing. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 84:32-44. [PMID: 25240108 DOI: 10.1016/j.plaphy.2014.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/01/2014] [Indexed: 05/22/2023]
Abstract
Rye-grass fast regrowth after defoliation results from an efficient mobilization of C reserves which are transported as sucrose towards regrowing leaves, and which can be supported by one or several sucrose transporters (SUTs) like LpSUT1. Therefore, our objectives were to isolate, identify, characterize and immunolocalize such sucrose transporters. A protein (LpSUT2) showing a twelve spanning trans-membrane domain, extended N terminal and internal cytoplasmic loop, and kinetic properties consistent with well-known sucrose transporters, was isolated and successfully characterized. Along with LpSUT1, it was mainly localized in mesophyll cells of leaf sheaths and elongating leaf bases. These transporters were also found in parenchyma bundle sheath (PBS) cells but they were not detected in the sieve element/companion cell complex of the phloem. Unlike LpSUT1 transcript levels which increased as a response to defoliation in source and sink tissues, LpSUT2 transcript levels were unaffected by defoliation and weakly expressed. Interestingly, sucrose transport by LpSUT2 was inhibited by fructose. LpSUT1 and LpSUT2 appeared to have different functions. LpSUT1 is proposed to play a key role in C storage and mobilization by allowing sucrose transport between PBS and mesophyll cells, depending on the plant C status. LpSUT2 could be involved in sucrose/fructose sensing at sub-cellular level.
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Affiliation(s)
- Alexandre Berthier
- Université de Caen Basse Normandie, UMR Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France; INRA UMR 950, Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France
| | - Frédéric Meuriot
- Université de Caen Basse Normandie, UMR Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France; INRA UMR 950, Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France
| | - Fabienne Dédaldéchamp
- UMR 7267 CNRS-Université de Poitiers équipe PHYMOTS, Université Poitiers, Bât Botanique (B5), BP 633, 86022 Poitiers, France
| | - Rémi Lemoine
- UMR 7267 CNRS-Université de Poitiers équipe PHYMOTS, Université Poitiers, Bât Botanique (B5), BP 633, 86022 Poitiers, France
| | - Marie-Pascale Prud'homme
- Université de Caen Basse Normandie, UMR Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France; INRA UMR 950, Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France
| | - Nathalie Noiraud-Romy
- Université de Caen Basse Normandie, UMR Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France; INRA UMR 950, Ecophysiologie Végétale, Agronomie and Nutritions NCS, F-14032 Caen, France.
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Braun DM, Wang L, Ruan YL. Understanding and manipulating sucrose phloem loading, unloading, metabolism, and signalling to enhance crop yield and food security. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1713-35. [PMID: 24347463 DOI: 10.1093/jxb/ert416] [Citation(s) in RCA: 227] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Sucrose is produced in, and translocated from, photosynthetically active leaves (sources) to support non-photosynthetic tissues (sinks), such as developing seeds, fruits, and tubers. Different plants can utilize distinct mechanisms to transport sucrose into the phloem sieve tubes in source leaves. While phloem loading mechanisms have been extensively studied in dicot plants, there is less information about phloem loading in monocots. Maize and rice are major dietary staples, which have previously been proposed to use different cellular routes to transport sucrose from photosynthetic cells into the translocation stream. The anatomical, physiological, and genetic evidence supporting these conflicting hypotheses is examined. Upon entering sink cells, sucrose often is degraded into hexoses for a wide range of metabolic and storage processes, including biosynthesis of starch, protein, and cellulose, which are all major constituents for food, fibre, and fuel. Sucrose, glucose, fructose, and their derivate, trehalose-6-phosphate, also serve as signalling molecules to regulate gene expression either directly or through cross-talk with other signalling pathways. As such, sugar transport and metabolism play pivotal roles in plant development and realization of crop yield that needs to be increased substantially to meet the projected population demand in the foreseeable future. This review will discuss the current understanding of the control of carbon partitioning from the cellular to whole-plant levels, focusing on (i) the pathways employed for phloem loading in source leaves, particularly in grasses, and the routes used in sink organs for phloem unloading; (ii) the transporter proteins responsible for sugar efflux and influx across plasma membranes; and (iii) the key enzymes regulating sucrose metabolism, signalling, and utilization. Examples of how sugar transport and metabolism can be manipulated to improve crop productivity and stress tolerance are discussed.
