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Scholtysek L, Poetsch A, Hofmann E, Hemschemeier A. The activation of Chlamydomonas reinhardtii alpha amylase 2 by glutamine requires its N-terminal aspartate kinase-chorismate mutase-tyrA (ACT) domain. PLANT DIRECT 2024; 8:e609. [PMID: 38911017 PMCID: PMC11190351 DOI: 10.1002/pld3.609] [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: 03/12/2024] [Revised: 05/08/2024] [Accepted: 05/16/2024] [Indexed: 06/25/2024]
Abstract
The coordination of assimilation pathways for all the elements that make up cellular components is a vital task for every organism. Integrating the assimilation and use of carbon (C) and nitrogen (N) is of particular importance because of the high cellular abundance of these elements. Starch is one of the most important storage polymers of photosynthetic organisms, and a complex regulatory network ensures that biosynthesis and degradation of starch are coordinated with photosynthetic activity and growth. Here, we analyzed three starch metabolism enzymes of Chlamydomonas reinhardtii that we captured by a cyclic guanosine monophosphate (cGMP) affinity chromatography approach, namely, soluble starch synthase STA3, starch-branching enzyme SBE1, and α-amylase AMA2. While none of the recombinant enzymes was directly affected by the presence of cGMP or other nucleotides, suggesting an indirect binding to cGMP, AMA2 activity was stimulated in the presence of L-glutamine (Gln). This activating effect required the enzyme's N-terminal aspartate kinase-chorismate mutase-tyrA domain. Gln is the first N assimilation product and not only a central compound for the biosynthesis of N-containing molecules but also a recognized signaling molecule for the N status. Our observation suggests that AMA2 might be a means to coordinate N and C metabolism at the enzymatic level, increasing the liberation of C skeletons from starch when high Gln levels signal an abundance of assimilated N.
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Affiliation(s)
- Lisa Scholtysek
- Faculty of Biology and Biotechnology, PhotobiotechnologyRuhr University BochumBochumGermany
| | - Ansgar Poetsch
- Faculty of Biology and Biotechnology, Department for Plant BiochemistryRuhr University BochumBochumGermany
- School of Basic Medical SciencesNanchang UniversityNanchangChina
| | - Eckhard Hofmann
- Faculty of Biology and Biotechnology, Protein CrystallographyRuhr University BochumBochumGermany
| | - Anja Hemschemeier
- Faculty of Biology and Biotechnology, PhotobiotechnologyRuhr University BochumBochumGermany
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Huang G, Zhao D, Lan C, Wu B, Li X, Lou S, Zheng Y, Huang Y, Hu Z, Jia B. Glucose-assisted trophic conversion of Chlamydomonas reinhardtii by expression of glucose transporter GLUT1. ALGAL RES 2022. [DOI: 10.1016/j.algal.2021.102626] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kato Y, Ho SH, Vavricka CJ, Chang JS, Hasunuma T, Kondo A. Evolutionary engineering of salt-resistant Chlamydomonas sp. strains reveals salinity stress-activated starch-to-lipid biosynthesis switching. BIORESOURCE TECHNOLOGY 2017. [PMID: 28624244 DOI: 10.1016/j.biortech.2017.06.035] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The aim of this study was to improve biomass production of the green microalga Chlamydomonas sp. JSC4 under high salinity conditions. For this purpose, heavy ion beam-coupled mutagenesis and evolutionary engineering were performed using JSC4 as the parent strain. After long-term and continuous cultivation with high salinity, salt-resistant strains that grow well even in the presence of 7% sea salt were successfully obtained. Transcriptional analysis revealed inactivation of starch-to-lipid biosynthesis switching, which resulted in delayed starch degradation and decreased lipid content in the salt-resistant strains. Cellular aggregation and hypertrophy during high salinity were relieved in these strains, indicating strong resistance to salt stress. These results suggest that high salinity stress, not the salinity condition itself, is important for activating lipid accumulation mechanisms in microalgae.
