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Martin Avila E, Gisby MF, Day A. Seamless editing of the chloroplast genome in plants. BMC PLANT BIOLOGY 2016; 16:168. [PMID: 27474038 PMCID: PMC4966725 DOI: 10.1186/s12870-016-0857-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 07/20/2016] [Indexed: 05/13/2023]
Abstract
BACKGROUND Gene editing technologies enable the precise insertion of favourable mutations and performance enhancing trait genes into chromosomes whilst excluding all excess DNA from modified genomes. The technology gives rise to a new class of biotech crops which is likely to have widespread applications in agriculture. Despite progress in the nucleus, the seamless insertions of point mutations and non-selectable foreign genes into the organelle genomes of crops have not been described. The chloroplast genome is an attractive target to improve photosynthesis and crop performance. Current chloroplast genome engineering technologies for introducing point mutations into native chloroplast genes leave DNA scars, such as the target sites for recombination enzymes. Seamless editing methods to modify chloroplast genes need to address reversal of site-directed point mutations by template mediated repair with the vast excess of wild type chloroplast genomes that are present early in the transformation process. RESULTS Using tobacco, we developed an efficient two-step method to edit a chloroplast gene by replacing the wild type sequence with a transient intermediate. This was resolved to the final edited gene by recombination between imperfect direct repeats. Six out of 11 transplastomic plants isolated contained the desired intermediate and at the second step this was resolved to the edited chloroplast gene in five of six plants tested. Maintenance of a single base deletion mutation in an imperfect direct repeat of the native chloroplast rbcL gene showed the limited influence of biased repair back to the wild type sequence. The deletion caused a frameshift, which replaced the five C-terminal amino acids of the Rubisco large subunit with 16 alternative residues resulting in a ~30-fold reduction in its accumulation. We monitored the process in vivo by engineering an overlapping gusA gene downstream of the edited rbcL gene. Translational coupling between the overlapping rbcL and gusA genes resulted in relatively high GUS accumulation (~0.5 % of leaf protein). CONCLUSIONS Editing chloroplast genomes using transient imperfect direct repeats provides an efficient method for introducing point mutations into chloroplast genes. Moreover, we describe the first synthetic operon allowing expression of a downstream overlapping gene by translational coupling in chloroplasts. Overlapping genes provide a new mechanism for co-ordinating the translation of foreign proteins in chloroplasts.
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Affiliation(s)
- Elena Martin Avila
- Faculty of Life Sciences, The University of Manchester, Manchester, M13 9PT UK
- Present address: Research School of Biology, The Australian National University, Acton, ACT 2601 Australia
| | - Martin F. Gisby
- Faculty of Life Sciences, The University of Manchester, Manchester, M13 9PT UK
| | - Anil Day
- Faculty of Life Sciences, The University of Manchester, Manchester, M13 9PT UK
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Scales JC, Parry MAJ, Salvucci ME. A non-radioactive method for measuring Rubisco activase activity in the presence of variable ATP: ADP ratios, including modifications for measuring the activity and activation state of Rubisco. PHOTOSYNTHESIS RESEARCH 2014; 119:355-65. [PMID: 24390640 PMCID: PMC3923112 DOI: 10.1007/s11120-013-9964-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/19/2013] [Indexed: 05/19/2023]
Abstract
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes carboxylation of ribulose-1,5-bisphosphate, the first in a series of reactions leading to the incorporation of atmospheric CO₂ into biomass. Rubisco requires Rubisco activase (RCA), an AAA+ ATPase that reactivates Rubisco by remodelling the conformation of inhibitor-bound sites. RCA is regulated by the ratio of ADP:ATP, with the precise response potentiated by redox regulation of the alpha-isoform. Measuring the effects of ADP on the activation of Rubisco by RCA using the well-established photometric assay is problematic because of the adenine nucleotide requirement of 3-phosphoglycerate (3-PGA) kinase. Described here is a novel assay for measuring RCA activity in the presence of variable ratios of ADP:ATP. The assay couples the formation of 3-PGA from ribulose 1,5-bisphosphate and CO₂ to NADH oxidation through cofactor-dependent phosphoglycerate mutase, enolase, PEP carboxylase and malate dehydrogenase. The assay was used to determine the effects of Rubisco and RCA concentration and ADP:ATP ratio on RCA activity, and to measure the activation of a modified Rubisco by RCA. Variations of the basic assay were used to measure the activation state of Rubisco in leaf extracts and the activity of purified Rubisco. The assay can be automated for high-throughput processing by conducting the reactions in two stages.
