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He JZ, Dorion S, Lacroix M, Rivoal J. Sustained substrate cycles between hexose phosphates and free sugars in phosphate-deficient potato (Solanum tuberosum) cell cultures. Planta 2019; 249:1319-1336. [PMID: 30627889 DOI: 10.1007/s00425-019-03088-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 01/03/2019] [Indexed: 06/09/2023]
Abstract
Futile cycling between free sugars and hexose phosphates occurring under phosphate deficiency could be involved in the maintenance of a threshold level of free cellular phosphate to preserve respiratory metabolism. We studied the metabolic response of potato cell cultures growing in Pi sufficient (2.5 mM, +Pi) or deficient (125 µM, -Pi) conditions. Under Pi deficiency, cellular growth was severely affected, however -Pi cells were able to maintain a low but steady level of free Pi. We surveyed the activities of 33 primary metabolic enzymes during the course of a 12 days Pi deficiency period. Our results show that many of these enzymes had higher specific activity in -Pi cells. Among these, we found typical markers of Pi deficiency such as phosphoenolpyruvate phosphatase and phosphoenolpyruvate carboxylase as well as enzymes involved in the biosynthesis of organic acids. Intriguingly, several ATP-consuming enzymes such as hexokinase (HK) and phosphofructokinase also displayed increased activity in -Pi condition. For HK, this was associated with an increase in the steady state of a specific HK polypeptide. Quantification of glycolytic intermediates showed a pronounced decrease in phosphate esters under Pi deficiency. Adenylate levels also decreased in -Pi cells, but the Adenylate Energy Charge was not affected by the treatment. To investigate the significance of HK induction under low Pi, [U-14C]-glucose tracer studies were conducted. We found in vivo evidence of futile cycling between pools of hexose phosphates and free sugars under Pi deficiency. Our study suggests that the futile cycling between hexose phosphates and free sugars which is active under +Pi conditions is sustained under Pi deficiency. The possibility that this process represents a metabolic adaptation to Pi deficiency is discussed with respect to Pi homeostasis in Pi-deficient conditions.
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Affiliation(s)
- Jiang Zhou He
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke est, Montréal, Qc, H1X 2B2, Canada
| | - Sonia Dorion
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke est, Montréal, Qc, H1X 2B2, Canada
| | - Mélanie Lacroix
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke est, Montréal, Qc, H1X 2B2, Canada
| | - Jean Rivoal
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Sherbrooke est, Montréal, Qc, H1X 2B2, Canada.
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Troncoso-Ponce MA, Rivoal J, Dorion S, Sánchez R, Venegas-Calerón M, Moreno-Pérez AJ, Baud S, Garcés R, Martínez-Force E. Molecular and biochemical characterization of the sunflower (Helianthus annuus L.) cytosolic and plastidial enolases in relation to seed development. Plant Sci 2018; 272:117-130. [PMID: 29807582 DOI: 10.1016/j.plantsci.2018.04.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/08/2018] [Accepted: 04/10/2018] [Indexed: 05/19/2023]
Abstract
In the present study, we describe the molecular and biochemical characterization of sunflower (Helianthus annuus L.) enolase (ENO, EC 4.2.1.11) proteins, which catalyze the formation of phosphoenolpyruvate, the penultimate intermediate in the glycolytic pathway. We cloned and characterized three cDNAs encoding different ENO isoforms from developing sunflower seeds. Studies using fluorescently tagged ENOs confirmed the predicted subcellular localization of ENO isoforms: HaENO1 in the plastid while HaENO2 and HaENO3 were found in the cytosol. The cDNAs were used to express the corresponding 6(His)-tagged proteins in Escherichia coli. The proteins were purified to electrophoretic homogeneity, using immobilized metal ion affinity chromatography, and biochemically characterized. Recombinant HaENO1 and HaENO2, but not HaENO3 were shown to have enolase activity, in agreement with data obtained with the Arabidopsis homolog proteins. Site directed mutagenesis of several critical amino acids was used to attempt to recover enolase activity in recombinant HaENO3, resulting in very small increases that were not additive. A kinetic characterization of the two active isoforms showed that pH had similar effect on their velocity, that they had similar affinity for 2-phosphoglycerate, but that the kcat/Km of the plastidial enzyme was higher than that of the cytosolic isoform. Even though HaENO2 was always the most highly expressed transcript, the levels of expression of the three ENO genes were remarkably distinct in all the vegetative and reproductive tissues studied. This indicates that in seeds the conversion of 2-phosphoglycerate to phosphoenolpyruvate takes place through the cytosolic and the plastidial pathways therefore both routes could contribute to the supply of carbon for lipid synthesis. The identity of the main source of carbon during the period of stored products synthesis is discussed.
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Affiliation(s)
- M A Troncoso-Ponce
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain; Sorbonne University, Université de technologie de Compiègne, CNRS, Institute for Enzyme and Cell Engineering, Centre de recherche Royallieu, CS 60 319, 60 203 Compiègne cedex, France.