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Affiliation(s)
- Yuichi Kato
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Shih-Hsin Ho
- State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, PR China
| | - Christopher J Vavricka
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Jo-Shu Chang
- Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan
| | - Tomohisa Hasunuma
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan.
| | - Akihiko Kondo
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan; Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
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Brasil BDSAF, de Siqueira FG, Salum TFC, Zanette CM, Spier MR. Microalgae and cyanobacteria as enzyme biofactories. ALGAL RES 2017. [DOI: 10.1016/j.algal.2017.04.035] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Dynamic metabolic profiling together with transcription analysis reveals salinity-induced starch-to-lipid biosynthesis in alga Chlamydomonas sp. JSC4. Sci Rep 2017; 7:45471. [PMID: 28374798 PMCID: PMC5379629 DOI: 10.1038/srep45471] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 02/27/2017] [Indexed: 12/24/2022] Open
Abstract
Biodiesel production using microalgae would play a pivotal role in satisfying future global energy demands. Understanding of lipid metabolism in microalgae is important to isolate oleaginous strain capable of overproducing lipids. It has been reported that reducing starch biosynthesis can enhance lipid accumulation. However, the metabolic mechanism controlling carbon partitioning from starch to lipids in microalgae remains unclear, thus complicating the genetic engineering of algal strains. We here used “dynamic” metabolic profiling and essential transcription analysis of the oleaginous green alga Chlamydomonas sp. JSC4 for the first time to demonstrate the switching mechanisms from starch to lipid synthesis using salinity as a regulator, and identified the metabolic rate-limiting step for enhancing lipid accumulation (e.g., pyruvate-to-acetyl-CoA). These results, showing salinity-induced starch-to-lipid biosynthesis, will help increase our understanding of dynamic carbon partitioning in oleaginous microalgae. Moreover, we successfully determined the changes of several key lipid-synthesis-related genes (e.g., acetyl-CoA carboxylase, pyruvate decarboxylase, acetaldehyde dehydrogenase, acetyl-CoA synthetase and pyruvate ferredoxin oxidoreductase) and starch-degradation related genes (e.g., starch phosphorylases), which could provide a breakthrough in the marine microalgal production of biodiesel.
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Vitova M, Bisova K, Kawano S, Zachleder V. Accumulation of energy reserves in algae: From cell cycles to biotechnological applications. Biotechnol Adv 2015; 33:1204-18. [DOI: 10.1016/j.biotechadv.2015.04.012] [Citation(s) in RCA: 131] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 01/28/2023]
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Chapman SP, Paget CM, Johnson GN, Schwartz JM. Flux balance analysis reveals acetate metabolism modulates cyclic electron flow and alternative glycolytic pathways in Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2015; 6:474. [PMID: 26175742 PMCID: PMC4485056 DOI: 10.3389/fpls.2015.00474] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 06/15/2015] [Indexed: 05/18/2023]
Abstract
Cells of the green alga Chlamydomonas reinhardtii cultured in the presence of acetate perform mixotrophic growth, involving both photosynthesis and organic carbon assimilation. Under such conditions, cells exhibit a reduced capacity for photosynthesis but a higher growth rate, compared to phototrophic cultures. Better understanding of the down regulation of photosynthesis would enable more efficient conversion of carbon into valuable products like biofuels. In this study, Flux Balance Analysis (FBA) and Flux Variability Analysis (FVA) have been used with a genome scale model of C. reinhardtii to examine changes in intracellular flux distribution in order to explain their changing physiology. Additionally, a reaction essentiality analysis was performed to identify which reaction subsets are essential for a given growth condition. Our results suggest that exogenous acetate feeds into a modified tricarboxylic acid (TCA) cycle, which bypasses the CO2 evolution steps, explaining increases in biomass, consistent with experimental data. In addition, reactions of the oxidative pentose phosphate and glycolysis pathways, inactive under phototrophic conditions, show substantial flux under mixotrophic conditions. Importantly, acetate addition leads to an increased flux through cyclic electron flow (CEF), but results in a repression of CO2 fixation via Rubisco, explaining the down regulation of photosynthesis. However, although CEF enhances growth on acetate, it is not essential-impairment of CEF results in alternative metabolic pathways being increased. We have demonstrated how the reactions of photosynthesis interconnect with carbon metabolism on a global scale, and how systems approaches play a viable tool in understanding complex relationships at the scale of the organism.
