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Tian X, Zou H, Xiao Q, Xin H, Zhu L, Li Y, Ma B, Cui N, Ruan YL, Ma F, Li M. Uptake of glucose from the rhizosphere, mediated by apple MdHT1.2, regulates carbohydrate allocation. PLANT PHYSIOLOGY 2023; 193:410-425. [PMID: 37061824 DOI: 10.1093/plphys/kiad221] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 04/12/2023] [Indexed: 06/19/2023]
Abstract
Plant roots can absorb sugars from the rhizosphere, which reduces the consumption of carbon derived from photosynthesis. However, the underlying mechanisms that roots use to control sugar absorption from soil are poorly understood. Here, we identified an apple (Malus × domestica Borkh.) hexose transporter, MdHT1.2, that functions on the root epidermis to absorb glucose (Glc) from the rhizosphere. Based on RNA-seq data, MdHT1.2 showed the highest expression level among 29 MdHT genes in apple roots. Biochemical analyses demonstrated that MdHT1.2 was mainly expressed in the epidermal cells of fine roots, and its protein was located on the plasma membrane. The roots of transgenic apple and Solanum lycopersicum lines overexpressing MdHT1.2 had an increased capability to absorb Glc when fed with [13C]-labeled Glc or 2-NBDG, whereas silencing MdHT1.2 in apple showed the opposite results. Further studies established that MdHT1.2-mediated Glc absorption from the rhizosphere changed the carbon assimilate allocation between apple shoot and root, which regulated plant growth. Additionally, a grafting experiment in tomato confirmed that increasing the Glc uptake capacity in the root overexpressing MdHT1.2 could facilitate carbohydrate partitioning to the fruit. Collectively, our study demonstrated that MdHT1.2 functions on the root epidermis to absorb rhizospheric Glc, which regulates the carbohydrate allocation for plant growth and fruit sugar accumulation.
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Affiliation(s)
- Xiaocheng Tian
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Hui Zou
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Qian Xiao
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Haijun Xin
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Lingcheng Zhu
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Yuxing Li
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Baiquan Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Ningbo Cui
- State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China
| | - Yong-Ling Ruan
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia
| | - Fengwang Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
| | - Mingjun Li
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Shaanxi Key Laboratory of Apple, Northwest A&F University, Yangling 712100, China
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Wu C, Bai Y, Cao Z, Xu J, Xie Y, Zheng H, Jiang J, Mu C, Cheng W, Fang H, Gao J. Plasticity in the Morphology of Growing Bamboo: A Bayesian Analysis of Exogenous Treatment Effects on Plant Height, Internode Length, and Internode Numbers. PLANTS (BASEL, SWITZERLAND) 2023; 12:1713. [PMID: 37111934 PMCID: PMC10145155 DOI: 10.3390/plants12081713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/15/2023] [Accepted: 04/17/2023] [Indexed: 06/19/2023]
Abstract
Sucrose (Suc) and gibberellin (GA) can promote the elongation of certain internodes in bamboo. However, there is a lack of field studies to support these findings and no evidence concerning how Suc and GA promote the plant height of bamboo by regulating the internode elongation and number. We investigated the plant height, the length of each internode, and the total number of internodes of Moso bamboo (Phyllostachys edulis) under exogenous Suc, GA, and control group (CTRL) treatments in the field and analyzed how Suc and GA affected the height of Moso bamboo by promoting the internode length and number. The lengths of the 10th-50th internodes were significantly increased under the exogenous Suc and GA treatments, and the number of internodes was significantly increased by the exogenous Suc treatment. The increased effect of Suc and GA exogenous treatment on the proportion of longer internodes showed a weakening trend near the plant height of 15-16 m compared with the CTRL, suggesting that these exogenous treatments may be more effective in regions where bamboo growth is suboptimal. This study demonstrated that both the exogenous Suc and GA treatments could promote internode elongation of Moso bamboo in the field. The exogenous GA treatment had a stronger effect on internode elongation, and the exogenous Suc treatment had a stronger effect on increasing the internode numbers. The increase in plant height by the exogenous Suc and GA treatments was promoted by the co-elongation of most internodes or the increase in the proportion of longer internodes.
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Affiliation(s)
- Chongyang Wu
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Yucong Bai
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Zhihua Cao
- Anhui Academy of Forestry, Hefei 230036, China
| | - Junlei Xu
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Yali Xie
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Huifang Zheng
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Jutang Jiang
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Changhong Mu
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Wenlong Cheng
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Hui Fang
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
| | - Jian Gao
- Key Laboratory of National Forestry and Grassland Administration, Beijing for Bamboo & Rattan Science and Technology/International Center for Bamboo and Rattan, Beijing 100102, China; (C.W.); (Y.B.); (J.X.); (Y.X.); (J.J.); (C.M.); (W.C.); (H.F.)
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Zhang S, Wang H, Wang T, Liu W, Zhang J, Fang H, Zhang Z, Peng F, Chen X, Wang N. MdMYB305-MdbHLH33-MdMYB10 regulates sugar and anthocyanin balance in red-fleshed apple fruits. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023; 113:1062-1079. [PMID: 36606413 DOI: 10.1111/tpj.16100] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 12/19/2022] [Accepted: 01/03/2023] [Indexed: 06/17/2023]
Abstract
Sugar and anthocyanin are important indicators of fruit quality, and understanding the mechanism underlying their accumulation is essential for breeding high-quality fruit. We identified an R2R3-MYB transcription factor MdMYB305 in the red-fleshed apple progeny, which was positively correlated with fruit sugar content but negatively correlated with anthocyanin content. Transient injection, stable expression [overexpressing and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)], and heterologous transformation of tomato confirmed that MdMYB305 promotes the accumulation of sugar and inhibits the synthesis of anthocyanin. A series of molecular experiments (such as electrophoretic mobility shift and luciferase assays) confirmed that MdMYB305 combines with sugar-related genes (MdCWI1/MdVGT3/MdTMT2) and anthocyanin-related genes (MdF3H/MdDFR/MdUFGT), promoting and inhibiting their activities, and finally regulating the sugar and anthocyanin content of fruits. In addition, the study also found that MdMYB305 competes with MdMYB10 for the MdbHLH33 binding site to balance sugar and anthocyanin accumulation in the fruits, which provides a reference value for exploring more functions of the MYB-bHLH-MYB complex and the balance relationship between sugar and anthocyanin in the future.
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Affiliation(s)
- Shuhui Zhang
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Hui Wang
- College of Horticulture, Northwest A&F University, Yangling, Shanxi, 712100, China
| | - Tong Wang
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Wenjun Liu
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Jing Zhang
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Hongcheng Fang
- State Forestry and Grassland Administration Key Laboratory of Silviculture in the Downstream Areas of the Yellow River, College of Forestry, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Zongying Zhang
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Futian Peng
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Xuesen Chen
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
| | - Nan Wang
- State Key Laboratory of Crop Biology, College of Horticulture Sciences and Engineering, Shandong Agricultural University, Tai'an, 271018, Shandong, China
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Wu H, Li Z. Nano-enabled agriculture: How do nanoparticles cross barriers in plants? PLANT COMMUNICATIONS 2022; 3:100346. [PMID: 35689377 PMCID: PMC9700125 DOI: 10.1016/j.xplc.2022.100346] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 05/12/2022] [Accepted: 06/06/2022] [Indexed: 05/15/2023]
Abstract
Nano-enabled agriculture is a topic of intense research interest. However, our knowledge of how nanoparticles enter plants, plant cells, and organelles is still insufficient. Here, we discuss the barriers that limit the efficient delivery of nanoparticles at the whole-plant and single-cell levels. Some commonly overlooked factors, such as light conditions and surface tension of applied nano-formulations, are discussed. Knowledge gaps regarding plant cell uptake of nanoparticles, such as the effect of electrochemical gradients across organelle membranes on nanoparticle delivery, are analyzed and discussed. The importance of controlling factors such as size, charge, stability, and dispersibility when properly designing nanomaterials for plants is outlined. We mainly focus on understanding how nanoparticles travel across barriers in plants and plant cells and the major factors that limit the efficient delivery of nanoparticles, promoting a better understanding of nanoparticle-plant interactions. We also provide suggestions on the design of nanomaterials for nano-enabled agriculture.
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Affiliation(s)
- Honghong Wu
- MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science & Technology, Huazhong Agricultural University, Wuhan 430070, China; Hubei Hongshan Laboratory, Wuhan 430070, China; College of Agronomy and Biotechnology, China Agricultural University, Beijing 100083, China.
| | - Zhaohu Li
- MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science & Technology, Huazhong Agricultural University, Wuhan 430070, China; Hubei Hongshan Laboratory, Wuhan 430070, China; College of Agronomy and Biotechnology, China Agricultural University, Beijing 100083, China.
