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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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2
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Lecomte JTJ, Johnson EA. The globins of cyanobacteria and green algae: An update. Adv Microb Physiol 2024; 85:97-144. [PMID: 39059824 DOI: 10.1016/bs.ampbs.2024.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2024]
Abstract
The globin superfamily of proteins is ancient and diverse. Regular assessments based on the increasing number of available genome sequences have elaborated on a complex evolutionary history. In this review, we present a summary of a decade of advances in characterising the globins of cyanobacteria and green algae. The focus is on haem-containing globins with an emphasis on recent experimental developments, which reinforce links to nitrogen metabolism and nitrosative stress response in addition to dioxygen management. Mention is made of globins that do not bind haem to provide an encompassing view of the superfamily and perspective on the field. It is reiterated that an effort toward phenotypical and in-vivo characterisation is needed to elucidate the many roles that these versatile proteins fulfil in oxygenic photosynthetic microbes. It is also proposed that globins from oxygenic organisms are promising proteins for applications in the biotechnology arena.
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Affiliation(s)
- Juliette T J Lecomte
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, United States.
| | - Eric A Johnson
- Department of Biology, Johns Hopkins University, Baltimore, MD, United States
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3
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Shandilya M, Kumar G, Gomkale R, Singh S, Khan MA, Kateriya S, Kundu S. Multiple putative methemoglobin reductases in C. reinhardtii may support enzymatic functions for its multiple hemoglobins. Int J Biol Macromol 2021; 171:465-479. [PMID: 33428952 DOI: 10.1016/j.ijbiomac.2021.01.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 12/26/2020] [Accepted: 01/05/2021] [Indexed: 10/22/2022]
Abstract
The ubiquitous nature of hemoglobins, their presence in multiple forms and low cellular expression in organisms suggests alternative physiological functions of hemoglobins in addition to oxygen transport and storage. Previous research has proposed enzymatic function of hemoglobins such as nitric oxide dioxygenase, nitrite reductase and hydroxylamine reductase. In all these enzymatic functions, active ferrous form of hemoglobin is converted to ferric form and reconversion of ferric to ferrous through reduction partners is under active investigation. The model alga C. reinhardtii contains multiple globins and is thus expected to have multiple putative methemoglobin reductases to augment the physiological functions of the novel hemoglobins. In this regard, three putative methemoglobin reductases and three algal hemoglobins were characterized. Our results signify that the identified putative methemoglobin reductases can reduce algal methemoglobins in a nonspecific manner under in vitro conditions. Enzyme kinetics of two putative methemoglobin reductases with methemoglobins as substrates and in silico analysis support interaction between the hemoglobins and the two reduction partners as also observed in vitro. Our investigation on algal methemoglobin reductases underpins the valuable chemistry of nitric oxide with the newly discovered hemoglobins to ensure their physiological relevance, with multiple hemoglobins probably necessitating the presence of multiple reductases.
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Affiliation(s)
- Manish Shandilya
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India; Amity School of Applied Sciences, Amity University Haryana, Gurugram 122413, India
| | - Gaurav Kumar
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India
| | - Ridhima Gomkale
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India
| | - Swati Singh
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India
| | - Mohd Asim Khan
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India
| | - Suneel Kateriya
- School of Biotechnology, Jawaharlal Nehru University, New Delhi 110021, India
| | - Suman Kundu
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India.
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Distinctive structural properties of THB11, a pentacoordinate Chlamydomonas reinhardtii truncated hemoglobin with N- and C-terminal extensions. J Biol Inorg Chem 2020; 25:267-283. [PMID: 32048044 PMCID: PMC7082302 DOI: 10.1007/s00775-020-01759-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 01/14/2020] [Indexed: 12/20/2022]
Abstract
Hemoglobins (Hbs) utilize heme b as a cofactor and are found in all kingdoms of life. The current knowledge reveals an enormous variability of Hb primary sequences, resulting in topological, biochemical and physiological individuality. As Hbs appear to modulate their reactivities through specific combinations of structural features, predicting the characteristics of a given Hb is still hardly possible. The unicellular green alga Chlamydomonas reinhardtii contains 12 genes encoding diverse Hbs of the truncated lineage, several of which possess extended N- or C-termini of unknown function. Studies on some of the Chlamydomonas Hbs revealed yet unpredictable structural and biochemical variations, which, along with a different expression of their genes, suggest diverse physiological roles. Chlamydomonas thus represents a promising system to analyze the diversification of Hb structure, biochemistry and physiology. Here, we report the crystal structure, resolved to 1.75 Å, of the heme-binding domain of cyanomet THB11 (Cre16.g662750), one of the pentacoordinate algal Hbs, which offer a free Fe-coordination site in the reduced state. The overall fold of THB11 is conserved, but individual features such as a kink in helix E, a tilted heme plane and a clustering of methionine residues at a putative tunnel exit appear to be unique. Both N- and C-termini promote the formation of oligomer mixtures, and the absence of the C terminus results in reduced nitrite reduction rates. This work widens the structural and biochemical knowledge on the 2/2Hb family and suggests that the N- and C-terminal extensions of the Chlamydomonas 2/2Hbs modulate their reactivity by intermolecular interactions.
