1
|
Caccamo A, Vega de Luna F, Wahni K, Volkov AN, Przybyla-Toscano J, Amelii A, Kriznik A, Rouhier N, Messens J, Remacle C. Ascorbate Peroxidase 2 (APX2) of Chlamydomonas Binds Copper and Modulates the Copper Insertion into Plastocyanin. Antioxidants (Basel) 2023; 12:1946. [PMID: 38001799 PMCID: PMC10669542 DOI: 10.3390/antiox12111946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/18/2023] [Accepted: 10/27/2023] [Indexed: 11/26/2023] Open
Abstract
Recent phylogenetic studies have unveiled a novel class of ascorbate peroxidases called "ascorbate peroxidase-related" (APX-R). These enzymes, found in green photosynthetic eukaryotes, lack the amino acids necessary for ascorbate binding. This study focuses on the sole APX-R from Chlamydomonas reinhardtii referred to as ascorbate peroxidase 2 (APX2). We used immunoblotting to locate APX2 within the chloroplasts and in silico analysis to identify key structural motifs, such as the twin-arginine transport (TAT) motif for lumen translocation and the metal-binding MxxM motif. We also successfully expressed recombinant APX2 in Escherichia coli. Our in vitro results showed that the peroxidase activity of APX2 was detected with guaiacol but not with ascorbate as an electron donor. Furthermore, APX2 can bind both copper and heme, as evidenced by spectroscopic, and fluorescence experiments. These findings suggest a potential interaction between APX2 and plastocyanin, the primary copper-containing enzyme within the thylakoid lumen of the chloroplasts. Predictions from structural models and evidence from 1H-NMR experiments suggest a potential interaction between APX2 and plastocyanin, emphasizing the influence of APX2 on the copper-binding abilities of plastocyanin. In summary, our results propose a significant role for APX2 as a regulator in copper transfer to plastocyanin. This study sheds light on the unique properties of APX-R enzymes and their potential contributions to the complex processes of photosynthesis in green algae.
Collapse
Affiliation(s)
- Anna Caccamo
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium; (A.C.); (F.V.d.L.); (J.P.-T.); (A.A.)
- VIB-VUB Center for Structural Biology, 1050 Brussels, Belgium; (K.W.); (A.N.V.)
- Brussels Center for Redox Biology, 1050 Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Félix Vega de Luna
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium; (A.C.); (F.V.d.L.); (J.P.-T.); (A.A.)
| | - Khadija Wahni
- VIB-VUB Center for Structural Biology, 1050 Brussels, Belgium; (K.W.); (A.N.V.)
- Brussels Center for Redox Biology, 1050 Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Alexander N. Volkov
- VIB-VUB Center for Structural Biology, 1050 Brussels, Belgium; (K.W.); (A.N.V.)
- Jean Jeener NMR Centre, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Jonathan Przybyla-Toscano
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium; (A.C.); (F.V.d.L.); (J.P.-T.); (A.A.)
| | - Antonello Amelii
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium; (A.C.); (F.V.d.L.); (J.P.-T.); (A.A.)
| | - Alexandre Kriznik
- CNRS, IMoPA and IBSLor, Université de Lorraine, F-54000 Nancy, France;
| | | | - Joris Messens
- VIB-VUB Center for Structural Biology, 1050 Brussels, Belgium; (K.W.); (A.N.V.)
- Brussels Center for Redox Biology, 1050 Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Claire Remacle
- Genetics and Physiology of Microalgae, InBios/Phytosystems Research Unit, University of Liège, 4000 Liège, Belgium; (A.C.); (F.V.d.L.); (J.P.-T.); (A.A.)
| |
Collapse
|
2
|
Kircheva N, Angelova S, Dobrev S, Petkova V, Nikolova V, Dudev T. Cu +/Ag + Competition in Type I Copper Proteins (T1Cu). Biomolecules 2023; 13:biom13040681. [PMID: 37189429 DOI: 10.3390/biom13040681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/13/2023] [Accepted: 04/14/2023] [Indexed: 05/17/2023] Open
Abstract
Due to the similarity in the basic coordination behavior of their mono-charged cations, silver biochemistry is known to be linked to that of copper in biological systems. Still, Cu+/2+ is an essential micronutrient in many organisms, while no known biological process requires silver. In human cells, copper regulation and trafficking is strictly controlled by complex systems including many cytosolic copper chaperones, whereas some bacteria exploit the so-called "blue copper" proteins. Therefore, evaluating the controlling factors of the competition between these two metal cations is of enormous interest. By employing the tools of computational chemistry, we aim to delineate the extent to which Ag+ might be able to compete with the endogenous copper in its Type I (T1Cu) proteins, and where and if, alternatively, it is handled uniquely. The effect of the surrounding media (dielectric constant) and the type, number, and composition of amino acid residues are taken into account when modelling the reactions in the present study. The obtained results clearly indicate the susceptibility of the T1Cu proteins to a silver attack due to the favorable composition and geometry of the metal-binding centers, along with the similarity between the Ag+/Cu+-containing structures. Furthermore, by exploring intriguing questions of both metals' coordination chemistry, an important background for understanding the metabolism and biotransformation of silver in organisms is provided.