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Göttlinger T, Lohaus G. Comparative analyses of the metabolite and ion concentrations in nectar, nectaries, and leaves of 36 bromeliads with different photosynthesis and pollinator types. FRONTIERS IN PLANT SCIENCE 2022; 13:987145. [PMID: 36092434 PMCID: PMC9459329 DOI: 10.3389/fpls.2022.987145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/08/2022] [Indexed: 06/15/2023]
Abstract
Floral nectar contains mainly sugars as well as smaller amounts of amino acids and further compounds. The nectar composition varies between different plant species and it is related to the pollination type of the plant. In addition to this, other factors can influence the composition. Nectar is produced in and secreted from nectaries. A few models exist to explain the origin of nectar for dicotyl plant species, a complete elucidation of the processes, however, has not yet been achieved. This is particularly true for monocots or plant species with CAM photosynthesis. To get closer to such an elucidation, nectar, nectaries, and leaves of 36 bromeliad species were analyzed for sugars, starch, amino acids, and inorganic ions. The species studied include different photosynthesis types (CAM/C3), different pollination types (trochilophilous/chiropterophilous), or different live forms. The main sugars in nectar and nectaries were glucose, fructose, and sucrose, the total sugar concentration was about twofold higher in nectar than in nectaries, which suggests that sugars are actively transported from the nectaries into the nectar. The composition of amino acids in nectar is already determined in the nectaries, but the concentration is much lower in nectar than in nectaries, which suggests selective retention of amino acids during nectar secretion. The same applies to inorganic ions. Statistical analyses showed that the photosynthesis type and the pollination type can explain more data variation in nectar than in nectaries and leaves. Furthermore, the pollinator type has a stronger influence on the nectar or nectary composition than the photosynthesis type. Trochilophilous C3 plants showed significant correlations between the nitrate concentration in leaves and the amino acid concentration in nectaries and nectar. It can be assumed that the more nitrate is taken up, the more amino acids are synthesized in leaves and transported to the nectaries and nectar. However, chiropterophilous C3 plants show no such correlation, which means that the secretion of amino acids into the nectar is regulated by further factors. The results help understand the physiological properties that influence nectaries and nectar as well as the manner of metabolite and ion secretion from nectaries to nectar.
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Nam H, Gupta A, Nam H, Lee S, Cho HS, Park C, Park S, Park SJ, Hwang I. JULGI-mediated increment in phloem transport capacity relates to fruit yield in tomato. PLANT BIOTECHNOLOGY JOURNAL 2022; 20:1533-1545. [PMID: 35478430 PMCID: PMC9342617 DOI: 10.1111/pbi.13831] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 04/19/2022] [Accepted: 04/21/2022] [Indexed: 06/14/2023]
Abstract
The continuous growth of the global population and the increase in the amount of arid land has severely constrained agricultural crop production. To solve this problem, many researchers have attempted to increase productivity through the efficient distribution of energy; however, the direct relationship between the plant vasculature, specifically phloem development, and crop yield is not well established. Here, we demonstrate that an optimum increase in phloem-transportation capacity by reducing SIJUL expression leads to improved sink strength in tomato (Solanum lycopersicum L.). SIJUL, a negative regulator of phloem development, suppresses the translation of a positive regulator of phloem development, SlSMXL5. The suppression of SlJUL increases the number of phloem cells and sucrose transport, but only an optimal reduction of SlJUL function greatly enhances sink strength in tomato, improving fruit setting, and yield contents by 37% and 60%, respectively. We show that the increment in phloem cell number confers spare transport capacity. Our results suggest that the control of phloem-transport capacity within the threshold could enhance the commitment of photosynthates to instigate yield improvement.
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Affiliation(s)
- Hoyoung Nam
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Aarti Gupta
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Heejae Nam
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Seungchul Lee
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Hyun Seob Cho
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Chanyoung Park
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Soyoung Park
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
| | - Soon Ju Park
- Division of Biological Sciences and Research Institute for Basic ScienceWonkwang UniversityIksanKorea
| | - Ildoo Hwang
- Department of Life SciencesPOSTECH Biotech CenterPohang University of Science and TechnologyPohangKorea
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Potkay A, Hölttä T, Trugman AT, Fan Y. Turgor-limited predictions of tree growth, height and metabolic scaling over tree lifespans. TREE PHYSIOLOGY 2022; 42:229-252. [PMID: 34296275 DOI: 10.1093/treephys/tpab094] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 07/18/2021] [Indexed: 06/13/2023]
Abstract
Increasing evidence suggests that tree growth is sink-limited by environmental and internal controls rather than by carbon availability. However, the mechanisms underlying sink-limitations are not fully understood and thus not represented in large-scale vegetation models. We develop a simple, analytically solved, mechanistic, turgor-driven growth model (TDGM) and a phloem transport model (PTM) to explore the mechanics of phloem transport and evaluate three hypotheses. First, phloem transport must be explicitly considered to accurately predict turgor distributions and thus growth. Second, turgor-limitations can explain growth-scaling with size (metabolic scaling). Third, turgor can explain realistic growth rates and increments. We show that mechanistic, sink-limited growth schemes based on plant turgor limitations are feasible for large-scale model implementations with minimal computational demands. Our PTM predicted nearly uniform sugar concentrations along the phloem transport path regardless of phloem conductance, stem water potential gradients and the strength of sink-demands contrary to our first hypothesis, suggesting that phloem transport is not limited generally by phloem transport capacity per se but rather by carbon demand for growth and respiration. These results enabled TDGM implementation without explicit coupling to the PTM, further simplifying computation. We test the TDGM by comparing predictions of whole-tree growth rate to well-established observations (site indices) and allometric theory. Our simple TDGM predicts realistic tree heights, growth rates and metabolic scaling over decadal to centurial timescales, suggesting that tree growth is generally sink and turgor limited. Like observed trees, our TDGM captures tree-size- and resource-based deviations from the classical ¾ power-law metabolic scaling for which turgor is responsible.
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Affiliation(s)
- Aaron Potkay
- Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854, USA
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki FI-00014, Finland
| | - Anna T Trugman
- Department of Geography, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ying Fan
- Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854, USA
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Babst BA, Braun DM, Karve AA, Frank Baker R, Tran TM, Kenny DJ, Rohlhill J, Knoblauch J, Knoblauch M, Lohaus G, Tappero R, Scherzer S, Hedrich R, Jensen KH. Sugar loading is not required for phloem sap flow in maize plants. NATURE PLANTS 2022; 8:171-180. [PMID: 35194203 DOI: 10.1038/s41477-022-01098-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 12/20/2021] [Accepted: 01/07/2022] [Indexed: 06/14/2023]
Abstract
Phloem transport of photoassimilates from leaves to non-photosynthetic organs, such as the root and shoot apices and reproductive organs, is crucial to plant growth and yield. For nearly 90 years, evidence has been generally consistent with the theory of a pressure-flow mechanism of phloem transport. Central to this hypothesis is the loading of osmolytes, principally sugars, into the phloem to generate the osmotic pressure that propels bulk flow. Here we used genetic and light manipulations to test whether sugar import into the phloem is required as the driving force for phloem sap flow. Using carbon-11 radiotracer, we show that a maize sucrose transporter1 (sut1) loss-of-function mutant has severely reduced export of carbon from photosynthetic leaves (only ~4% of the wild type level). Yet, the mutant remarkably maintains phloem pressure at ~100% and sap flow speeds at ~50-75% of those of wild type. Potassium (K+) abundance in the phloem was elevated in sut1 mutant leaves. Fluid dynamic modelling supports the conclusion that increased K+ loading compensated for decreased sucrose loading to maintain phloem pressure, and thereby maintained phloem transport via the pressure-flow mechanism. Furthermore, these results suggest that sap flow and transport of other phloem-mobile nutrients and signalling molecules could be regulated independently of sugar loading into the phloem, potentially influencing carbon-nutrient homoeostasis and the distribution of signalling molecules in plants encountering different environmental conditions.
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Affiliation(s)
- Benjamin A Babst
- Biosciences Department, Brookhaven National Laboratory, Upton, NY, USA.
- Arkansas Forest Resources Center, University of Arkansas at Monticello, Monticello, AR, USA.
| | - David M Braun
- Divisions of Plant and Biological Sciences, University of Missouri, Columbia, MO, USA.
| | - Abhijit A Karve
- Biosciences Department, Brookhaven National Laboratory, Upton, NY, USA
- Office of Technology Commercialization, Purdue University, West Lafayette, IN, USA
| | - R Frank Baker
- Divisions of Plant and Biological Sciences, University of Missouri, Columbia, MO, USA
| | - Thu M Tran
- Divisions of Plant and Biological Sciences, University of Missouri, Columbia, MO, USA
| | - Douglas J Kenny
- Biosciences Department, Brookhaven National Laboratory, Upton, NY, USA
- Department of Chemistry and Chemical Biology, Harvard Medical School, Boston, MA, USA
| | - Julia Rohlhill
- Biosciences Department, Brookhaven National Laboratory, Upton, NY, USA
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA
| | - Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Gertrud Lohaus
- Department of Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany
| | - Ryan Tappero
- Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY, USA
| | - Sönke Scherzer
- Department of Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, Germany
| | - Rainer Hedrich
- Department of Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, Germany
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
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Zhang GP, Marasini M, Li WW, Zhang FL. Grain filling leads to backflow of surplus water from the maize grain to the cob and plant via the xylem. FRONTIERS IN PLANT SCIENCE 2022; 13:1008896. [PMID: 36544873 PMCID: PMC9762273 DOI: 10.3389/fpls.2022.1008896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 11/16/2022] [Indexed: 05/12/2023]
Abstract
Rapid dehydration of maize grain is one of the main characteristics of cultivar selection for mechanical grain harvest; however, the dominant driving forces and mechanisms of grain dehydration before physiological maturity remain disputable and obscure. This study compared the grain moisture content and dehydration rate of coated treatment (no surface evaporation) and control grains. Meanwhile, the xylem-mobile dye was infused from stem and cob, and its movement was observed in cob, ear-stalk and stem xylem. The development dynamics of husk, grain and cob were analyzed to determine the mechanism of grain dehydration. The results showed that, from grain formation to 5-10 days before physiological maturity, the main driving force of grain dehydration of the early and middle-maturity maize cultivars was filling, followed by surface evaporation. In the dye movement experiment, the movement of the stem-infused xylem-mobile dye through the pedicel xylem was observed during but not after the grain formation period. Moreover, the cob-infused xylem-mobile dye moved to the ear- stalk and the stem via the xylem. There was a significantly positive correlation between grain filling rate and dehydration rate from grain formation to physiological maturity. According to these results, we proposed that in the grain dehydration phase driven by filling, the surplus water in the grain flows back to the cob via the pedicel xylem, of which some flowed back to the plant via the cob and ear- stalk xylem. This provides a new theoretical basis for selecting and breeding maize cultivars suitable for mechanical grain harvesting.
