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Xu Y, Schmiege SC, Sharkey TD. The oxidative pentose phosphate pathway in photosynthesis: a tale of two shunts. THE NEW PHYTOLOGIST 2024; 242:2453-2463. [PMID: 38567702 DOI: 10.1111/nph.19730] [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: 12/07/2023] [Accepted: 03/17/2024] [Indexed: 05/24/2024]
Abstract
CO2 release in the light (RL) and its presumed source, oxidative pentose phosphate pathways, were found to be insensitive to CO2 concentration. The oxidative pentose phosphate pathways form glucose 6-phosphate (G6P) shunts that bypass the nonoxidative pentose phosphate reactions of the Calvin-Benson cycle. Using adenosine diphosphate glucose and uridine diphosphate glucose as proxies for labeling of G6P in the stroma and cytosol respectively, it was found that only the cytosolic shunt was active. Uridine diphosphate glucose, a proxy for cytosolic G6P, and 6-phosphogluconate (6PG) were significantly less labeled than Calvin-Benson cycle intermediates in the light. But ADP glucose, a proxy for stromal G6P, is labeled to the same degree as Calvin-Benson cycle intermediates and much greater than 6PG. A metabolically inert pool of sedoheptulose bisphosphate can slowly equilibrate keeping the label in sedoheptulose lower than in other stromal metabolites. Finally, phosphorylation of fructose 6-phosphate (F6P) in the cytosol can allow some unlabeled carbon in cytosolic F6P to dilute label in phosphenolpyruvate. The results clearly show that there is oxidative pentose phosphate pathway activity in the cytosol that provides a shunt around the nonoxidative pentose phosphate pathway reactions of the Calvin-Benson cycle and is not strongly CO2-sensitive.
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Affiliation(s)
- Yuan Xu
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
| | - Stephanie C Schmiege
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biology, Western University, London, ON, N6A 5B7, Canada
| | - Thomas D Sharkey
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
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2
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Xu Y, Koroma AA, Weise SE, Fu X, Sharkey TD, Shachar-Hill Y. Daylength variation affects growth, photosynthesis, leaf metabolism, partitioning, and metabolic fluxes. PLANT PHYSIOLOGY 2023; 194:475-490. [PMID: 37726946 PMCID: PMC10756764 DOI: 10.1093/plphys/kiad507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 09/01/2023] [Accepted: 09/01/2023] [Indexed: 09/21/2023]
Abstract
Daylength, a seasonal and latitudinal variable, exerts a substantial impact on plant growth. However, the relationship between daylength and growth is nonproportional, suggesting the existence of adaptive mechanisms. Thus, our study aimed to comprehensively investigate the adaptive strategies employed by plants in response to daylength variation. We grew false flax (Camelina sativa) plants, a model oilseed crop, under long-day (LD) and short-day (SD) conditions and used growth measurements, gas exchange measurements, and isotopic labeling techniques, including 13C, 14C, and 2H2O, to determine responses to different daylengths. Our findings revealed that daylength influences various growth parameters, photosynthetic physiology, carbon partitioning, metabolic fluxes, and metabolite levels. SD plants employed diverse mechanisms to compensate for reduced CO2 fixation in the shorter photoperiod. These mechanisms included enhanced photosynthetic rates and reduced respiration in the light (RL), leading to increased shoot investment. Additionally, SD plants exhibited reduced rates of the glucose 6-phosphate (G6P) shunt and greater partitioning of sugars into starch, thereby sustaining carbon availability during the longer night. Isotopic labeling results further demonstrated substantial alterations in the partitioning of amino acids and TCA cycle intermediates between rapidly and slowly turning over pools. Overall, the results point to multiple developmental, physiological, and metabolic ways in which plants adapt to different daylengths to maintain growth.
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Affiliation(s)
- Yuan Xu
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Abubakarr A Koroma
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
- Department of Microbiology and Immunology, Emory University, Atlanta, GA 30329, USA
| | - Sean E Weise
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Xinyu Fu
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Thomas D Sharkey
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI 48824, USA
| | - Yair Shachar-Hill
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
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3
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Wang X, Choi YM, Jeon YA, Yi J, Shin MJ, Desta KT, Yoon H. Analysis of Genetic Diversity in Adzuki Beans ( Vigna angularis): Insights into Environmental Adaptation and Early Breeding Strategies for Yield Improvement. PLANTS (BASEL, SWITZERLAND) 2023; 12:4154. [PMID: 38140482 PMCID: PMC10747723 DOI: 10.3390/plants12244154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 12/10/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023]
Abstract
Adzuki beans are widely cultivated in East Asia and are one of the earliest domesticated crops. In order to gain a deeper understanding of the genetic diversity and domestication history of adzuki beans, we conducted Genotyping by Sequencing (GBS) analysis on 366 landraces originating from Korea, China, and Japan, resulting in 6586 single-nucleotide polymorphisms (SNPs). Population structure analysis divided these 366 landraces into three subpopulations. These three subpopulations exhibited distinctive distributions, suggesting that they underwent extended domestication processes in their respective regions of origin. Phenotypic variance analysis of the three subpopulations indicated that the Korean-domesticated subpopulation exhibited significantly higher 100-seed weights, the Japanese-domesticated subpopulation showed significantly higher numbers of grains per pod, and the Chinese-domesticated subpopulation displayed significantly higher numbers of pods per plant. We speculate that these differences in yield-related traits may be attributed to varying emphases placed by early breeders in these regions on the selection of traits related to yield. A large number of genes related to biotic/abiotic stress resistance and defense were found in most quantitative trait locus (QTL) for yield-related traits using genome-wide association studies (GWAS). Genomic sliding window analysis of Tajima's D and a genetic differentiation coefficient (Fst) revealed distinct domestication selection signatures and genotype variations on these QTLs within each subpopulation. These findings indicate that each subpopulation would have been subjected to varied biotic/abiotic stress events in different origins, of which these stress events have caused balancing selection differences in the QTL of each subpopulation. In these balancing selections, plants tend to select genotypes with strong resistance under biotic/abiotic stress, but reduce the frequency of high-yield genotypes to varying degrees. These biotic/abiotic stressors impact crop yield and may even lead to selection purging, resulting in the loss of several high-yielding genotypes among landraces. However, this also fuels the flow of crop germplasms. Overall, balancing selection appears to have a more significant impact on the three yield-related traits compared to breeder-driven domestication selection. These findings are crucial for understanding the impact of domestication selection history on landraces and yield-related traits, aiding in the improvement of adzuki bean varieties.
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Affiliation(s)
| | | | | | | | | | | | - Hyemyeong Yoon
- National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54874, Republic of Korea; (X.W.); (Y.-M.C.); (Y.-a.J.); (J.Y.); (M.-J.S.)
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4
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Ozawa Y, Tanaka A, Suzuki T, Sugiura D. Sink-source imbalance triggers delayed photosynthetic induction: Transcriptomic and physiological evidence. PHYSIOLOGIA PLANTARUM 2023; 175:e14000. [PMID: 37882282 DOI: 10.1111/ppl.14000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/01/2023] [Accepted: 08/06/2023] [Indexed: 10/27/2023]
Abstract
Sink-source imbalance causes accumulation of nonstructural carbohydrates (NSCs) and photosynthetic downregulation. However, despite numerous studies, it remains unclear whether NSC accumulation or N deficiency more directly decreases steady-state maximum photosynthesis and photosynthetic induction, as well as underlying gene expression profiles. We evaluated the relationship between photosynthetic capacity and NSC accumulation induced by cold girdling, sucrose feeding, and low nitrogen treatment in Glycine max and Phaseolus vulgaris. In G. max, changes in transcriptome profiles were further investigated, focusing on the physiological processes of photosynthesis and NSC accumulation. NSC accumulation decreased the maximum photosynthetic capacity and delayed photosynthetic induction in both species. In G. max, such photosynthetic downregulation was explained by coordinated downregulation of photosynthetic genes involved in the Calvin cycle, Rubisco activase, photochemical reactions, and stomatal opening. Furthermore, sink-source imbalance may have triggered a change in the balance of sugar-phosphate translocators in chloroplast membranes, which may have promoted starch accumulation in chloroplasts. Our findings provide an overall picture of photosynthetic downregulation and NSC accumulation in G. max, demonstrating that photosynthetic downregulation is triggered by NSC accumulation and cannot be explained solely by N deficiency.
