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Zhang B, Ma Z, Guo H, Chen S, Liu J. Single-cell RNA-sequencing provides new insights into the cell-specific expression patterns and transcriptional regulation of photosynthetic genes in bermudagrass leaf blades. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 213:108857. [PMID: 38905728 DOI: 10.1016/j.plaphy.2024.108857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 06/06/2024] [Accepted: 06/18/2024] [Indexed: 06/23/2024]
Abstract
As an important warm-season turfgrass species, bermudagrass (Cynodon dactylon L.) flourishes in warm areas around the world due to the existence of the C4 photosynthetic pathway. However, how C4 photosynthesis operates in bermudagrass leaves is still poorly understood. In this study, we performed single-cell RNA-sequencing on 5296 cells from bermudagrass leaf blades. Eight cell clusters corresponding to mesophyll, bundle sheath, epidermis and vascular bundle cells were successfully identified using known cell marker genes. Expression profiling indicated that genes encoding NADP-dependent malic enzymes (NADP-MEs) were highly expressed in bundle sheath cells, whereas NAD-ME genes were weakly expressed in all cell types, suggesting C4 photosynthesis of bermudagrass leaf blades might be NADP-ME type rather than NAD-ME type. The results also indicated that starch synthesis-related genes showed preferential expression in bundle sheath cells, whereas starch degradation-related genes were highly expressed in mesophyll cells, which agrees with the observed accumulation of starch-filled chloroplasts in bundle sheath cells. Gene co-expression analysis further revealed that different families of transcription factors were co-expressed with multiple C4 photosynthesis-related genes, suggesting a complex transcription regulatory network of C4 photosynthesis might exist in bermudagrass leaf blades. These findings collectively provided new insights into the cell-specific expression patterns and transcriptional regulation of photosynthetic genes in bermudagrass.
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Affiliation(s)
- Bing Zhang
- College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China.
| | - Ziyan Ma
- College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China
| | - Hailin Guo
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China
| | - Si Chen
- College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China
| | - Jianxiu Liu
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China
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2
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Chen L, Ghannoum O, Furbank RT. Sugar sensing in C4 source leaves: a gap that needs to be filled. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:3818-3834. [PMID: 38642398 PMCID: PMC11233418 DOI: 10.1093/jxb/erae166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 04/18/2024] [Indexed: 04/22/2024]
Abstract
Plant growth depends on sugar production and export by photosynthesizing source leaves and sugar allocation and import by sink tissues (grains, roots, stems, and young leaves). Photosynthesis and sink demand are tightly coordinated through metabolic (substrate, allosteric) feedback and signalling (sugar, hormones) mechanisms. Sugar signalling integrates sugar production with plant development and environmental cues. In C3 plants (e.g. wheat and rice), it is well documented that sugar accumulation in source leaves, due to source-sink imbalance, negatively feeds back on photosynthesis and plant productivity. However, we have a limited understanding about the molecular mechanisms underlying those feedback regulations, especially in C4 plants (e.g. maize, sorghum, and sugarcane). Recent work with the C4 model plant Setaria viridis suggested that C4 leaves have different sugar sensing thresholds and behaviours relative to C3 counterparts. Addressing this research priority is critical because improving crop yield requires a better understanding of how plants coordinate source activity with sink demand. Here we review the literature, present a model of action for sugar sensing in C4 source leaves, and suggest ways forward.
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Affiliation(s)
- Lily Chen
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, NSW, 2753, Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, NSW, 2753, Australia
| | - Robert T Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
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3
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Ludwig M, Hartwell J, Raines CA, Simkin AJ. The Calvin-Benson-Bassham cycle in C 4 and Crassulacean acid metabolism species. Semin Cell Dev Biol 2024; 155:10-22. [PMID: 37544777 DOI: 10.1016/j.semcdb.2023.07.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 07/03/2023] [Accepted: 07/25/2023] [Indexed: 08/08/2023]
Abstract
The Calvin-Benson-Bassham (CBB) cycle is the ancestral CO2 assimilation pathway and is found in all photosynthetic organisms. Biochemical extensions to the CBB cycle have evolved that allow the resulting pathways to act as CO2 concentrating mechanisms, either spatially in the case of C4 photosynthesis or temporally in the case of Crassulacean acid metabolism (CAM). While the biochemical steps in the C4 and CAM pathways are known, questions remain on their integration and regulation with CBB cycle activity. The application of omic and transgenic technologies is providing a more complete understanding of the biochemistry of C4 and CAM species and will also provide insight into the CBB cycle in these plants. As the global population increases, new solutions are required to increase crop yields and meet demands for food and other bioproducts. Previous work in C3 species has shown that increasing carbon assimilation through genetic manipulation of the CBB cycle can increase biomass and yield. There may also be options to improve photosynthesis in species using C4 photosynthesis and CAM through manipulation of the CBB cycle in these plants. This is an underexplored strategy and requires more basic knowledge of CBB cycle operation in these species to enable approaches for increased productivity.