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Babst BA, Karve A, Sementilli A, Dweikat I, Braun DM. Physiology and whole-plant carbon partitioning during stem sugar accumulation in sweet dwarf sorghum. PLANTA 2021; 254:80. [PMID: 34546416 DOI: 10.1007/s00425-021-03718-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
A greater rate of phloem unloading and storage in the stem, not a higher rate of sugar production by photosynthesis or sugar export from leaves, is the main factor that results in sugar accumulation in sweet dwarf sorghum compared to grain sorghum. At maturity, the stem internodes of sweet sorghum varieties accumulate high concentrations of fermentable sugars and represent an efficient feedstock for bioethanol production. Although stem sugar accumulation is a heritable trait, additional factors that drive sugar accumulation in sorghum have not been identified. To identify the constraints on stem sugar accumulation in sweet sorghum, we used a combination of carbon-11 (11C) radiotracer, physiological and biochemical approaches, and compared a grain sorghum and sweet dwarf sorghum line that have similar growth characteristics including height. Photosynthesis did not increase during development or differ between the sorghum lines. During the developmental transition to the reproductive stage, export of 11C from leaves approximately doubled in both sorghum lines, but 11C export in the sweet dwarf line did not exceed that of the grain sorghum. Defoliation to manipulate relative sink demand did not result in increased photosynthetic rates, indicating that the combined accumulation of C by all sink tissues was limited by the maximum photosynthetic capacity of source leaves. Nearly 3/4 of the 11C exported from leaves was transported to the lower stem in sweet sorghum within 2 h, whereas in grain sorghum nearly 3/4 of the 11C was in the panicle. Accordingly, the transcripts of several sucrose transporter (SUT) genes were more abundant in the stem internodes of the sweet dwarf line compared to the grain sorghum. Overall, these results indicate that sugar accumulation in sweet sorghum stems is influenced by the interplay of different sink tissues for the same sugars, but is likely driven by elevated sugar phloem unloading and uptake capacity in mature stem internodes.
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Affiliation(s)
- Benjamin A Babst
- Biological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
- Arkansas Forest Resources Center, and College of Forestry, Ag. and Natural Resources, University of Arkansas at Monticello, Monticello, AR, 71656, USA.
| | - Abhijit Karve
- Biological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA
- Purdue Research Foundation, West Lafayette, IN, 47906, USA
| | - Anthony Sementilli
- Biological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA
- Department of Physical Sciences, St Joseph's College, Patchogue, NY, 11772, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Ismail Dweikat
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, 68583-0915, USA
| | - David M Braun
- Divisions of Plant and Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
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11
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Walker RP, Bonghi C, Varotto S, Battistelli A, Burbidge CA, Castellarin SD, Chen ZH, Darriet P, Moscatello S, Rienth M, Sweetman C, Famiani F. Sucrose Metabolism and Transport in Grapevines, with Emphasis on Berries and Leaves, and Insights Gained from a Cross-Species Comparison. Int J Mol Sci 2021; 22:7794. [PMID: 34360556 PMCID: PMC8345980 DOI: 10.3390/ijms22157794] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/09/2021] [Accepted: 07/13/2021] [Indexed: 01/14/2023] Open
Abstract
In grapevines, as in other plants, sucrose and its constituents glucose and fructose are fundamentally important and carry out a multitude of roles. The aims of this review are three-fold. First, to provide a summary of the metabolism and transport of sucrose in grapevines, together with new insights and interpretations. Second, to stress the importance of considering the compartmentation of metabolism. Third, to outline the key role of acid invertase in osmoregulation associated with sucrose metabolism and transport in plants.
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Affiliation(s)
| | - Claudio Bonghi
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova Agripolis, 35020 Legnaro, Italy;
| | - Serena Varotto
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova Agripolis, 35020 Legnaro, Italy;
| | - Alberto Battistelli
- Istituto di Ricerca sugli Ecosistemi Terrestri, Consiglio Nazionale delle Ricerche, 05010 Porano, Italy; (A.B.); (S.M.)
| | | | - Simone D. Castellarin
- Wine Research Centre, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 0Z4, Canada;
| | - Zhi-Hui Chen
- College of Life Science, University of Dundee, Dundee DD1 5EH, UK;
| | - Philippe Darriet
- Cenologie, Institut des Sciences de la Vigne et du Vin (ISVV), 33140 Villenave d’Ornon, France;
| | - Stefano Moscatello
- Istituto di Ricerca sugli Ecosistemi Terrestri, Consiglio Nazionale delle Ricerche, 05010 Porano, Italy; (A.B.); (S.M.)
| | - Markus Rienth
- Changins College for Viticulture and Oenology, University of Sciences and Art Western Switzerland, 1260 Nyon, Switzerland;
| | - Crystal Sweetman
- College of Science & Engineering, Flinders University, GPO Box 5100, Adelaide, SA 5001, Australia;
| | - Franco Famiani
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, 06121 Perugia, Italy
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12
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Pan K, Lu C, Nie P, Hu M, Zhou X, Chen X, Wang W. Predominantly symplastic phloem unloading of photosynthates maintains efficient starch accumulation in the cassava storage roots (Manihot esculenta Crantz). BMC PLANT BIOLOGY 2021; 21:318. [PMID: 34217217 PMCID: PMC8254309 DOI: 10.1186/s12870-021-03088-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 06/08/2021] [Indexed: 06/01/2023]
Abstract
BACKGROUND Cassava (Manihot esculenta Crantz) efficiently accumulates starch in its storage roots. However, how photosynthates are transported from the leaves to the phloem (especially how they are unloaded into parenchymal cells of storage roots) remains unclear. RESULTS Here, we investigated the sucrose unloading pattern and its impact on cassava storage root development using microstructural and physiological analyses, namely, carboxyfluorescein (CF) and C14 isotope tracing. The expression profiling of genes involved in symplastic and apoplastic transport was performed, which included enzyme activity, protein gel blot analysis, and transcriptome sequencing analyses. These finding showed that carbohydrates are transported mainly in the form of sucrose, and more than 54.6% was present in the stem phloem. Sucrose was predominantly unloaded symplastically from the phloem into storage roots; in addition, there was a shift from apoplastic to symplastic unloading accompanied by the onset of root swelling. Statistical data on the microstructures indicated an enrichment of plasmodesmata within sieve, companion, and parenchyma cells in the developing storage roots of a cultivar but not in a wild ancestor. Tracing tests with CF verified the existence of a symplastic channel, and [14C] Suc demonstrated that sucrose could rapidly diffuse into root parenchyma cells from phloem cells. The relatively high expression of genes encoding sucrose synthase and associated proteins appeared in the middle and late stages of storage roots but not in primary fibrous roots, or secondary fibrous roots. The inverse expression pattern of sucrose transporters, cell wall acid invertase, and soluble acid invertase in these corresponding organs supported the presence of a symplastic sucrose unloading pathway. The transcription profile of genes involved in symplastic unloading and their significantly positive correlation with the starch yield at the population level confirmed that symplastic sucrose transport is vitally important in the development of cassava storage roots. CONCLUSIONS In this study, we revealed that the cassava storage root phloem sucrose unloading pattern was predominantly a symplastic unloading pattern. This pattern is essential for efficient starch accumulation in high-yielding varieties compared with low-yielding wild ancestors.
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Affiliation(s)
- Kun Pan
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
- Hainan Medical University, Haikou, 571199, China
| | - Cheng Lu
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Peixian Nie
- Shandong Institute of Pomology, Shandong Academy of Agricultural Sciences, Taian, 271000, Shandong, China
| | - Meizhen Hu
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Xincheng Zhou
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Xin Chen
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Wenquan Wang
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China.