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Affiliation(s)
- David M Braun
- Division of Biological Sciences, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, Columbia, MO 65211, USA
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32
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Deol KK, Mukherjee S, Gao F, Brûlé-Babel A, Stasolla C, Ayele BT. Identification and characterization of the three homeologues of a new sucrose transporter in hexaploid wheat (Triticum aestivum L.). BMC PLANT BIOLOGY 2013; 13:181. [PMID: 24237613 PMCID: PMC4225610 DOI: 10.1186/1471-2229-13-181] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 11/11/2013] [Indexed: 05/05/2023]
Abstract
BACKGROUND Sucrose transporters (SUTs) play important roles in regulating the translocation of assimilates from source to sink tissues. Identification and characterization of new SUTs in economically important crops such as wheat provide insights into their role in determining seed yield. To date, however, only one SUT of wheat has been reported and functionally characterized. The present study reports the isolation and characterization of a new SUT, designated as TaSUT2, and its homeologues (TaSUT2A, TaSUT2B and TaSUT2D) in hexaploid wheat (Triticum aestivum L.). RESULTS TaSUT2A and TaSUT2B genes each encode a protein with 506 amino acids, whereas TaSUT2D encodes a protein of 508 amino acids. The molecular mass of these proteins is predicted to be ~ 54 kDA. Topological analysis of the amino acid sequences of the three homeologues revealed that they contain 12 transmembrane spanning helices, which are described as distinct characteristic features of glycoside-pentoside-hexuronide cation symporter family that includes all known plant SUTs, and a histidine residue that appears to be localized at and associated conformationally with the sucrose binding site. Yeast SUSY7/ura3 strain cells transformed with TaSUT2A, TaSUT2B and TaSUT2D were able to uptake sucrose and grow on a medium containing sucrose as a sole source of carbon; however, our subcellular localization study with plant cells revealed that TaSUT2 is localized to the tonoplast. The expression of TaSUT2 was detected in the source, including flag leaf blade, flag leaf sheath, peduncle, glumes, palea and lemma, and sink (seed) tissues. The relative contributions of the three genomes of wheat to the total expression of TaSUT2 appear to differ with tissues and developmental stages. At the cellular level, TaSUT2 is expressed mainly in the vein of developing seeds and subepidermal mesophyll cells of the leaf blade. CONCLUSION This study demonstrated that TaSUT2 is a new wheat SUT protein. Given that TaSUT2 is localized to the tonoplast and sucrose is temporarily stored in the vacuoles of both source and sink tissues, our data imply that TaSUT2 is involved in the intracellular partitioning of sucrose, particularly between the vacuole and cytoplasm.
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Affiliation(s)
- Kirandeep K Deol
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
| | - Shalini Mukherjee
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
| | - Feng Gao
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
| | - Anita Brûlé-Babel
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
| | - Claudio Stasolla
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
| | - Belay T Ayele
- Department of Plant Science, 222 Agriculture Building, University of Manitoba, Winnipeg, Manitoba R3T 2 N2, Canada
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Patrick JW. Does Don Fisher's high-pressure manifold model account for phloem transport and resource partitioning? FRONTIERS IN PLANT SCIENCE 2013; 4:184. [PMID: 23802003 PMCID: PMC3685801 DOI: 10.3389/fpls.2013.00184] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/21/2013] [Indexed: 05/03/2023]
Abstract
The pressure flow model of phloem transport envisaged by Münch (1930) has gained wide acceptance. Recently, however, the model has been questioned on structural and physiological grounds. For instance, sub-structures of sieve elements may reduce their hydraulic conductances to levels that impede flow rates of phloem sap and observed magnitudes of pressure gradients to drive flow along sieve tubes could be inadequate in tall trees. A variant of the Münch pressure flow model, the high-pressure manifold model of phloem transport introduced by Donald Fisher may serve to reconcile at least some of these questions. To this end, key predicted features of the high-pressure manifold model of phloem transport are evaluated against current knowledge of the physiology of phloem transport. These features include: (1) An absence of significant gradients in axial hydrostatic pressure in sieve elements from collection to release phloem accompanied by transport properties of sieve elements that underpin this outcome; (2) Symplasmic pathways of phloem unloading into sink organs impose a major constraint over bulk flow rates of resources translocated through the source-path-sink system; (3) Hydraulic conductances of plasmodesmata, linking sieve elements with surrounding phloem parenchyma cells, are sufficient to support and also regulate bulk flow rates exiting from sieve elements of release phloem. The review identifies strong circumstantial evidence that resource transport through the source-path-sink system is consistent with the high-pressure manifold model of phloem transport. The analysis then moves to exploring mechanisms that may link demand for resources, by cells of meristematic and expansion/storage sinks, with plasmodesmal conductances of release phloem. The review concludes with a brief discussion of how these mechanisms may offer novel opportunities to enhance crop biomass yields.