Collapse
Affiliation(s)
- Nikoleta Kircheva
- Institute of Optical Materials and Technologies "Acad. J. Malinowski", Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Silvia Angelova
- Institute of Optical Materials and Technologies "Acad. J. Malinowski", Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Stefan Dobrev
- Institute of Optical Materials and Technologies "Acad. J. Malinowski", Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Vladislava Petkova
- Institute of Optical Materials and Technologies "Acad. J. Malinowski", Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Valya Nikolova
- Faculty of Chemistry and Pharmacy, Sofia University "St. Kliment Ohridski", 1164 Sofia, Bulgaria
| | - Todor Dudev
- Faculty of Chemistry and Pharmacy, Sofia University "St. Kliment Ohridski", 1164 Sofia, Bulgaria
| |
Collapse
|
3
|
Zamora RA, López-Ortiz M, Sales-Mateo M, Hu C, Croce R, Maniyara RA, Pruneri V, Giannotti MI, Gorostiza P. Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer. ACS Nano 2022; 16:15155-15164. [PMID: 36067071 DOI: 10.1021/acsnano.2c06454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Photosynthesis is a fundamental process that converts photons into chemical energy, driven by large protein complexes at the thylakoid membranes of plants, cyanobacteria, and algae. In plants, water-soluble plastocyanin (Pc) is responsible for shuttling electrons between cytochrome b6f complex and the photosystem I (PSI) complex in the photosynthetic electron transport chain (PETC). For an efficient turnover, a transient complex must form between PSI and Pc in the PETC, which implies a balance between specificity and binding strength. Here, we studied the binding frequency and the unbinding force between suitably oriented plant PSI and Pc under redox control using single molecule force spectroscopy (SMFS). The binding frequency (observation of binding-unbinding events) between PSI and Pc depends on their respective redox states. The interaction between PSI and Pc is independent of the redox state of PSI when Pc is reduced, and it is disfavored in the dark (reduced P700) when Pc is oxidized. The frequency of interaction between PSI and Pc is higher when at least one of the partners is in a redox state ready for electron transfer (ET), and the post-ET situation (PSIRed-PcOx) leads to lower binding. In addition, we show that the binding of ET-ready PcRed to PSI can be regulated externally by Mg2+ ions in solution.
Collapse
Affiliation(s)
- Ricardo A Zamora
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
| | - Manuel López-Ortiz
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
| | - Montserrat Sales-Mateo
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
| | - Chen Hu
- Biophysics of Photosynthesis. Dep. Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Roberta Croce
- Biophysics of Photosynthesis. Dep. Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Rinu Abraham Maniyara
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels 08860, Spain
| | - Valerio Pruneri
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels 08860, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona 08010, Spain
| | - Marina I Giannotti
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
- Department of Materials Science and Physical Chemistry, University of Barcelona, Martí i Franquès 10, Barcelona 08028, Spain
| | - Pau Gorostiza
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona 08010, Spain
| |
Collapse
|
4
|
Hao C, Yang Y, Du J, Deng XW, Li L. The PCY-SAG14 phytocyanin module regulated by PIFs and miR408 promotes dark-induced leaf senescence in Arabidopsis. Proc Natl Acad Sci U S A 2022; 119:e2116623119. [PMID: 35022242 PMCID: PMC8784109 DOI: 10.1073/pnas.2116623119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 12/08/2021] [Indexed: 11/21/2022] Open
Abstract
Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via forward genetics and functional assessment of senescence-associated genes (SAGs) via reverse genetics, the senescence signal and the molecular mechanism that perceives and transduces the signal remain elusive. Here, using dark-induced senescence (DIS) of Arabidopsis leaf as the experimental system, we show that exogenous copper induces the senescence syndrome and transcriptomic changes in light-grown plants parallel to those in DIS. By profiling the transcriptomes and tracking the subcellular copper distribution, we found that reciprocal regulation of plastocyanin, the thylakoid lumen mobile electron carrier in the Z scheme of photosynthetic electron transport, and SAG14 and plantacyanin (PCY), a pair of interacting small blue copper proteins located on the endomembrane, is a common thread in different leaf senescence scenarios, including DIS. Genetic and molecular experiments confirmed that the PCY-SAG14 module is necessary and sufficient for promoting DIS. We also found that the PCY-SAG14 module is repressed by a conserved microRNA, miR408, which in turn is repressed by phytochrome interacting factor 3/4/5 (PIF3/4/5), the key trio of transcription factors promoting DIS. Together, these findings indicate that intracellular copper redistribution mediated by PCY-SAG14 has a regulatory role in DIS. Further deciphering the copper homeostasis mechanism and its interaction with other senescence-regulating pathways should provide insights into our understanding of the fundamental question of how plants age.
Collapse
Affiliation(s)
- Chen Hao
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Yanzhi Yang
- School of Advanced Agricultural Sciences, Peking University, Beijing 100871, China
| | - Jianmei Du
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Xing Wang Deng
- School of Advanced Agricultural Sciences, Peking University, Beijing 100871, China;
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Lei Li
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China;
- School of Advanced Agricultural Sciences, Peking University, Beijing 100871, China
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| |
Collapse
|
5
|
Balti H, Abassi M, Dietz KJ, Kumar V. Differences in Ionic, Enzymatic, and Photosynthetic Features Characterize Distinct Salt Tolerance in Eucalyptus Species. Plants (Basel) 2021; 10:1401. [PMID: 34371604 DOI: 10.3390/plants10071401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 07/01/2021] [Accepted: 07/06/2021] [Indexed: 11/16/2022]
Abstract
In the face of rising salinity along coastal regions and in irrigated areas, molecular breeding of tolerant crops and reforestation of exposed areas using tolerant woody species is a two-way strategy. Thus, identification of tolerant plants and of existing tolerance mechanisms are of immense value. In the present study, three Eucalyptus ecotypes with potentially differential salt sensitivity were compared. Soil-grown Eucalyptus plants were exposed to 80 and 170 mM NaCl for 30 days. Besides analysing salt effects on ionic/osmotic balance, and hydrolytic enzymes, plants were compared for dynamics of light-induced redox changes in photosynthetic electron transport chain (pETC) components, namely plastocyanin (PC), photosystem I (PSI) and ferredoxin (Fd), parallel to traditional chlorophyll a fluorescence-based PSII-related parameters. Deconvoluted signals for PC and Fd from PSI allowed identification of PC and PSI as the prime salinity-sensitive components of pETC in tested Eucalyptus species. Eucalyptus loxophleba portrayed efficient K+-Na+ balance (60–90% increased K+) along with a more dynamic range of redox changes for pETC components in old leaves. Young leaves in Eucalyptus loxophleba showed robust endomembrane homeostasis, as underlined by an increased response of hydrolytic enzymes at lower salt concentration (~1.7–2.6-fold increase). Findings are discussed in context of salinity dose dependence among different Eucalyptus species.