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Affiliation(s)
- Yui Ozawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Aiko Tanaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Takamasa Suzuki
- College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan
| | - Daisuke Sugiura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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Huang W, Krishnan A, Plett A, Meagher M, Linka N, Wang Y, Ren B, Findinier J, Redekop P, Fakhimi N, Kim RG, Karns DA, Boyle N, Posewitz MC, Grossman AR. Chlamydomonas mutants lacking chloroplast TRIOSE PHOSPHATE TRANSPORTER3 are metabolically compromised and light-sensitive. THE PLANT CELL 2023:koad095. [PMID: 36970811 DOI: 10.1093/plcell/koad095] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/08/2023] [Accepted: 03/23/2023] [Indexed: 06/18/2023]
Abstract
Modulation of photoassimilate export from the chloroplast is essential for controlling the distribution of fixed carbon in the cell and maintaining optimum photosynthetic rates. In this study we identified chloroplast TRIOSE PHOSPHATE/PHOSPHATE TRANSLOCATOR2 (CreTPT2) and CreTPT3 in the green alga Chlamydomonas (Chlamydomonas reinhardtii), which exhibit similar substrate specificities but whose encoding genes are differentially expressed over the diurnal cycle. We focused mostly on CreTPT3 because of its high level of expression and the severe phenotype exhibited by tpt3 relative to tpt2 mutants. Null mutants for CreTPT3 had a pleiotropic phenotype that affected growth, photosynthetic activities, metabolite profiles, carbon partitioning, and organelle-specific accumulation of H2O2. These analyses demonstrated that CreTPT3 is a dominant conduit on the chloroplast envelope for the transport of photoassimilates. In addition, CreTPT3 can serve as a safety valve that moves excess reductant out of the chloroplast and appears to be essential for preventing cells from experiencing oxidative stress and accumulating reactive oxygen species, even under low/moderate light intensities. Finally, our studies indicate subfunctionalization of the CreTPT transporters and suggest that there are differences in managing the export of photoassimilates from the chloroplasts of Chlamydomonas and vascular plants.
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Affiliation(s)
- Weichao Huang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Anagha Krishnan
- Department of Chemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Anastasija Plett
- Institute of Plant Biochemistry, Heinrich-Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Michelle Meagher
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA
| | - Nicole Linka
- Institute of Plant Biochemistry, Heinrich-Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Yongsheng Wang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
- School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Bijie Ren
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Justin Findinier
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Petra Redekop
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Neda Fakhimi
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Rick G Kim
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Devin A Karns
- Department of Chemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Nanette Boyle
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO 80401, USA
| | - Matthew C Posewitz
- Department of Chemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA
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6
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Photosynthetic acclimation to changing environments. Biochem Soc Trans 2023; 51:473-486. [PMID: 36892145 DOI: 10.1042/bst20211245] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 02/03/2023] [Accepted: 02/21/2023] [Indexed: 03/10/2023]
Abstract
Plants are exposed to environments that fluctuate of timescales varying from seconds to months. Leaves that develop in one set of conditions optimise their metabolism to the conditions experienced, in a process called developmental acclimation. However, when plants experience a sustained change in conditions, existing leaves will also acclimate dynamically to the new conditions. Typically this process takes several days. In this review, we discuss this dynamic acclimation process, focussing on the responses of the photosynthetic apparatus to light and temperature. We briefly discuss the principal changes occurring in the chloroplast, before examining what is known, and not known, about the sensing and signalling processes that underlie acclimation, identifying likely regulators of acclimation.
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Zirngibl ME, Araguirang GE, Kitashova A, Jahnke K, Rolka T, Kühn C, Nägele T, Richter AS. Triose phosphate export from chloroplasts and cellular sugar content regulate anthocyanin biosynthesis during high light acclimation. PLANT COMMUNICATIONS 2023; 4:100423. [PMID: 35962545 PMCID: PMC9860169 DOI: 10.1016/j.xplc.2022.100423] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 07/22/2022] [Accepted: 08/09/2022] [Indexed: 05/07/2023]
Abstract
Plants have evolved multiple strategies to cope with rapid changes in the environment. During high light (HL) acclimation, the biosynthesis of photoprotective flavonoids, such as anthocyanins, is induced. However, the exact nature of the signal and downstream factors for HL induction of flavonoid biosynthesis (FB) is still under debate. Here, we show that carbon fixation in chloroplasts, subsequent export of photosynthates by triose phosphate/phosphate translocator (TPT), and rapid increase in cellular sugar content permit the transcriptional and metabolic activation of anthocyanin biosynthesis during HL acclimation. In combination with genetic and physiological analysis, targeted and whole-transcriptome gene expression studies suggest that reactive oxygen species and phytohormones play only a minor role in rapid HL induction of the anthocyanin branch of FB. In addition to transcripts of FB, sugar-responsive genes showed delayed repression or induction in tpt-2 during HL treatment, and a significant overlap with transcripts regulated by SNF1-related protein kinase 1 (SnRK1) was observed, including a central transcription factor of FB. Analysis of mutants with increased and repressed SnRK1 activity suggests that sugar-induced inactivation of SnRK1 is required for HL-mediated activation of anthocyanin biosynthesis. Our study emphasizes the central role of chloroplasts as sensors for environmental changes as well as the vital function of sugar signaling in plant acclimation.
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Affiliation(s)
- Max-Emanuel Zirngibl
- Humboldt-Universität zu Berlin, Institute of Biology, Physiology of Plant Cell Organelles, Philippstrasse 13, 10115 Berlin, Germany
| | - Galileo Estopare Araguirang
- University of Rostock, Institute for Biosciences, Physiology of Plant Metabolism, Albert-Einstein-Strasse 3, 18059 Rostock, Germany; Humboldt-Universität zu Berlin, Institute of Biology, Physiology of Plant Cell Organelles, Philippstrasse 13, 10115 Berlin, Germany
| | - Anastasia Kitashova
- Ludwig-Maximilians-Universität München, Faculty of Biology, Plant Evolutionary Cell Biology, 82152 Planegg-Martinsried, Germany
| | - Kathrin Jahnke
- University of Rostock, Institute for Biosciences, Physiology of Plant Metabolism, Albert-Einstein-Strasse 3, 18059 Rostock, Germany
| | - Tobias Rolka
- Humboldt-Universität zu Berlin, Institute of Biology, Physiology of Plant Cell Organelles, Philippstrasse 13, 10115 Berlin, Germany
| | - Christine Kühn
- University of Rostock, Institute for Biosciences, Physiology of Plant Metabolism, Albert-Einstein-Strasse 3, 18059 Rostock, Germany
| | - Thomas Nägele
- Ludwig-Maximilians-Universität München, Faculty of Biology, Plant Evolutionary Cell Biology, 82152 Planegg-Martinsried, Germany
| | - Andreas S Richter
- University of Rostock, Institute for Biosciences, Physiology of Plant Metabolism, Albert-Einstein-Strasse 3, 18059 Rostock, Germany; Humboldt-Universität zu Berlin, Institute of Biology, Physiology of Plant Cell Organelles, Philippstrasse 13, 10115 Berlin, Germany.