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Affiliation(s)
- Martha Ludwig
- School of Molecular Sciences, University of Western Australia, Perth, Western Australia, Australia.
| | - James Hartwell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | | | - Andrew J Simkin
- University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
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4
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Berasategui JA, Žerdoner Čalasan A, Zizka A, Kadereit G. Global distribution, climatic preferences and photosynthesis-related traits of C 4 eudicots and how they differ from those of C 4 grasses. Ecol Evol 2023; 13:e10720. [PMID: 37964791 PMCID: PMC10641307 DOI: 10.1002/ece3.10720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 10/25/2023] [Accepted: 10/30/2023] [Indexed: 11/16/2023] Open
Abstract
C₄ is one of three known photosynthetic processes of carbon fixation in flowering plants. It evolved independently more than 61 times in multiple angiosperm lineages and consists of a series of anatomical and biochemical modifications to the ancestral C3 pathway increasing plant productivity under warm and light-rich conditions. The C4 lineages of eudicots belong to seven orders and 15 families, are phylogenetically less constrained than those of monocots and entail an enormous structural and ecological diversity. Eudicot C4 lineages likely evolved the C4 syndrome along different evolutionary paths. Therefore, a better understanding of this diversity is key to understanding the evolution of this complex trait as a whole. By compiling 1207 recognised C4 eudicots species described in the literature and presenting trait data among these species, we identify global centres of species richness and of high phylogenetic diversity. Furthermore, we discuss climatic preferences in the context of plant functional traits. We identify two hotspots of C4 eudicot diversity: arid regions of Mexico/Southern United States and Australia, which show a similarly high number of different C4 eudicot genera but differ in the number of C4 lineages that evolved in situ. Further eudicot C4 hotspots with many different families and genera are in South Africa, West Africa, Patagonia, Central Asia and the Mediterranean. In general, C4 eudicots are diverse in deserts and xeric shrublands, tropical and subtropical grasslands, savannas and shrublands. We found C4 eudicots to occur in areas with less annual precipitation than C4 grasses which can be explained by frequently associated adaptations to drought stress such as among others succulence and salt tolerance. The data indicate that C4 eudicot lineages utilising the NAD-ME decarboxylating enzyme grow in drier areas than those using the NADP-ME decarboxylating enzyme indicating biochemical restrictions of the later system in higher temperatures. We conclude that in most eudicot lineages, C4 evolved in ancestrally already drought-adapted clades and enabled these to further spread in these habitats and colonise even drier areas.
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Affiliation(s)
- Jessica A. Berasategui
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
- Institute for Molecular PhysiologyJohannes Gutenberg‐University MainzMainzGermany
| | - Anže Žerdoner Čalasan
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
| | - Alexander Zizka
- Department of BiologyPhilipps‐University MarburgMarburgGermany
| | - Gudrun Kadereit
- Prinzessin Therese von Bayern Lehrstuhl für Systematik, Biodiversität & Evolution der PflanzenLudwig‐Maximilians Universität MünchenMünchenGermany
- Botanischer Garten München‐Nymphenburg und Botanische Staatssammlung MünchenStaatliche Naturwissenschaftliche Sammlungen BayernsMünchenGermany
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5
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Benning UF, Chen L, Watson-Lazowski A, Henry C, Furbank RT, Ghannoum O. Spatial expression patterns of genes encoding sugar sensors in leaves of C4 and C3 grasses. ANNALS OF BOTANY 2023; 131:985-1000. [PMID: 37103118 PMCID: PMC10332396 DOI: 10.1093/aob/mcad057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 04/26/2023] [Indexed: 06/19/2023]
Abstract
BACKGROUND AND AIMS The mechanisms of sugar sensing in grasses remain elusive, especially those using C4 photosynthesis even though a large proportion of the world's agricultural crops utilize this pathway. We addressed this gap by comparing the expression of genes encoding components of sugar sensors in C3 and C4 grasses, with a focus on source tissues of C4 grasses. Given C4 plants evolved into a two-cell carbon fixation system, it was hypothesized this may have also changed how sugars were sensed. METHODS For six C3 and eight C4 grasses, putative sugar sensor genes were identified for target of rapamycin (TOR), SNF1-related kinase 1 (SnRK1), hexokinase (HXK) and those involved in the metabolism of the sugar sensing metabolite trehalose-6-phosphate (T6P) using publicly available RNA deep