Collapse
|
6
|
García-Cañas R, Giner-Lamia J, Florencio FJ, López-Maury L. A protease-mediated mechanism regulates the cytochrome c 6/plastocyanin switch in Synechocystis sp. PCC 6803. Proc Natl Acad Sci U S A 2021; 118:e2017898118. [PMID: 33495331 DOI: 10.1073/pnas.2017898118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
After the Great Oxidation Event (GOE), iron availability was greatly decreased, and photosynthetic organisms evolved several alternative proteins and mechanisms. One of these proteins, plastocyanin, is a type I blue-copper protein that can replace cytochrome c 6 as a soluble electron carrier between cytochrome b 6 f and photosystem I. In most cyanobacteria, expression of these two alternative proteins is regulated by copper availability, but the regulatory system remains unknown. Herein, we provide evidence that the regulatory system is composed of a BlaI/CopY-family transcription factor (PetR) and a BlaR-membrane protease (PetP). PetR represses petE (plastocyanin) expression and activates petJ (cytochrome c 6), while PetP controls PetR levels in vivo. Using whole-cell extracts, we demonstrated that PetR degradation requires both PetP and copper. Transcriptomic analysis revealed that the PetRP system regulates only four genes (petE, petJ, slr0601, and slr0602), highlighting its specificity. Furthermore, the presence of petE and petRP in early branching cyanobacteria indicates that acquisition of these genes could represent an early adaptation to decreased iron bioavailability following the GOE.
Collapse
|
7
|
Mattila H, Khorobrykh S, Hakala-Yatkin M, Havurinne V, Kuusisto I, Antal T, Tyystjärvi T, Tyystjärvi E. Action spectrum of the redox state of the plastoquinone pool defines its function in plant acclimation. Plant J 2020; 104:1088-1104. [PMID: 32889743 DOI: 10.1111/tpj.14983] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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: 01/20/2020] [Revised: 08/11/2020] [Accepted: 08/17/2020] [Indexed: 05/09/2023]
Abstract
The plastoquinone (PQ) pool mediates electron flow and regulates photoacclimation in plants. Here we report the action spectrum of the redox state of the PQ pool in Arabidopsis thaliana, showing that 470-500, 560 or 650-660 nm light favors Photosystem II (PSII) and reduces the PQ pool, whereas 420-440, 520 or 690 nm light favors Photosystem I (PSI) and oxidizes PQ. These data were used to construct a model predicting the redox state of PQ from the spectrum of any polychromatic light source. Moderate reduction of the PQ pool induced transition to light state 2, whereas state 1 required highly oxidized PQ. In low-intensity PSI light, PQ was more oxidized than in darkness and became gradually reduced with light intensity, while weak PSII light strongly reduced PQ. Natural sunlight was found to favor PSI, which enables plants to use the redox state of the PQ pool as a measure of light intensity.
Collapse
Affiliation(s)
- Heta Mattila
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Sergey Khorobrykh
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Marja Hakala-Yatkin
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Vesa Havurinne
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Iiris Kuusisto
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Taras Antal
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
- Department of Botany and Plant Ecology, Pskov State University, Pskov, 180000, Russia
| | - Taina Tyystjärvi
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| | - Esa Tyystjärvi
- Department of Biochemistry/Molecular Plant Biology, University of Turku, Turku, FI-20014, Finland
| |
Collapse
|
8
|
Höhner R, Pribil M, Herbstová M, Lopez LS, Kunz HH, Li M, Wood M, Svoboda V, Puthiyaveetil S, Leister D, Kirchhoff H. Plastocyanin is the long-range electron carrier between photosystem II and photosystem I in plants. Proc Natl Acad Sci U S A 2020; 117:15354-62. [PMID: 32541018 DOI: 10.1073/pnas.2005832117] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by macromolecular crowding. For thylakoid membranes of higher plants, a long-standing question has been which of the two mobile electron carriers, plastoquinone or plastocyanin, mediates electron transport from stacked grana thylakoids where photosystem II (PSII) is localized to distant unstacked regions of the thylakoids that harbor PSI. Here, we confirm that plastocyanin is the long-range electron carrier by employing mutants with different grana diameters. Furthermore, our results explain why higher plants have a narrow range of grana diameters since a larger diffusion distance for plastocyanin would jeopardize the efficiency of electron transport. In the light of recent findings that the lumen of thylakoids, which forms the diffusion space of plastocyanin, undergoes dynamic swelling/shrinkage, this study demonstrates that plastocyanin diffusion is a crucial regulatory element of plant photosynthetic electron transport.