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Affiliation(s)
- Joanna C. Scales
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ UK
| | - Martin A. J. Parry
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ UK
| | - Michael E. Salvucci
- Arid-Land Agricultural Research Center, U.S. Department of Agriculture-Agricultural Research Service, 21881 N. Cardon Lane, Maricopa, AZ 85138 USA
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Krech K, Fu HY, Thiele W, Ruf S, Schöttler MA, Bock R. Reverse genetics in complex multigene operons by co-transformation of the plastid genome and its application to the open reading frame previously designated psbN. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:1062-74. [PMID: 23738654 DOI: 10.1111/tpj.12256] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 05/24/2013] [Accepted: 06/03/2013] [Indexed: 05/28/2023]
Abstract
Reverse genetics approaches have contributed enormously to the elucidation of gene functions in plastid genomes and the determination of structure-function relationships in chloroplast multiprotein complexes. Gene knock-outs are usually performed by disrupting the reading frame of interest with a selectable marker cassette. Site-directed mutagenesis is done by placing the marker into the adjacent intergenic spacer and relying on co-integration of the desired mutation by homologous recombination. These strategies are not applicable to genes residing in large multigene operons or other gene-dense genomic regions, because insertion of the marker cassette into an operon-internal gene or into the nearest intergenic spacer is likely to interfere with expression of adjacent genes in the operon or disrupt cis-elements for the expression of neighboring genes and operons. Here we have explored the possibility of using a co-transformation strategy to mutate a small gene of unknown function (psbN) that is embedded in a complex multigene operon. Although inactivation of psbN resulted in strong impairment of photosynthesis, homoplasmic knock-out lines were readily recovered by co-transformation with a selectable marker integrating >38 kb away from the targeted psbN. Our results suggest co-transformation as a suitable strategy for the functional analysis of plastid genes and operons, which allows the recovery of unselected homoplasmic mutants even if the introduced mutations entail a significant selective disadvantage. Moreover, our data provide evidence for involvement of the psbN gene product in the biogenesis of both photosystem I and photosystem II. We therefore propose to rename the gene product 'photosystem biogenesis factor 1' and the gene pbf1.
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Affiliation(s)
- Katharina Krech
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany
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Hanson MR, Gray BN, Ahner BA. Chloroplast transformation for engineering of photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:731-42. [PMID: 23162121 DOI: 10.1093/jxb/ers325] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Many efforts are underway to engineer improvements in photosynthesis to meet the challenges of increasing demands for food and fuel in rapidly changing environmental conditions. Various transgenes have been introduced into either the nuclear or plastid genomes in attempts to increase photosynthetic efficiency. We examine the current knowledge of the critical features that affect levels of expression of plastid transgenes and protein accumulation in transplastomic plants, such as promoters, 5' and 3' untranslated regions, RNA-processing sites, translation signals and amino acid sequences that affect protein turnover. We review the prior attempts to manipulate the properties of ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) through plastid transformation. We illustrate how plastid operons could be created for expression of the multiple genes needed to introduce new pathways or enzymes to enhance photosynthetic rates or reduce photorespiration. We describe here the past accomplishments and future prospects for manipulating plant enzymes and pathways to enhance carbon assimilation through plastid transformation.
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Affiliation(s)
- Maureen R Hanson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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Maliga P, Svab Z. Engineering the plastid genome of Nicotiana sylvestris, a diploid model species for plastid genetics. Methods Mol Biol 2011; 701:37-50. [PMID: 21181523 DOI: 10.1007/978-1-61737-957-4_2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The plastids of higher plants have their own ∼120-160-kb genome that is present in 1,000-10,000 copies per cell. Engineering of the plastid genome (ptDNA) is based on homologous recombination between the plastid genome and cloned ptDNA sequences in the vector. A uniform population of engineered ptDNA is obtained by selection for marker genes encoded in the vectors. Manipulations of ptDNA include (1) insertion of transgenes in intergenic regions; (2) posttransformation excision of marker genes to obtain marker-free plants; (3) gene knockouts and gene knockdowns, and (4) cotransformation with multiple plasmids to introduce nonselected genes without physical linkage to marker genes. Most experiments on plastome engineering have been carried out in the allotetraploid Nicotiana tabacum. We report here for the first time plastid transformation in Nicotiana sylvestris, a diploid ornamental species. We demonstrate that the protocols and vectors developed for plastid transformation in N. tabacum are directly applicable to N. sylvestris with the advantage that the N. sylvestris transplastomic lines are suitable for mutant screens.