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Filina V, Grinko A, Ermilova E. Truncated Hemoglobins 1 and 2 Are Implicated in the Modulation of Phosphorus Deficiency-Induced Nitric Oxide Levels in Chlamydomonas. Cells 2019; 8:cells8090947. [PMID: 31438612 PMCID: PMC6770159 DOI: 10.3390/cells8090947] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 08/16/2019] [Accepted: 08/19/2019] [Indexed: 12/16/2022] Open
Abstract
Truncated hemoglobins (trHbs) form a widely distributed family of proteins found in archaea, bacteria, and eukaryotes. Accumulating evidence suggests that trHbs may be implicated in functions other than oxygen delivery, but these roles are largely unknown. Characterization of the conditions that affect trHb expression and investigation of their regulatory mechanisms will provide a framework for elucidating the functions of these globins. Here, the transcription of Chlamydomonas trHb genes (THB1–12) under conditions of phosphorus (P) deprivation was analyzed. Three THB genes, THB1, THB2, and THB12 were expressed at the highest level. For the first time, we demonstrate the synthesis of nitric oxide (NO) under P-limiting conditions and the production of NO by cells via a nitrate reductase-independent pathway. To clarify the functions of THB1 and THB2, we generated and analyzed strains in which these THBs were strongly under-expressed by using an artificial microRNA approach. Similar to THB1 knockdown, the depletion of THB2 led to a decrease in cell size and chlorophyll levels. We provide evidence that the knockdown of THB1 or THB2 enhanced NO production under P deprivation. Overall, these results demonstrate that THB1 and THB2 are likely to contribute, at least in part, to acclimation responses in P-deprived Chlamydomonas.
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Affiliation(s)
- Valentina Filina
- Biological Faculty, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg 199034, Russia
| | - Alexandra Grinko
- Biological Faculty, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg 199034, Russia
| | - Elena Ermilova
- Biological Faculty, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg 199034, Russia.
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Sasso S, Stibor H, Mittag M, Grossman AR. From molecular manipulation of domesticated Chlamydomonas reinhardtii to survival in nature. eLife 2018; 7:39233. [PMID: 30382941 PMCID: PMC6211829 DOI: 10.7554/elife.39233] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 10/12/2018] [Indexed: 01/19/2023] Open
Abstract
In the mid-20th century, the unicellular and genetically tractable green alga Chlamydomonas reinhardtii was first developed as a model organism to elucidate fundamental cellular processes such as photosynthesis, light perception and the structure, function and biogenesis of cilia. Various studies of C. reinhardtii have profoundly advanced plant and cell biology, and have also impacted algal biotechnology and our understanding of human disease. However, the 'real' life of C. reinhardtii in the natural environment has largely been neglected. To extend our understanding of the biology of C. reinhardtii, it will be rewarding to explore its behavior in its natural habitats, learning more about its abundance and life cycle, its genetic and physiological diversity, and its biotic and abiotic interactions.
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Affiliation(s)
- Severin Sasso
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Herwig Stibor
- Department Biology II, Ludwig Maximilian University, Munich, Germany
| | - Maria Mittag
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
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Düner M, Lambertz J, Mügge C, Hemschemeier A. The soluble guanylate cyclase CYG12 is required for the acclimation to hypoxia and trophic regimes in Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:311-337. [PMID: 29161457 DOI: 10.1111/tpj.13779] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/03/2017] [Accepted: 11/09/2017] [Indexed: 05/27/2023]
Abstract
Oxygenic phototrophs frequently encounter environmental conditions that result in intracellular energy crises. Growth of the unicellular green alga Chlamydomonas reinhardtii in hypoxia in the light depends on acclimatory responses of which the induction of photosynthetic cyclic electron flow is essential. The microalga cannot grow in the absence of molecular oxygen (O2 ) in the dark, although it possesses an elaborate fermentation metabolism. Not much is known about how the microalga senses and signals the lack of O2 or about its survival strategies during energy crises. Recently, nitric oxide (NO) has emerged to be required for the acclimation of C. reinhardtii to hypoxia. In this study, we show that the soluble guanylate cyclase (sGC) CYG12, a homologue of animal NO sensors, is also involved in this response. CYG12 is an active sGC, and post-transcriptional down-regulation of the CYG12 gene impairs hypoxic growth and gene expression in C. reinhardtii. However, it also results in a disturbed photosynthetic apparatus under standard growth conditions and the inability to grow heterotrophically. Transcriptome profiles indicate that the mis-expression of CYG12 results in a perturbation of responses that, in the wild-type, maintain the cellular energy budget. We suggest that CYG12 is required for the proper operation of the photosynthetic apparatus which, in turn, is essential for survival in hypoxia and darkness.