Collapse
|
9
|
Shahbaz M, Pilon M. Conserved Cu-MicroRNAs in Arabidopsis thaliana Function in Copper Economy under Deficiency. Plants (Basel) 2019; 8:plants8060141. [PMID: 31146453 PMCID: PMC6631055 DOI: 10.3390/plants8060141] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/23/2019] [Accepted: 05/24/2019] [Indexed: 12/18/2022]
Abstract
Copper (Cu) is a micronutrient for plants. Three small RNAs, which are up-regulated by Cu deficiency and target transcripts for Cu proteins, are among the most conserved microRNAs in plants. It was hypothesized that these Cu-microRNAs help save Cu for the most essential Cu-proteins under deficiency. Testing this hypothesis has been a challenge due to the redundancy of the Cu microRNAs and the properties of the regulatory circuits that control Cu homeostasis. In order to investigate the role of Cu-microRNAs in Cu homeostasis during vegetative growth, we used a tandem target mimicry strategy to simultaneously inhibit the function of three conserved Cu-microRNAs in Arabidopsis thaliana. When compared to wild-type, transgenic lines that express the tandem target mimicry construct showed reduced Cu-microRNA accumulation and increased accumulation of transcripts that encode Cu proteins. As a result, these mimicry lines showed impaired photosynthesis and growth compared to wild type on low Cu, which could be ascribed to a defect in accumulation of plastocyanin, a Cu-containing photosynthetic electron carrier, which is itself not a Cu-microRNA target. These data provide experimental support for a Cu economy model where the Cu-microRNAs together function to allow maturation of essential Cu proteins under impending deficiency.
Collapse
Affiliation(s)
- Muhammad Shahbaz
- Biology Department, Colorado State University, Fort Collins, CO 80523-1878, USA.
| | - Marinus Pilon
- Biology Department, Colorado State University, Fort Collins, CO 80523-1878, USA.
| |
Collapse
|
10
|
Schöttler MA, Thiele W, Belkius K, Bergner SV, Flügel C, Wittenberg G, Agrawal S, Stegemann S, Ruf S, Bock R. The plastid-encoded PsaI subunit stabilizes photosystem I during leaf senescence in tobacco. J Exp Bot 2017; 68:1137-1155. [PMID: 28180288 PMCID: PMC5429015 DOI: 10.1093/jxb/erx009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
PsaI is the only subunit of PSI whose precise physiological function has not yet been elucidated in higher plants. While PsaI is involved in PSI trimerization in cyanobacteria, trimerization was lost during the evolution of the eukaryotic PSI, and the entire PsaI side of PSI underwent major structural remodelling to allow for binding of light harvesting complex II antenna proteins during state transitions. Here, we have generated a tobacco (Nicotiana tabacum) knockout mutant of the plastid-encoded psaI gene. We show that PsaI is not required for the redox reactions of PSI. Neither plastocyanin oxidation nor the processes at the PSI acceptor side are impaired in the mutant, and both linear and cyclic electron flux rates are unaltered. The PSI antenna cross section is unaffected, state transitions function normally, and binding of other PSI subunits to the reaction centre is not compromised. Under a wide range of growth conditions, the mutants are phenotypically and physiologically indistinguishable from wild-type tobacco. However, in response to high-light and chilling stress, and especially during leaf senescence, PSI content is reduced in the mutants, indicating that the I-subunit plays a role in stabilizing PSI complexes.
Collapse
Affiliation(s)
- Mark Aurel Schöttler
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Wolfram Thiele
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Karolina Belkius
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Sonja Verena Bergner
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Claudia Flügel
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Gal Wittenberg
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Shreya Agrawal
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Sandra Stegemann
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Stephanie Ruf
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Ralph Bock
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| |
Collapse
|
11
|
Hurd CA, Besley NA, Robinson D. A QM/MM study of the nature of the entatic state in plastocyanin. J Comput Chem 2016; 38:1431-1437. [PMID: 27859435 PMCID: PMC5434870 DOI: 10.1002/jcc.24666] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/23/2016] [Accepted: 10/27/2016] [Indexed: 11/27/2022]
Abstract
Plastocyanin is a copper containing protein that is involved in the electron transfer process in photosynthetic organisms. The active site of plastocyanin is described as an entatic state whereby its structure represents a compromise between the structures favored by the oxidized and reduced forms. In this study, the nature of the entatic state is investigated through density functional theory‐based hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations. The strain energy is computed to be 12.8 kcal/mol and 14.5 kcal/mol for the oxidized and reduced forms of the protein, indicating that the active site has an intermediate structure. It is shown that the energy gap between the oxidized and reduced forms varies significantly with the fluctuations in the structure of the active site at room temperature. An accurate determination of the reorganization energy requires averaging over conformation and a large region of the protein around the active site to be treated at the quantum mechanical level. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Catherine A Hurd
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| | - Nicholas A Besley
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| | - David Robinson
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| |
Collapse
|
12
|
Tapken W, Ravet K, Shahbaz M, Pilon M. Regulation of Cu delivery to chloroplast proteins. Plant Signal Behav 2015; 10:e1046666. [PMID: 26251885 PMCID: PMC4622755 DOI: 10.1080/15592324.2015.1046666] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [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: 04/10/2015] [Revised: 04/23/2015] [Accepted: 04/24/2015] [Indexed: 05/29/2023]
Abstract
Plastocyanin is a copper (Cu)-requiring protein that functions in photosynthetic electron transport in the thylakoid lumen of plants. To allow plastocyanin maturation, Cu must first be transported into the chloroplast stroma by means of the PAA1/HMA6 transporter and then into the thylakoid lumen by the PAA2/HMA8 transporter. Recent evidence indicated that the chloroplast regulates Cu transport into the thylakoids via Clp protease-mediated turnover of PAA2/HMA8. Here we present further genetic evidence that this regulatory mechanism for the adjustment of intra-cellular Cu distribution depends on stromal Cu levels. A key transcription factor mediating Cu homeostasis in plants is SQUAMOSA promoter binding protein-like7 (SPL7). SPL7 transcriptionally regulates Cu homeostasis when the nutrient becomes limiting by up-regulating expression of Cu importers at the cell membrane, and down-regulating expression of seemingly non-essential cuproproteins. It was proposed that this latter mechanism favors Cu delivery to the chloroplast. We propose a 2-tiered system which functions to control plant leaf Cu homeostasis: SPL7 dependent transcriptional regulation of cuproproteins, and PAA2/HMA8 turnover by the Clp system, which is independent on SPL7.