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Affiliation(s)
- Pal Maliga
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
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Whitney SM, Kane HJ, Houtz RL, Sharwood RE. Rubisco oligomers composed of linked small and large subunits assemble in tobacco plastids and have higher affinities for CO2 and O2. PLANT PHYSIOLOGY 2009; 149:1887-95. [PMID: 19233903 PMCID: PMC2663749 DOI: 10.1104/pp.109.135210] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2009] [Accepted: 02/15/2009] [Indexed: 05/19/2023]
Abstract
Manipulation of Rubisco within higher plants is complicated by the different genomic locations of the large (L; rbcL) and small (S; RbcS) subunit genes. Although rbcL can be accurately modified by plastome transformation, directed genetic manipulation of the multiple nuclear-encoded RbcS genes is more challenging. Here we demonstrate the viability of linking the S and L subunits of tobacco (Nicotiana tabacum) Rubisco using a flexible 40-amino acid tether. By replacing the rbcL in tobacco plastids with an artificial gene coding for a S40L fusion peptide, we found that the fusions readily assemble into catalytic (S40L)8 and (S40L)16 oligomers that are devoid of unlinked S subunits. While there was little or no change in CO2/O2 specificity or carboxylation rate of the Rubisco oligomers, their Kms for CO2 and O2 were reduced 10% to 20% and 45%, respectively. In young maturing leaves of the plastome transformants (called ANtS40L), the S40L-Rubisco levels were approximately 20% that of wild-type controls despite turnover of the S40L-Rubisco oligomers being only slightly enhanced relative to wild type. The reduced Rubisco content in ANtS40L leaves is partly attributed to problems with folding and assembly of the S40L peptides in tobacco plastids that relegate approximately 30% to 50% of the S40L pool to the insoluble protein fraction. Leaf CO2-assimilation rates in ANtS40L at varying pCO2 corresponded with the kinetics and reduced content of the Rubisco oligomers. This fusion strategy provides a novel platform to begin simultaneously engineering Rubisco L and S subunits in tobacco plastids.
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Affiliation(s)
- Spencer Michael Whitney
- Molecular Plant Physiology, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
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Muto M, Henry RE, Mayfield SP. Accumulation and processing of a recombinant protein designed as a cleavable fusion to the endogenous Rubisco LSU protein in Chlamydomonas chloroplast. BMC Biotechnol 2009; 9:26. [PMID: 19323825 PMCID: PMC2671499 DOI: 10.1186/1472-6750-9-26] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 03/26/2009] [Indexed: 12/04/2022] Open
Abstract
Background Expression of recombinant proteins in green algal chloroplast holds substantial promise as a platform for the production of human therapeutic proteins. A number of proteins have been expressed in the chloroplast of Chlamydomonas reinhardtii, including complex mammalian proteins, but many of these proteins accumulate to significantly lower levels than do endogenous chloroplast proteins. We examined if recombinant protein accumulation could be enhanced by genetically fusing the recombinant reporter protein, luciferase, to the carboxy-terminal end of an abundant endogenous protein, the large subunit of ribulose bisphosphate carboxylase (Rubisco LSU). Additionally, as recombinant proteins fused to endogenous proteins are of little clinical or commercial value, we explored the possibility of engineering our recombinant protein to be cleavable from the endogenous protein in vivo. This strategy would obviate the need for further in vitro processing steps in order to produce the desired recombinant protein. To achieve this, a native protein-processing site from preferredoxin (preFd) was placed between the Rubisco LSU and luciferase coding regions in the fusion protein construct. Results The luciferase from the fusion protein accumulated to significantly higher levels than luciferase expressed alone. By eliminating the endogenous Rubisco large subunit gene (rbcL), we achieved a further increase in luciferase accumulation with respect to luciferase expression in the WT background. Importantly, near-wild type levels of functional Rubisco holoenzyme were generated following the proteolytic removal of the fused luciferase, while luciferase activity for the fusion protein was almost ~33 times greater than luciferase expressed alone. These data demonstrate the utility of using fusion proteins to enhance recombinant protein accumulation in algal chloroplasts, and also show that engineered proteolytic processing sites can be used to liberate the exogenous protein from the endogenous fusion partner, allowing for the purification of the intended mature protein. Conclusion These results demonstrate the utility of fusion proteins in algal chloroplast as a method to increase accumulation of recombinant proteins that are difficult to express. Since Rubisco is ubiquitous to land plants and green algae, this strategy may also be applied to higher plant transgenic expression systems.