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8
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Alameldin HF, Montgomery BL. Plasticity of Arabidopsis rosette transcriptomes and photosynthetic responses in dynamic light conditions. PLANT DIRECT 2023; 7:e475. [PMID: 36628154 PMCID: PMC9822700 DOI: 10.1002/pld3.475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/03/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
With the high variability of natural growth environments, plants exhibit flexibility and resilience in regard to the strategies they employ to maintain overall fitness, including maximizing light use for photosynthesis, while simultaneously limiting light-associated damage. We measured distinct parameters of photosynthetic performance of Arabidopsis thaliana plants under dynamic light regimes. Plants were grown to maturity then subjected to the following 5-day (16 h light, 8 h dark) regime: Day 1 at constant light (CL) intensity during light period, representative of a common lab growth condition; Day 2 under sinusoidal variation in light intensity (SL) during the light period that is representative of changes occurring during a clear sunny day; Day 3 under fluctuating light (FL) intensity during the light period that simulates sudden changes that might occur with the movements of clouds in and out of the view of the sun; Day 4, repeat of CL; and Day 5, repeat of FL. We also examined the global transcriptome profile in these growth conditions based on obtaining RNA-sequencing (RNA-seq) data for whole plant rosettes. Our transcriptomic analyses indicated downregulation of photosystem I (PSI) and II (PSII) associated genes, which were correlated with elevated levels of photoinhibition as indicated by measurements of nonphotochemical quenching (NPQ), energy-dependent quenching (qE), and inhibitory quenching (qI) under both SL and FL conditions. Furthermore, our transcriptomic results indicated downregulation of tetrapyrrole biosynthesis associated genes, coupled with reduced levels of chlorophyll under both SL and FL compared with CL, as well as downregulation of photorespiration-associated genes under SL. We also noticed an enrichment of the stress response gene ontology (GO) terms for genes differentially regulated under FL when compared with SL. Collectively, our phenotypic and transcriptome analyses serve as useful resources for probing the underlying molecular mechanisms associated with plant acclimation to rapid light intensity changes in the natural environment.
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Affiliation(s)
- Hussien F. Alameldin
- DOE‐Plant Research LaboratoryMichigan State UniversityEast LansingMichiganUSA
- Agricultural Genetic Engineering Research Institute (AGERI)Agriculture Research Center (ARC)GizaEgypt
| | - Beronda L. Montgomery
- DOE‐Plant Research LaboratoryMichigan State UniversityEast LansingMichiganUSA
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingMichiganUSA
- Department of Microbiology and Molecular GeneticsMichigan State UniversityEast LansingMichiganUSA
- Department of BiologyGrinnell CollegeGrinnellIowaUSA
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Hao DL, Zhou JY, Huang YN, Wang HR, Li XH, Guo HL, Liu JX. Roles of plastid-located phosphate transporters in carotenoid accumulation. FRONTIERS IN PLANT SCIENCE 2022; 13:1059536. [PMID: 36589064 PMCID: PMC9798012 DOI: 10.3389/fpls.2022.1059536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
Enhanced carotenoid accumulation in plants is crucial for the nutritional and health demands of the human body since these beneficial substances are acquired through dietary intake. Plastids are the major organelles to accumulate carotenoids in plants and it is reported that manipulation of a single plastid phosphate transporter gene enhances carotenoid accumulation. Amongst all phosphate transport proteins including phosphate transporters (PHTs), plastidial phosphate translocators (pPTs), PHOSPHATE1 (PHO1), vacuolar phosphate efflux transporter (VPE), and Sulfate transporter [SULTR]-like phosphorus distribution transporter (SPDT) in plants, plastidic PHTs (PHT2 & PHT4) are found as the only clade that is plastid located, and manipulation of which affects carotenoid accumulation. Manipulation of a single chromoplast PHT (PHT4;2) enhances carotenoid accumulation, whereas manipulation of a single chloroplast PHT has no impact on carotenoid accumulation. The underlying mechanism is mainly attributed to their different effects on plastid orthophosphate (Pi) concentration. PHT4;2 is the only chromoplast Pi efflux transporter, and manipulating this single chromoplast PHT significantly regulates chromoplast Pi concentration. This variation subsequently modulates the carotenoid accumulation by affecting the supply of glyceraldehyde 3-phosphate, a substrate for carotenoid biosynthesis, by modulating the transcript abundances of carotenoid biosynthesis limited enzyme genes, and by regulating chromoplast biogenesis (facilitating carotenoid storage). However, at least five orthophosphate influx PHTs are identified in the chloroplast, and manipulating one of the five does not substantially modulate the chloroplast Pi concentration in a long term due to their functional redundancy. This stable chloroplast Pi concentration upon one chloroplast PHT absence, therefore, is unable to modulate Pi-involved carotenoid accumulation processes and finally does affect carotenoid accumulation in photosynthetic tissues. Despite these advances, several cases including the precise location of plastid PHTs, the phosphate transport direction mediated by these plastid PHTs, the plastid PHTs participating in carotenoid accumulation signal pathway, the potential roles of these plastid PHTs in leaf carotenoid accumulation, and the roles of these plastid PHTs in other secondary metabolites are waiting for further research. The clarification of the above-mentioned cases is beneficial for breeding high-carotenoid accumulation plants (either in photosynthetic or non-photosynthetic edible parts of plants) through the gene engineering of these transporters.
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Affiliation(s)
- Dong-Li Hao
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Jin-Yan Zhou
- Department of Agronomy and Horticulture, Jiangsu Vocational College of Agriculture and Forest, Jurong, China
| | - Ya-Nan Huang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
| | - Hao-Ran Wang
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Xiao-Hui Li
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Hai-Lin Guo
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
| | - Jian-Xiu Liu
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing, China
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10
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Chadee A, Mohammad M, Vanlerberghe GC. Evidence that mitochondrial alternative oxidase respiration supports carbon balance in source leaves of Nicotiana tabacum. JOURNAL OF PLANT PHYSIOLOGY 2022; 279:153840. [PMID: 36265227 DOI: 10.1016/j.jplph.2022.153840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 10/07/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
Alternative oxidase (AOX) represents a non-energy conserving pathway within the mitochondrial electron transport chain. One potential physiological role of AOX could be to manage leaf carbohydrate amounts by supporting respiratory carbon oxidation reactions. In this study, several approaches tested the hypothesis that AOX1a gene expression in Nicotiana tabacum leaf is enhanced in conditions expected to promote an increased leaf carbohydrate status. These approaches included supplying leaves with exogenous carbohydrates, comparing plants grown at different atmospheric CO2 concentrations, comparing sink leaves with source leaves, comparing plants with different ratios of source to sink activity, and examining gene expression over the diel cycle. In each case, the pattern of AOX1a gene expression was compared with that of other genes known to respond to carbohydrates and/or other factors related to source:sink activity. These included GPT1 and GPT3 (that encode chloroplast glucose 6-phosphate/phosphate translocators), SPS (that encodes sucrose phosphate synthase), SUT1 (that encodes a sucrose/H+ symporter involved in phloem loading) and UCP1 (that encodes a mitochondrial uncoupling protein). The AOX1a transcript amount was higher following the leaf sink-to-source transition, and in plants with higher source relative to sink activity due to increasing plant age. Further, these effects were amplified in plants grown at elevated CO2 to stimulate source activity, particularly at end-of-day time periods. The AOX1a transcript amount was also higher following treatment of leaves with carbohydrate, in particular sucrose. Overall, the results provide evidence that, while source leaf sucrose accumulation may signal for a down-regulation of sucrose synthesis and transport, it also signals for means to manage the excess cytosolic carbohydrate pools. This includes increased AOX respiration to support carbon oxidation pathways even if energy charge is high, in combination perhaps with some return flux of carbohydrate from cytosol to stroma through the GPT3 translocator. As discussed, these activities could contribute to maintaining plant source:sink balance, as well as photosynthetic and phloem loading capacity.
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Affiliation(s)
- Avesh Chadee
- Department of Biological Sciences, And Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C1A4, Canada
| | - Masoom Mohammad
- Department of Biological Sciences, And Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C1A4, Canada
| | - Greg C Vanlerberghe
- Department of Biological Sciences, And Department of Cell and Systems Biology, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C1A4, Canada.