Collapse
Key Words
- CCS, copper chaperone for superoxide dismutase
- COPT, copper transporter
- CSD, Cu/Zn superoxide dismutase
- CSD, Cu/Zn superoxide dismutase dismutase
- Clp protease
- Clp, caseinolytic protease
- Cu, copper
- P-type ATPase
- PAA1/2, P-type ATPase of Arabidopsis 1/2
- PAA2/HMA8
- PC, plastocyanin
- PCH1, Plastid Copper Chaperone 1
- PPO, Polyphenol Oxidase
- SPL7
- SPL7, SQUAMOSA promoter binding protein-like7
- chloroplast
- copper
- homeostasis
- plastocyanin
Collapse
Affiliation(s)
- Wiebke Tapken
- Biology Department; Colorado State University; Fort Collins, CO USA
| | - Karl Ravet
- Biology Department; Colorado State University; Fort Collins, CO USA
| | - Muhammad Shahbaz
- Biology Department; Colorado State University; Fort Collins, CO USA
| | - Marinus Pilon
- Biology Department; Colorado State University; Fort Collins, CO USA
| |
Collapse
|
13
|
Abstract
Copper is required for photosynthesis in chloroplasts of plants because it is a cofactor of plastocyanin, an essential electron carrier in the thylakoid lumen. Other chloroplast copper proteins are copper/zinc superoxide dismutase and polyphenol oxidase, but these proteins seem to be dispensable under conditions of low copper supply when transcripts for these proteins undergo microRNA-mediated down regulation. Two ATP-driven copper transporters function in tandem to deliver copper to chloroplast compartments. This review seeks to summarize the mechanisms of copper delivery to chloroplast proteins and its regulation. We also delineate some of the unanswered questions that still remain in this field.
Collapse
|
14
|
Shahbaz M, Ravet K, Peers G, Pilon M. Prioritization of copper for the use in photosynthetic electron transport in developing leaves of hybrid poplar. Front Plant Sci 2015; 6:407. [PMID: 26089828 PMCID: PMC4452806 DOI: 10.3389/fpls.2015.00407] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 05/21/2015] [Indexed: 05/13/2023]
Abstract
Plastocyanin (PC) is an essential and abundant copper (Cu) protein required for photosynthesis in higher plants. Severe copper deprivation has the potential to cause a defect in photosynthetic electron transport due to a lack in PC. The Cu-microRNAs, which are up-regulated under Cu deficiency, down-regulate the expression of target Cu proteins other than PC, cytochrome-c oxidase and the ethylene receptors. It has been proposed that this mechanism saves Cu for PC maturation. We aimed to test how hybrid poplar, a species that has capacity to rapidly expand its photosynthetically active tissue, responds to variations in Cu availability over time. Measurement of chlorophyll fluorescence after Cu depletion revealed a drastic effect on photosynthesis in hybrid poplar. The decrease in photosynthetic capacity was correlated with a reduction in PC protein levels. Compared to older leaves, PC decreased more strongly in developing leaves, which also lost more photosynthetic electron transport capacity. The effect of Cu depletion on older and more developed leaves was minor and these leaves maintained much of their photosynthetic capacity. Interestingly, upon resupply of Cu to the medium a very rapid recovery of Cu levels was seen in the younger leaves with a concomitant rise in the expression and activity of PC. In contrast, the expression of those Cu proteins, which are targets of microRNAs was under the same circumstances delayed. At the same time, Cu resupply had only minor effects on the older leaves. The data suggest a model where rapid recovery of photosynthetic capacity in younger leaves is made possible by a preferred allocation of Cu to PC in younger leaves, which is supported by Cu-microRNA expression.
Collapse
Affiliation(s)
| | | | | | - Marinus Pilon
- *Correspondence: Marinus Pilon, Department of Biology, Colorado State University, 1878 Campus Delivery, 200 West Lake Street, Fort Collins, CO 80523-1878, USA
| |
Collapse
|
15
|
Giner-Lamia J, López-Maury L, Florencio FJ. CopM is a novel copper-binding protein involved in copper resistance in Synechocystis sp. PCC 6803. Microbiologyopen 2014; 4:167-85. [PMID: 25545960 PMCID: PMC4335983 DOI: 10.1002/mbo3.231] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 11/13/2014] [Accepted: 11/20/2014] [Indexed: 01/15/2023] Open
Abstract
Copper resistance system in the cyanobacterium Synechocystis sp. PCC 6803 comprises two operons, copMRS and copBAC, which are expressed in response to copper in the media. copBAC codes for a heavy-metal efflux–resistance nodulation and division (HME-RND) system, while copMRS codes for a protein of unknown function, CopM, and a two-component system CopRS, which controls the expression of these two operons. Here, we report that CopM is a periplasmic protein able to bind Cu(I) with high affinity (KD ∼3 × 10−16). Mutants lacking copM showed a sensitive copper phenotype similar to mutants affected in copB, but lower than mutants of the two-component system CopRS, suggesting that CopBAC and CopM constitute two independent resistance mechanisms. Moreover, constitutive expression of copM is able to partially suppress the copper sensitivity of the copR mutant strain, pointing out that CopM per se is able to confer copper resistance. Furthermore, constitutive expression of copM was able to reduce total cellular copper content of the copR mutant to the levels determined in the wild-type (WT) strain. Finally, CopM was localized not only in the periplasm but also in the extracellular space, suggesting that CopM can also prevent copper accumulation probably by direct copper binding outside the cell.