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Affiliation(s)
- John W. Patrick
- School of Environmental and Life Sciences, The University of NewcastleCallaghan, NSW, Australia
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Tang AC, Boyer JS. Differences in membrane selectivity drive phloem transport to the apoplast from which maize florets develop. ANNALS OF BOTANY 2013; 111:551-62. [PMID: 23388879 PMCID: PMC3605948 DOI: 10.1093/aob/mct012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 12/14/2012] [Indexed: 05/09/2023]
Abstract
BACKGROUND AND AIMS Floral development depends on photosynthetic products delivered by the phloem. Previous work suggested the path to the flower involved either the apoplast or the symplast. The objective of the present work was to determine the path and its mechanism of operation. METHODS Maize (Zea mays) plants were grown until pollination. For simplicity, florets were harvested before fertilization to ensure that all tissues were of maternal origin. Because sucrose from phloem is hydrolysed to glucose on its way to the floret, the tissues were imaged and analysed for glucose using an enzyme-based assay. Also, carboxyfluorescein diacetate was fed to the stems and similarly imaged and analysed. KEY RESULTS The images of live sections revealed that phloem contents were released to the pedicel apoplast below the nucellus of the florets. Glucose or carboxyfluorescein were detected and could be washed out. For carboxyfluorescein, the plasma membranes of the phloem parenchyma appeared to control the release. After release, the nucellus absorbed apoplast glucose selectively, rejecting carboxyfluorescein. CONCLUSIONS Despite the absence of an embryo, the apoplast below the nucellus was a depot for phloem contents, and the strictly symplast path is rejected. Because glucose and carboxyfluorescein were released non-selectively, the path to the floret resembled the one later when an embryo is present. The non-selective release indicates that turgor at phloem termini cannot balance the full osmotic potential of the phloem contents and would create a downward pressure gradient driving bulk flow toward the sink. Such a gradient was previously measured by Fisher and Cash-Clark in wheat. At the same time, selective absorption from the apoplast by the nucellar membranes would support full turgor in this tissue, isolating the embryo sac from the maternal plant. The isolation should continue later when an embryo develops.
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Affiliation(s)
| | - John S. Boyer
- College of Marine Studies (now College of Earth, Ocean and Environment), and College of Agriculture and Natural Resources, University of Delaware, Lewes, DE 19958, USA
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Tognetti JA, Pontis HG, Martínez-Noël GM. Sucrose signaling in plants: a world yet to be explored. PLANT SIGNALING & BEHAVIOR 2013; 8:e23316. [PMID: 23333971 PMCID: PMC3676498 DOI: 10.4161/psb.23316] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 12/17/2012] [Indexed: 05/18/2023]
Abstract
The role of sucrose as a signaling molecule in plants was originally proposed several decades ago. However, recognition of sucrose as a true signal has been largely debated and only recently this role has been fully accepted. The best-studied cases of sucrose signaling involve metabolic processes, such as the induction of fructan or anthocyanin synthesis, but a large volume of scattered information suggests that sucrose signals may control a vast array of developmental processes along the whole life cycle of the plant. Also, wide gaps exist in our current understanding of the intracellular steps that mediate sucrose action. Sucrose concentration in plant tissues tends to be directly related to light intensity, and inversely related to temperature, and accordingly, exogenous sucrose supply often mimics the effect of high light and cold. However, many exceptions to this rule seem to occur due to interactions with other signaling pathways. In conclusion, the sucrose role as a signal molecule in plants is starting to be unveiled and much research is still needed to have a complete map of its significance in plant function.