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Gámez-Arcas S, Muñoz FJ, Ricarte-Bermejo A, Sánchez-López ÁM, Baslam M, Baroja-Fernández E, Bahaji A, Almagro G, De Diego N, Doležal K, Novák O, Leal-López J, León Morcillo RJ, Castillo AG, Pozueta-Romero J. Glucose-6-P/phosphate translocator2 mediates the phosphoglucose-isomerase1-independent response to microbial volatiles. PLANT PHYSIOLOGY 2022; 190:2137-2154. [PMID: 36111879 PMCID: PMC9706466 DOI: 10.1093/plphys/kiac433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/26/2022] [Indexed: 06/15/2023]
Abstract
In Arabidopsis (Arabidopsis thaliana), the plastidial isoform of phosphoglucose isomerase (PGI1) mediates photosynthesis, metabolism, and development, probably due to its involvement in the synthesis of isoprenoid-derived signals in vascular tissues. Microbial volatile compounds (VCs) with molecular masses of <45 Da promote photosynthesis, growth, and starch overaccumulation in leaves through PGI1-independent mechanisms. Exposure to these compounds in leaves enhances the levels of GLUCOSE-6-PHOSPHATE/PHOSPHATE TRANSLOCATOR2 (GPT2) transcripts. We hypothesized that the PGI1-independent response to microbial volatile emissions involves GPT2 action. To test this hypothesis, we characterized the responses of wild-type (WT), GPT2-null gpt2-1, PGI1-null pgi1-2, and pgi1-2gpt2-1 plants to small fungal VCs. In addition, we characterized the responses of pgi1-2gpt2-1 plants expressing GPT2 under the control of a vascular tissue- and root tip-specific promoter to small fungal VCs. Fungal VCs promoted increases in growth, starch content, and photosynthesis in WT and gpt2-1 plants. These changes were substantially weaker in VC-exposed pgi1-2gpt2-1 plants but reverted to WT levels with vascular and root tip-specific GPT2 expression. Proteomic analyses did not detect enhanced levels of GPT2 protein in VC-exposed leaves and showed that knocking out GPT2 reduced the expression of photosynthesis-related proteins in pgi1-2 plants. Histochemical analyses of GUS activity in plants expressing GPT2-GUS under the control of the GPT2 promoter showed that GPT2 is mainly expressed in root tips and vascular tissues around hydathodes. Overall, the data indicated that the PGI1-independent response to microbial VCs involves resetting of the photosynthesis-related proteome in leaves through long-distance GPT2 action.
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Affiliation(s)
- Samuel Gámez-Arcas
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | | | - Adriana Ricarte-Bermejo
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | - Ángela María Sánchez-López
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | - Marouane Baslam
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
- Laboratory of Biochemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan
| | - Edurne Baroja-Fernández
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | - Abdellatif Bahaji
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | - Goizeder Almagro
- Instituto de Agrobiotecnología (IdAB), CSIC-Gobierno de Navarra, Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain
| | - Nuria De Diego
- Centre of Region Haná for Biotechnological and Agricultural Research, Czech Advanced Technology and Research Institute, Olomouc, Czech Republic
| | - Karel Doležal
- Department of Chemical Biology, Faculty of Science, Palacký University, Olomouc CZ-78371, Czech Republic
- Laboratory of Growth Regulators, Faculty of Science of Palacký University and Institute of Experimental Botany of the Czech Academy of Sciences, Olomouc CZ-78371, Czech Republic
| | - Ondřej Novák
- Laboratory of Growth Regulators, Faculty of Science of Palacký University and Institute of Experimental Botany of the Czech Academy of Sciences, Olomouc CZ-78371, Czech Republic
| | - Jesús Leal-López
- Institute for Mediterranean and Subtropical Horticulture “La Mayora” (IHSM), CSIC-UMA, 29010 Málaga, Spain
| | - Rafael Jorge León Morcillo
- Institute for Mediterranean and Subtropical Horticulture “La Mayora” (IHSM), CSIC-UMA, 29010 Málaga, Spain
| | - Araceli G Castillo
- Institute for Mediterranean and Subtropical Horticulture “La Mayora” (IHSM), CSIC-UMA, 29010 Málaga, Spain
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12
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Ruan M, He W, Sun H, Cui C, Wang X, Li R, Wang X, Bi Y. Cytosolic glucose-6-phosphate dehydrogenases play a pivotal role in Arabidopsis seed development. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2022; 186:207-219. [PMID: 35870442 DOI: 10.1016/j.plaphy.2022.07.017] [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: 03/03/2022] [Revised: 07/08/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
Embryo development is essential for seed yield and post-germination growth. Glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in oxidative pentose phosphate pathway (OPPP), is widely involved in plant development and stress tolerance by providing nicotinamide adenine dinucleotide phosphate (NADPH). In this study, the double mutant (g6pd5/6), overexpression line (G6PD5/6OE) and complementation line (g6pd5/6Comp) of cytosolic glucose-6-phosphate dehydrogenases (Cyt-G6PD) were used to investigate Cyt-G6PD roles in embryo development of Arabidopsis. The results showed that the germination rate of g6pd5/6 seeds was delayed in comparison with that of Col-0; moreover, 11.5% of g6pd5/6 seeds did not germinate. The dysfunction of Cyt-G6PD resulted in decreased fresh weight and primary root length of g6pd5/6 seedlings. The height and silique length of g6pd5/6 plants were also decreased. Moreover, the abortion rate of siliques and seeds of g6pd5/6 plants were increased compared with those of Col-0, G6PD5/6OE and g6pd5/6Comp lines. However, the dysfunction of Cyt-G6PD did not affect pollen activity; but in g6pd5/6, the embryo development was partially delayed or inhibited. The contents of fatty acids and storage proteins, two main storage materials in Arabidopsis seeds, were decreased in g6pd5/6 seeds. Exogenous application of fatty acids (C18:2; C18:3) alleviated the delayed germination of g6pd5/6 seeds. RT-qPCR results further demonstrated that the early embryo development genes were down-regulated in g6pd5/6. Taken together, Cyt-G6PD plays a pivotal role in plant seed development by regulating the transcriptions of early embryo development genes and the accumulation of storage materials (especially fatty acids).
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Affiliation(s)
- Mengjiao Ruan
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Wenliang He
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Hao Sun
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Chaiyan Cui
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Xiangxiang Wang
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Ruiling Li
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Xiaomin Wang
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
| | - Yurong Bi
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, PR China.
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13
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Biochemical, Sensory, and Molecular Evaluation of Flavour and Consumer Acceptability in Australian Papaya (Carica papaya L.) Varieties. Int J Mol Sci 2022; 23:ijms23116313. [PMID: 35682992 PMCID: PMC9181177 DOI: 10.3390/ijms23116313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 05/27/2022] [Accepted: 06/03/2022] [Indexed: 12/04/2022] Open
Abstract
Inconsistency in flavour is one of the major challenges to the Australian papaya industry. However, objectively measurable standards of the compound profiles that provide preferable taste and aroma, together with consumer acceptability, have not been set. In this study, three red-flesh papayas (i.e., ‘RB1’, ‘RB4’, and ‘Skybury’) and two yellow-flesh papayas (i.e., ‘1B’ and ‘H13’) were presented to a trained sensory panel and a consumer panel to assess sensory profiles and liking. The papaya samples were also examined for sugar components, total soluble solids, and 14 selected volatile compounds. Additionally, the expression patterns of 10 genes related to sweetness and volatile metabolism were assessed. In general, red papaya varieties had higher sugar content and tasted sweeter than yellow varieties, while yellow varieties had higher concentrations of citrus floral aroma volatiles and higher aroma intensity. Higher concentrations of glucose, linalool oxide, and terpinolene were significantly associated with decreased consumer liking. Significant differences were observed in the expression profiles of all the genes assessed among the selected papaya varieties. Of these, cpGPT2 and cpBGLU31 were positively correlated to glucose production and were expressed significantly higher in ‘1B’ than in ‘RB1’ or ‘Skybury’. These findings will assist in the strategic selective breeding for papaya to better match consumer and, hence, market demand.
