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López-Calcagno PE, Brown KL, Simkin AJ, Fisk SJ, Vialet-Chabrand S, Lawson T, Raines CA. Stimulating photosynthetic processes increases productivity and water-use efficiency in the field. NATURE PLANTS 2020; 6:1054-1063. [PMID: 32782406 DOI: 10.1038/s41477-020-0740-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 07/08/2020] [Indexed: 05/20/2023]
Abstract
Previous studies have demonstrated that the independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multigene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or the overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with the expression of the red algal protein cytochrome c6, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved. Furthermore, we provide evidence that the stimulation of both electron transport and RuBP regeneration can lead to enhanced intrinsic water-use efficiency under field conditions.
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Chida H, Nakazawa A, Akazaki H, Hirano T, Suruga K, Ogawa M, Satoh T, Kadokura K, Yamada S, Hakamata W, Isobe K, Ito TI, Ishii R, Nishio T, Sonoike K, Oku T. Expression of the algal cytochrome c6 gene in Arabidopsis enhances photosynthesis and growth. PLANT & CELL PHYSIOLOGY 2007; 48:948-57. [PMID: 17548374 DOI: 10.1093/pcp/pcm064] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Photosynthetic plants convert light energy into ATP and NADPH in photosynthetic electron transfer and photophosphorylation, and synthesize mainly carbohydrates in the Calvin-Benson cycle. Here we report the enhancement of photosynthesis and growth of plants by introducing the gene of an algal cytochrome c6, which has been evolutionarily eliminated from higher plant chloroplasts, into the model plant Arabidopsis thaliana. At 60 d after planting, the plant height, leaf length and root length of the transformants were 1.3-, 1.1- and 1.3-fold those in the wild-type plants, respectively. At the same time, in the transgenic plants, the amounts of chlorophyll, protein, ATP, NADPH and starch were 1.2-, 1.1-, 1.9-, 1.4- and 1.2-fold those in the wild-type plants, respectively. The CO2 assimilation capacity of the transgenic plants was 1.3-fold that of the wild type. Moreover, in transgenic Arabidopsis expressing algal cytochrome c6, the 1-qP, which reflects the reduced state of the plastoquinone pool, is 30% decreased compared with the wild type. These results show that the electron transfer of photosynthesis of Arabidopsis would be accelerated by the expression of algal cytochrome c6. Our results demonstrate that the growth and photosynthesis of Arabidopsis plants could be enhanced by the expression of the algal cytochrome c6 gene.
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Quinn JM, Kropat J, Merchant S. Copper response element and Crr1-dependent Ni(2+)-responsive promoter for induced, reversible gene expression in Chlamydomonas reinhardtii. EUKARYOTIC CELL 2004; 2:995-1002. [PMID: 14555481 PMCID: PMC219375 DOI: 10.1128/ec.2.5.995-1002.2003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Cpx1 and Cyc6 genes of Chlamydomonas reinhardtii are activated in copper-deficient cells via a signal transduction pathway that requires copper response elements (CuREs) and a copper response regulator defined by the CRR1 locus. The two genes can also be activated by provision of nickel or cobalt ions in the medium. The response to nickel ions requires at least one CuRE and also CRR1 function, suggesting that nickel interferes with a component in the nutritional copper signal transduction pathway. Nickel does not act by preventing copper uptake/utilization because (i) holoplastocyanin formation is unaffected in Ni(2+)-treated cells and (ii) provision of excess copper cannot reverse the Ni-dependent activation of the target genes. The CuRE is sufficient for conferring Ni-responsive expression to a reporter gene, which suggests that the system has practical application as a vehicle for inducible gene expression. The inducer can be removed either by replacing the medium or by chelating the inducer with excess EDTA, either of which treatments reverses the activation of the target genes.