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Affiliation(s)
- Jorge A. Tognetti
- Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC); Buenos Aires, Argentina
- Facultad de Ciencias Agrarias; Universidad Nacional de Mar del Plata; Buenos Aires, Argentina
| | - Horacio G. Pontis
- Fundación para Investigaciones Biológicas Aplicadas; Buenos Aires, Argentina
| | - Giselle M.A. Martínez-Noël
- Fundación para Investigaciones Biológicas Aplicadas; Buenos Aires, Argentina
- Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC)- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Buenos Aires, Argentina
- Correspondence to: Giselle M.A. Martínez-Noël,
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Etxeberria E, Pozueta-Romero J, Gonzalez P. In and out of the plant storage vacuole. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 190:52-61. [PMID: 22608519 DOI: 10.1016/j.plantsci.2012.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/15/2012] [Accepted: 03/29/2012] [Indexed: 05/08/2023]
Abstract
The plant storage vacuole is involved in a wide variety of metabolic functions a great many of which necessitate the transport of substances across the tonoplast. Some solutes, depending on the origin, have to cross the plasma membrane as well. The cell is equipped with a complex web of transport systems, cellular routes, and unique intracellular environments that support their transport and accumulation against a concentration gradient. These are capable of processing a diverse nature of substances of distinct sizes, chemical properties, and origins. In this review we describe the various mechanism involved in solute transport into the vacuole of storage cells with special emphasis placed on solutes arriving through the apoplast. Transport of solutes from the cytosol to the vacuole is carried out by tonoplast-bound ABC transporters, solute/H(+) antiporters, and ion channels whereas transport from the apoplast requires additional plasma membrane-bound solute/H(+) symporters and fluid-phase endocytosis. In addition, and based on new evidence accumulated within the last decade, we re-evaluate the current notion of extracellular solute uptake as partially based on facilitated diffusion, and offer an alternative interpretation that involves membrane bound transporters and fluid-phase endocytosis. Finally, we make several assertions in regards to solute export from the vacuole as predicted by the limited available data suggesting that both membrane-bound carriers and vesicle mediated exocytosis are involved during solute mobilization.
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Affiliation(s)
- Ed Etxeberria
- University of Florida/IFAS, Department of Horticultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850, USA.
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Li F, Ma C, Wang X, Gao C, Zhang J, Wang Y, Cong N, Li X, Wen J, Yi B, Shen J, Tu J, Fu T. Characterization of Sucrose transporter alleles and their association with seed yield-related traits in Brassica napus L. BMC PLANT BIOLOGY 2011; 11:168. [PMID: 22112023 PMCID: PMC3248380 DOI: 10.1186/1471-2229-11-168] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 11/23/2011] [Indexed: 05/20/2023]
Abstract
BACKGROUND Sucrose is the primary photosynthesis product and the principal translocating form within higher plants. Sucrose transporters (SUC/SUT) play a critical role in phloem loading and unloading. Photoassimilate transport is a major limiting factor for seed yield. Our previous research demonstrated that SUT co-localizes with yield-related quantitative trait loci. This paper reports the isolation of BnA7.SUT1 alleles and their promoters and their association with yield-related traits. RESULTS Two novel BnA7.SUT1 genes were isolated from B. napus lines 'Eagle' and 'S-1300' and designated as BnA7.SUT1.a and BnA7.SUT1.b, respectively. The BnA7.SUT1 protein exhibited typical SUT features and showed high amino acid homology with related species. Promoters of BnA7.SUT1.a and BnA7.SUT1.b were also isolated and classified as pBnA7.SUT1.a and pBnA7.SUT1.b, respectively. Four dominant sequence-characterized amplified region markers were developed to distinguish BnA7.SUT1.a and BnA7.SUT1.b. The two genes were estimated as alleles with two segregating populations (F2 and BC1) obtained by crossing '3715'×'3769'. BnA7.SUT1 was mapped to the A7 linkage group of the TN doubled haploid population. In silico analysis of 55 segmental BnA7.SUT1 alleles resulted three BnA7.SUT1 clusters: pBnA7.SUT1.a- BnA7.SUT1.a (type I), pBnA7.SUT1.b- BnA7.SUT1.a (type II), and pBnA7.SUT1.b- BnA7.SUT1.b (type III). Association analysis with a diverse panel of 55 rapeseed lines identified single nucleotide polymorphisms (SNPs) in promoter and coding domain sequences of BnA7.SUT1 that were significantly associated with one of three yield-related traits: number of effective first branches (EFB), siliques per plant (SP), and seed weight (n = 1000) (TSW) across all four environments examined. SNPs at other BnA7.SUT1 sites were also significantly associated with at least one of six yield-related traits: EFB, SP, number of seeds per silique, seed yield per plant, block yield, and TSW. Expression levels varied over various tissue/organs at the seed-filling stage, and BnA7.SUT1 expression positively correlated with EFB and TSW. CONCLUSIONS Sequence, mapping, association, and expression analyses collectively showed significant diversity between the two BnA7.SUT1 alleles, which control some of the phenotypic variation for branch number and seed weight in B. napus consistent with expression levels. The associations between allelic variation and yield-related traits may facilitate selection of better genotypes in breeding.