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Transcriptomic Data Meta-Analysis Sheds Light on High Light Response in Arabidopsis thaliana L. Int J Mol Sci 2022; 23:ijms23084455. [PMID: 35457273 PMCID: PMC9026532 DOI: 10.3390/ijms23084455] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/13/2022] [Accepted: 04/15/2022] [Indexed: 12/24/2022] Open
Abstract
The availability and intensity of sunlight are among the major factors of growth, development and metabolism in plants. However, excessive illumination disrupts the electronic balance of photosystems and leads to the accumulation of reactive oxygen species in chloroplasts, further mediating several regulatory mechanisms at the subcellular, genetic, and molecular levels. We carried out a comprehensive bioinformatic analysis that aimed to identify genetic systems and candidate transcription factors involved in the response to high light stress in Arabidopsis thaliana L. using resources GEO NCBI, string-db, ShinyGO, STREME, and Tomtom, as well as programs metaRE, CisCross, and Cytoscape. Through the meta-analysis of five transcriptomic experiments, we selected a set of 1151 differentially expressed genes, including 453 genes that compose the gene network. Ten significantly enriched regulatory motifs for TFs families ZF-HD, HB, C2H2, NAC, BZR, and ARID were found in the promoter regions of differentially expressed genes. In addition, we predicted families of transcription factors associated with the duration of exposure (RAV, HSF), intensity of high light treatment (MYB, REM), and the direction of gene expression change (HSF, S1Fa-like). We predicted genetic components systems involved in a high light response and their expression changes, potential transcriptional regulators, and associated processes.
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15
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Saunders HA, Calzadilla PI, Schwartz JM, Johnson GN. Cytosolic fumarase acts as a metabolic fail-safe for both high and low temperature acclimation of Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2112-2124. [PMID: 34951633 DOI: 10.1093/jxb/erab560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
Plants acclimate their photosynthetic capacity (Pmax) in response to changing environmental conditions. In Arabidopsis thaliana, photosynthetic acclimation to cold requires the accumulation of the organic acid fumarate, catalysed by a cytosolically localized fumarase, FUM2. However, the role of this accumulation is currently unknown. Here, we use an integrated experimental and modelling approach to examine the role of FUM2 and fumarate across the physiological temperature range. We have studied three genotypes: Col-0; a fum2 mutant in a Col-0 background; and C24, an accession with reduced FUM2 expression. While low temperature causes an increase in Pmax in the Col-0 plants, this parameter decreases following exposure of plants to 30 °C for 7 d. Plants in which fumarate accumulation is partially (C24) or completely (fum2) abolished show a reduced acclimation of Pmax across the physiological temperature range (i.e. Pmax changes less in response to changing temperature). To understand the role of fumarate accumulation, we have adapted a reliability engineering technique, Failure Mode and Effect Analysis (FMEA), to formalize a rigorous approach for ranking metabolites according to the potential risk that they pose to the metabolic system. FMEA identifies fumarate as a low-risk metabolite, while its precursor, malate, is shown to be high risk and liable to cause system instability. We propose that the role of FUM2 is to provide a fail-safe in order to control malate concentration, maintaining system stability in a changing environment. We suggest that FMEA is a technique that is not only useful in understanding plant metabolism but can also be used to study reliability in other systems and synthetic pathways.
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Affiliation(s)
- Helena A Saunders
- Department of Earth and Environmental Sciences, Faculty of Science and Engineering, University of Manchester, Manchester M13 9PT, UK
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| | - Pablo I Calzadilla
- Department of Earth and Environmental Sciences, Faculty of Science and Engineering, University of Manchester, Manchester M13 9PT, UK
| | - Jean-Marc Schwartz
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| | - Giles N Johnson
- Department of Earth and Environmental Sciences, Faculty of Science and Engineering, University of Manchester, Manchester M13 9PT, UK
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16
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Wu Z, Wang Z, Zhang K. Isolation and functional characterization of a glucose-6-phosphate/phosphate translocator (IbG6PPT1) from sweet potato (Ipomoea batatas (L.) Lam.). BMC PLANT BIOLOGY 2021; 21:595. [PMID: 34915842 PMCID: PMC8675480 DOI: 10.1186/s12870-021-03372-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/29/2021] [Indexed: 05/05/2023]
Abstract
Sweet potato (Ipomoea batatas (L.) Lam.) is a good source of carbohydrates, an excellent raw material for starch-based industries, and a strong candidate for biofuel production due to its high starch content. However, the molecular basis of starch biosynthesis and accumulation in sweet potato is still insufficiently understood. Glucose-6-phosphate/phosphate translocators (GPTs) mediate the import of glucose-6-phosphate (Glc6P) into plastids for starch synthesis. Here, we report the isolation of a GPT-encoding gene, IbG6PPT1, from sweet potato and the identification of two additional IbG6PPT1 gene copies in the sweet potato genome. IbG6PPT1 encodes a chloroplast membrane-localized GPT belonging to the GPT1 group and highly expressed in storage root of sweet potato. Heterologous expression of IbG6PPT1 resulted in increased starch content in the leaves, root tips, and seeds and soluble sugar in seeds of Arabidopsis thaliana, but a reduction in soluble sugar in the leaves. These findings suggested that IbG6PPT1 might play a critical role in the distribution of carbon sources in source and sink and the accumulation of carbohydrates in storage tissues and would be a good candidate gene for controlling critical starch properties in sweet potato.
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Affiliation(s)
- Zhengdan Wu
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing, 400715, P. R. China
| | - Zhiqian Wang
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing, 400715, P. R. China
| | - Kai Zhang
- College of Agronomy and Biotechnology, Southwest University, Beibei, Chongqing, 400715, P. R. China.
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17
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Landi S, Capasso G, Esposito S. Different G6PDH isoforms show specific roles in acclimation to cold stress at various growth stages of barley (Hordeum vulgare) and Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 169:190-202. [PMID: 34801973 DOI: 10.1016/j.plaphy.2021.11.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 10/19/2021] [Accepted: 11/11/2021] [Indexed: 06/13/2023]
Abstract
Low temperatures (0-10 °C) represent a major physiological stress for plants, negatively affecting both their growth rates and overall growth. Cold stress may induce a wide range of negative physiological effects, from oxidative stress to photosynthetic damage. We investigated the effects of low temperatures in two different model plants, Arabidopsis thaliana and Hordeum vulgare. We tested whether the oxidative pentose phosphate pathway (OPPP) is involved in the increase of reductants' levels needed to counteract oxidative stress induced by cold. The expression, occurrence, and activity of different glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) isoforms during cold stress and plant recovery from low temperatures, were measured at different growth stages from early germinated to mature pot-grown plants. Our results showed plants exhibited changes in different stress markers; ascorbate peroxidase - APX, catalase - CAT, proline, malondialdehyde, H2O2, NADPH/NADP+. We found that a major role in cold acclimation for cytosolic- and peroxisome-located G6PDHs, and different roles for plastidial/chloroplastic isoforms. This suggests that G6PDH isoforms may regulate redox homeostasis in low temperatures, in order to support the increased and continued demand of reductants during both cold stress and recovery stages. Furthermore, we found a significant involvement of (6PGDH), strengthening the idea that the contribution of the whole oxidative pentose phosphate pathway (OPPP) is required to sustain reductant supply under cold stress.
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Affiliation(s)
- Simone Landi
- Department of Biology, University of Naples Federico II, Complesso Monte Sant'Angelo, Via Cinthia, 80126, Napoli, Italy
| | - Giorgia Capasso
- Department of Biology, University of Naples Federico II, Complesso Monte Sant'Angelo, Via Cinthia, 80126, Napoli, Italy
| | - Sergio Esposito
- Department of Biology, University of Naples Federico II, Complesso Monte Sant'Angelo, Via Cinthia, 80126, Napoli, Italy.