sequencing data. For several of these grasses, expression was compared in three ways: source (leaf) versus sink (seed), along the gradient of the leaf, and bundle sheath versus mesophyll cells. KEY RESULTS No positive selection of codons associated with the evolution of C4 photosynthesis was identified in sugar sensor proteins here. Expressions of genes encoding sugar sensors were relatively ubiquitous between source and sink tissues as well as along the leaf gradient of both C4 and C3 grasses. Across C4 grasses, SnRK1β1 and TPS1 were preferentially expressed in the mesophyll and bundle sheath cells, respectively. Species-specific differences of gene expression between the two cell types were also apparent. CONCLUSIONS This comprehensive transcriptomic study provides an initial foundation for elucidating sugar-sensing genes within major C4 and C3 crops. This study provides some evidence that C4 and C3 grasses do not differ in how sugars are sensed. While sugar sensor gene expression has a degree of stability along the leaf, there are some contrasts between the mesophyll and bundle sheath cells.
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Affiliation(s)
- Urs F Benning
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Lily Chen
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | | | - Clemence Henry
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Robert T Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Oula Ghannoum
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
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6
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Rojas BE, Tonetti T, Figueroa CM. Trehalose 6-phosphate metabolism in C 4 species. CURRENT OPINION IN PLANT BIOLOGY 2023; 72:102347. [PMID: 36806837 DOI: 10.1016/j.pbi.2023.102347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 01/09/2023] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
Trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, is an essential signal metabolite in plants, linking growth and development to carbon status. Our current understanding of Tre6P metabolism and signaling pathways in plants is based almost entirely on studies performed with Arabidopsis thaliana, a model plant that performs C3 photosynthesis. Conversely, our knowledge on the molecular mechanisms involved in Tre6P regulation of carbon partitioning and metabolism in C4 plants is scarce. This topic is especially relevant due to the agronomic importance of crops performing C4 photosynthesis, such as maize, sorghum and sugarcane. In this review, we focused our attention on recent developments related to Tre6P metabolism in C4 species and raised some open questions that should be addressed in the near future to improve the yield of economically important crops.
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Affiliation(s)
- Bruno E Rojas
- Instituto de Agrobiotecnología del Litoral, UNL, CONICET, FBCB, Santa Fe, Argentina
| | - Tomás Tonetti
- Instituto de Agrobiotecnología del Litoral, UNL, CONICET, FBCB, Santa Fe, Argentina
| | - Carlos M Figueroa
- Instituto de Agrobiotecnología del Litoral, UNL, CONICET, FBCB, Santa Fe, Argentina.
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7
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Ermakova M, Lopez-Calcagno PE, Furbank RT, Raines CA, von Caemmerer S. Increased sedoheptulose-1,7-bisphosphatase content in Setaria viridis does not affect C4 photosynthesis. PLANT PHYSIOLOGY 2023; 191:885-893. [PMID: 36282540 PMCID: PMC9922425 DOI: 10.1093/plphys/kiac484] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 09/28/2022] [Indexed: 05/05/2023]
Abstract
Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and increasing the abundance of SBPase in C3 plants provides higher photosynthetic rates and stimulates biomass and yield. C4 plants usually have higher photosynthetic rates because they operate a biochemical CO2-concentrating mechanism between mesophyll and bundle sheath cells. In the C4 system, SBPase and other enzymes of the Calvin cycle are localized to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C4 photosynthesis. Using green foxtail millet (Setaria viridis), a model C4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2 times higher SBPase content compared to wild-type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localization of the protein. The abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit was not affected in transgenic plants overexpressing SBPase, and neither was leaf chlorophyll content or photosynthetic electron transport parameters. We found no association between SBPase content in S. viridis and saturating rates of CO2 assimilation. Moreover, a detailed analysis of CO2 assimilation rates at different CO2 partial pressures, irradiances, and leaf temperatures showed no improvement of photosynthesis in plants overexpressing SBPase. We discuss the potential implications of these results for understanding the role of SBPase in regulation of C4 photosynthesis.