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Affiliation(s)
- Melis Düner
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Jan Lambertz
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Carolin Mügge
- Junior Research Group for Microbial Biotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Anja Hemschemeier
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
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8
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Minaeva E, Zalutskaya Z, Filina V, Ermilova E. Truncated hemoglobin 1 is a new player in Chlamydomonas reinhardtii acclimation to sulfur deprivation. PLoS One 2017; 12:e0186851. [PMID: 29049377 PMCID: PMC5648252 DOI: 10.1371/journal.pone.0186851] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/09/2017] [Indexed: 12/23/2022] Open
Abstract
Truncated hemoglobins constitute a large family, present in bacteria, in archaea and in eukaryotes. However, a majority of physiological functions of these proteins remains to be elucidated. Identification and characterization of a novel role of truncated hemoglobins in the model alga provides a framework for a more complete understanding of their biological functions. Here, we use quantitative RT-PCR to show that three truncated hemoglobins of Chlamydomonas reinhardtii, THB1, THB2 and THB12, are induced under conditions of depleted sulfur (S) supply. THB1 underexpression results in the decrease in cell size, as well in levels of proteins, chlorophylls and mRNA of several S-responsive genes under S starvation. We provide evidence that knock-down of THB1 enhances NO production under S deprivation. In S-deprived cells, a subset of S limitation-responsive genes is controlled by NO in THB1-dependent pathway. Moreover, we demonstrate that deficiency for S represses the nitrate reduction and that THB1 is involved in this control. Thus, our data support the idea that in S-deprived cells THB1 plays a dual role in NO detoxification and in coordinating sulfate limitation with nitrate assimilation. This study uncovers a new function for the Chlamydomonas reinhardtii THB1 in the control of proper response to S deprivation.
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Affiliation(s)
- Ekaterina Minaeva
- Biological Faculty, Saint-Petersburg State University, Saint-Petersburg, Russia
| | - Zhanneta Zalutskaya
- Biological Faculty, Saint-Petersburg State University, Saint-Petersburg, Russia
| | - Valentina Filina
- Biological Faculty, Saint-Petersburg State University, Saint-Petersburg, Russia
| | - Elena Ermilova
- Biological Faculty, Saint-Petersburg State University, Saint-Petersburg, Russia
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Schuth N, Mebs S, Huwald D, Wrzolek P, Schwalbe M, Hemschemeier A, Haumann M. Effective intermediate-spin iron in O 2-transporting heme proteins. Proc Natl Acad Sci U S A 2017; 114:8556-8561. [PMID: 28739893 PMCID: PMC5559043 DOI: 10.1073/pnas.1706527114] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Proteins carrying an iron-porphyrin (heme) cofactor are essential for biological O2 management. The nature of Fe-O2 bonding in hemoproteins is debated for decades. We used energy-sampling and rapid-scan X-ray Kβ emission and K-edge absorption spectroscopy as well as quantum chemistry to determine molecular and electronic structures of unligated (deoxy), CO-inhibited (carboxy), and O2-bound (oxy) hemes in myoglobin (MB) and hemoglobin (HB) solutions and in porphyrin compounds at 20-260 K. Similar metrical and spectral features revealed analogous heme sites in MB and HB and the absence of low-spin (LS) to high-spin (HS) conversion. Amplitudes of Kβ main-line emission spectra were directly related to the formal unpaired Fe(d) spin count, indicating HS Fe(II) in deoxy and LS Fe(II) in carboxy. For oxy, two unpaired Fe(d) spins and, thus by definition, an intermediate-spin iron center, were revealed by our static and kinetic X-ray data, as supported by (time-dependent) density functional theory and complete-active-space self-consistent-field calculations. The emerging Fe-O2 bonding situation includes in essence a ferrous iron center, minor superoxide character of the noninnocent ligand, significant double-bond properties of the interaction, and three-center electron delocalization as in ozone. It resolves the apparently contradictory classical models of Pauling, Weiss, and McClure/Goddard into a unifying view of O2 bonding, tuned toward reversible oxygen transport.
