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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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Zhu Y, Tian Y, Han S, Wang J, Liu Y, Yin J. Structure, evolution, and roles of SWEET proteins in growth and stress responses in plants. Int J Biol Macromol 2024; 263:130441. [PMID: 38417760 DOI: 10.1016/j.ijbiomac.2024.130441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/23/2024] [Accepted: 02/23/2024] [Indexed: 03/01/2024]
Abstract
Carbohydrates are exported by the SWEET family of transporters, which is a novel class of carriers that can transport sugars across cell membranes and facilitate sugar's long-distance transport from source to sink organs in plants. SWEETs play crucial roles in a wide range of physiologically important processes by regulating apoplastic and symplastic sugar concentrations. These processes include host-pathogen interactions, abiotic stress responses, and plant growth and development. In the present review, we (i) describe the structure and organization of SWEETs in the cell membrane, (ii) discuss the roles of SWEETs in sugar loading and unloading processes, (iii) identify the distinct functions of SWEETs in regulating plant growth and development including flower, fruit, and seed development, (iv) shed light on the importance of SWEETs in modulating abiotic stress resistance, and (v) describe the role of SWEET genes during plant-pathogen interaction. Finally, several perspectives regarding future investigations for improving the understanding of sugar-mediated plant defenses are proposed.
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Affiliation(s)
- Yongxing Zhu
- Hubei Key Laboratory of Waterlogging Disaster and Agricultural Use of Wetland/College of Agriculture, Yangtze University, Jingzhou 434000, Hubei, China; Spice Crops Research Institute, College of Horticulture and Gardening, Yangtze University, Jingzhou 434000, Hubei, China.
| | - Ye Tian
- Spice Crops Research Institute, College of Horticulture and Gardening, Yangtze University, Jingzhou 434000, Hubei, China
| | - Shuo Han
- Hubei Key Laboratory of Waterlogging Disaster and Agricultural Use of Wetland/College of Agriculture, Yangtze University, Jingzhou 434000, Hubei, China.
| | - Jie Wang
- Spice Crops Research Institute, College of Horticulture and Gardening, Yangtze University, Jingzhou 434000, Hubei, China.
| | - Yiqing Liu
- Spice Crops Research Institute, College of Horticulture and Gardening, Yangtze University, Jingzhou 434000, Hubei, China
| | - Junliang Yin
- Hubei Key Laboratory of Waterlogging Disaster and Agricultural Use of Wetland/College of Agriculture, Yangtze University, Jingzhou 434000, Hubei, China.
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Xue X, Beuchat G, Wang J, Yu YC, Moose S, Chen J, Chen LQ. Sugar accumulation enhancement in sorghum stem is associated with reduced reproductive sink strength and increased phloem unloading activity. FRONTIERS IN PLANT SCIENCE 2023; 14:1233813. [PMID: 37767289 PMCID: PMC10519796 DOI: 10.3389/fpls.2023.1233813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 08/21/2023] [Indexed: 09/29/2023]
Abstract
Sweet sorghum has emerged as a promising source of bioenergy mainly due to its high biomass and high soluble sugar yield in stems. Studies have shown that loss-of-function Dry locus alleles have been selected during sweet sorghum domestication, and decapitation can further boost sugar accumulation in sweet sorghum, indicating that the potential for improving sugar yields is yet to be fully realized. To maximize sugar accumulation, it is essential to gain a better understanding of the mechanism underlying the massive accumulation of soluble sugars in sweet sorghum stems in addition to the Dry locus. We performed a transcriptomic analysis upon decapitation of near-isogenic lines for mutant (d, juicy stems, and green leaf midrib) and functional (D, dry stems and white leaf midrib) alleles at the Dry locus. Our analysis revealed that decapitation suppressed photosynthesis in leaves, but accelerated starch metabolic processes in stems. SbbHLH093 negatively correlates with sugar levels supported by genotypes (DD vs. dd), treatments (control vs. decapitation), and developmental stages post anthesis (3d vs.10d). D locus gene SbNAC074A and other programmed cell death-related genes were downregulated by decapitation, while sugar transporter-encoding gene SbSWEET1A was induced. Both SbSWEET1A and Invertase 5 were detected in phloem companion cells by RNA in situ assay. Loss of the SbbHLH093 homolog, AtbHLH093, in Arabidopsis led to a sugar accumulation increase. This study provides new insights into sugar accumulation enhancement in bioenergy crops, which can be potentially achieved by reducing reproductive sink strength and enhancing phloem unloading.