Collapse
Affiliation(s)
- Joaquín Giner-Lamia
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, E-41092, Sevilla, Spain
| | | | | |
Collapse
|
16
|
Schöttler MA, Tóth SZ. Photosynthetic complex stoichiometry dynamics in higher plants: environmental acclimation and photosynthetic flux control. Front Plant Sci 2014; 5:188. [PMID: 24860580 PMCID: PMC4026699 DOI: 10.3389/fpls.2014.00188] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 04/22/2014] [Indexed: 05/02/2023]
Abstract
The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity and light quality, and to changing metabolic demands for ATP and NADPH imposed by stresses and leaf aging. By changing photosynthetic complex stoichiometry, a long-term imbalance between the photosynthetic production of ATP and NADPH and their metabolic consumption is avoided, and cytotoxic side reactions are minimized. Otherwise, an excess capacity of the light reactions, relative to the demands of primary metabolism, could result in a disturbance of cellular redox homeostasis and an increased production of reactive oxygen species, leading to the destruction of the photosynthetic apparatus and the initiation of cell death programs. In this review, changes of the abundances of the different constituents of the photosynthetic apparatus in response to environmental conditions and during leaf ontogenesis are summarized. The contributions of the different photosynthetic complexes to photosynthetic flux control and the regulation of electron transport are discussed.
Collapse
Affiliation(s)
- Mark A. Schöttler
- Max Planck Institute of Molecular Plant PhysiologyPotsdam-Golm, Germany
| | | |
Collapse
|
17
|
Laisk A, Oja V, Eichelmann H, Dall'Osto L. Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1. Biochim Biophys Acta 2013; 1837:315-25. [PMID: 24333386 DOI: 10.1016/j.bbabio.2013.12.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 10/30/2013] [Accepted: 12/03/2013] [Indexed: 11/30/2022]
Abstract
The spectral global quantum yield (YII, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (YI) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4·O2 evolution) which arrived at the PSI donor side after a delay of 2ms. The intrinsic quantum yield of PSI (yI, electrons per photon absorbed by PSI) was measured at 712nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (aI) and PSII (aII) in leaves. For comparison, pigment-protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (yI=0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield yII=0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence Fv/Fm, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145-155). At wavelengths less than 580nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment-protein complexes.
Collapse
Affiliation(s)
- Agu Laisk
- Tartu Ülikooli Molekulaar- ja Rakubioloogia Instituut, Riia tn. 23, Tartu 51010, Estonia.
| | - Vello Oja
- Tartu Ülikooli Molekulaar- ja Rakubioloogia Instituut, Riia tn. 23, Tartu 51010, Estonia
| | - Hillar Eichelmann
- Tartu Ülikooli Molekulaar- ja Rakubioloogia Instituut, Riia tn. 23, Tartu 51010, Estonia
| | - Luca Dall'Osto
- Università di Verona, Dipartimento di Biotecnologie, Strada Le Grazie, 15 37135 Verona, Italy
| |
Collapse
|
18
|
Saif Hasan S, Yamashita E, Cramer WA. Transmembrane signaling and assembly of the cytochrome b6f-lipidic charge transfer complex. Biochim Biophys Acta 2013; 1827:1295-308. [PMID: 23507619 DOI: 10.1016/j.bbabio.2013.03.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/27/2013] [Accepted: 03/06/2013] [Indexed: 12/30/2022]
Abstract
Structure-function properties of the cytochrome b6f complex are sufficiently unique compared to those of the cytochrome bc1 complex that b6f should not be considered a trivially modified bc1 complex. A unique property of the dimeric b6f complex is its involvement in transmembrane signaling associated with the p-side oxidation of plastoquinol. Structure analysis of lipid binding sites in the cyanobacterial b6f complex prepared by hydrophobic chromatography shows that the space occupied by the H transmembrane helix in the cytochrome b subunit of the bc1 complex is mostly filled by a lipid in the b6f crystal structure. It is suggested that this space can be filled by the domain of a transmembrane signaling protein. The identification of lipid sites and likely function defines the intra-membrane conserved central core of the b6f complex, consisting of the seven trans-membrane helices of the cytochrome b and subunit IV polypeptides. The other six TM helices, contributed by cytochrome f, the iron-sulfur protein, and the four peripheral single span subunits, define a peripheral less conserved domain of the complex. The distribution of conserved and non-conserved domains of each monomer of the complex, and the position and inferred function of a number of the lipids, suggests a model for the sequential assembly in the membrane of the eight subunits of the b6f complex, in which the assembly is initiated by formation of the cytochrome b6-subunit IV core sub-complex in a monomer unit. Two conformations of the unique lipidic chlorophyll a, defined in crystal structures, are described, and functions of the outlying β-carotene, a possible 'latch' in supercomplex formation, are discussed. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.