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13
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Baslam M, Mitsui T, Sueyoshi K, Ohyama T. Recent Advances in Carbon and Nitrogen Metabolism in C3 Plants. Int J Mol Sci 2020; 22:E318. [PMID: 33396811 PMCID: PMC7795015 DOI: 10.3390/ijms22010318] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/23/2020] [Accepted: 12/23/2020] [Indexed: 12/19/2022] Open
Abstract
C and N are the most important essential elements constituting organic compounds in plants. The shoots and roots depend on each other by exchanging C and N through the xylem and phloem transport systems. Complex mechanisms regulate C and N metabolism to optimize plant growth, agricultural crop production, and maintenance of the agroecosystem. In this paper, we cover the recent advances in understanding C and N metabolism, regulation, and transport in plants, as well as their underlying molecular mechanisms. Special emphasis is given to the mechanisms of starch metabolism in plastids and the changes in responses to environmental stress that were previously overlooked, since these changes provide an essential store of C that fuels plant metabolism and growth. We present general insights into the system biology approaches that have expanded our understanding of core biological questions related to C and N metabolism. Finally, this review synthesizes recent advances in our understanding of the trade-off concept that links C and N status to the plant's response to microorganisms.
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Affiliation(s)
- Marouane Baslam
- Laboratory of Biochemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan; (M.B.); (T.M.)
| | - Toshiaki Mitsui
- Laboratory of Biochemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan; (M.B.); (T.M.)
- Department of Life and Food Sciences, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan;
| | - Kuni Sueyoshi
- Department of Life and Food Sciences, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan;
| | - Takuji Ohyama
- Department of Life and Food Sciences, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan;
- Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo 156-8502, Japan
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14
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Beuchat G, Xue X, Chen LQ. Review: The Next Steps in Crop Improvement: Adoption of Emerging Strategies to Identify Bottlenecks in Sugar Flux. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 301:110675. [PMID: 33218639 DOI: 10.1016/j.plantsci.2020.110675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 09/03/2020] [Accepted: 09/07/2020] [Indexed: 05/24/2023]
Abstract
Sugar allocation in plants is the fundamental process that transports sugar from source to sink tissues and has a dramatic impact on crop yields. Controlling sugar allocation is required to increase crop yields, as well as biomass for biofuel production. Successful examples have demonstrated that genetic engineering of sugar partitioning offers a promising strategy to achieve this goal. However, improvement has thus far been limited by gaps in understanding of the underlying mechanisms controlling the allocation of sugars. The dynamics of sugar partitioning are minimally predictable under different conditions, between species, or in response to abiotic stresses. Here, we discuss four methodologies that have not been sufficiently exploited for the identification of bottlenecks in sugar flux. Furthermore, we suggest how these strategies can be used and combined to provide the insight needed to maximize crop yields or biomass, especially under conditions of environmental stress.
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Affiliation(s)
- Gabriel Beuchat
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; DOE Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Xueyi Xue
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; DOE Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Li-Qing Chen
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; DOE Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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15
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Genome-Wide Identification and Expression Profiling of Monosaccharide Transporter Genes Associated with High Harvest Index Values in Rapeseed ( Brassica napus L.). Genes (Basel) 2020; 11:genes11060653. [PMID: 32549312 PMCID: PMC7349323 DOI: 10.3390/genes11060653] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/10/2020] [Accepted: 06/12/2020] [Indexed: 01/15/2023] Open
Abstract
Sugars are important throughout a plant’s lifecycle. Monosaccharide transporters (MST) are essential sugar transporters that have been identified in many plants, but little is known about the evolution or functions of MST genes in rapeseed (Brassica napus). In this study, we identified 175 MST genes in B. napus, 87 in Brassica oleracea, and 83 in Brassica rapa. These genes were separated into the sugar transport protein (STP), polyol transporter (PLT), vacuolar glucose transporter (VGT), tonoplast monosaccharide transporter (TMT), inositol transporter (INT), plastidic glucose transporter (pGlcT), and ERD6-like subfamilies, respectively. Phylogenetic and syntenic analysis indicated that gene redundancy and gene elimination have commonly occurred in Brassica species during polyploidization. Changes in exon-intron structures during evolution likely resulted in the differences in coding regions, expression patterns, and functions seen among BnMST genes. In total, 31 differentially expressed genes (DEGs) were identified through RNA-seq among materials with high and low harvest index (HI) values, which were divided into two categories based on the qRT-PCR results, expressed more highly in source or sink organs. We finally identified four genes, including BnSTP5, BnSTP13, BnPLT5, and BnERD6-like14, which might be involved in monosaccharide uptake or unloading and further affect the HI of rapeseed. These findings provide fundamental information about MST genes in Brassica and reveal the importance of BnMST genes to high HI in B. napus.
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16
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Ganusova EE, Reagan BC, Fernandez JC, Azim MF, Sankoh AF, Freeman KM, McCray TN, Patterson K, Kim C, Burch-Smith TM. Chloroplast-to-nucleus retrograde signalling controls intercellular trafficking via plasmodesmata formation. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190408. [PMID: 32362251 DOI: 10.1098/rstb.2019.0408] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The signalling pathways that regulate intercellular trafficking via plasmodesmata (PD) remain largely unknown. Analyses of mutants with defects in intercellular trafficking led to the hypothesis that chloroplasts are important for controlling PD, probably by retrograde signalling to the nucleus to regulate expression of genes that influence PD formation and function, an idea encapsulated in the organelle-nucleus-PD signalling (ONPS) hypothesis. ONPS is supported by findings that point to chloroplast redox state as also modulating PD. Here, we have attempted to further elucidate details of ONPS. Through reverse genetics, expression of select nucleus-encoded genes with known or predicted roles in chloroplast gene expression was knocked down, and the effects on intercellular trafficking were then assessed. Silencing most genes resulted in chlorosis, and the expression of several photosynthesis and tetrapyrrole biosynthesis associated nuclear genes was repressed in all silenced plants. PD-mediated intercellular trafficking was changed in the silenced plants, consistent with predictions of the ONPS hypothesis. One striking observation, best exemplified by silencing the PNPase homologues, was that the degree of chlorosis of silenced leaves was not correlated with the capacity for intercellular trafficking. Finally, we measured the distribution of PD in silenced leaves and found that intercellular trafficking was positively correlated with the numbers of PD. Together, these results not only provide further support for ONPS but also point to a genetic mechanism for PD formation, clarifying a longstanding question about PD and intercellular trafficking. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.
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Affiliation(s)
- Elena E Ganusova
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Brandon C Reagan
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Jessica C Fernandez
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Mohammad F Azim
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Amie F Sankoh
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | | | - Tyra N McCray
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Kelsey Patterson
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Chinkee Kim
- Departments of Science and Mathematics, RIT/National Technical Institute for the Deaf (NTID), Rochester, NY 14623, USA
| | - Tessa M Burch-Smith
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
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17
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Epron D, Dannoura M, Ishida A, Kosugi Y. Estimation of phloem carbon translocation belowground at stand level in a hinoki cypress stand. TREE PHYSIOLOGY 2019; 39:320-331. [PMID: 29474703 DOI: 10.1093/treephys/tpy016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 01/15/2018] [Accepted: 01/27/2018] [Indexed: 06/08/2023]
Abstract
At stand level, carbon translocation in tree stems has to match canopy photosynthesis and carbohydrate requirements to sustain growth and the physiological activities of belowground sinks. This study applied the Hagen-Poiseuille equation to the pressure-flow hypothesis to estimate phloem carbon translocation and evaluate what percentage of canopy photosynthate can be transported belowground in a hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.) stand. An anatomical study revealed that, in contrast to sieve cell density, conductive phloem thickness and sieve cell hydraulic diameter at 1.3 m in height increased with increasing tree diameter, as did the concentration of soluble sugars in the phloem sap. At tree level, hydraulic conductivity increased by two orders of magnitude from the smallest to the largest trees in the stand, resulting in a stand-level hydraulic conductance of 1.7 × 10-15 m Pa-1 s-1. The osmotic potential of the sap extracted from the inner bark was -0.75 MPa. Assuming that phloem water potential equalled foliage water potential at predawn, the turgor pressure in the phloem at 1.3 m in height was estimated at 0.22 MPa, 0.59 MPa lower than values estimated in the foliage. With this maximal turgor pressure gradient, which would be lower during day-time when foliage water potential drops, the estimated stand-level rate of carbon translocation was 2.0 gC m-2 day-1 (30% of daily gross canopy photosynthesis), at a time of the year when aboveground growth and related respiration is thought to consume a large fraction of photosynthate, at the expense of belowground activity. Despite relying on some assumptions and approximations, this approach, when coupled with measurements of canopy photosynthesis, may further be used to provide qualitative insight into the seasonal dynamics of belowground carbon allocation.