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Affiliation(s)
| | | | | | - Jean-Marc Schwartz
- *Correspondence: Jean-Marc Schwartz, Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
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Gagat P, Bodył A, Mackiewicz P. How protein targeting to primary plastids via the endomembrane system could have evolved? A new hypothesis based on phylogenetic studies. Biol Direct 2013; 8:18. [PMID: 23845039 PMCID: PMC3716720 DOI: 10.1186/1745-6150-8-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Accepted: 07/02/2013] [Indexed: 01/21/2023] Open
Abstract
Background It is commonly assumed that a heterotrophic ancestor of the supergroup Archaeplastida/Plantae engulfed a cyanobacterium that was transformed into a primary plastid; however, it is still unclear how nuclear-encoded proteins initially were imported into the new organelle. Most proteins targeted to primary plastids carry a transit peptide and are transported post-translationally using Toc and Tic translocons. There are, however, several proteins with N-terminal signal peptides that are directed to higher plant plastids in vesicles derived from the endomembrane system (ES). The existence of these proteins inspired a hypothesis that all nuclear-encoded, plastid-targeted proteins initially carried signal peptides and were targeted to the ancestral primary plastid via the host ES. Results We present the first phylogenetic analyses of Arabidopsis thaliana α-carbonic anhydrase (CAH1), Oryza sativa nucleotide pyrophosphatase/phosphodiesterase (NPP1), and two O. sativa α-amylases (αAmy3, αAmy7), proteins that are directed to higher plant primary plastids via the ES. We also investigated protein disulfide isomerase (RB60) from the green alga Chlamydomonas reinhardtii because of its peculiar dual post- and co-translational targeting to both the plastid and ES. Our analyses show that these proteins all are of eukaryotic rather than cyanobacterial origin, and that their non-plastid homologs are equipped with signal peptides responsible for co-translational import into the host ES. Our results indicate that vesicular trafficking of proteins to primary plastids evolved long after the cyanobacterial endosymbiosis (possibly only in higher plants) to permit their glycosylation and/or transport to more than one cellular compartment. Conclusions The proteins we analyzed are not relics of ES-mediated protein targeting to the ancestral primary plastid. Available data indicate that Toc- and Tic-based translocation dominated protein import into primary plastids from the beginning. Only a handful of host proteins, which already were targeted through the ES, later were adapted to reach the plastid via the vesicular trafficking. They represent a derived class of higher plant plastid-targeted proteins with an unusual evolutionary history. Reviewers This article was reviewed by Prof. William Martin, Dr. Philippe Deschamps (nominated by Dr. Purificacion Lopez-Garcia) and Dr Simonetta Gribaldo.
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Affiliation(s)
- Przemysław Gagat
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Przybyszewskiego 63/77, Wrocław 51-148, Poland
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Transcriptome for photobiological hydrogen production induced by sulfur deprivation in the green alga Chlamydomonas reinhardtii. EUKARYOTIC CELL 2008; 7:1965-79. [PMID: 18708561 DOI: 10.1128/ec.00418-07] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Photobiological hydrogen production using microalgae is being developed into a promising clean fuel stream for the future. In this study, microarray analyses were used to obtain global expression profiles of mRNA abundance in the green alga Chlamydomonas reinhardtii at different time points before the onset and during the course of sulfur-depleted hydrogen production. These studies were followed by real-time quantitative reverse transcription-PCR and protein analyses. The present work provides new insights into photosynthesis, sulfur acquisition strategies, and carbon metabolism-related gene expression during sulfur-induced hydrogen production. A general trend toward repression of transcripts encoding photosynthetic genes was observed. In contrast to all other LHCBM genes, the abundance of the LHCBM9 transcript (encoding a major light-harvesting polypeptide) and its protein was strongly elevated throughout the experiment. This suggests a major remodeling of the photosystem II light-harvesting complex as well as an important function of LHCBM9 under sulfur starvation and photobiological hydrogen production. This paper presents the first global transcriptional analysis of C. reinhardtii before, during, and after photobiological hydrogen production under sulfur deprivation.
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Dauvillée D, Colleoni C, Mouille G, Morell MK, d'Hulst C, Wattebled F, Liénard L, Delvallé D, Ral JP, Myers AM, Ball SG. Biochemical characterization of wild-type and mutant isoamylases of Chlamydomonas reinhardtii supports a function of the multimeric enzyme organization in amylopectin maturation. PLANT PHYSIOLOGY 2001; 125:1723-31. [PMID: 11299353 PMCID: PMC88829 DOI: 10.1104/pp.125.4.1723] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2000] [Revised: 11/30/2000] [Accepted: 01/04/2001] [Indexed: 05/17/2023]
Abstract
Chlamydomonas reinhardtii mutants of the STA8 gene produce reduced amounts of high amylose starch and phytoglycogen. In contrast to the previously described phytoglycogen-producing mutants of C. reinhardtii that contain no residual isoamylase activity, the sta8 mutants still contained 35% of the normal amount of enzyme activity. We have purified this residual isoamylase and compared it with the wild-type C. reinhardtii enzyme. We have found that the high-mass multimeric enzyme has reduced its average mass at least by one-half. This coincides with the disappearance of two out of the three activity bands that can be seen on zymogram gels. Wild-type and mutant enzymes are shown to be located within the plastid. In addition, they both act by cleaving off the outer branches of polysaccharides with no consistent difference in enzyme specificity. Because the mutant enzyme was demonstrated to digest phytoglycogen to completion in vitro, we propose that its inability to do so in vivo supports a function of the enzyme complex architecture in the processing of pre-amylopectin chains.