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18
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Chadee A, Alber NA, Dahal K, Vanlerberghe GC. The Complementary Roles of Chloroplast Cyclic Electron Transport and Mitochondrial Alternative Oxidase to Ensure Photosynthetic Performance. FRONTIERS IN PLANT SCIENCE 2021; 12:748204. [PMID: 34650584 PMCID: PMC8505746 DOI: 10.3389/fpls.2021.748204] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/30/2021] [Indexed: 05/29/2023]
Abstract
Chloroplasts use light energy and a linear electron transport (LET) pathway for the coupled generation of NADPH and ATP. It is widely accepted that the production ratio of ATP to NADPH is usually less than required to fulfill the energetic needs of the chloroplast. Left uncorrected, this would quickly result in an over-reduction of the stromal pyridine nucleotide pool (i.e., high NADPH/NADP+ ratio) and under-energization of the stromal adenine nucleotide pool (i.e., low ATP/ADP ratio). These imbalances could cause metabolic bottlenecks, as well as increased generation of damaging reactive oxygen species. Chloroplast cyclic electron transport (CET) and the chloroplast malate valve could each act to prevent stromal over-reduction, albeit in distinct ways. CET avoids the NADPH production associated with LET, while the malate valve consumes the NADPH associated with LET. CET could operate by one of two different pathways, depending upon the chloroplast ATP demand. The NADH dehydrogenase-like pathway yields a higher ATP return per electron flux than the pathway involving PROTON GRADIENT REGULATION5 (PGR5) and PGR5-LIKE PHOTOSYNTHETIC PHENOTYPE1 (PGRL1). Similarly, the malate valve could couple with one of two different mitochondrial electron transport pathways, depending upon the cytosolic ATP demand. The cytochrome pathway yields a higher ATP return per electron flux than the alternative oxidase (AOX) pathway. In both Arabidopsis thaliana and Chlamydomonas reinhardtii, PGR5/PGRL1 pathway mutants have increased amounts of AOX, suggesting complementary roles for these two lesser-ATP yielding mechanisms of preventing stromal over-reduction. These two pathways may become most relevant under environmental stress conditions that lower the ATP demands for carbon fixation and carbohydrate export.
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Affiliation(s)
- Avesh Chadee
- Department of Biological Sciences, and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ON, Canada
| | - Nicole A. Alber
- Department of Biological Sciences, and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ON, Canada
| | - Keshav Dahal
- Fredericton Research and Development Centre, Agriculture and Agri-Food Canada, Fredericton, NB, Canada
| | - Greg C. Vanlerberghe
- Department of Biological Sciences, and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ON, Canada
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19
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Stitt M, Luca Borghi G, Arrivault S. Targeted metabolite profiling as a top-down approach to uncover interspecies diversity and identify key conserved operational features in the Calvin-Benson cycle. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5961-5986. [PMID: 34473300 PMCID: PMC8411860 DOI: 10.1093/jxb/erab291] [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: 06/21/2021] [Indexed: 05/02/2023]
Abstract
Improving photosynthesis is a promising avenue to increase crop yield. This will be aided by better understanding of natural variance in photosynthesis. Profiling of Calvin-Benson cycle (CBC) metabolites provides a top-down strategy to uncover interspecies diversity in CBC operation. In a study of four C4 and five C3 species, principal components analysis separated C4 species from C3 species and also separated different C4 species. These separations were driven by metabolites that reflect known species differences in their biochemistry and pathways. Unexpectedly, there was also considerable diversity between the C3 species. Falling atmospheric CO2 and changing temperature, nitrogen, and water availability have driven evolution of C4 photosynthesis in multiple lineages. We propose that analogous selective pressures drove lineage-dependent evolution of the CBC in C3 species. Examples of species-dependent variation include differences in the balance between the CBC and the light reactions, and in the balance between regulated steps in the CBC. Metabolite profiles also reveal conserved features including inactivation of enzymes in low irradiance, and maintenance of CBC metabolites at relatively high levels in the absence of net CO2 fixation. These features may be important for photosynthetic efficiency in low light, fluctuating irradiance, and when stomata close due to low water availability.
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Affiliation(s)
- Mark Stitt
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Gian Luca Borghi
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Stéphanie Arrivault
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
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20
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Gao F, Zhang H, Zhang W, Wang N, Zhang S, Chu C, Liu C. Engineering of the cytosolic form of phosphoglucose isomerase into chloroplasts improves plant photosynthesis and biomass. THE NEW PHYTOLOGIST 2021; 231:315-325. [PMID: 33774822 DOI: 10.1111/nph.17368] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/20/2021] [Indexed: 06/12/2023]
Abstract
Starch is the most abundant carbohydrate synthesized in plant chloroplast as the product of photosynthetic carbon assimilation, serving a crucial role in the carbon budget as storage energy. Phosphoglucose isomerase (PGI) catalyzes the interconversion between glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P), which are important metabolic molecules in starch synthesis within chloroplasts and sucrose synthesis in cytosol. Here, we found that the specific activity of recombinantly purified PGI localized in cytosolic PGI (PGIc) was much higher than its plastidic isoenzyme counterpart (PGIp) originated from wheat, rice and Arabidopsis, with wheat PGIc having by far the highest activity. Crystal structures of wheat TaPGIc and TaPGIp proteins were solved and the functional units were homodimers. The active sites of PGIc and PGIp, constituted by the same amino acids, formed different binding pockets. Moreover, PGIc showed slightly lower affinity to the substrate F6P but with much faster turnover rates. Engineering of TaPGIc into chloroplasts of a pgip mutant of Arabidopsis thaliana (atpgip) resulted in starch overaccumulation, increased CO2 assimilation, up to 19% more plant biomass and 27% seed yield productivity. These results show that manipulating starch metabolic pathways in chloroplasts can improve plant biomass and yield productivity.
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Affiliation(s)
- Fei Gao
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Huijun Zhang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Wenjuan Zhang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Ning Wang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Shijia Zhang
- Key Laboratory of Molecular and Cell Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China
| | - Chengcai Chu
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Cuimin Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
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21
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Sharkey TD. Pentose Phosphate Pathway Reactions in Photosynthesizing Cells. Cells 2021; 10:cells10061547. [PMID: 34207480 PMCID: PMC8234502 DOI: 10.3390/cells10061547] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 06/11/2021] [Accepted: 06/11/2021] [Indexed: 12/14/2022] Open
Abstract
The pentose phosphate pathway (PPP) is divided into an oxidative branch that makes pentose phosphates and a non-oxidative branch that consumes pentose phosphates, though the non-oxidative branch is considered reversible. A modified version of the non-oxidative branch is a critical component of the Calvin–Benson cycle that converts CO2 into sugar. The reaction sequence in the Calvin–Benson cycle is from triose phosphates to pentose phosphates, the opposite of the typical direction of the non-oxidative PPP. The photosynthetic direction is favored by replacing the transaldolase step of the normal non-oxidative PPP with a second aldolase reaction plus sedoheptulose-1,7-bisphosphatase. This can be considered an anabolic version of the non-oxidative PPP and is found in a few situations other than photosynthesis. In addition to the strong association of the non-oxidative PPP with photosynthesis metabolism, there is recent evidence that the oxidative PPP reactions are also important in photosynthesizing cells. These reactions can form a shunt around the non-oxidative PPP section of the Calvin–Benson cycle, consuming three ATP per glucose 6-phosphate consumed. A constitutive operation of this shunt occurs in the cytosol and gives rise to an unusual labeling pattern of photosynthetic metabolites while an inducible shunt in the stroma may occur in response to stress.