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Affiliation(s)
- Daniel Epron
- Université de Lorraine, INRA, UMR SILVA, Faculté des Sciences et Technologies, Vandœuvre-lès-Nancy, France
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Atsushi Ishida
- Kyoto University, Center for Ecological Research, Otsu, Shiga, Japan
| | - Yoshiko Kosugi
- Kyoto University, Laboratory of Forest Hydrology, Graduate School of Agriculture, Kyoto, Japan
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18
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Sellier D, Mammeri Y. Diurnal dynamics of phloem loading: theoretical consequences for transport efficiency and flow characteristics. TREE PHYSIOLOGY 2019; 39:300-311. [PMID: 30753675 DOI: 10.1093/treephys/tpz001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 12/20/2018] [Accepted: 01/07/2019] [Indexed: 06/09/2023]
Abstract
Phloem transport is the process by which plants internally distribute assimilates. The loading of assimilates near the photosynthetic source is responsible for generating enough osmotic pressure to drive sap flow towards the sink tissues where assimilates are consumed. Phloem loading is variable and subject to a diurnal cycle. It is dominated by photosynthesis during the day and by degradation of leaf starch to sugars at night. Most studies ignore the effect of the loading cycle on transport and assume that sugar flow operates at equilibrium. In this study, phloem transport was simulated for three successive days using a finite element model of time-dependent Münch-Horwitz equations. The spatial and temporal distributions of phloem pressure, sucrose concentration, sap velocity and sucrose flux were predicted for five different time variations in sucrose loading. Results showed that periodic loading induces an alternance of two distinct transport phases: one with high pressure, concentration and sucrose flux magnitudes and another with low magnitudes. In contrast, phloem water velocity remained remarkably stable. The alternating phases persisted over time and, under source-driven variation, transport did not reach steady-state conditions for the tested configuration. However, the impact of loading dynamics on transport was mitigated by pathway effects. Oscillations were not only delayed as one travelled away from the source, their amplitude was also reduced over distance. That behaviour stabilized the supply of sucrose to the sink, which continued at moderate levels during the dark cycles. This finding suggests that transport would assist night conversion of starch to sugars in the leaf to prevent carbon starvation at distant sinks in the early morning. The propagation velocity of pressure/concentration waves in phloem was predicted to vary by a factor up to 2.5 depending on the time series chosen to describe the dynamics of loading. Finally, the model predicted that up to 87% of the amount of sucrose loaded over 48 h would be unloaded under time-dependent loading, whereas only 76% would under constant-rate loading. This additional efficiency was periodic. It did not increase significantly the overall efficiency of the system but could be responsible for inducing rhythms in sink activity.
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Affiliation(s)
- Damien Sellier
- New Zealand Forest Research Institute (trading as SCION), Private Bag 3020, Rotorua, New Zealand
| | - Youcef Mammeri
- Laboratoire Amiénois de Mathématique Fondamentale et Appliquée, CNRS UMR 7352, Université de Picardie Jules Verne, Amiens, France
- Institut de Génétique, Environnement et Protection des Plantes, INRA UMR 1349, Le Rheu, France
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19
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Ganusova EE, Burch-Smith TM. Review: Plant-pathogen interactions through the plasmodesma prism. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2019; 279:70-80. [PMID: 30709495 DOI: 10.1016/j.plantsci.2018.05.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/18/2018] [Accepted: 05/23/2018] [Indexed: 06/09/2023]
Abstract
Plasmodesmata (PD) allow membrane and cytoplasmic continuity between plant cells, and they are essential for intercellular communication and signaling in addition to metabolite partitioning. Plant pathogens have evolved a variety of mechanisms to subvert PD to facilitate their infection of plant hosts. PD are implicated not only in local spread around infection sites but also in the systemic spread of pathogens and pathogen-derived molecules. In turn, plants have developed strategies to limit pathogen spread via PD, and there is increasing evidence that PD may also be active players in plant defense responses. The last few years have seen important advances in understanding the roles of PD in plant-pathogen infection. Nonetheless, several critical areas remain to be addressed. Here we highlight some of these, focusing on the need to consider the effects of pathogen-PD interaction on the trafficking of endogenous molecules, and the involvement of chloroplasts in regulating PD during pathogen defense. By their very nature, PD are recalcitrant to most currently used investigative techniques, therefore answering these questions will require creative imaging and novel quantification approaches.
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Affiliation(s)
- Elena E Ganusova
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, United States
| | - Tessa M Burch-Smith
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, United States.
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20
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Hennion N, Durand M, Vriet C, Doidy J, Maurousset L, Lemoine R, Pourtau N. Sugars en route to the roots. Transport, metabolism and storage within plant roots and towards microorganisms of the rhizosphere. PHYSIOLOGIA PLANTARUM 2019; 165:44-57. [PMID: 29704246 DOI: 10.1111/ppl.12751] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/24/2018] [Accepted: 04/26/2018] [Indexed: 05/04/2023]
Abstract
In plants, the root is a typical sink organ that relies exclusively on the import of sugar from the aerial parts. Sucrose is delivered by the phloem to the most distant root tips and, en route to the tip, is used by the different root tissues for metabolism and storage. Besides, a certain portion of this carbon is exuded in the rhizosphere, supplied to beneficial microorganisms and diverted by parasitic microbes. The transport of sugars toward these numerous sinks either occurs symplastically through cell connections (plasmodesmata) or is apoplastically mediated through membrane transporters (MST, mononsaccharide tranporters, SUT/SUC, H+/sucrose transporters and SWEET, Sugar will eventually be exported transporters) that control monosaccharide and sucrose fluxes. Here, we review recent progresses on carbon partitioning within and outside roots, discussing membrane transporters involved in plant responses to biotic and abiotic factors.
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Affiliation(s)
- Nils Hennion
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
| | - Mickael Durand
- INRA-AgroParisTech, Institut Jean-Pierre Bourgin, UMR1318, ERL CNRS 3559, Saclay Plant Sciences, 78026, Versailles, France
| | - Cécile Vriet
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
| | - Joan Doidy
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
| | - Laurence Maurousset
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
| | - Rémi Lemoine
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
| | - Nathalie Pourtau
- Université de Poitiers, UMR CNRS 7267 EBI Ecologie et Biologie des Interactions, Equipe "Sucres & Echanges Végétaux-Environnement", TSA 51106, 86073, Poitiers Cedex 9, France
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21
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Smith MR, Rao IM, Merchant A. Source-Sink Relationships in Crop Plants and Their Influence on Yield Development and Nutritional Quality. FRONTIERS IN PLANT SCIENCE 2018; 9:1889. [PMID: 30619435 PMCID: PMC6306447 DOI: 10.3389/fpls.2018.01889] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 12/06/2018] [Indexed: 05/02/2023]
Abstract
For seed crops, yield is the cumulative result of both source and sink strength for photoassimilates and nutrients over the course of seed development. Source strength for photoassimilates is dictated by both net photosynthetic rate and the rate of photoassimilate remobilisation from source tissues. This review focuses on the current understanding of how the source-sink relationship in crop plants influences rates of yield development and the resilience of yield and nutritional quality. We present the limitations of current approaches to accurately measure sink strength and emphasize differences in coordination between photosynthesis and yield under varying environmental conditions. We highlight the potential to exploit source-sink dynamics, in order to improve yields and emphasize the importance of resilience in yield and nutritional quality with implications for plant breeding strategies.
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Affiliation(s)
- Millicent R. Smith
- School of Life and Environmental Sciences, Faculty of Science, Sydney Institute of Agriculture, The University of Sydney, Sydney, NSW, Australia
| | | | - Andrew Merchant
- School of Life and Environmental Sciences, Faculty of Science, Sydney Institute of Agriculture, The University of Sydney, Sydney, NSW, Australia
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22
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Yang Z, Liu D, Ji H. Sucrose metabolism in developing oil-rich tubers of Cyperus esculentus: comparative transcriptome analysis. BMC PLANT BIOLOGY 2018; 18:151. [PMID: 30041609 PMCID: PMC6056992 DOI: 10.1186/s12870-018-1363-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 07/05/2018] [Indexed: 05/10/2023]
Abstract
BACKGROUND Cyperus esculentus is unique in that it can accumulate significant amounts of oil, starch and sugar as major storage reserves in tubers with high tuber yield and therefore considered as a novel model to study carbon allocation into different storage reserves in underground sink tissues such as tubers and roots. Sucrose (Suc) plays a central role in control of carbon flux toward biosynthesis of different storage reserves; however, it remains unclear for the molecular mechanism underlying Suc metabolism in underground oil-rich storage tissues. In the present study, a comprehensive transcriptome analysis of C. esculentus oil tuber compared to other plant oil- or carbohydrate-rich storage tissues was made for the expression patterns of genes related to the Suc metabolism. RESULTS The results revealed some species-specific features of gene transcripts in oil tuber of C. esculentus, indicating that: (i) the expressions of genes responsible for Suc metabolism are developmentally regulated and displayed a pattern dissimilar to other plant storage tissues; (ii) both of Suc breakdown and biosynthesis processes might be the major pathways associated with Suc metabolism; (iii) it was probably that Suc degradation could be primarily through the action of Suc synthase (SUS) other than invertase (INV) during tuber development. The orthologs of SUS1, SUS3 and SUS4 are the main SUS isoforms catalyzing Suc breakdown while the vacuolar INV (VIN) is the leading determinant controlling sugar composition; (iv) cytosolic hexose phosphorylation possibly relies more on fructose as substrate and uridine diphosphate glucose pyrophosphorylase (UGP) plays an important role in this pathway; (v) it is Suc-phosphate synthase (SPS) B- and C-family members rather than SPS A that are the principal contributors to SPS enzymes and play crucial roles in Suc biosynthesis pathway. CONCLUSIONS We have successfully identified the Suc metabolic pathways in C. esculentus tubers, highlighting several conserved and distinct expressions that might contribute to sugar accumulation in this unique underground storage tissue. The specific and differential expression genes revealed in this study might indicate the special molecular mechanism and transcriptional regulation of Suc metabolism occurred in oil tubers of C. esculentus.