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Affiliation(s)
- Maria Ermakova
- Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Canberra 2600, Australia
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
| | - Patricia E Lopez-Calcagno
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK
- School of Natural and Environmental Sciences, Newcastle University, Newcastle NE1 7RU, UK
| | - Robert T Furbank
- Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Canberra 2600, Australia
| | - Christine A Raines
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK
| | - Susanne von Caemmerer
- Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Canberra 2600, Australia
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8
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Walsh CA, Bräutigam A, Roberts MR, Lundgren MR. Evolutionary implications of C2 photosynthesis: how complex biochemical trade-offs may limit C4 evolution. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:707-722. [PMID: 36437625 PMCID: PMC9899418 DOI: 10.1093/jxb/erac465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 11/22/2022] [Indexed: 06/16/2023]
Abstract
The C2 carbon-concentrating mechanism increases net CO2 assimilation by shuttling photorespiratory CO2 in the form of glycine from mesophyll to bundle sheath cells, where CO2 concentrates and can be re-assimilated. This glycine shuttle also releases NH3 and serine into the bundle sheath, and modelling studies suggest that this influx of NH3 may cause a nitrogen imbalance between the two cell types that selects for the C4 carbon-concentrating mechanism. Here we provide an alternative hypothesis outlining mechanisms by which bundle sheath NH3 and serine play vital roles to not only influence the status of C2 plants along the C3 to C4 evolutionary trajectory, but to also convey stress tolerance to these unique plants. Our hypothesis explains how an optimized bundle sheath nitrogen hub interacts with sulfur and carbon metabolism to mitigate the effects of high photorespiratory conditions. While C2 photosynthesis is typically cited for its intermediary role in C4 photosynthesis evolution, our alternative hypothesis provides a mechanism to explain why some C2 lineages have not made this transition. We propose that stress resilience, coupled with open flux tricarboxylic acid and photorespiration pathways, conveys an advantage to C2 plants in fluctuating environments.
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Affiliation(s)
- Catherine A Walsh
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
| | - Andrea Bräutigam
- Faculty of Biology, Bielefeld University, Universität str. 27, D-33615 Bielefeld, Germany
| | - Michael R Roberts
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
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9
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Boatwright JL, Sapkota S, Myers M, Kumar N, Cox A, Jordan KE, Kresovich S. Dissecting the Genetic Architecture of Carbon Partitioning in Sorghum Using Multiscale Phenotypes. FRONTIERS IN PLANT SCIENCE 2022; 13:790005. [PMID: 35665170 PMCID: PMC9159972 DOI: 10.3389/fpls.2022.790005] [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: 10/05/2021] [Accepted: 04/19/2022] [Indexed: 06/15/2023]
Abstract
Carbon partitioning in plants may be viewed as a dynamic process composed of the many interactions between sources and sinks. The accumulation and distribution of fixed carbon is not dictated simply by the sink strength and number but is dependent upon the source, pathways, and interactions of the system. As such, the study of carbon partitioning through perturbations to the system or through focus on individual traits may fail to produce actionable developments or a comprehensive understanding of the mechanisms underlying this complex process. Using the recently published sorghum carbon-partitioning panel, we collected both macroscale phenotypic characteristics such as plant height, above-ground biomass, and dry weight along with microscale compositional traits to deconvolute the carbon-partitioning pathways in this multipurpose crop. Multivariate analyses of traits resulted in the identification of numerous loci associated with several distinct carbon-partitioning traits, which putatively regulate sugar content, manganese homeostasis, and nitrate transportation. Using a multivariate adaptive shrinkage approach, we identified several loci associated with multiple traits suggesting that pleiotropic and/or interactive effects may positively influence multiple carbon-partitioning traits, or these overlaps may represent molecular switches mediating basal carbon allocating or partitioning networks. Conversely, we also identify a carbon tradeoff where reduced lignin content is associated with increased sugar content. The results presented here support previous studies demonstrating the convoluted nature of carbon partitioning in sorghum and emphasize the importance of taking a holistic approach to the study of carbon partitioning by utilizing multiscale phenotypes.