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Affiliation(s)
- Thomas D Sharkey
- MSU-DOE Plant Research Laboratory, Plant Resilience Institute, Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48823, USA
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22
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High-throughput insertional mutagenesis reveals novel targets for enhancing lipid accumulation in Nannochloropsis oceanica. Metab Eng 2021; 66:239-258. [PMID: 33971293 DOI: 10.1016/j.ymben.2021.04.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/07/2021] [Accepted: 04/18/2021] [Indexed: 12/17/2022]
Abstract
The microalga Nannochloropsis oceanica is considered a promising platform for the sustainable production of high-value lipids and biofuel feedstocks. However, current lipid yields of N. oceanica are too low for economic feasibility. Gaining fundamental insights into the lipid metabolism of N. oceanica could open up various possibilities for the optimization of this species through genetic engineering. Therefore, the aim of this study was to discover novel genes associated with an elevated neutral lipid content. We constructed an insertional mutagenesis library of N. oceanica, selected high lipid mutants by five rounds of fluorescence-activated cell sorting, and identified disrupted genes using a novel implementation of a rapid genotyping procedure. One particularly promising mutant (HLM23) was disrupted in a putative APETALA2-like transcription factor gene. HLM23 showed a 40%-increased neutral lipid content, increased photosynthetic performance, and no growth impairment. Furthermore, transcriptome analysis revealed an upregulation of genes related to plastidial fatty acid biosynthesis, glycolysis and the Calvin-Benson-Bassham cycle in HLM23. Insights gained in this work can be used in future genetic engineering strategies for increased lipid productivity of Nannochloropsis.
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Source of 12C in Calvin-Benson cycle intermediates and isoprene emitted from plant leaves fed with 13CO2. Biochem J 2021; 477:3237-3252. [PMID: 32815532 DOI: 10.1042/bcj20200480] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/12/2020] [Accepted: 08/20/2020] [Indexed: 12/11/2022]
Abstract
Feeding 14CO2 was crucial to uncovering the path of carbon in photosynthesis. Feeding 13CO2 to photosynthesizing leaves emitting isoprene has been used to develop hypotheses about the sources of carbon for the methylerythritol 4-phosphate pathway, which makes the precursors for terpene synthesis in chloroplasts and bacteria. Both photosynthesis and isoprene studies found that products label very quickly (<10 min) up to 80-90% but the last 10-20% of labeling requires hours indicating a source of 12C during photosynthesis and isoprene emission. Furthermore, studies with isoprene showed that the proportion of slow label could vary significantly. This was interpreted as a variable contribution of carbon from sources other than the Calvin-Benson cycle (CBC) feeding the methylerythritol 4-phosphate pathway. Here, we measured the degree of label in isoprene and photosynthetic metabolites 20 min after beginning to feed 13CO2. Isoprene labeling was the same as labeling of photosynthesis intermediates. High temperature reduced the label in isoprene and photosynthesis intermediates by the same amount indicating no role for alternative carbon sources for isoprene. A model assuming glucose, fructose, and/or sucrose reenters the CBC as ribulose 5-phosphate through a cytosolic shunt involving glucose 6-phosphate dehydrogenase was consistent with the observations.
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Karim MF, Johnson GN. Acclimation of Photosynthesis to Changes in the Environment Results in Decreases of Oxidative Stress in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2021; 12:683986. [PMID: 34630448 PMCID: PMC8495028 DOI: 10.3389/fpls.2021.683986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 08/18/2021] [Indexed: 05/08/2023]
Abstract
The dynamic acclimation of photosynthesis plays an important role in increasing the fitness of a plant under variable light environments. Since acclimation is partially mediated by a glucose-6-phosphate/phosphate translocator 2 (GPT2), this study examined whether plants lacking GPT2, which consequently have defective acclimation to increases in light, are more susceptible to oxidative stress. To understand this mechanism, we used the model plant Arabidopsis thaliana [accession Wassilewskija-4 (Ws-4)] and compared it with mutants lacking GPT2. The plants were then grown at low light (LL) at 100 μmol m-2 s-1 for 7 weeks. For the acclimation experiments, a set of plants from LL was transferred to 400 μmol m-2 s-1 conditions for 7 days. Biochemical and physiological analyses showed that the gpt2 mutant plants had significantly greater activity for ascorbate peroxidase (APX), guiacol peroxidase (GPOX), and superoxide dismutase (SOD). Furthermore, the mutant plants had significantly lower maximum quantum yields of photosynthesis (Fv/Fm). A microarray analysis also showed that gpt2 plants exhibited a greater induction of stress-related genes relative to wild-type (WT) plants. We then concluded that photosynthetic acclimation to a higher intensity of light protects plants against oxidative stress.
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Preiser AL, Banerjee A, Weise SE, Renna L, Brandizzi F, Sharkey TD. Phosphoglucoisomerase Is an Important Regulatory Enzyme in Partitioning Carbon out of the Calvin-Benson Cycle. FRONTIERS IN PLANT SCIENCE 2020; 11:580726. [PMID: 33362810 PMCID: PMC7758399 DOI: 10.3389/fpls.2020.580726] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 11/18/2020] [Indexed: 05/04/2023]
Abstract
Phosphoglucoisomerase (PGI) isomerizes fructose 6-phosphate (F6P) and glucose 6-phosphate (G6P) in starch and sucrose biosynthesis. Both plastidic and cytosolic isoforms are found in plant leaves. Using recombinant enzymes and isolated chloroplasts, we have characterized the plastidic and cytosolic isoforms of PGI. We have found that the Arabidopsis plastidic PGI K m for G6P is three-fold greater compared to that for F6P and that erythrose 4-phosphate is a key regulator of PGI activity. Additionally, the K m of spinach plastidic PGI can be dynamically regulated in the dark compared to the light and increases by 200% in the dark. We also found that targeting Arabidopsis cytosolic PGI into plastids of Nicotiana tabacum disrupts starch accumulation and degradation. Our results, in combination with the observation that plastidic PGI is not in equilibrium, indicates that PGI is an important regulatory enzyme that restricts flow and acts as a one-way valve preventing backflow of G6P into the Calvin-Benson cycle. We propose the PGI may be manipulated to improve flow of carbon to desired targets of biotechnology.
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Affiliation(s)
- Alyssa L. Preiser
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, United States
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
| | - Aparajita Banerjee
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
| | - Sean E. Weise
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, United States
| | - Luciana Renna
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, United States
| | - Federica Brandizzi
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, United States
- Department of Plant Biology, Michigan State University, East Lansing, MI, United States
| | - Thomas D. Sharkey
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, United States
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
- Plant Resilience Institute, Michigan State University, East Lansing, MI, United States
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26
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Emerging research in plant photosynthesis. Emerg Top Life Sci 2020; 4:137-150. [PMID: 32573736 DOI: 10.1042/etls20200035] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 12/27/2022]
Abstract
Photosynthesis involves capturing light energy and, most often, converting it to chemical energy stored as reduced carbon. It is the source of food, fuel, and fiber and there is a resurgent interest in basic research on photosynthesis. Plants make excellent use of visible light energy; leaves are ideally suited to optimize light use by having a large area per amount of material invested and also having leaf angles to optimize light utilization. It is thought that plants do not use green light but in fact they use green light better than blue light under some conditions. Leaves also have mechanisms to protect against excess light and how these work in a stochastic light environment is currently a very active area of current research. The speed at which photosynthesis can begin when leaves are first exposed to light and the speed of induction of protective mechanisms, as well as the speed at which protective mechanisms dissipate when light levels decline, have recently been explored. Research is also focused on reducing wasteful processes such as photorespiration, when oxygen instead of carbon dioxide is used. Some success has been reported in altering the path of carbon in photorespiration but on closer inspection there appears to be unforeseen effects contributing to the good news. The stoichiometry of interaction of light reactions with carbon metabolism is rigid and the time constants vary tremendously presenting large challenges to regulatory mechanisms. Regulatory mechanisms will be the topic of photosynthesis research for some time to come.