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Affiliation(s)
- Machiko Muto
- The Department of Cell Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Pines Rd. La Jolla, CA 92037, USA.
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Craig W, Lenzi P, Scotti N, De Palma M, Saggese P, Carbone V, McGrath Curran N, Magee AM, Medgyesy P, Kavanagh TA, Dix PJ, Grillo S, Cardi T. Transplastomic tobacco plants expressing a fatty acid desaturase gene exhibit altered fatty acid profiles and improved cold tolerance. Transgenic Res 2008; 17:769-82. [PMID: 18214708 DOI: 10.1007/s11248-008-9164-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 01/02/2008] [Indexed: 10/22/2022]
Abstract
The possibility of altering the unsaturation level of fatty acids in plant lipids by genetic transformation has implications for the stress tolerance of higher plants as well as for their nutritional value and industrial utilisation. While the integration and expression of transgenes in the plastome has several potential advantages over nuclear transformation, very few attempts have been made to manipulate fatty acid biosynthesis using plastid transformation. We produced transplastomic tobacco plants that express a Delta(9) desaturase gene from either the wild potato species Solanum commersonii or the cyanobacterium Anacystis nidulans, using PEG-mediated DNA uptake by protoplasts. Incorporation of chloroplast antibiotic-insensitive point mutations in the transforming DNA was used to select transformants. The presence of the transcript and the Delta(9) desaturase protein in transplastomic plants was confirmed by northern and western blot analyses. In comparison with control plants, transplastomic plants showed altered fatty acid profiles and an increase in their unsaturation level both in leaves and seeds. The two transgenes produced comparable results. The results obtained demonstrate the feasibility of using plastid transformation to engineer lipid metabolic pathways in both vegetative and reproductive tissues and suggest an increase of cold tolerance in transplastomic plants showing altered leaf fatty acid profiles. This is the first example of transplastomic plants expressing an agronomically relevant gene produced with the "binding-type" vectors, which do not contain a heterologous marker gene. In fact, the transplastomic plants expressing the S. commersonii gene contain only plant-derived sequences, a clear attraction from a public acceptability perspective.
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Affiliation(s)
- Wendy Craig
- CNR-IGV, Institute of Plant Genetics-Portici, Portici, NA, Italy
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Abstract
Biolistic delivery of DNA initiated plastid transformation research and still is the most widelyused approach to generate transplastomic lines in both algae and higher plants. The principal designof transformation vectors is similar in both phylogenetic groups. Although important additions tothe list of species transformed in their plastomes have been made in algae and in higher plants, thekey organisms in the area are still the two species, in which stable plastid transformation was initiallysuccessful, i.e., Chlamydomonas reinhardtii and tobacco. Basicresearch into organelle biology has substantially benefited from the homologous recombination-basedcapability to precisely insert at predetermined loci, delete, disrupt, or exchange plastid genomesequences. Successful expression of recombinant proteins, including pharmaceutical proteins, hasbeen demonstrated in Chlamydomonas as well as in higher plants,where some interesting agronomic traits were also engineered through plastid transformation.