Collapse
|
19
|
Tapken W, Ravet K, Pilon M. Plastocyanin controls the stabilization of the thylakoid Cu-transporting P-type ATPase PAA2/HMA8 in response to low copper in Arabidopsis. J Biol Chem 2012; 287:18544-50. [PMID: 22493454 PMCID: PMC3365703 DOI: 10.1074/jbc.m111.318204] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 03/20/2012] [Indexed: 11/06/2022] Open
Abstract
PAA2/HMA8 (P-type ATPase of Arabidopsis/Heavy-metal-associated 8) is a thylakoid located copper (Cu)-transporter in Arabidopsis thaliana. In tandem with PAA1/HMA6, which is located in the inner chloroplast envelope, it supplies Cu to plastocyanin (PC), an essential cuproenzyme of the photosynthetic machinery. We investigated whether the chloroplast Cu transporters are affected by Cu addition to the growth media. Immunoblots showed that PAA2 protein abundance decreased significantly and specifically when Cu in the media was increased, while PAA1 remained unaffected. The function of SPL7, the transcriptional regulator of Cu homeostasis, was not required for this regulation of PAA2 protein abundance and Cu addition did not affect PAA2 transcript levels, as determined by qRT-PCR. We used the translational inhibitor cycloheximide to analyze turnover and observed that the stability of the PAA2 protein was decreased in plants grown with elevated Cu. Interestingly, PAA2 protein abundance was significantly increased in paa1 mutants, in which the Cu content in the chloroplast is half of that of the wild-type, due to impaired Cu import into the organelle. In contrast in a pc2 insertion mutant, which has strongly reduced plastocyanin expression, the PAA2 protein levels were low regardless of Cu addition to the growth media. Together, these data indicate that plastid Cu levels control PAA2 stability and that plastocyanin, which is the target of PAA2 mediated Cu delivery in thylakoids, is a major determinant of this regulatory mechanism.
Collapse
Affiliation(s)
- Wiebke Tapken
- From the Biology Department and Program in Molecular Plant Biology Colorado State University, Fort Collins, Colorado 80523-1878
| | - Karl Ravet
- From the Biology Department and Program in Molecular Plant Biology Colorado State University, Fort Collins, Colorado 80523-1878
| | - Marinus Pilon
- From the Biology Department and Program in Molecular Plant Biology Colorado State University, Fort Collins, Colorado 80523-1878
| |
Collapse
|
20
|
Yamasaki H, Pilon M, Shikanai T. How do plants respond to copper deficiency? Plant Signal Behav 2008; 3:231-2. [PMID: 19704637 PMCID: PMC2634185 DOI: 10.4161/psb.3.4.5094] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 09/27/2007] [Indexed: 05/21/2023]
Abstract
The transition metal copper is essential for all organisms yet excess copper is toxic because of production of free radicals via its free form. Therefore, the levels of copper are precisely regulated in a cell. Under copper depleted conditions, the expression of Cu/Zn superoxide dismutase (SOD) is downregulated and its function is compensated by Fe SOD in chloroplasts of higher plants. We presented evidence that a microRNA, miR398, is involved in this downregulation of Cu/Zn SOD genes in Arabidopsis thaliana when grown at low copper levels, corresponding to less than 1 microM Cu in tissue culture media. However, a green alga, Chlamydomonas reinhardtii, adjusts to copper depletion by modifying the photosynthetic apparatus from copper containing plastocyanin to iron containing cytochrome c(6). During evolution plants modified one of the main strategies to respond to copper deficiency probably to adapt to different metal environments.
Collapse
Affiliation(s)
- Hiroaki Yamasaki
- Graduate School of Agriculture; Kyushu University; Fukuoka, Japan
| | - Marinus Pilon
- Biology Department and Program in Molecular Plant Biology; Colorado State University; Fort Collins, Colorado USA
| | | |
Collapse
|
21
|
Schöttler MA, Flügel C, Thiele W, Stegemann S, Bock R. The plastome-encoded PsaJ subunit is required for efficient Photosystem I excitation, but not for plastocyanin oxidation in tobacco. Biochem J 2007; 403:251-60. [PMID: 17209805 PMCID: PMC1874242 DOI: 10.1042/bj20061573] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Revised: 12/19/2006] [Accepted: 01/09/2007] [Indexed: 11/17/2022]
Abstract
The functions of several small subunits of the large photosynthetic multiprotein complex PSI (Photosystem I) are not yet understood. To elucidate the function of the small plastome-encoded PsaJ subunit, we have produced knockout mutants by chloroplast transformation in tobacco (Nicotiana tabacum). PsaJ binds two chlorophyll-a molecules and is localized at the periphery of PSI, close to both the Lhca2- and Lhca3-docking sites and the plastocyanin-binding site. Tobacco psaJ-knockout lines do not display a visible phenotype. Despite a 25% reduction in the content of redox-active PSI, neither growth rate nor assimilation capacity are altered in the mutants. In vivo, redox equilibration of plastocyanin and PSI is as efficient as in the wild-type, indicating that PsaJ is not required for fast plastocyanin oxidation. However, PsaJ is involved in PSI excitation: altered 77 K chlorophyll-a fluorescence emission spectra and reduced accumulation of Lhca3 indicate that antenna binding and exciton transfer to the PSI reaction centre are impaired in DeltapsaJ mutants. Under limiting light intensities, growth of DeltapsaJ plants is retarded and the electron-transport chain is far more reduced than in the wild-type, indicating that PSI excitation might limit electron flux at sub-saturating light intensities. In addition to defining in vivo functions of PsaJ, our data may also have implications for the interpretation of the crystal structure of PSI.