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Research Support, U.S. Gov't, P.H.S. |
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Giner-Lamia J, López-Maury L, Florencio FJ. Global transcriptional profiles of the copper responses in the cyanobacterium Synechocystis sp. PCC 6803. PLoS One 2014; 9:e108912. [PMID: 25268225 PMCID: PMC4182526 DOI: 10.1371/journal.pone.0108912] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 08/27/2014] [Indexed: 12/22/2022] Open
Abstract
Copper is an essential element involved in fundamental processes like respiration and photosynthesis. However, it becomes toxic at high concentration, which has forced organisms to control its cellular concentration. We have recently described a copper resistance system in the cyanobacterium Synechocystis sp. PCC 6803, which is mediated by the two-component system, CopRS, a RND metal transport system, CopBAC and a protein of unknown function, CopM. Here, we report the transcriptional responses to copper additions at non-toxic (0.3 µM) and toxic concentrations (3 µM) in the wild type and in the copper sensitive copR mutant strain. While 0.3 µM copper slightly stimulated metabolism and promoted the exchange between cytochrome c6 and plastocyanin as soluble electron carriers, the addition of 3 µM copper catalyzed the formation of ROS, led to a general stress response and induced expression of Fe-S cluster biogenesis genes. According to this, a double mutant strain copRsufR, which expresses constitutively the sufBCDS operon, tolerated higher copper concentration than the copR mutant strain, suggesting that Fe-S clusters are direct targets of copper toxicity in Synechocystis. In addition we have also demonstrated that InrS, a nickel binding transcriptional repressor that belong to the CsoR family of transcriptional factor, was involved in heavy metal homeostasis, including copper, in Synechocystis. Finally, global gene expression analysis of the copR mutant strain suggested that CopRS only controls the expression of copMRS and copBAC operons in response to copper.
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Research Support, Non-U.S. Gov't |
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Yadav SK, Khatri K, Rathore MS, Jha B. Introgression of UfCyt c 6, a thylakoid lumen protein from a green seaweed Ulva fasciata Delile enhanced photosynthesis and growth in tobacco. Mol Biol Rep 2018; 45:1745-1758. [PMID: 30159639 DOI: 10.1007/s11033-018-4318-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 08/16/2018] [Indexed: 01/02/2023]
Abstract
Cytochromes are important components of photosynthetic electron transport chain. Here we report on genetic transformation of Cytochrome c6 (UfCyt c6) gene from Ulva fasciata Delile in tobacco for enhanced photosynthesis and growth. UfCyt c6 cDNA had an open reading frame of 330 bp encoding a polypeptide of 109 amino acids with a predicted molecular mass of 11.65 kDa and an isoelectric point of 5.21. UfCyt c6 gene along with a tobacco petE transit peptide sequence under control of CaMV35S promoter was transformed in tobacco through Agrobacterium mediated genetic transformation. Transgenic tobacco grew normal and exhibited enhanced growth as compared to wild type (WT) and vector control (VC) tobacco. Transgenic tobacco had higher contents of photosynthetic pigments and better ratios of photosynthetic pigments. The tobacco expressing UfCyt c6 gene exhibited higher photosynthetic rate and improved water use efficiency. Further activity of the water-splitting complex, photosystem II quantum yield, photochemical quenching, electron transfer rate, and photosynthetic yield were found comparatively higher in transgenic tobacco as compared to WT and VC tobacco. Alternatively basal quantum yield of non-photochemical processes in PSII and non-photochemical quenching were estimated lower in tobacco expressing UfCyt c6 gene. As a result of improved photosynthetic performance the transgenic tobacco had higher contents of sugar and starch, and exhibited comparatively better growth. To the best of our knowledge this is the first report on expression of UfCyt c6 gene from U. fasciata for improved photosynthesis and growth in tobacco.