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Affiliation(s)
- Nils Schuth
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Stefan Mebs
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Dennis Huwald
- Department of Plant Biochemistry, Section of Photobiotechnology, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Pierre Wrzolek
- Department of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Matthias Schwalbe
- Department of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Anja Hemschemeier
- Department of Plant Biochemistry, Section of Photobiotechnology, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Michael Haumann
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany;
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10
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Plouviez M, Wheeler D, Shilton A, Packer MA, McLenachan PA, Sanz-Luque E, Ocaña-Calahorro F, Fernández E, Guieysse B. The biosynthesis of nitrous oxide in the green alga Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 91:45-56. [PMID: 28333392 DOI: 10.1111/tpj.13544] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 02/27/2017] [Accepted: 03/17/2017] [Indexed: 05/13/2023]
Abstract
Over the last decades, several studies have reported emissions of nitrous oxide (N2 O) from microalgal cultures and aquatic ecosystems characterized by a high level of algal activity (e.g. eutrophic lakes). As N2 O is a potent greenhouse gas and an ozone-depleting pollutant, these findings suggest that large-scale cultivation of microalgae (and possibly, natural eutrophic ecosystems) could have a significant environmental impact. Using the model unicellular microalga Chlamydomonas reinhardtii, this study was conducted to investigate the molecular basis of microalgal N2 O synthesis. We report that C. reinhardtii supplied with nitrite (NO2- ) under aerobic conditions can reduce NO2- into nitric oxide (NO) using either a mitochondrial cytochrome c oxidase (COX) or a dual enzymatic system of nitrate reductase (NR) and amidoxime-reducing component, and that NO is subsequently reduced into N2 O by the enzyme NO reductase (NOR). Based on experimental evidence and published literature, we hypothesize that when nitrate (NO3- ) is the main Nitrogen source and the intracellular concentration of NO2- is low (i.e. under physiological conditions), microalgal N2 O synthesis involves the reduction of NO3- to NO2- by NR followed by the reduction of NO2- to NO by the dual system involving NR. This microalgal N2 O pathway has broad implications for environmental science and algal biology because the pathway of NO3- assimilation is conserved among microalgae, and because its regulation may involve NO.
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Affiliation(s)
- Maxence Plouviez
- School of Engineering and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - David Wheeler
- Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Andy Shilton
- School of Engineering and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Michael A Packer
- Cawthron Institute, 98 Halifax Street, Nelson, 7010, New Zealand
| | - Patricia A McLenachan
- Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Emanuel Sanz-Luque
- Department of Biochemistry and Molecular Biology, University of Cordoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain
| | - Francisco Ocaña-Calahorro
- Department of Biochemistry and Molecular Biology, University of Cordoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain
| | - Emilio Fernández
- Department of Biochemistry and Molecular Biology, University of Cordoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain
| | - Benoit Guieysse
- School of Engineering and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand
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Sanz-Luque E, Chamizo-Ampudia A, Llamas A, Galvan A, Fernandez E. Understanding nitrate assimilation and its regulation in microalgae. FRONTIERS IN PLANT SCIENCE 2015; 6:899. [PMID: 26579149 PMCID: PMC4620153 DOI: 10.3389/fpls.2015.00899] [Citation(s) in RCA: 152] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 10/09/2015] [Indexed: 05/02/2023]
Abstract
Nitrate assimilation is a key process for nitrogen (N) acquisition in green microalgae. Among Chlorophyte algae, Chlamydomonas reinhardtii has resulted to be a good model system to unravel important facts of this process, and has provided important insights for agriculturally relevant plants. In this work, the recent findings on nitrate transport, nitrate reduction and the regulation of nitrate assimilation are presented in this and several other algae. Latest data have shown nitric oxide (NO) as an important signal molecule in the transcriptional and posttranslational regulation of nitrate reductase and inorganic N transport. Participation of regulatory genes and proteins in positive and negative signaling of the pathway and the mechanisms involved in the regulation of nitrate assimilation, as well as those involved in Molybdenum cofactor synthesis required to nitrate assimilation, are critically reviewed.
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Affiliation(s)
| | | | | | | | - Emilio Fernandez
- Department of Biochemistry and Molecular Biology, University of CordobaCordoba, Spain
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12
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Abstract
In the last few years, advances in algal research have identified the participation of haemoglobins in nitrogen metabolism and the management of reactive nitrogen and oxygen species. This chapter summarises the state of knowledge concerning algal haemoglobins with a focus on the most widely used model system, namely, Chlamydomonas reinhardtii. Genetic, physiologic, structural, and chemical information is compiled to provide a framework for further studies.
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Affiliation(s)
- Eric A Johnson
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
| | - Juliette T J Lecomte
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA.
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