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Affiliation(s)
- Zhenle Yang
- Key Lab of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093 China
| | - Dantong Liu
- Key Lab of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Hongying Ji
- Key Lab of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
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23
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Anne P, Hardtke CS. Phloem function and development-biophysics meets genetics. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:22-28. [PMID: 29278791 DOI: 10.1016/j.pbi.2017.12.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 11/10/2017] [Accepted: 12/12/2017] [Indexed: 05/07/2023]
Abstract
Evolution of the vascular tissues allowed plants to efficiently settle land, occupy new ecological niches, and thereby crucially shape earth's biosphere. Of the two conducting cell types in the plant vasculature, the tubular network of phloem sieve elements transports phloem sap from source to sink organs. Recent years have witnessed the identification of ever more regulators of sieve element differentiation, as well as a more detailed understanding of phloem physiology and function. From molecular regulators of the commitment to sieve element fate, to enzymatic executors of the differentiation process, the toolbox to investigate sieve element formation has been greatly enlarged. To connect the various players in different genetic layers, and thus to ultimately attain a comprehensive description and understanding of sieve element development at the molecular level, appears to be within reach.
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Affiliation(s)
- Pauline Anne
- Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland
| | - Christian S Hardtke
- Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland.
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24
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Takahashi H, Xiaohua Q, Shimamura S, Yanagawa A, Hiraga S, Nakazono M. Sucrose supply from leaves is required for aerenchymatous phellem formation in hypocotyl of soybean under waterlogged conditions. ANNALS OF BOTANY 2018; 121:723-732. [PMID: 29370345 PMCID: PMC5853023 DOI: 10.1093/aob/mcx205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 12/12/2017] [Indexed: 05/21/2023]
Abstract
Background and Aims Soil waterlogging often causes oxygen deficiency in the root systems of plants and severely inhibits plant growth. Formation of aerenchyma - interconnected spaces that facilitate the movement of gases between and within the aerial and submerged parts of plants - is an adaptive trait for coping with waterlogged conditions. Soybean (Glycine max) forms porous secondary tissues known as aerenchymatous phellem (AP), which are derived from the outermost cell layer of phellogen. To understand what factors other than waterlogging are involved in phellogen and AP formation, we examined how their formation in soybean seedlings was affected by darkness, CO2 deficiency and blockage of phloem transport. Methods Aerenchymatous phellem and phellogen formation were expressed as area ratios in cross-sections of hypocotyl. CO2 was depleted by use of calcium oxide and sodium hydroxide. Phloem transport was blocked by heat-girdling of hypocotyls. Sucrose levels were measured by spectrophotometry. Key Results Under light conditions, waterlogging induced the accumulation of high concentrations of sucrose in hypocotyls, followed by phellogen and AP formation in hypocotyls. Phellogen formation and AP formation were inhibited by darkness, CO2 deficiency and blockage of phloem transport. Phellogen formation and AP formation were also inhibited by excision of shoots above the epicotyl, but they recovered following application of sucrose (but not glucose or fructose application) to the cut surface. Conclusions The results demonstrate that sucrose derived from leaves is essential for AP and phellogen formation in soybean hypocotyls under waterlogged soil conditions. Maintenance of a high sucrose concentration is thus essential for the development of phellogen and AP and the differentiation of phellogen to AP.
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Affiliation(s)
- Hirokazu Takahashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
| | - Qi Xiaohua
- Department of Horticulture, School of Horticulture and Plant Protection, Yangzhou University, Yangzhou, Jiangsu, P.R. China
| | - Satoshi Shimamura
- NARO Tohoku Agricultural Research Center, Kariwano, Daisen, Akita, Japan
| | - Asako Yanagawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
| | - Susumu Hiraga
- NARO Institute of Crop Science, Kannondai, Tsukuba, Ibaraki, Japan
| | - Mikio Nakazono
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
- School of Plant Biology, The University of Western Australia, Crawley, WA, Australia
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25
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Abstract
The phloem plays a central role in transporting resources and signalling molecules from fully expanded leaves to provide precursors for, and to direct development of, heterotrophic organs located throughout the plant body. We review recent advances in understanding mechanisms regulating loading and unloading of resources into, and from, the phloem network; highlight unresolved questions regarding the physiological significance of the vast array of proteins and RNAs found in phloem saps; and evaluate proposed structure/function relationships considered to account for bulk flow of sap, sustained at high rates and over long distances, through the transport phloem.
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Affiliation(s)
- Johannes Liesche
- Biomass Energy Center for Arid and Semi-arid lands, Northwest A&F University, Yangling, China
- College of Life Science, Northwest A&F University, Yangling , China
| | - John Patrick
- Department of Biological Sciences, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, Australia
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26
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Hölttä T, Lintunen A, Chan T, Mäkelä A, Nikinmaa E. A steady-state stomatal model of balanced leaf gas exchange, hydraulics and maximal source-sink flux. TREE PHYSIOLOGY 2017; 37:851-868. [PMID: 28338800 DOI: 10.1093/treephys/tpx011] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 01/23/2017] [Indexed: 05/16/2023]
Abstract
Trees must simultaneously balance their CO2 uptake rate via stomata, photosynthesis, the transport rate of sugars and rate of sugar utilization in sinks while maintaining a favourable water and carbon balance. We demonstrate using a numerical model that it is possible to understand stomatal functioning from the viewpoint of maximizing the simultaneous photosynthetic production, phloem transport and sink sugar utilization rate under the limitation that the transpiration-driven hydrostatic pressure gradient sets for those processes. A key feature in our model is that non-stomatal limitations to photosynthesis increase with decreasing leaf water potential and/or increasing leaf sugar concentration and are thus coupled to stomatal conductance. Maximizing the photosynthetic production rate using a numerical steady-state model leads to stomatal behaviour that is able to reproduce the well-known trends of stomatal behaviour in response to, e.g., light, vapour concentration difference, ambient CO2 concentration, soil water status, sink strength and xylem and phloem hydraulic conductance. We show that our results for stomatal behaviour are very similar to the solutions given by the earlier models of stomatal conductance derived solely from gas exchange considerations. Our modelling results also demonstrate how the 'marginal cost of water' in the unified stomatal conductance model and the optimal stomatal model could be related to plant structural and physiological traits, most importantly, the soil-to-leaf hydraulic conductance and soil moisture.
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Affiliation(s)
- Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Anna Lintunen
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Tommy Chan
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Annikki Mäkelä
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Eero Nikinmaa
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
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27
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Ross-Elliott TJ, Jensen KH, Haaning KS, Wager BM, Knoblauch J, Howell AH, Mullendore DL, Monteith AG, Paultre D, Yan D, Otero S, Bourdon M, Sager R, Lee JY, Helariutta Y, Knoblauch M, Oparka KJ. Phloem unloading in Arabidopsis roots is convective and regulated by the phloem-pole pericycle. eLife 2017; 6. [PMID: 28230527 PMCID: PMC5365319 DOI: 10.7554/elife.24125] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 02/17/2017] [Indexed: 02/05/2023] Open
Abstract
In plants, a complex mixture of solutes and macromolecules is transported by the phloem. Here, we examined how solutes and macromolecules are separated when they exit the phloem during the unloading process. We used a combination of approaches (non-invasive imaging, 3D-electron microscopy, and mathematical modelling) to show that phloem unloading of solutes in Arabidopsis roots occurs through plasmodesmata by a combination of mass flow and diffusion (convective phloem unloading). During unloading, solutes and proteins are diverted into the phloem-pole pericycle, a tissue connected to the protophloem by a unique class of ‘funnel plasmodesmata’. While solutes are unloaded without restriction, large proteins are released through funnel plasmodesmata in discrete pulses, a phenomenon we refer to as ‘batch unloading’. Unlike solutes, these proteins remain restricted to the phloem-pole pericycle. Our data demonstrate a major role for the phloem-pole pericycle in regulating phloem unloading in roots. DOI:http://dx.doi.org/10.7554/eLife.24125.001 A mechanism called photosynthesis allows plants to use energy from sunlight to make sugars from carbon dioxide gas and water. These sugars can then be used as fuel, or as building blocks for wood and other plant structures. Every part of the plant requires sugars, but most photosynthesis happens in the leaves and stems, so the sugars need to be able to move around the plant to wherever they are needed. Phloem tubes form a network that transports sugar, proteins and other molecules around the plant within a fluid known as sap. Because this network is so extensive, it is very difficult to study, which has left researchers with major questions about how it works. For example, it is not clear how the sugar and other molecules leave the phloem when they reach their destination. Ross-Elliot et al. used a combination of microscopy and mathematical modeling to investigate how sugars and other molecules leave the phloem in the roots of a plant called Arabidopsis thaliana. The experiments show that these molecules move directly into cells within a neighboring tissue called the phloem-pole pericycle via pores known as funnel plasmodesmata. Ross-Elliot et al. incorporated the experimental data into a mathematical model of phloem unloading. This model suggests that sugars and other small molecules move freely through the funnel plasmodesmata, but large proteins pass through these pores in pulses. Future challenges include finding out exactly how plants control phloem unloading and to investigate whether it is possible to modify the delivery of specific molecules to particular parts of the plant. DOI:http://dx.doi.org/10.7554/eLife.24125.002
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Affiliation(s)
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - Katrine S Haaning
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - Brittney M Wager
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Alexander H Howell
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Alexander G Monteith
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, United Kingdom
| | - Danae Paultre
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Dawei Yan
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Sofia Otero
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Matthieu Bourdon
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Ross Sager
- Department of Plant and Soil Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, United States
| | - Jung-Youn Lee
- Department of Plant and Soil Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, United States
| | - Ykä Helariutta
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Karl J Oparka
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
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28
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Milne RJ, Perroux JM, Rae AL, Reinders A, Ward JM, Offler CE, Patrick JW, Grof CPL. Sucrose Transporter Localization and Function in Phloem Unloading in Developing Stems. PLANT PHYSIOLOGY 2017; 173:1330-1341. [PMID: 27986867 PMCID: PMC5291036 DOI: 10.1104/pp.16.01594] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/14/2016] [Indexed: 05/05/2023]
Abstract
How sucrose transporters (SUTs) regulate phloem unloading in monocot stems is poorly understood and particularly so for species storing high Suc concentrations. To this end, Sorghum bicolor SUTs SbSUT1 and SbSUT5 were characterized by determining their transport properties heterologously expressed in yeast or Xenopus laevis oocytes, and their in planta cellular and subcellular localization. The plasma membrane-localized SbSUT1 and SbSUT5 exhibited a strong selectivity for Suc and high Suc affinities in X. laevis oocytes at pH 5-SbSUT1, 6.3 ± 0.7 mm, and SbSUT5, 2.4 ± 0.5 mm Suc. The Suc affinity of SbSUT1 was dependent on membrane potential and pH. In contrast, SbSUT5 Suc affinity was independent of membrane potential and pH but supported high transport rates at neutral pH. Suc transport by the tonoplast localized SbSUT4 could not be detected using yeast or X. laevis oocytes. Across internode development, SUTs, other than SbSUT4, were immunolocalized to sieve elements, while for elongating and recently elongated internodes, SUTs also were detected in storage parenchyma cells. We conclude that apoplasmic Suc unloading from de-energized protophloem sieve elements in meristematic zones may be mediated by reversal of SbSUT1 and/or by uniporting SWEETs. Storage parenchyma localized SbSUT1 and SbSUT5 may accumulate Suc from the stem apoplasms of elongating and recently elongated internodes, whereas SbSUT4 may function to release Suc from vacuoles. Transiting from an apoplasmic to symplasmic unloading pathway as the stem matures, SbSUT1 and SbSUT5 increasingly function in Suc retrieval into metaphloem sieve elements to maintain a high turgor to drive symplasmic unloading by bulk flow.