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Affiliation(s)
- Fupeng Li
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Chaozhi Ma
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Xia Wang
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Changbin Gao
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Jianfeng Zhang
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuanyuan Wang
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Na Cong
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Xinghua Li
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Jing Wen
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Bin Yi
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Jinxiong Shen
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Jinxing Tu
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
| | - Tingdong Fu
- National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China
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van Bel AJE, Furch ACU, Hafke JB, Knoblauch M, Patrick JW. (Questions)n on phloem biology. 2. Mass flow, molecular hopping, distribution patterns and macromolecular signalling. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 181:325-330. [PMID: 21889037 DOI: 10.1016/j.plantsci.2011.05.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 05/16/2011] [Indexed: 05/31/2023]
Abstract
This review speculates on correlations between mass flow in sieve tubes and the distribution of photoassimilates and macromolecular signals. Since micro- (low-molecular compounds) and macromolecules are withdrawn from, and released into, the sieve-tube sap at various rates, distribution patterns of these compounds do not strictly obey mass-flow predictions. Due to serial release and retrieval transport steps executed by sieve tube plasma membranes, micromolecules are proposed to "hop" between sieve element/companion cell complexes and phloem parenchyma cells under source-limiting conditions (apoplasmic hopping). Under sink-limiting conditions, micromolecules escape from sieve tubes via pore-plasmodesma units and are temporarily stored. It is speculated that macromolecules "hop" between sieve elements and companion cells using plasmodesmal trafficking mechanisms (symplasmic hopping). We explore how differential tagging may influence distribution patterns of macromolecules and how their bidirectional movement could arise. Effects of exudation techniques on the macromolecular composition of sieve-tube sap are discussed.
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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, Giessen, Germany.
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40
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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.
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Affiliation(s)
- Brian G Ayre
- University of North Texas, Department of Biological Sciences, Denton, Texas, USA.
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Ganeshan S, Drinkwater JM, Repellin A, Chibbar RN. Selected carbohydrate metabolism genes show coincident expression peaks in grains of in vitro-cultured immature spikes of wheat (Triticum aestivum L.). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:4193-4201. [PMID: 20235533 DOI: 10.1021/jf903861q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
An in vitro culture system is useful to study grain development under defined conditions to minimize confounding effects associated with whole plant studies and metabolite movement into the developing grains. The objective of this study was to monitor the expression patterns of carbohydrate metabolism genes during grain development in an in vitro wheat spike culture system. Immature spikes were cultured prior to anthesis, and grains were collected at various days postanthesis (DPA). Grains from cultured spikes showed maximum expression of starch metabolic genes by 10 DPA, with a rapid decline thereafter. The rapid increase and decrease in expression rate in the in vitro system was thought to be due to fructan exohydrolase (1-FEH and 6-FEH) or sucrose transporter 1 (SUT1) and sucrose synthase (SuSy) genes being highly expressed. SUT1 reached peak expression at 8 DPA, two days earlier than the other genes, and may account for the rapid early stage trigger in expression of the other genes. However, expression of 1-FEH and 6-FEH genes in in vitro-cultured spikes peaked at 12 DPA, two days later than the other genes, and could indicate that fructan catabolism was not a factor in the rapid accumulation of starch in the in vitro-cultured spikes. Accumulation of GBSSI polypeptides generally showed similar patterns in both systems, with the maximum amount in the in vitro system observed four days later than in the in planta spikes, reflecting different turnover controls of GBSSI transcripts. The in vitro system offers opportunities for further refinement and detailed grain development studies.