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Affiliation(s)
- Xueyi Xue
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Institute for Sustainability, Energy, and Environment, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Gabriel Beuchat
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Jiang Wang
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Ya-Chi Yu
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Stephen Moose
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Jin Chen
- Institute for Biomedical Informatics, University of Kentucky, Lexington, KY, United States
| | - Li-Qing Chen
- Department of Energy (DOE) Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
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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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Chen L, Ganguly DR, Shafik SH, Danila F, Grof CPL, Sharwood RE, Furbank RT. The role of SWEET4 proteins in the post-phloem sugar transport pathway of Setaria viridis sink tissues. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:2968-2986. [PMID: 36883216 PMCID: PMC10560085 DOI: 10.1093/jxb/erad076] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 03/06/2023] [Indexed: 05/21/2023]
Abstract
In the developing seeds of all higher plants, filial cells are symplastically isolated from the maternal tissue supplying photosynthate to the reproductive structure. Photoassimilates must be transported apoplastically, crossing several membrane barriers, a process facilitated by sugar transporters. Sugars Will Eventually be Exported Transporters (SWEETs) have been proposed to play a crucial role in apoplastic sugar transport during phloem unloading and the post-phloem pathway in sink tissues. Evidence for this is presented here for developing seeds of the C4 model grass Setaria viridis. Using immunolocalization, SvSWEET4 was detected in various maternal and filial tissues within the seed along the sugar transport pathway, in the vascular parenchyma of the pedicel, and in the xylem parenchyma of the stem. Expression of SvSWEET4a in Xenopus laevis oocytes indicated that it functions as a high-capacity glucose and sucrose transporter. Carbohydrate and transcriptional profiling of Setaria seed heads showed that there were some developmental shifts in hexose and sucrose content and consistent expression of SvSWEET4 homologues. Collectively, these results provide evidence for the involvement of SWEETs in the apoplastic transport pathway of sink tissues and allow a pathway for post-phloem sugar transport into the seed to be proposed.
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Affiliation(s)
- Lily Chen
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Diep R Ganguly
- Research School of Biology, ARC Centre of Excellence in Plant Energy Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- CSIRO Synthetic Biology Future Science Platform, Canberra, Australian Capital Territory 2601, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Florence Danila
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Christopher P L Grof
- Centre for Plant Science, School of Environmental and Life Sciences, College of Engineering Science and Environment, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Robert E Sharwood
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, New South Wales 2753, Australia
| | - Robert T Furbank
- Research School of Biology, ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Singh J, Das S, Jagadis Gupta K, Ranjan A, Foyer CH, Thakur JK. Physiological implications of SWEETs in plants and their potential applications in improving source-sink relationships for enhanced yield. PLANT BIOTECHNOLOGY JOURNAL 2022. [PMID: 36529911 PMCID: PMC10363763 DOI: 10.1111/pbi.13982] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 12/02/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
The sugars will eventually be exported transporters (SWEET) family of transporters in plants is identified as a novel class of sugar carriers capable of transporting sugars, sugar alcohols and hormones. Functioning in intercellular sugar transport, SWEETs influence a wide range of physiologically important processes. SWEETs regulate the development of sink organs by providing nutritional support from source leaves, responses to abiotic stresses by maintaining intracellular sugar concentrations, and host-pathogen interactions through the modulation of apoplastic sugar levels. Many bacterial and fungal pathogens activate the expression of SWEET genes in species such as rice and Arabidopsis to gain access to the nutrients that support virulence. The genetic manipulation of SWEETs has led to the generation of bacterial blight (BB)-resistant rice varieties. Similarly, while the overexpression of the SWEETs involved in sucrose export from leaves and pathogenesis led to growth retardation and yield penalties, plants overexpressing SWEETs show improved disease resistance. Such findings demonstrate the complex functions of SWEETs in growth and stress tolerance. Here, we review the importance of SWEETs in plant-pathogen and source-sink interactions and abiotic stress resistance. We highlight the possible applications of SWEETs in crop improvement programmes aimed at improving sink and source strengths important for enhancing the sustainability of yield. We discuss how the adverse effects of the overexpression of SWEETs on plant growth may be overcome.