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Chadee A, Vanlerberghe GC. Distinctive mitochondrial and chloroplast components contributing to the maintenance of carbon balance during plant growth at elevated CO 2. PLANT SIGNALING & BEHAVIOR 2020; 15:1795395. [PMID: 32705929 PMCID: PMC8550537 DOI: 10.1080/15592324.2020.1795395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Plant carbon balance depends upon the difference between photosynthetic carbon gain and respiratory carbon loss. In C3 plants, growth at an elevated atmospheric concentration of CO2 (ECO2) stimulates photosynthesis and raises the leaf carbohydrate status, but how respiration responds is less understood. In this study, growth of Nicotiana tabacum at ECO2 increased the protein amount of the non-energy conserving mitochondrial alternative oxidase (AOX). Growth at ECO2 increased AOX1a transcript amount, and the transcript amount of a putative sugar-responsive gene encoding a chloroplast glucose-6-phosphate/phosphate translocator (GPT3). We suggest that the elevated amounts of AOX and GPT3 represent distinctive mitochondrial and chloroplast mechanisms to manage an excessive cytosolic pool of sugar phosphates. AOX respiration could consume cytosolic sugar phosphates, without this activity being restricted by rates of ATP turnover. GPT3 could allow accumulating cytosolic glucose-6-phosphate to return to the chloroplast. This could feed starch synthesis or a glucose-6-phosphate shunt in the Calvin cycle. AOX and GPT3 activities could buffer against Pi depletions that might otherwise disrupt mitochondrial and chloroplast electron transport chain activities. AOX and GPT3 activities could also buffer against a down-regulation of photosynthetic capacity by preventing a persistent imbalance between photosynthetic carbon gain and the activity of carbon utilizing sinks.
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Affiliation(s)
- Avesh Chadee
- Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ON, Canada
| | - Greg C. Vanlerberghe
- Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ON, Canada
- CONTACT Greg C. Vanlerberghe Department of Biological Sciences and Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, ONM1C1A4, Canada
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28
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Baune MC, Lansing H, Fischer K, Meyer T, Charton L, Linka N, von Schaewen A. The Arabidopsis Plastidial Glucose-6-Phosphate Transporter GPT1 is Dually Targeted to Peroxisomes via the Endoplasmic Reticulum. THE PLANT CELL 2020; 32:1703-1726. [PMID: 32111666 PMCID: PMC7203913 DOI: 10.1105/tpc.19.00959] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 01/28/2020] [Accepted: 02/28/2020] [Indexed: 05/22/2023]
Abstract
Studies on Glucose-6-phosphate (G6P)/phosphate translocator isoforms GPT1 and GPT2 reported the viability of Arabidopsis (Arabidopsis thaliana) gpt2 mutants, whereas heterozygous gpt1 mutants exhibited a variety of defects during fertilization/seed set, indicating that GPT1 is essential for this process. Among other functions, GPT1 was shown to be important for pollen and embryo-sac development. Because our previous work on the irreversible part of the oxidative pentose phosphate pathway (OPPP) revealed comparable effects, we investigated whether GPT1 may dually localize to plastids and peroxisomes. In reporter fusions, GPT2 localized to plastids, but GPT1 also localized to the endoplasmic reticulum (ER) and around peroxisomes. GPT1 contacted two oxidoreductases and also peroxins that mediate import of peroxisomal membrane proteins from the ER, hinting at dual localization. Reconstitution in yeast (Saccharomyces cerevisiae) proteoliposomes revealed that GPT1 preferentially exchanges G6P for ribulose-5-phosphate (Ru5P). Complementation analyses of heterozygous +/gpt1 plants demonstrated that GPT2 is unable to compensate for GPT1 in plastids, whereas GPT1 without the transit peptide (enforcing ER/peroxisomal localization) increased gpt1 transmission significantly. Because OPPP activity in peroxisomes is essential for fertilization, and immunoblot analyses hinted at the presence of unprocessed GPT1-specific bands, our findings suggest that GPT1 is indispensable in both plastids and peroxisomes. Together with its G6P-Ru5P exchange preference, GPT1 appears to play a role distinct from that of GPT2 due to dual targeting.
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Affiliation(s)
- Marie-Christin Baune
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Hannes Lansing
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Kerstin Fischer
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Tanja Meyer
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Lennart Charton
- Biochemie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Nicole Linka
- Biochemie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Antje von Schaewen
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
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29
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Morales A, Kaiser E. Photosynthetic Acclimation to Fluctuating Irradiance in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:268. [PMID: 32265952 PMCID: PMC7105707 DOI: 10.3389/fpls.2020.00268] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 02/20/2020] [Indexed: 05/07/2023]
Abstract
Unlike the short-term responses of photosynthesis to fluctuating irradiance, the long-term response (i.e., acclimation) at the chloroplast, leaf, and plant level has received less attention so far. The ability of plants to acclimate to irradiance fluctuations and the speed at which this acclimation occurs are potential limitations to plant growth under field conditions, and therefore this process deserves closer study. In the first section of this review, we look at the sources of natural irradiance fluctuations, their effects on short-term photosynthesis, and the interaction of these effects with circadian rhythms. This is followed by an overview of the mechanisms that are involved in acclimation to fluctuating (or changes of) irradiance. We highlight the chain of events leading to acclimation: retrograde signaling, systemic acquired acclimation (SAA), gene transcription, and changes in protein abundance. We also review how fluctuating irradiance is applied in experiments and highlight the fact that they are significantly slower than natural fluctuations in the field, although the technology to achieve realistic fluctuations exists. Finally, we review published data on the effects of growing plants under fluctuating irradiance on different plant traits, across studies, spatial scales, and species. We show that, when plants are grown under fluctuating irradiance, the chlorophyll a/b ratio and plant biomass decrease, specific leaf area increases, and photosynthetic capacity as well as root/shoot ratio are, on average, unaffected.
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Affiliation(s)
- Alejandro Morales
- Centre for Crop Systems Analysis, Plant Science Group, Wageningen University and Research, Wageningen, Netherlands
- Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands
- Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands
| | - Elias Kaiser
- Horticulture and Product Physiology, Plant Science Group, Wageningen University and Research, Wageningen, Netherlands
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30
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Allen DK, Young JD. Tracing metabolic flux through time and space with isotope labeling experiments. Curr Opin Biotechnol 2019; 64:92-100. [PMID: 31864070 PMCID: PMC7302994 DOI: 10.1016/j.copbio.2019.11.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/02/2019] [Accepted: 11/04/2019] [Indexed: 12/11/2022]
Abstract
Metabolism is dynamic and must function in context-specific ways to adjust to changes in the surrounding cellular and ecological environment. When isotopic tracers are used, metabolite flow (i.e. metabolic flux) can be quantified through biochemical networks to assess metabolic pathway operation. The cellular activities considered across multiple tissues and organs result in the observed phenotype and can be analyzed to discover emergent, whole-system properties of biology and elucidate misconceptions about network operation. However, temporal and spatial challenges remain significant hurdles and require novel approaches and creative solutions. We survey current investigations in higher plant and animal systems focused on dynamic isotope labeling experiments, spatially resolved measurement strategies, and observations from re-analysis of our own studies that suggest prospects for future work. Related discoveries will be necessary to push the frontier of our understanding of metabolism to suggest novel solutions to cure disease and feed a growing future world population.
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Affiliation(s)
- Doug K Allen
- United States Department of Agriculture-Agricultural Research Service, Plant Genetics Research Unit, 975 North Warson Road, St. Louis, MO 63132, United States; Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO 63132, United States.
| | - Jamey D Young
- Department of Chemical & Biomolecular Engineering, Vanderbilt University, PMB 351604, 2301 Vanderbilt Place, Nashville, TN 37235, United States; Department of Molecular Physiology & Biophysics, Vanderbilt University, PMB 351604, 2301 Vanderbilt Place, Nashville, TN 37235, United States.
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