Collapse
Key Words
- lhca
- photosynthesis
- photosystem i
- psaj
- plastocyanin
- chl, chlorophyll
- cyt, cytochrome
- cyt-bf, cytochrome-b6f complex
- ddm, β-dodecylmaltoside
- ep, electron pair
- hp, high-potential form
- lhc, light-harvesting complex
- lp, low-potential form
- p700, chl-a dimer of the photosystem i reaction centre
- pc, plastocyanin
- pq, plastoquinone
- ps, photosystem
- rflp, restriction fragment length polymorphism
- rmop, regeneration medium of plants
- rnai, rna interference
- tmpd, tetramethyl-1,4-phenylenediamine
- wt, wild-type
Collapse
Affiliation(s)
- Mark A Schöttler
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany.
| | | | | | | | | |
Collapse
|
22
|
Díaz-Moreno I, Díaz-Moreno S, Subías G, De la Rosa MA, Díaz-Quintana A. The atypical iron-coordination geometry of cytochrome f remains unchanged upon binding to plastocyanin, as inferred by XAS. Photosynth Res 2006; 90:23-8. [PMID: 17111237 PMCID: PMC1769345 DOI: 10.1007/s11120-006-9102-8] [Citation(s) in RCA: 3] [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] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2006] [Accepted: 08/25/2006] [Indexed: 05/12/2023]
Abstract
The transient complex between cytochrome f and plastocyanin from the cyanobacterium Nostoc sp. PCC 7119 has been analysed by X-ray Absorption Spectroscopy in solution, using both proteins in their oxidized and reduced states. Fe K-edge data mainly shows that the atypical metal coordination geometry of cytochrome f, in which the N-terminal amino acid acts as an axial ligand of the heme group, remains unaltered upon binding to its redox partner, plastocyanin. This fact suggests that cytochrome f provides a stable binding site for plastocyanin and minimizes the reorganization energy required in the transient complex formation, which could facilitate the electron transfer between the two redox partners.
Collapse
Affiliation(s)
- Irene Díaz-Moreno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla y Consejo Superior de Investigaciones Científicas, Américo Vespucio 49, 41092, Sevilla, Spain.
| | | | | | | | | |
Collapse
|
23
|
Bergkvist A, Ejdebäck M, Ubbink M, Karlsson BG. Surface interactions in the complex between cytochrome f and the E43Q/D44N and E59K/E60Q plastocyanin double mutants as determined by (1)H-NMR chemical shift analysis. Protein Sci 2001; 10:2623-6. [PMID: 11714931 PMCID: PMC2374039 DOI: 10.1110/ps.27101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2001] [Revised: 08/29/2001] [Accepted: 08/31/2001] [Indexed: 10/21/2022]
Abstract
A combination of site-directed mutagenesis and NMR chemical shift perturbation analysis of backbone and side-chain protons has been used to characterize the transient complex of the photosynthetic redox proteins plastocyanin and cytochrome f. To elucidate the importance of charged residues on complex formation, the complex of cytochrome f and E43Q/D44N or E59K/E60Q spinach plastocyanin double mutants was studied by full analysis of the (1)H chemical shifts by use of two-dimensional homonuclear NMR spectra. Both mutants show a significant overall decrease in chemical shift perturbations compared with wild-type plastocyanin, in agreement with a large decrease in binding affinity. Qualitatively, the E43Q/D44N mutant showed a similar interaction surface as wild-type plastocyanin. The interaction surface in the E59K/E60Q mutant was distinctly different from wild type. It is concluded that all four charged residues contribute to the affinity and that residues E59 and E60 have an additional role in fine tuning the orientation of the proteins in the complex.
Collapse
Affiliation(s)
- A Bergkvist
- Biochemistry and Biophysics, Department of Chemistry, Göteborg University, SE-405 30 Göteborg, Sweden
| | | | | | | |
Collapse
|
24
|
Sandhu JS, Webster CI, Gray JC. A/T-rich sequences act as quantitative enhancers of gene expression in transgenic tobacco and potato plants. Plant Mol Biol 1998; 37:885-96. [PMID: 9678583 PMCID: PMC7089012 DOI: 10.1023/a:1006051832213] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The role of an A/T-rich positive regulatory region (P268, -444 to -177 from the translation start site) of the pea plastocyanin gene (PetE) promoter has been investigated in transgenic plants containing chimeric promoters fused to the beta-glucuronidase (GUS) reporter gene. This region enhanced GUS expression in leaves of transgenic tobacco plants when fused in either orientation to a minimal pea PetE promoter (-176 to +4) and in roots when fused in either orientation upstream or downstream of a minimal cauliflower mosaic virus 35S promoter (-90 to +5). The region was also able to enhance GUS expression in microtubers of transgenic potato plants when placed in either orientation upstream of a minimal class I patatin promoter (-332 to +14). Dissection of P268 revealed that cis elements responsible for enhancing GUS expression from the minimal PetE promoter were distributed throughout P268. Multiple copies of a 31 bp A/T-rich sequence from within P268 and of a 26 bp random A/T sequence were able to enhance GUS expression from the minimal PetE promoter, indicating that A/T-rich sequences are able to act as quantitative, non-tissue-specific enhancer elements in higher plants.
Collapse
Affiliation(s)
- J S Sandhu
- Department of Plant Sciences and Cambridge Centre for Molecular Recognition, University of Cambridge, UK
| | | | | |
Collapse
|