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Affiliation(s)
- D Dauvillée
- Laboratoire de Chimie Biologique, Unité Mixte de Recherche du Centre National de la Recherche Scientifique, No. 8576, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'ascq cedex, France
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11
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Maeda I, Hikawa H, Mizoguchi T, Yagi K. Repression of starch degradation under anaerobic conditions by irregularly high levels of ATP in Chlamydomonas sp. MGA161. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2001; 160:629-634. [PMID: 11448738 DOI: 10.1016/s0168-9452(00)00438-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is generally known that in green algal species the acceleration of starch degradation upon transition from aerobic to anaerobic conditions is a result of the Pasteur effect in glycolysis. However, the acceleration of starch degradation did not occur in cells of Chlamydomonas sp. MGA161. In MGA161 cells, the anaerobic ATP level, which decreased to about half of the aerobic ATP level in cells of Chlamydomonas reinhardtii after fermentation for 2 h, was kept higher than its aerobic ATP level. Gramicidin D, a monovalent cation ionophore, markedly decreased the anaerobic and aerobic ATP levels due to the increase in ATP demand, accompanied by the acceleration of starch degradation in MGA161 cells. Although the anaerobic ATP level of C. reinhardtii cells was partially decreased by gramicidin D, starch degradation did not accelerate markedly when compared with the result in MGA161 cells. Therefore, starch was degraded at nearly the maximum rate in C. reinhardtii cells under anaerobic conditions; in contrast, the high level of ATP in MGA161 cells repressed starch degradation even under anaerobic conditions, resulting in the absence of the Pasteur effect.
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Affiliation(s)
- I Maeda
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, 565-0871, Osaka, Japan
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12
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Dauvillée D, Mestre V, Colleoni C, Slomianny M, Mouille G, Delrue B, d'Hulst C, Bliard C, Nuzillard J, Ball S. The debranching enzyme complex missing in glycogen accumulating mutants of Chlamydomonas reinhardtii displays an isoamylase-type specificity. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2000; 157:145-156. [PMID: 10960727 DOI: 10.1016/s0168-9452(00)00256-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To investigate the functions of debranching enzymes in starch biosynthesis, we have partially purified and characterized these activities from wild type and mutant sta7 Chlamydomonas reinhardtii. Mutants of the STA7 locus substitute synthesis of insoluble granular starch by that of small amounts of glycogen-like material. The mutants were previously shown to lack an 88 kDa debranching enzyme. Two distinct debranching activities were detected in wild-type strains. The 88 kDa debranching enzyme subunit missing in glycogen-producing mutants (CIS1) is shown to be part of a multimeric enzyme complex. A monomeric 95 kDa debranching enzyme (CLD1) cleaved alpha-1,6 linkages separated by as few as three glucose residues while the multimeric complex was unable to do so. Both enzymes were able to debranch amylopectin while the alpha-1,6 linkages of glycogen were completely debranched by the multimeric complex only. Therefore CLD1 and the multimeric debranching enzyme display respectively the limit-dextrinase (pullulanase) and isoamylase-type specificities. Various mutations in the STA7 locus caused the loss of both CIS1 and of the multimeric isoamylase complex. In contrast to rice and maize mutants that accumulate phytoglycogen owing to mutation of an isoamylase-type DBE, isoamylase depletion in Chlamydomonas did not result in any qualitative or quantitative difference in pullulanase activity.