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Marcaida MJ, Schlarb-Ridley BG, Worrall JAR, Wastl J, Evans TJ, Bendall DS, Luisi BF, Howe CJ. Structure of cytochrome c6A, a novel dithio-cytochrome of Arabidopsis thaliana, and its reactivity with plastocyanin: implications for function. J Mol Biol 2006; 360:968-77. [PMID: 16815443 DOI: 10.1016/j.jmb.2006.05.065] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 05/24/2006] [Accepted: 05/28/2006] [Indexed: 11/20/2022]
Abstract
Cytochrome c6A is a unique dithio-cytochrome present in land plants and some green algae. Its sequence and occurrence in the thylakoid lumen suggest that it is derived from cytochrome c6, which functions in photosynthetic electron transfer between the cytochrome b6f complex and photosystem I. Its known properties, however, and a strong indication that the disulfide group is not purely structural, indicate that it has a different, unidentified function. To help in the elucidation of this function the crystal structure of cytochrome c6A from Arabidopsis thaliana has been determined in the two redox states of the heme group, at resolutions of 1.2 A (ferric) and 1.4 A (ferrous). These two structures were virtually identical, leading to the functionally important conclusion that the heme and disulfide groups do not communicate by conformational change. They also show, however, that electron transfer between the reduced disulfide and the heme is feasible. We therefore suggest that the role of cytochrome c6A is to use its disulfide group to oxidize dithiol/disulfide groups of other proteins of the thylakoid lumen, followed by internal electron transfer from the dithiol to the heme, and re-oxidation of the heme by another thylakoid oxidant. Consistent with this model, we found a rapid electron transfer between ferro-cytochrome c6A and plastocyanin, with a second-order rate constant, k2=1.2 x 10(7) M(-1) s(-1).
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Haddadian EJ, Gross EL. A Brownian dynamics study of the effects of cytochrome f structure and deletion of its small domain in interactions with cytochrome c6 and plastocyanin in Chlamydomonas reinhardtii. Biophys J 2006; 90:566-77. [PMID: 16239335 PMCID: PMC1367061 DOI: 10.1529/biophysj.105.067058] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Accepted: 09/13/2005] [Indexed: 11/18/2022] Open
Abstract
The availability of seven different structures of cytochrome f (cyt f) from Chlamydomonas reinhardtii allowed us, using Brownian dynamics simulations, to model interactions between these molecules and their redox partners, plastocyanin (PC) and cytochrome c6 (cyt c6) in the same species to study the effect of cyt f structure on its function. Our results showed that different cyt f structures, which are very similar, produced different reaction rates in interactions with PC and cyt c6. We were able to attribute this to structural differences among these molecules, particularly to a small flexible loop between A-184 and G-191 (which has some of the highest crystallographic temperature factors in all of the cyt f structures) on the cyt f small domain. We also showed that deletion of the cyt f small domain affected cyt c6 more than PC, due to their different binding positions on cyt f. One function of the small domain in cyt f may be to guide PC or cyt c6 to a uniform dock with cyt f, especially due to electrostatic interactions with K-188 and K-189 on this domain. Our results could serve as a good guide for future experimental work on these proteins to understand better the electron transfer process between them. Also, these results demonstrated the sensitivity and the power of the Brownian dynamics simulations in the study of molecular interactions.
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Schlarb-Ridley BG, Nimmo RH, Purton S, Howe CJ, Bendall DS. Cytochrome c(6A) is a funnel for thiol oxidation in the thylakoid lumen. FEBS Lett 2006; 580:2166-9. [PMID: 16581069 DOI: 10.1016/j.febslet.2006.03.052] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 03/17/2006] [Accepted: 03/20/2006] [Indexed: 11/25/2022]
Abstract
Cytochrome c(6A) is a dithio-cytochrome recently discovered in land plants and green algae, and believed to be derived from the well-known cytochrome c(6). The function of cytochrome c(6A) is unclear. We propose that it catalyses the formation of disulphide bridges in thylakoid lumen proteins in a single-step disulphide exchange reaction, with subsequent transfer of the reducing equivalents to plastocyanin. The haem group of cytochrome c(6A) acts as an electron sink, allowing rapid resolution of a radical intermediate formed during reoxidation of cytochrome c(6A). Our model is consistent with previously published data on mutant plants, and the likely evolution of the protein.