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Affiliation(s)
- Ricky J Milne
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - Jai M Perroux
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - Anne L Rae
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - Anke Reinders
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - John M Ward
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - Christina E Offler
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - John W Patrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.)
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.)
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
| | - Christopher P L Grof
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia (R.J.M., C.E.O., J.W.P., C.P.L.G.);
- CSIRO Agriculture and Food, Crace, Australian Capital Territory 2911, Australia (R.J.M.);
- CSIRO Agriculture and Food, St Lucia, Queensland 4067, Australia (J.M.P., A.L.R.); and
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108 (A.R., J.M.W.)
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29
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Knoblauch M, Knoblauch J, Mullendore DL, Savage JA, Babst BA, Beecher SD, Dodgen AC, Jensen KH, Holbrook NM. Testing the Münch hypothesis of long distance phloem transport in plants. eLife 2016; 5:e15341. [PMID: 27253062 PMCID: PMC4946904 DOI: 10.7554/elife.15341] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/01/2016] [Indexed: 02/03/2023] Open
Abstract
Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.
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Affiliation(s)
- Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jessica A Savage
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
- Arnold Arboretum of Harvard University, Boston, United States
| | - Benjamin A Babst
- Department of Biosciences, Brookhaven National Laboratory, Upton, New York
| | - Sierra D Beecher
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Adam C Dodgen
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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30
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Savage JA, Clearwater MJ, Haines DF, Klein T, Mencuccini M, Sevanto S, Turgeon R, Zhang C. Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology? PLANT, CELL & ENVIRONMENT 2016; 39:709-25. [PMID: 26147312 DOI: 10.1111/pce.12602] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 05/30/2015] [Accepted: 06/19/2015] [Indexed: 05/02/2023]
Abstract
Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.
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Affiliation(s)
- Jessica A Savage
- Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA, 02131, USA
| | | | - Dustin F Haines
- Department of Environmental Conservation, University of Massachusetts, 160 Holdsworth Way, Amherst, MA, 01003, USA
| | - Tamir Klein
- Institute of Botany, University of Basel, Schoenbeinstrasse 6, 4056, Basel, Switzerland
| | - Maurizio Mencuccini
- School of GeoSciences, University of Edinburgh, Crew Building, West Mains Road, EH9 3JN, Edinburgh, UK
- ICREA at CREAF, Campus de UAB, Cerdanyola del Valles, Barcelona, 08023, Spain
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA
| | - Cankui Zhang
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
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Karve AA, Alexoff D, Kim D, Schueller MJ, Ferrieri RA, Babst BA. In vivo quantitative imaging of photoassimilate transport dynamics and allocation in large plants using a commercial positron emission tomography (PET) scanner. BMC PLANT BIOLOGY 2015; 15:273. [PMID: 26552889 PMCID: PMC4640171 DOI: 10.1186/s12870-015-0658-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 11/02/2015] [Indexed: 05/09/2023]
Abstract
BACKGROUND Although important aspects of whole-plant carbon allocation in crop plants (e.g., to grain) occur late in development when the plants are large, techniques to study carbon transport and allocation processes have not been adapted for large plants. Positron emission tomography (PET), developed for dynamic imaging in medicine, has been applied in plant studies to measure the transport and allocation patterns of carbohydrates, nutrients, and phytohormones labeled with positron-emitting radioisotopes. However, the cost of PET and its limitation to smaller plants has restricted its use in plant biology. Here we describe the adaptation and optimization of a commercial clinical PET scanner to measure transport dynamics and allocation patterns of (11)C-photoassimilates in large crops. RESULTS Based on measurements of a phantom, we optimized instrument settings, including use of 3-D mode and attenuation correction to maximize the accuracy of measurements. To demonstrate the utility of PET, we measured (11)C-photoassimilate transport and allocation in Sorghum bicolor, an important staple crop, at vegetative and reproductive stages (40 and 70 days after planting; DAP). The (11)C-photoassimilate transport speed did not change over the two developmental stages. However, within a stem, transport speeds were reduced across nodes, likely due to higher (11)C-photoassimilate unloading in the nodes. Photosynthesis in leaves and the amount of (11)C that was exported to the rest of the plant decreased as plants matured. In young plants, exported (11)C was allocated mostly (88 %) to the roots and stem, but in flowering plants (70 DAP) the majority of the exported (11)C (64 %) was allocated to the apex. CONCLUSIONS Our results show that commercial PET scanners can be used reliably to measure whole-plant C-allocation in large plants nondestructively including, importantly, allocation to roots in soil. This capability revealed extreme changes in carbon allocation in sorghum plants, as they advanced to maturity. Further, our results suggest that nodes may be important control points for photoassimilate distribution in crops of the family Poaceae. Quantifying real-time carbon allocation and photoassimilate transport dynamics, as demonstrated here, will be important for functional genomic studies to unravel the mechanisms controlling phloem transport in large crop plants, which will provide crucial insights for improving yields.
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Affiliation(s)
- Abhijit A Karve
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
- Present address: Purdue Research Foundation, West Lafayette, IN, 47906, USA.
| | - David Alexoff
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
- Present address: Five Eleven Pharma Inc, Philadelphia, PA, 19104, USA.
| | - Dohyun Kim
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - Michael J Schueller
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - Richard A Ferrieri
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - Benjamin A Babst
- Biological, Environmental, and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, 11973, USA.
- Present address: School of Forestry and Natural Resources, University of Arkansas at Monticello, Monticello, AR, 71656, USA.
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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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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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Atwell BJ, Greenway H, Colmer TD. Efficient use of energy in anoxia-tolerant plants with focus on germinating rice seedlings. THE NEW PHYTOLOGIST 2015; 206:36-56. [PMID: 25472708 DOI: 10.1111/nph.13173] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 10/09/2014] [Indexed: 05/08/2023]
Abstract
Anoxia tolerance in plants is distinguished by direction of the sparse supply of energy to processes crucial to cell maintenance and sometimes to growth, as in rice seedlings. In anoxic rice coleoptiles energy is used to synthesise proteins, take up K(+) , synthesise cell walls and lipids, and in cell maintenance. Maintenance of electrochemical H(+) gradients across the tonoplast and plasma membrane is crucial for solute compartmentation and thus survival. These gradients sustain some H(+) -solute cotransport and regulate cytoplasmic pH. Pyrophosphate (PPi ), the alternative energy donor to ATP, allows direction of energy to the vacuolar H(+) -PPi ase, sustaining H(+) gradients across the tonoplast. When energy production is critically low, operation of a biochemical pHstat allows H(+) -solute cotransport across plasma membranes to continue for at least for 18 h. In active (e.g. growing) cells, PPi produced during substantial polymer synthesis allows conversion of PPi to ATP by PPi -phosphofructokinase (PFK). In quiescent cells with little polymer synthesis and associated PPi formation, the PPi required by the vacuolar H(+) -PPi ase and UDPG pyrophosphorylase involved in sucrose mobilisation via sucrose synthase might be produced by conversion of ATP to PPi through reversible glycolytic enzymes, presumably pyruvate orthophosphate dikinase. These hypotheses need testing with species characterised by contrasting anoxia tolerance.