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Affiliation(s)
- D Dauvillée
- Laboratoire de Chimie Biologique, Unité Mixte de Recherche du C.N.R.S. no 8576, Bâtiment C9, Cité Scientifique, Université des Sciences et Technologies de Lille, 59655 Cedex, Villeneuve d'Ascq, France
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Singh KK, Chen C, Epstein DK, Gibbs M. Respiration of Sugars in Spinach (Spinacia oleracea), Maize (Zea mays), and Chlamydomonas reinhardtii F-60 Chloroplasts with Emphasis on the Hexose Kinases. PLANT PHYSIOLOGY 1993; 102:587-593. [PMID: 12231848 PMCID: PMC158816 DOI: 10.1104/pp.102.2.587] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The role of hexokinase in carbohydrate degradation in isolated, intact chloroplasts was evaluated. This was accomplished by monitoring the evolution of 14CO2 from darkened spinach (Spinacia oleracea), maize (Zea mays) mesophyll, and Chlamydomonas reinhardtii chloroplasts externally supplied with 14C-labeled fructose, glucose, mannose, galactose, maltose, and ribose. Glucose and ribose were the preferred substrates with the Chlamydomonas and maize chloroplasts, respectively. The rate of CO2 release from fructose was about twice that from glucose in the spinach chloroplast. Externally supplied ATP stimulated the rate of CO2 release. The pH optimum for CO2 release was 7.5 with ribose and fructose and 8.5 with glucose as substrates. Probing the outer membrane polypeptides of the intact spinach chloroplast with two proteases, trypsin and thermolysin, decreased 14CO2 release from glucose about 50% but had little effect when fructose was the substrate. Tryptic digestion decreased CO2 release from glucose in the Chlamydomonas chloroplast about 70%. 14CO2 evolution from [1-14C]-glucose-6-phosphate in both chloroplasts was unaffected by treatment with trypsin. Enzymic analysis of the supernatant (stroma) of the lysed spinach chloroplast indicated a hexokinase active primarily with fructose but with some affinity for glucose. The pellet (membranal fraction) contained a hexokinase utilizing both glucose and fructose but with considerably less total activity than the stromal enzyme. Treatment with trypsin and thermolysin eliminated more than 50% of the glucokinase activity but had little effect on fructokinase activity in the spinach chloroplast. Tryptic digestion of the Chlamydomonas chloroplast resulted in a loss of about 90% of glucokinase activity.
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Affiliation(s)
- K. K. Singh
- Institute for Photobiology of Cell and Organelles, Brandeis University, Waltham, Massachusetts 02254
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14
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Chen C, Gibbs M. Coupling of Carbon Dioxide Fixation to the Oxyhydrogen Reaction in the Isolated Chloroplast of Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 1992; 100:1361-5. [PMID: 16653129 PMCID: PMC1075790 DOI: 10.1104/pp.100.3.1361] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The oxyhydrogen reaction (the reduction of O(2) to water by H(2)) in the presence of CO(2) was studied in the isolated Chlamydomonas reinhardtii chloroplast by monitoring the rate of (14)CO(2) incorporation into acid-stable products in the dark. The endogenous rate of CO(2) uptake (50-125 nmol/mg chlorophyll per h) was increased about 3- to 4-fold by ATP and additionally when combined with glucose, ribose-5-phosphate, and glycerate-3-phosphate. The rate was diminished 50 to 75%, respectively, when H(2) was replaced by N(2) or by air. Decrease in CO(2) uptake by dl-glyceraldehyde was taken to indicate that the regenerative phase and complete Calvin cycle turnover were involved. Diminution of CO(2) incorporation by rotenone, antimycin A, and 2,5-dibromo-3-methyl-6-isopropanol-p-benzoquinone was attributed to an inhibition of the oxyhydrogen reaction, resulting in an elevated NADPH/NADP ratio. If so, then the diminished CO(2) uptake could have been by "product inhibition" of the carbon metabolic network. Our data are consistent with the proposal (H. Gaffron [1942] J Gen Physiol 26: 241-267) that CO(2) fixation coupled to the oxyhydrogen reaction is dependent to some extent on exchloroplastic metabolism. This support is primarily ATP provided by mitochondrial respiration.