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Sommer F, Drepper F, Haehnel W, Hippler M. Identification of precise electrostatic recognition sites between cytochrome c6 and the photosystem I subunit PsaF using mass spectrometry. J Biol Chem 2006; 281:35097-103. [PMID: 16984911 DOI: 10.1074/jbc.m607384200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reduction of the photo-oxidized special chlorophyll pair P700 of photosystem I (PSI) in the photosynthetic electron transport chain of eukaryotic organisms is facilitated by the soluble copper-containing protein plastocyanin (pc). In the absence of copper, pc is functionally replaced by the heme-containing protein cytochrome c6 (cyt c6) in the green alga Chlamydomonas reinhardtii. Binding and electron transfer between both donors and PSI follows a two-step mechanism that depends on electrostatic and hydrophobic recognition between the partners. Although the electrostatic and hydrophobic recognition sites on pc and PSI are well known, the precise electrostatic recognition site on cyt c6 is unknown. To specify the interaction sites on a molecular level, we cross-linked cyt c6 and PSI using a zero-length cross-linker and obtained a cross-linked complex competent in fast and efficient electron transfer. As shown previously, cyt c6 cross-links specifically with the PsaF subunit of PSI. Mass spectrometric analysis of tryptic peptides from the cross-linked product revealed specific interaction sites between residues Lys27 of PsaF and Glu69 of cyt c6 and between Lys23 of PsaF and Glu69/Glu70 of cyt c6. Using these new data, we present a molecular model of the intermolecular electron transfer complex between eukaryotic cyt c6 and PSI.
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Chida H, Yokoyama T, Kawai F, Nakazawa A, Akazaki H, Takayama Y, Hirano T, Suruga K, Satoh T, Yamada S, Kawachi R, Unzai S, Nishio T, Park SY, Oku T. Crystal structure of oxidized cytochromec6AfromArabidopsis thaliana. FEBS Lett 2006; 580:3763-8. [PMID: 16777100 DOI: 10.1016/j.febslet.2006.05.067] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Revised: 05/12/2006] [Accepted: 05/27/2006] [Indexed: 10/24/2022]
Abstract
Compared with algal and cyanobacterial cytochrome c(6), cytochrome c(6A) from higher plants contains an additional loop of 12 amino acid residues. We have determined the first crystal structure of cytochrome c(6A) from Arabidopsis thaliana at 1.5 Angstrom resolution in order to help elucidate its function. The overall structure of cytochrome c(6A) follows the topology of class I c-type cytochromes in which the heme prosthetic group covalently binds to Cys16 and Cys19, and the iron has octahedral coordination with His20 and Met60 as the axial ligands. Two cysteine residues (Cys67 and Cys73) within the characteristic 12 amino acids loop form a disulfide bond, contributing to the structural stability of cytochrome c(6A). Our model provides a chemical basis for the known low redox potential of cytochrome c(6A) which makes it an unsuitable electron carrier between cytochrome b(6)f and PSI.