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Affiliation(s)
- Seedhabadee Ganeshan
- Department of Plant Sciences, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Martinez-Noël GA, Tognetti JA, Salerno GL, Pontis HG. Sugar signaling of fructan metabolism: New insights on protein phosphatases in sucrose-fed wheat leaves. PLANT SIGNALING & BEHAVIOR 2010; 230:1071-9. [PMID: 20220311 DOI: 10.1007/s00425-009-1002-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Accepted: 08/05/2009] [Indexed: 05/21/2023]
Abstract
Protein phosphatase type 2A (PP2A) activity is required for the sucrose induction of fructan metabolism in wheat leaves, as shown in experiments with the addition of the specific inhibitor okadaic acid (OA) together with sucrose. However, a decrease in total PP2A activity has been found along sucrose treatment. Here we analyze the effect of sucrose feeding to wheat leaves on PP2A activity profiles after Deae-Sephacel and Superose separation, in comparison with those of control leaves. The results show no evidence of changes in PP2A activity profiles as a consequence of sucrose feeding. In all, our data suggest that constitutive levels of PP2A activity may be sufficient for the sucrose-mediated induction of fructan metabolism and that general decrease of PP2A activity produced by long-term treatment with sucrose may be due to a negative feedback regulation.
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Berthier A, Desclos M, Amiard V, Morvan-Bertrand A, Demmig-Adams B, Adams WW, Turgeon R, Prud'homme MP, Noiraud-Romy N. Activation of sucrose transport in defoliated Lolium perenne L.: an example of apoplastic phloem loading plasticity. PLANT & CELL PHYSIOLOGY 2009; 50:1329-44. [PMID: 19520670 DOI: 10.1093/pcp/pcp081] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The pathway of carbon phloem loading was examined in leaf tissues of the forage grass Lolium perenne. The effect of defoliation (leaf blade removal) on sucrose transport capacity was assessed in leaf sheaths as the major carbon source for regrowth. The pathway of carbon transport was assessed via a combination of electron microscopy, plasmolysis experiments and plasma membrane vesicles (PMVs) purified by aqueous two-phase partitioning from the microsomal fraction. Results support an apoplastic phloem loading mechanism. Imposition of an artificial proton-motive force to PMVs from leaf sheaths energized an active, transient and saturable uptake of sucrose (Suc). The affinity of Suc carriers for Suc was 580 microM in leaf sheaths of undefoliated plants. Defoliation induced a decrease of K(m) followed by an increase of V(max). A transporter was isolated from stubble (including leaf sheaths) cDNA libraries and functionally expressed in yeast. The level of L.perenne SUcrose Transporter 1 (LpSUT1) expression increased in leaf sheaths in response to defoliation. Taken together, the results indicate that Suc transport capacity increased in leaf sheaths of L. perenne in response to leaf blade removal. This increase might imply de novo synthesis of Suc transporters, including LpSUT1, and may represent one of the mechanisms contributing to rapid refoliation.
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Affiliation(s)
- Alexandre Berthier
- UMR INRA-UCBN 950, Ecophysiologie Végétale, Agronomie and nutritions NCS, irba, Esplanade de la Paix, Université de Caen, Caen, France
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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.
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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.
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Affiliation(s)
- Yi Ma
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Schmitt B, Stadler R, Sauer N. Immunolocalization of solanaceous SUT1 proteins in companion cells and xylem parenchyma: new perspectives for phloem loading and transport. PLANT PHYSIOLOGY 2008; 148:187-99. [PMID: 18614713 PMCID: PMC2528081 DOI: 10.1104/pp.108.120410] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 06/22/2008] [Indexed: 05/18/2023]
Abstract
Leaf sucrose (Suc) transporters are essential for phloem loading and long-distance partitioning of assimilates in plants that load their phloem from the apoplast. Suc loading into the phloem is indispensable for the generation of the osmotic potential difference that drives phloem bulk flow and is central for the long-distance movement of phloem sap compounds, including hormones and signaling molecules. In previous analyses, solanaceous SUT1 Suc transporters from tobacco (Nicotiana tabacum), potato (Solanum tuberosum), and tomato (Solanum lycopersicum) were immunolocalized in plasma membranes of enucleate sieve elements. Here, we present data that identify solanaceous SUT1 proteins with high specificity in phloem companion cells. Moreover, comparisons of SUT1 localization in the abaxial and adaxial phloem revealed higher levels of SUT1 protein in the abaxial phloem of all three solanaceous species, suggesting different physiological roles for these two types of phloem. Finally, SUT1 proteins were identified in files of xylem parenchyma cells, mainly in the bicollateral veins. Together, our data provide new insight into the role of SUT1 proteins in solanaceous species.