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Affiliation(s)
- Brian J Atwell
- Department of Biological Sciences, Faculty of Science, Macquarie University, Sydney, 2109, NSW, Australia
| | - Hank Greenway
- School of Plant Biology and the UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, 6009, WA, Australia
| | - Timothy D Colmer
- School of Plant Biology and the UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, 6009, WA, Australia
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Abstract
Movement of nutrients and signaling compounds from cell to cell is an essential process for plant growth and development. To understand processes such as carbon allocation, cell communication, and reaction to pathogen attack it is important to know a specific molecule's capacity to pass a specific cell wall interface. Transport through plasmodesmata, the cell wall channels that directly connect plant cells, is regulated not only by a fixed size exclusion limit, but also by physiological and pathological adaptation. The noninvasive approach described here offers the possibility of precisely determining the plasmodesmata-mediated cell wall permeability for small molecules in living cells.The method is based on photoactivation of the fluorescent tracer caged fluorescein. Non-fluorescent caged fluorescein is applied to a target tissue, where it is taken up passively into all cells. Imaged by confocal microscopy, loaded tracer is activated by UV illumination in a target cell and its spread to neighboring cells monitored. When combined with high-speed acquisition by resonant scanning or spinning disc confocal microscopy, the high signal-to-noise ratio of photoactivation allows collection of three-dimensional (3D) time series. These contain all necessary functional and anatomical data to measure cell coupling in complex tissues noninvasively.
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Affiliation(s)
- Johannes Liesche
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark,
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Patrick JW, Colyvas K. Crop yield components - photoassimilate supply- or utilisation limited-organ development? FUNCTIONAL PLANT BIOLOGY : FPB 2014; 41:893-913. [PMID: 32481043 DOI: 10.1071/fp14048] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/18/2014] [Indexed: 06/11/2023]
Abstract
Yield potential is the genome-encoded capacity of a crop species to generate yield in an optimal growth environment. Ninety per cent of plant biomass is derived from the photosynthetic reduction of carbon dioxide to organic carbon (photoassimilates - primarily sucrose). Thus, development of yield components (organ numbers and individual organ masses) can be limited by photoassimilate supply (photosynthesis arranged in series with phloem transport) or by their inherent capacity to utilise imported photoassimilates for growth or storage. To this end, photoassimilate supply/utilisation of crop yield has been quantitatively re-evaluated using published responses of yield components to elevated carbon dioxide concentrations across a selection of key crop species including cereal and pulse grains, fleshy fruits, tubers and sugar storing stems and tap roots. The analysis demonstrates that development of harvested organ numbers is strongly limited by photoassimilate supply. Vegetative branching and, to a lesser extent, flower/pod/fleshy fruit abortion, are the major yield components contributing to sensitivity of organ numbers to photoassimilate supply. In contrast, harvested organ size is partially dependent (eudicots), or completely independent (cereals), of photoassimilate supply. Processes limiting photoassimilate utilisation by harvested organs include membrane transport of soluble sugars and their allocation into polymeric storage products.
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Affiliation(s)
- John W Patrick
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Kim Colyvas
- School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
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Takahashi H, Greenway H, Matsumura H, Tsutsumi N, Nakazono M. Rice alcohol dehydrogenase 1 promotes survival and has a major impact on carbohydrate metabolism in the embryo and endosperm when seeds are germinated in partially oxygenated water. ANNALS OF BOTANY 2014; 113:851-9. [PMID: 24431339 PMCID: PMC3962239 DOI: 10.1093/aob/mct305] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 12/02/2013] [Indexed: 05/05/2023]
Abstract
BACKGROUND AND AIMS Rice (Oryza sativa) has the rare ability to germinate and elongate a coleoptile under oxygen-deficient conditions, which include both hypoxia and anoxia. It has previously been shown that ALCOHOL DEHYDROGENASE 1 (ADH1) is required for cell division and cell elongation in the coleoptile of submerged rice seedlings by means of studies using a rice ADH1-deficient mutant, reduced adh activity (rad). The aim of this study was to understand how low ADH1 in rice affects carbohydrate metabolism in the embryo and endosperm, and lactate and alanine synthesis in the embryo during germination and subsequent coleoptile growth in submerged seedlings. METHODS Wild-type and rad mutant rice seeds were germinated and grown under complete submergence. At 1, 3, 5 and 7 d after imbibition, the embryo and endosperm were separated and several of their metabolites were measured and compared. KEY RESULTS In the rad embryo, the rate of ethanol fermentation was halved, while lactate and alanine concentrations were 2·4- and 5·7- fold higher in the mutant than in the wild type. Glucose and fructose concentrations in the embryos increased with time in the wild type, but not in the rad mutant. The rad mutant endosperm had lower amounts of the α-amylases RAMY1A and RAMY3D, resulting in less starch degradation and lower glucose concentrations. CONCLUSIONS These results suggest that ADH1 is essential for sugar metabolism via glycolysis to ethanol fermentation in both the embryo and endosperm. In the endosperm, energy is presumably needed for synthesis of the amylases and for sucrose synthesis in the endosperm, as well as for sugar transport to the embryo.
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Affiliation(s)
- Hirokazu Takahashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan
| | - Hank Greenway
- Faculty of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawly, Western Australia, 6009, Australia
| | - Hideo Matsumura
- Gene Research Center, Shinshu University, 3-15-1 Tokita, Ueda, Nagano 386-8567, Japan
| | - Nobuhiro Tsutsumi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
| | - Mikio Nakazono
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan
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Ruan YL, Patrick JW, Shabala S, Slewinski TL. Uptake and regulation of resource allocation for optimal plant performance and adaptation to stress. FRONTIERS IN PLANT SCIENCE 2013; 4:455. [PMID: 24294215 PMCID: PMC3827556 DOI: 10.3389/fpls.2013.00455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 10/23/2013] [Indexed: 05/12/2023]
Affiliation(s)
- Yong-Ling Ruan
- School of Environmental and Life Sciences, The University of NewcastleCallaghan, NSW, Australia
- Australia-China Research Centre for Crop Improvement, The University of NewcastleCallaghan, NSW, Australia
| | - John W. Patrick
- School of Environmental and Life Sciences, The University of NewcastleCallaghan, NSW, Australia
- Australia-China Research Centre for Crop Improvement, The University of NewcastleCallaghan, NSW, Australia
| | - Sergey Shabala
- School of Agricultural Science, University of TasmaniaHobart, TAS, Australia
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Andriunas FA, Zhang HM, Xia X, Patrick JW, Offler CE. Intersection of transfer cells with phloem biology-broad evolutionary trends, function, and induction. FRONTIERS IN PLANT SCIENCE 2013; 4:221. [PMID: 23847631 PMCID: PMC3696738 DOI: 10.3389/fpls.2013.00221] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 06/07/2013] [Indexed: 05/18/2023]
Abstract
Transfer cells (TCs) are ubiquitous throughout the plant kingdom. Their unique ingrowth wall labyrinths, supporting a plasma membrane enriched in transporter proteins, provides these cells with an enhanced membrane transport capacity for resources. In certain plant species, TCs have been shown to function to facilitate phloem loading and/or unloading at cellular sites of intense resource exchange between symplasmic/apoplasmic compartments. Within the phloem, the key cellular locations of TCs are leaf minor veins of collection phloem and stem nodes of transport phloem. In these locations, companion and phloem parenchyma cells trans-differentiate to a TC morphology consistent with facilitating loading and re-distribution of resources, respectively. At a species level, occurrence of TCs is significantly higher in transport than in collection phloem. TCs are absent from release phloem, but occur within post-sieve element unloading pathways and particularly at interfaces between generations of developing Angiosperm seeds. Experimental accessibility of seed TCs has provided opportunities to investigate their inductive signaling, regulation of ingrowth wall formation and membrane transport function. This review uses this information base to explore current knowledge of phloem transport function and inductive signaling for phloem-associated TCs. The functional role of collection phloem and seed TCs is supported by definitive evidence, but no such information is available for stem node TCs that present an almost intractable experimental challenge. There is an emerging understanding of inductive signals and signaling pathways responsible for initiating trans-differentiation to a TC morphology in developing seeds. However, scant information is available to comment on a potential role for inductive signals (auxin, ethylene and reactive oxygen species) that induce seed TCs, in regulating induction of phloem-associated TCs. Biotic phloem invaders have been used as a model to speculate on involvement of these signals.
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Affiliation(s)
| | | | | | | | - Christina E. Offler
- Department of Biological Sciences, School of Environmental and Life Sciences, The University of NewcastleCallaghan, NSW, Australia
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