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Affiliation(s)
- Jitender Singh
- National Institute of Plant Genome Research, New Delhi, India
| | - Shubhashis Das
- National Institute of Plant Genome Research, New Delhi, India
| | | | - Aashish Ranjan
- National Institute of Plant Genome Research, New Delhi, India
| | - Christine H Foyer
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, UK
| | - Jitendra Kumar Thakur
- National Institute of Plant Genome Research, New Delhi, India
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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Singh J, Garai S, Das S, Thakur JK, Tripathy BC. Role of C4 photosynthetic enzyme isoforms in C3 plants and their potential applications in improving agronomic traits in crops. PHOTOSYNTHESIS RESEARCH 2022; 154:233-258. [PMID: 36309625 DOI: 10.1007/s11120-022-00978-9] [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: 06/02/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
As compared to C3, C4 plants have higher photosynthetic rates and better tolerance to high temperature and drought. These traits are highly beneficial in the current scenario of global warming. Interestingly, all the genes of the C4 photosynthetic pathway are present in C3 plants, although they are involved in diverse non-photosynthetic functions. Non-photosynthetic isoforms of carbonic anhydrase (CA), phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), the decarboxylating enzymes NAD/NADP-malic enzyme (NAD/NADP-ME), and phosphoenolpyruvate carboxykinase (PEPCK), and finally pyruvate orthophosphate dikinase (PPDK) catalyze reactions that are essential for major plant metabolism pathways, such as the tricarboxylic acid (TCA) cycle, maintenance of cellular pH, uptake of nutrients and their assimilation. Consistent with this view differential expression pattern of these non-photosynthetic C3 isoforms has been observed in different tissues across the plant developmental stages, such as germination, grain filling, and leaf senescence. Also abundance of these C3 isoforms is increased considerably in response to environmental fluctuations particularly during abiotic stress. Here we review the vital roles played by C3 isoforms of C4 enzymes and the probable mechanisms by which they help plants in acclimation to adverse growth conditions. Further, their potential applications to increase the agronomic trait value of C3 crops is discussed.
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Affiliation(s)
- Jitender Singh
- National Institute of Plant Genome Research, New Delhi, 110067, India.
| | - Sampurna Garai
- International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
| | - Shubhashis Das
- National Institute of Plant Genome Research, New Delhi, 110067, India
| | - Jitendra Kumar Thakur
- National Institute of Plant Genome Research, New Delhi, 110067, India.
- International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India.
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Yao T, Gai XT, Pu ZJ, Gao Y, Xuan YH. From Functional Characterization to the Application of SWEET Sugar Transporters in Plant Resistance Breeding. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:5273-5283. [PMID: 35446562 DOI: 10.1021/acs.jafc.2c00582] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The occurrence of plant diseases severely affects the quality and quantity of plant production. Plants adapt to the constant invasion of pathogens and gradually form a series of defense mechanisms, such as pathogen-associated molecular pattern-triggered immunity and microbial effector-triggered immunity. Moreover, many pathogens have evolved to inhibit the immune defense system and acquire plant nutrients as a result of their coevolution with plants. The sugars will eventually be exported transporters (SWEETs) are a novel family of sugar transporters that function as uniporters. They provide a channel for pathogens, including bacteria, fungi, and viruses, to hijack sugar from the host. In this review, we summarize the functions of SWEETs in nectar secretion, grain loading, senescence, and long-distance transport. We also focus on the interaction between the SWEET genes and pathogens. In addition, we provide insight into the potential application of SWEET genes to enhance disease resistance through the use of genome editing tools. The summary and perspective of this review will deepen our understanding of the role of SWEETs during the process of pathogen infection and provide insights into resistance breeding.
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Affiliation(s)
- Tingshan Yao
- Citrus Research Institute, Southwest University, Chongqing 400712, People's Republic of China
- National Citrus Engineering Research Center, Chongqing 400712, People's Republic of China
| | - Xiao Tong Gai
- Agronomy Research Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650021, People's Republic of China
| | - Zhong Ji Pu
- Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
| | - Yue Gao
- College of Plant Protection, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Yuan Hu Xuan
- College of Plant Protection, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
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