| | - J Rivoal
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Rue Sherbrooke est, Montréal, QC, Canada
| | - S Dorion
- Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Rue Sherbrooke est, Montréal, QC, Canada
| | - R Sánchez
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain
| | - M Venegas-Calerón
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain
| | - A J Moreno-Pérez
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain
| | - S Baud
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000 Versailles, France
| | - R Garcés
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain
| | - E Martínez-Force
- Instituto de la Grasa (CSIC), Edificio 46, Campus Universitario Pablo de Olavide, Carretera de Utrera Km 1, 41013, Sevilla, Spain
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Lyons BM, McHenry MA, Barrington DS. Insights into evolution in Andean Polystichum (Dryopteridaceae) from expanded understanding of the cytosolic phosphoglucose isomerase gene. Mol Phylogenet Evol 2017; 112:36-46. [PMID: 28411162 DOI: 10.1016/j.ympev.2017.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 03/08/2017] [Accepted: 04/10/2017] [Indexed: 12/19/2022]
Abstract
Cytosolic phosphoglucose isomerase (pgiC) is an enzyme essential to glycolysis found universally in eukaryotes, but broad understanding of variation in the gene coding for pgiC is lacking for ferns. We used a substantially expanded representation of the gene for Andean species of the fern genus Polystichum to characterize pgiC in ferns relative to angiosperms, insects, and an amoebozoan; assess the impact of selection versus neutral evolutionary processes on pgiC; and explore evolutionary relationships of selected Andean species. The dataset of complete sequences comprised nine accessions representing seven species and one hybrid from the Andes and Serra do Mar. The aligned sequences of the full data set comprised 3376 base pairs (70% of the entire gene) including 17 exons and 15 introns from two central areas of the gene. The exons are highly conserved relative to angiosperms and retain substantial homology to insect pgiC, but intron length and structure are unique to the ferns. Average intron size is similar to angiosperms; intron number and location in insects are unlike those of the plants we considered. The introns included an array of indels and, in intron 7, an extensive microsatellite array with potential utility in analyzing population-level histories. Bayesian and maximum-parsimony analysis of 129 variable nucleotides in the Andean polystichums revealed that 59 (1.7% of the 3376 total) were phylogenetically informative; most of these united sister accessions. The phylogenetic trees for the Andean polystichums were incongruent with previously published cpDNA trees for the same taxa, likely the result of rapid evolutionary change in the introns and contrasting stability in the exons. The exons code a total of seven amino-acid substitutions. Comparison of non-synonymous to synonymous substitutions did not suggest that the pgiC gene is under selection in the Andes. Variation in pgiC including two additional accessions represented by incomplete sequences provided new insights into reticulate relationships among Andean taxa.
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Dorion S, Clendenning A, Jeukens J, Salas JJ, Parveen N, Haner AA, Law RD, Force EM, Rivoal J. A large decrease of cytosolic triosephosphate isomerase in transgenic potato roots affects the distribution of carbon in primary metabolism. Planta 2012; 236:1177-90. [PMID: 22678033 DOI: 10.1007/s00425-012-1675-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 05/23/2012] [Indexed: 05/04/2023]
Abstract
Triosephosphate isomerase (TPI, EC 5.3.1.1) catalyzes the interconversion of dihydroxyacetone-P and glyceraldehyde 3-P in the glycolytic pathway. A constitutively expressed antisense construct for cytosolic TPI was introduced into potato (Solanum tuberosum) using Agrobacterium rhizogenes to examine the metabolic effects of a reduction in cytosolic TPI in roots. We obtained a population of transgenic root clones displaying ~36 to 100 % of the TPI activity found in control clones carrying an empty binary vector. Ion exchange chromatography and immunoblot analysis showed that the antisense strategy significantly decreased the cytosolic TPI isoform, while levels of plastidial TPI activity remained apparently unaffected. Transgenic roots were characterized with respect to the activity of glycolytic enzymes, their metabolite contents and carbon fluxes. Metabolite profiling of sugars, organic acids, amino acids and lipids showed elevated levels of sucrose, glucose, fructose, fumarate, isocitrate, 4-aminobutyrate, alanine, glycine, aromatic amino acids and saturated long chain fatty acids in roots containing the lowest TPI activity. Labelings with (14)C-glucose, (14)C-sucrose and (14)C-acetate indicated that a reduction of cytosolic TPI activity in roots increased carbon metabolism through the pentose phosphate pathway, O(2) uptake and catabolism of sucrose to CO(2), and capacity for lipid synthesis. These results demonstrate that a large reduction of cytosolic TPI alters the distribution of carbon in plant primary metabolism.
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Affiliation(s)
- Sonia Dorion
- IRBV, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC H1X 2B2, Canada
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Troncoso-Ponce MA, Rivoal J, Venegas-Calerón M, Dorion S, Sánchez R, Cejudo FJ, Garcés R, Martínez-Force E. Molecular cloning and biochemical characterization of three phosphoglycerate kinase isoforms from developing sunflower (Helianthus annuus L.) seeds. Phytochemistry 2012; 79:27-38. [PMID: 22552275 DOI: 10.1016/j.phytochem.2012.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/27/2012] [Accepted: 04/03/2012] [Indexed: 05/13/2023]
Abstract
Three cDNAs encoding different phosphoglycerate kinase (PGK, EC 2.7.2.3) isoforms, two cytosolic (HacPGK1 and HacPGK2) and one plastidic (HapPGK), were cloned and characterized from developing sunflower (Helianthus annuus L.) seeds. The expression profiles of these genes showed differences in heterotrophic tissues, such as developing seeds and roots, where HacPGK1 was predominant, while HapPGK was highly expressed in photosynthetic tissues. The cDNAs were expressed in Escherichia coli, and the corresponding proteins purified to electrophoretic homogeneity, using immobilized metal ion affinity chromatography, and biochemically characterized. Despite the high level of identity between sequences, the HacPGK1 isoform showed strong differences in terms of specific activity, temperature stability and pH sensitivity in comparison to HacPGK2 and HapPGK. A polyclonal immune serum was raised against the purified HacPGK1 isoform, which showed cross-immunoreactivity with the other PGK isoforms. This serum allowed the localization of high expression levels of PGK isozymes in embryo tissues.
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Affiliation(s)
- M A Troncoso-Ponce
- Instituto de la Grasa, CSIC, Avda. Padre Garcia Tejero 4, 41012 Seville, Spain
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