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Durán RV, Hervás M, De la Cerda B, De la Rosa MA, Navarro JA. A Laser Flash-Induced Kinetic Analysis of in Vivo Photosystem I Reduction by Site-Directed Mutants of Plastocyanin and Cytochrome c6 in Synechocystis sp. PCC 6803. Biochemistry 2005; 45:1054-60. [PMID: 16411782 DOI: 10.1021/bi052090w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In cyanobacteria, plastocyanin and cytochrome c6 are two soluble metalloproteins which can alternately serve as electron donors to photosystem I. From site-directed mutagenesis studies in vitro, it is well-established that both hydrophobic and electrostatic forces are involved in the interaction between the donor proteins and photosystem I. Hence, two isofunctional areas, a hydrophobic one in the north and an acidic one in the east, have been described on the surface of both electron donors. In this work, we have tested the relevance of such kinds of interactions in the photosystem I reduction inside the cell. Several plastocyanin and cytochrome c6 site-directed mutant strains affecting both the acidic and hydrophobic regions of the two metalloproteins, which were previously characterized in vitro, have been constructed. The photosystem I reduction kinetics of the different mutants have been analyzed by laser flash absorption spectroscopy. Relevant differences have been found between the in vitro and in vivo results, mainly regarding the role played by the electrostatic interactions. Adding positive electrostatic charges to the acidic patch of plastocyanin and cytochrome c6 promotes an enhanced interaction with photosystem I in vitro but yields the opposite effect in vivo. These discrepancies are discussed in view of the different environmental conditions, in vitro and in vivo, for the reaction mechanism of photosystem I reduction, namely, differential interaction of the electron donors with the thylakoidal membrane and kinetics of donor exchange.
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Rochaix JD, Surzycki R, Ramundo S. Tools for regulated gene expression in the chloroplast of Chlamydomonas. Methods Mol Biol 2014; 1132:413-24. [PMID: 24599871 DOI: 10.1007/978-1-62703-995-6_28] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The green unicellular alga Chlamydomonas reinhardtii has emerged as a very attractive model system for chloroplast genetic engineering. Algae can be transformed readily at the chloroplast level through bombardment of cells with a gene gun, and transformants can be selected using antibiotic resistance or phototrophic growth. An inducible chloroplast gene expression system could be very useful for several reasons. First, it could be used to elucidate the function of essential chloroplast genes required for cell growth and survival. Second, it could be very helpful for expressing proteins which are toxic to the algal cells. Third, it would allow for the reversible depletion of photosynthetic complexes thus making it possible to study their biogenesis in a controlled fashion. Fourth, it opens promising possibilities for hydrogen production in Chlamydomonas. Here we describe an inducible/repressible chloroplast gene expression system in Chlamydomonas in which the copper-regulated Cyc6 promoter drives the expression of the nuclear Nac2 gene encoding a protein which is targeted to the chloroplast where it acts specifically on the chloroplast psbD 5'-untranslated region and is required for the stable accumulation of the psbD mRNA and photosystem II. The system can be used for any chloroplast gene or transgene by placing it under the control of the psbD 5'-untranslated region.
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Akazaki H, Kawai F, Chida H, Matsumoto Y, Hirayama M, Hoshikawa K, Unzai S, Hakamata W, Nishio T, Park SY, Oku T. Cloning, expression and purification of cytochrome c(6) from the brown alga Hizikia fusiformis and complete X-ray diffraction analysis of the structure. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:674-80. [PMID: 18678931 PMCID: PMC2494970 DOI: 10.1107/s1744309108017752] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2008] [Accepted: 06/11/2008] [Indexed: 11/10/2022]
Abstract
The primary sequence of cytochrome c(6) from the brown alga Hizikia fusiformis has been determined by cDNA cloning and the crystal structure has been solved at 1.6 A resolution. The crystal belonged to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 84.58, c = 232.91 A and six molecules per asymmetric unit. The genome code, amino-acid sequence and crystal structure of H. fusiformis cytochrome c(6) were most similar to those of red algal cytochrome c(6). These results support the hypothesis that brown algae acquired their chloroplasts via secondary endosymbiosis involving a red algal endosymbiont and a eukaryote host.