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Affiliation(s)
- Bianca Schmitt
- Molekulare Pflanzenphysiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
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Sun AJ, Xu HL, Gong WK, Zhai HL, Meng K, Wang YQ, Wei XL, Xiao GF, Zhu Z. Cloning and expression analysis of rice sucrose transporter genes OsSUT2M and OsSUT5Z. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2008; 50:62-75. [PMID: 18666953 DOI: 10.1111/j.1744-7909.2007.00596.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Two sucrose transporter (SUT) cDNAs, OsSUT2M and OsSUT5Z, were isolated from rice (Oryza sativa L.) by reverse transcription polymerase chain reaction (RT-PCR). Sequencing results indicate they are 1,531 bp and 1,635 bp in length including complete open reading frame 1,506 bp and 1,608 bp, which encode 502 amino acids and 536 amino acids, respectively. The TopPred program suggested that both sucrose transporter proteins, OsSUT2M and OsSUT5Z, consist of potentially 12 transmembrane domains. Semi-quantitative RT-PCR was carried out to investigate the gene expression patterns of OsSUT2M and OsSUT5Z. In vegetative organs, transcripts of OsSUT2M were higher in source leaf blades than in other organs at the same development stage, whereas transcripts of OsSUT5Z were less traceable in all organs investigated. In reproductive organs, both transcripts of these two genes were high in panicles from the booting stage to 7 days after flowering (DAF) and then sharply declined. The potential physiology functions of these two sucrose transporters are discussed.
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Affiliation(s)
- Ai-Jun Sun
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, Beijing 100101, China
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Zhang WH, Zhou Y, Dibley KE, Tyerman SD, Furbank RT, Patrick JW. Review: Nutrient loading of developing seeds. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:314-331. [PMID: 32689358 DOI: 10.1071/fp06271] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 01/30/2007] [Indexed: 05/03/2023]
Abstract
Interest in nutrient loading of seeds is fuelled by its central importance to plant reproductive success and human nutrition. Rates of nutrient loading, imported through the phloem, are regulated by transport and transfer processes located in sources (leaves, stems, reproductive structures), phloem pathway and seed sinks. During the early phases of seed development, most control is likely to be imposed by a low conductive pathway of differentiating phloem cells serving developing seeds. Following the onset of storage product accumulation by seeds, and, depending on nutrient species, dominance of path control gives way to regulation by processes located in sources (nitrogen, sulfur, minor minerals), phloem path (transition elements) or seed sinks (sugars and major mineral elements, such as potassium). Nutrients and accompanying water are imported into maternal seed tissues and unloaded from the conducting sieve elements into an extensive post-phloem symplasmic domain. Nutrients are released from this symplasmic domain into the seed apoplasm by poorly understood membrane transport mechanisms. As seed development progresses, increasing volumes of imported phloem water are recycled back to the parent plant by process(es) yet to be discovered. However, aquaporins concentrated in vascular and surrounding parenchyma cells of legume seed coats could provide a gated pathway of water movement in these tissues. Filial cells, abutting the maternal tissues, take up nutrients from the seed apoplasm by membrane proteins that include sucrose and amino acid/H+ symporters functioning in parallel with non-selective cation channels. Filial demand for nutrients, that comprise the major osmotic species, is integrated with their release and phloem import by a turgor-homeostat mechanism located in maternal seed tissues. It is speculated that turgors of maternal unloading cells are sensed by the cytoskeleton and transduced by calcium signalling cascades.
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Affiliation(s)
- Wen-Hao Zhang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China
| | - Yuchan Zhou
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2238, Australia
| | - Katherine E Dibley
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2238, Australia
| | - Stephen D Tyerman
- School of Agriculture, Food and Wine, Adelaide University, Waite Campus, PMB #1, Glen Osmond, SA 5064, Australia
| | - Robert T Furbank
- CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia
| | - John W Patrick
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2238, Australia
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