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Affiliation(s)
- J. Lucas Boatwright
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, United States
| | - Sirjan Sapkota
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
| | - Matthew Myers
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
| | - Neeraj Kumar
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, United States
| | - Alex Cox
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
| | - Kathleen E. Jordan
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
| | - Stephen Kresovich
- Advanced Plant Technology, Clemson University, Clemson, SC, United States
- Feed the Future Innovation Lab for Crop Improvement, Cornell University, Ithaca, NY, United States
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10
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Chen L, Ganguly DR, Shafik SH, Ermakova M, Pogson BJ, Grof CPL, Sharwood RE, Furbank RT. Elucidating the role of SWEET13 in phloem loading of the C 4 grass Setaria viridis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:615-632. [PMID: 34780111 DOI: 10.1111/tpj.15581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/11/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
Photosynthetic efficiency and sink demand are tightly correlated with rates of phloem loading, where maintaining low cytosolic sugar concentrations is paramount to prevent the downregulation of photosynthesis. Sugars Will Eventually be Exported Transporters (SWEETs) are thought to have a pivotal role in the apoplastic phloem loading of C4 grasses. SWEETs have not been well studied in C4 species, and their investigation is complicated by photosynthesis taking place across two cell types and, therefore, photoassimilate export can occur from either one. SWEET13 homologues in C4 grasses have been proposed to facilitate apoplastic phloem loading. Here, we provide evidence for this hypothesis using the C4 grass Setaria viridis. Expression analyses on the leaf gradient of C4 species Setaria and Sorghum bicolor show abundant transcript levels for SWEET13 homologues. Carbohydrate profiling along the Setaria leaf shows total sugar content to be significantly higher in the mature leaf tip compared with the younger tissue at the base. We present the first known immunolocalization results for SvSWEET13a and SvSWEET13b using novel isoform-specific antisera. These results show localization to the bundle sheath and phloem parenchyma cells of both minor and major veins. We further present the first transport kinetics study of C4 monocot SWEETs by using a Xenopus laevis oocyte heterologous expression system. We demonstrate that SvSWEET13a and SvSWEET13b are high-capacity transporters of glucose and sucrose, with a higher apparent Vmax for sucrose, compared with glucose, typical of clade III SWEETs. Collectively, these results provide evidence for an apoplastic phloem loading pathway in Setaria and possibly other C4 species.
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Affiliation(s)
- Lily Chen
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- School of Science, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales, 2753, Australia
| | - Diep R Ganguly
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- CSIRO Synthetic Biology Future Science Platform, Canberra, Australian Capital Territory, 2601, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Maria Ermakova
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Barry J Pogson
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Christopher P L Grof
- Centre for Plant Science, School of Environmental and Life Sciences, College of Engineering Science and Environment, University of Newcastle, Callaghan, New South Wales, 2308, Australia
| | - Robert E Sharwood
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
- School of Science, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales, 2753, Australia
| | - Robert T Furbank
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
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11
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Hancock RD, Smirnoff N, Lunn JE. Journal of Experimental Botany 70th anniversary: plant metabolism in a changing world. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5939-5941. [PMID: 34473301 PMCID: PMC8411604 DOI: 10.1093/jxb/erab352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Robert D Hancock
- Cell and Molecular Sciences, The James Hutton Institute, Dundee DD2 5DA, UK
| | - Nicholas Smirnoff
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - John E Lunn
- Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm, Germany
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12
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Furbank RT, Kelly S. Finding the C4 sweet spot: cellular compartmentation of carbohydrate metabolism in C4 photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:6018-6026. [PMID: 34142128 PMCID: PMC8411606 DOI: 10.1093/jxb/erab290] [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: 03/29/2021] [Accepted: 06/14/2021] [Indexed: 05/10/2023]
Abstract
The two-cell type C4 photosynthetic pathway requires both anatomical and biochemical specialization to achieve a functional CO2-concentrating mechanism. While a great deal of research has been done on Kranz anatomy and cell-specific expression and activity of enzymes in the C4 pathway, less attention has been paid to partitioning of carbohydrate synthesis between the cell types of C4 leaves. As early as the 1970s it became apparent that, in the small number of species examined at the time, sucrose was predominantly synthesized in the mesophyll cells and starch in the bundle sheath cells. Here we discuss how this partitioning is achieved in C4 plants and explore whether this is a consequence of C4 metabolism or indeed a requirement for its evolution and efficient operation.
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Affiliation(s)
- Robert T Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia
| | - Steven Kelly
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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