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Reyes-Sosa FM, Gil-Martínez J, Molina-Heredia FP. Cytochrome c6-like protein as a putative donor of electrons to photosystem I in the cyanobacterium Nostoc sp. PCC 7119. PHOTOSYNTHESIS RESEARCH 2011; 110:61-72. [PMID: 21984388 DOI: 10.1007/s11120-011-9694-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 09/22/2011] [Indexed: 05/31/2023]
Abstract
Most organisms performing oxygenic photosynthesis contain either cytochrome c(6) or plastocyanin, or both, to transfer electrons from cytochrome b(6)-f to photosystem I. Even though plastocyanin has superseded cytochrome c(6) along evolution, plants contain a modified cytochrome c(6), the so called cytochrome c(6A), whose function still remains unknown. In this article, we describe a second cytochrome c(6) (the so called cytochrome c(6)-like protein), which is found in some cyanobacteria but is phylogenetically more related to plant cytochrome c(6A) than to cyanobacterial cytochrome c(6). In this article, we conclude that the cytochrome c(6)-like protein is a putative electron donor to photosystem I, but does play a role different to that of cytochrome c(6) and plastocyanin as it cannot accept electrons from cytochrome f. The existence of this third electron donor to PSI could explain why some cyanobacteria are able to grow photoautotrophically in the absence of both cytochrome c(6) and plastocyanin. In any way, the Cyt c(6)-like protein from Nostoc sp. PCC 7119 would be potentially utilized for the biohydrogen production, using cell-free photosystem I catalytic nanoparticles.
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Falke S, Feiler C, Chapman H, Sarrou I. Crystal structures of native cytochrome c 6 from Thermosynechococcus elongatus in two different space groups and implications for its oligomerization. Acta Crystallogr F Struct Biol Commun 2020; 76:444-452. [PMID: 32880593 PMCID: PMC7470040 DOI: 10.1107/s2053230x20010249] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 07/23/2020] [Indexed: 11/10/2022] Open
Abstract
Native cytochrome c6 was purified from an extract of strain BP-1 of the thermophilic cyanobacterium Thermosynechococcus elongatus. The protein was crystallized, and with only slight modifications of the buffer and vapour-diffusion conditions two different space groups were observed, namely H3 and C2. Both crystal structures were solved; they contained three and six molecules per asymmetric unit and were refined to 1.7 and 2.25 Å resolution, respectively. To date, the structure of native cytochrome c6 from T. elongatus has only been reported as a monomer using NMR spectroscopy, i.e. without addressing putative oligomerization, and related structures have only previously been solved using X-ray crystallography after recombinant gene overexpression in Escherichia coli. The reported space groups of related cyanobacterial cytochrome c6 structures differ from those reported here. Interestingly, the protein-protein interfaces that were observed utilizing X-ray crystallography could also explain homo-oligomerization in solution; specifically, trimerization is indicated by infra-red dynamic light scattering and blue native gel electrophoresis in solution. Trimers were also detected by mass spectrometry. Furthermore, there is an indication of post-translational methylation in the crystal structure. Additionally, the possibility of modifying the crystal size and the redox activity in the context of photosynthesis is shaping the investigated cytochrome as a highly suitable model protein for advanced serial crystallography at highly brilliant X-ray free-electron laser sources.
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Slater B, Kosmützky D, Nisbet RER, Howe CJ. The Evolution of the Cytochrome c6 Family of Photosynthetic Electron Transfer Proteins. Genome Biol Evol 2021; 13:evab146. [PMID: 34165554 PMCID: PMC8358224 DOI: 10.1093/gbe/evab146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2021] [Indexed: 12/15/2022] Open
Abstract
During photosynthesis, electrons are transferred between the cytochrome b6f complex and photosystem I. This is carried out by the protein plastocyanin in plant chloroplasts, or by either plastocyanin or cytochrome c6 in many cyanobacteria and eukaryotic algal species. There are three further cytochrome c6 homologs: cytochrome c6A in plants and green algae, and cytochromes c6B and c6C in cyanobacteria. The function of these proteins is unknown. Here, we present a comprehensive analysis of the evolutionary relationship between the members of the cytochrome c6 family in photosynthetic organisms. Our phylogenetic analyses show that cytochromes c6B and c6C are likely to be orthologs that arose from a duplication of cytochrome c6, but that there is no evidence for separate origins for cytochromes c6B and c6C. We therefore propose renaming cytochrome c6C as cytochrome c6B. We show that cytochrome c6A is likely to have arisen from cytochrome c6B rather than by an independent duplication of cytochrome c6, and present evidence for an independent origin of a protein with some of the features of cytochrome c6A in peridinin dinoflagellates. We conclude with a new comprehensive model of the evolution of the cytochrome c6 family which is an integral part of understanding the function of the enigmatic cytochrome c6 homologs.