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Affiliation(s)
- C Chen
- Institute for Photobiology of Cells and Organelles, Brandeis University, Waltham, Massachusetts 02254
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15
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Ball S, Marianne T, Dirick L, Fresnoy M, Delrue B, Decq A. A Chlamydomonas reinhardtii low-starch mutant is defective for 3-phosphoglycerate activation and orthophosphate inhibition of ADP-glucose pyrophosphorylase. PLANTA 1991; 185:17-26. [PMID: 24186274 DOI: 10.1007/bf00194509] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/1990] [Accepted: 02/14/1991] [Indexed: 05/19/2023]
Abstract
A low-starch mutant accumulating less than 5% of wild-type amounts was isolated after X-ray mutagenesis of Chlamydomonas reinhardtii cells. The recessive st-1-1 defect segregated as a single mendelian mutation through meiosis, and led to a severe decrease in starch accumulation under all culture conditions tested, whether in the light or in darkness. Adenosine 5'-diphosphoglucose pyrophosphorylase (in the absence of 3-phosphoglycerate), starch synthase, phosphoglucomutase, phosphorylase and starch-branching enzyme were all characterized and shown to be unaffected by the mutation. However, ADP-glucose pyrophosphorylase in the mutant had its sensitivity to activation by 3-phosphoglycerate lowered dramatically and became less responsive to orthophosphate. Our results are consistent both with a mutation in a structural gene of a multisubunit enzyme or in a regulatory gene responsible for switching ADP-glucose pyrophosphorylase from a 3-phosphoglycerate-insensitive to a 3-phosphoglycerate-sensitive form. These results provide definite proof of the in-vivo requirement for 3-phosphoglycerate activation to obtain substantial starch synthesis in plants. The conclusions hold both for synthesis from CO2 in the light or from exogenous organic carbon sources in darkness. A model is presented in which the existence of a 3-phosphoglycerate gradient explains localized starch synthesis around the pyrenoid of lower plants.
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Affiliation(s)
- S Ball
- Laboratoire de Chimie Biologique, Université des Sciences et Techniques de Lille Flandres-Artois, Bâtiment C9, F-59655, Villeneuve d'Ascq cedex, France
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Jacobsen JV, Hanson AD, Chandler PC. Water stress enhances expression of an alpha-amylase gene in barley leaves. PLANT PHYSIOLOGY 1986; 80:350-9. [PMID: 16664625 PMCID: PMC1075116 DOI: 10.1104/pp.80.2.350] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The amylases of the second leaves of barley seedlings (Hordeum vulgare L. cv Betzes) were resolved into eight isozymes by isoelectric focusing, seven of which were beta-amylase and the other, alpha-amylase. The alpha-amylase had the same isoelectric point as one of the gibberellin-induced alpha-amylase isozymes in the aleurone layer. This and other enzyme characteristics indicated that the leaf isozyme corresponded to the type A aleurone alpha-amylase (low pI group). Crossing experiments indicated that leaf and type A aleurone isozymes resulted from expression of the same genes.In unwatered seedlings, leaf alpha-amylase increased as leaf water potential decreased and ABA increased. Water stress had no effect on beta-amylase. alpha-Amylase occurred uniformly along the length of the leaf but beta-amylase was concentrated in the basal half of the leaf. Cell fractionation studies indicated that none of the leaf alpha-amylase occurred inside chloroplasts.Leaf radiolabeling experiments followed by extraction of alpha-amylase by affinity chromatography and immunoprecipitation showed that increase of alpha-amylase activity involved synthesis of the enzyme. However, water stress caused no major change in total protein synthesis. Hybridization of a radiolabeled alpha-amylase-related cDNA clone to size fractionated RNA showed that water-stressed leaves contained much more alpha-amylase mRNA than unstressed plants. The results of these and other studies indicate that regulation of gene expression may be a component in water-stress induced metabolic changes.
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Affiliation(s)
- J V Jacobsen
- Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, Canberra, A.C.T. 2601, Australia
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Klein U. Compartmentation of glycolysis and of the oxidative pentose-phosphate pathway in Chlamydomonas reinhardii. PLANTA 1986; 167:81-86. [PMID: 24241735 DOI: 10.1007/bf00446372] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/1985] [Accepted: 09/02/1985] [Indexed: 06/02/2023]
Abstract
Glycolytic enzyme activities and enzyme activities of the oxidative pentose-phosphate pathway were measured in intact chloroplasts from Chlamydomonas reinhardii. By comparison with the total enzyme activities of intact protoplasts of the alga the data were used to locate these enzymes quantitatively in the algal chloroplast. It was found that the glycolytic chain in C. reinhardii is roughly split into a plastidic and an extraplastidic part. More than 90% of the first part of glycolysis (from fructose-6-phosphate to triose-phosphate is located in the plastid while more than 95% of the second part (from glycerate-3-phosphate to pyruvate) is outside. Around 70% of glucose-6-phosphate dehydrogenase and gluconate-6-phosphate dehydrogenase, two key enzymes of the oxidative pentose phosphate pathway, are located in the plastid. It is concluded that in C. reinhardii the major part of hexose breakdown to triose-phosphate occurs in the chloroplast and that a tight cooperation between the plastid and the cytoplasm is required for appreciable sugar breakdown to occur in the algal cell.
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Affiliation(s)
- U Klein
- Botanisches Institut der Universität, Kirschallee 1, D-5300, Bonn 1, Germany
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