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Yadav SK, Khatri K, Rathore MS, Jha B. Introgression of UfCyt c 6, a thylakoid lumen protein from a green seaweed Ulva fasciata Delile enhanced photosynthesis and growth in tobacco. Mol Biol Rep 2018; 45:1745-1758. [PMID: 30159639 DOI: 10.1007/s11033-018-4318-4311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 08/16/2018] [Indexed: 05/24/2023]
Abstract
Cytochromes are important components of photosynthetic electron transport chain. Here we report on genetic transformation of Cytochrome c6 (UfCyt c6) gene from Ulva fasciata Delile in tobacco for enhanced photosynthesis and growth. UfCyt c6 cDNA had an open reading frame of 330 bp encoding a polypeptide of 109 amino acids with a predicted molecular mass of 11.65 kDa and an isoelectric point of 5.21. UfCyt c6 gene along with a tobacco petE transit peptide sequence under control of CaMV35S promoter was transformed in tobacco through Agrobacterium mediated genetic transformation. Transgenic tobacco grew normal and exhibited enhanced growth as compared to wild type (WT) and vector control (VC) tobacco. Transgenic tobacco had higher contents of photosynthetic pigments and better ratios of photosynthetic pigments. The tobacco expressing UfCyt c6 gene exhibited higher photosynthetic rate and improved water use efficiency. Further activity of the water-splitting complex, photosystem II quantum yield, photochemical quenching, electron transfer rate, and photosynthetic yield were found comparatively higher in transgenic tobacco as compared to WT and VC tobacco. Alternatively basal quantum yield of non-photochemical processes in PSII and non-photochemical quenching were estimated lower in tobacco expressing UfCyt c6 gene. As a result of improved photosynthetic performance the transgenic tobacco had higher contents of sugar and starch, and exhibited comparatively better growth. To the best of our knowledge this is the first report on expression of UfCyt c6 gene from U. fasciata for improved photosynthesis and growth in tobacco.
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Caccamo A, Vega de Luna F, Misztak AE, Pyr dit Ruys S, Vertommen D, Cardol P, Messens J, Remacle C. APX2 Is an Ascorbate Peroxidase-Related Protein that Regulates the Levels of Plastocyanin in Chlamydomonas. PLANT & CELL PHYSIOLOGY 2024; 65:644-656. [PMID: 38591346 PMCID: PMC11094752 DOI: 10.1093/pcp/pcae019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 01/29/2024] [Accepted: 02/19/2024] [Indexed: 04/10/2024]
Abstract
The function of ascorbate peroxidase-related (APX-R) proteins, present in all green photosynthetic eukaryotes, remains unclear. This study focuses on APX-R from Chlamydomonas reinhardtii, namely, ascorbate peroxidase 2 (APX2). We showed that apx2 mutants exhibited a faster oxidation of the photosystem I primary electron donor, P700, upon sudden light increase and a slower re-reduction rate compared to the wild type, pointing to a limitation of plastocyanin. Spectroscopic, proteomic and immunoblot analyses confirmed that the phenotype was a result of lower levels of plastocyanin in the apx2 mutants. The redox state of P700 did not differ between wild type and apx2 mutants when the loss of function in plastocyanin was nutritionally complemented by growing apx2 mutants under copper deficiency. In this case, cytochrome c6 functionally replaces plastocyanin, confirming that lower levels of plastocyanin were the primary defect caused by the absence of APX2. Overall, the results presented here shed light on an unexpected regulation of plastocyanin level under copper-replete conditions, induced by APX2 in Chlamydomonas.
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