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Picault N, Cazalé AC, Beyly A, Cuiné S, Carrier P, Luu DT, Forestier C, Peltier G. Chloroplast targeting of phytochelatin synthase in Arabidopsis: effects on heavy metal tolerance and accumulation. Biochimie 2006; 88:1743-50. [PMID: 16766112 DOI: 10.1016/j.biochi.2006.04.016] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Accepted: 04/21/2006] [Indexed: 11/26/2022]
Abstract
The enzymatically synthesized thiol peptide phytochelatin (PC) plays a central role in heavy metal tolerance and detoxification in plants. In response to heavy metal exposure, the constitutively expressed phytochelatin synthase enzyme (PCS) is activated leading to synthesis of PCs in the cytosol. Recent attempts to increase plant metal accumulation and tolerance reported that PCS over-expression in transgenic plants paradoxically induced cadmium hypersensitivity. In the present paper, we investigate the possibility of synthesizing PCs in plastids by over-expressing a plastid targeted phytochelatin synthase (PCS). Plastids represent a relatively important cellular volume and offer the advantage of containing glutathione, the precursor of PC synthesis. Using a constitutive CaMV 35S promoter and a RbcS transit peptide, we successfully addressed AtPCS1 to chloroplasts, significant PCS activity being measured in this compartment in two independent transgenic lines. A substantial increase in the PC content and a decrease in the glutathione pool were observed in response to cadmium exposure, when compared to wild-type plants. While over-expressing AtPCS1 in the cytosol importantly decreased cadmium tolerance, both cadmium tolerance and accumulation of plants expressing plastidial AtPCS1 were not significantly affected compared to wild-type. Interestingly, targeting AtPCS1 to chloroplasts induced a marked sensitivity to arsenic while plants over-expressing AtPCS1 in the cytoplasm were more tolerant to this metalloid. These results are discussed in relation to heavy metal trafficking pathways in higher plants and to the interest of using plastid expression of PCS for biotechnological applications.
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Affiliation(s)
- N Picault
- CEA Cadarache, DSV, DEVM, laboratoire d'écophysiologie de la photosynthèse, UMR 6191 CNRS-CEA, Aix Marseille II, 13108 Saint-Paul-lez-Durance, France
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Shingu Y, Yokomizo S, Kimura M, Ono Y, Yamaguchi I, Hamamoto H. Conferring cadmium resistance to mature tobacco plants through metal-adsorbing particles of tomato mosaic virus vector. PLANT BIOTECHNOLOGY JOURNAL 2006; 4:281-8. [PMID: 17147634 DOI: 10.1111/j.1467-7652.2006.00180.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Tomato mosaic virus vectors were designed that produced, by a translational readthrough, a fusion protein consisting of coat protein and metal-binding peptide, as a result of which particles were expected to present the metal-binding peptides on their surface. When inoculated in plants, they were expected to replicate and form a metal-adsorbing artificial sink in the cytoplasm, so as to reduce metal toxicity. Vectors were constructed harbouring sequences encoding various lengths of polyhistidine as a metal-binding peptide. One of the vectors, TLRT6His, which contains a 6 x histidine sequence, moved systemically in tobacco plants, and its particles were shown to retain cadmium ions by an in vitro assay. When a toxic amount of cadmium was applied, the toxic effect was much reduced in TLRT6His-inoculated tobacco plants, probably as a result of cadmium adsorption by TLRT6His particles in the cytosol. This shows the possible use of an artificial sink for metal tolerance and the advantage of employing a plant viral vector for phytoremediation.
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Affiliation(s)
- Yoshinori Shingu
- Environmental Plant Research Group, RIKEN Plant Science Center, Suehiro-cho 1-7-22, Tsurumi, Yokohama, 230-0045, Japan
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Nugent GD, Ten Have M, van der Gulik A, Dix PJ, Uijtewaal BA, Mordhorst AP. Plastid transformants of tomato selected using mutations affecting ribosome structure. PLANT CELL REPORTS 2005; 24:341-9. [PMID: 15965679 DOI: 10.1007/s00299-005-0930-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Revised: 12/08/2004] [Accepted: 01/01/2005] [Indexed: 05/03/2023]
Abstract
Tomato plastid transformants were obtained using two vectors containing cloned plastid DNA of either Nicotiana tabacum or Solanum nigrum and including point mutations conferring resistance to spectinomycin and streptomycin. Transformants were recovered after PEG-mediated direct DNA uptake into protoplasts, followed by selection on spectinomycin-containing medium. Sixteen lines contained the point mutation, as confirmed by mapping restriction enzyme sites. One line obtained with each vector was analysed in more detail, in comparison with a spontaneous spectinomycin-resistant mutant. Integration of the cloned Solanum or Nicotiana plastid DNA, by multiple recombination events, into the tomato plastome was confirmed by sequence analysis of the targeted region of plastid DNA in the inverted repeat region. Maternal inheritance of spectinomycin and streptomycin resistances or sensitivity in seedlings also confirmed the transplastomic status of the two transformants. The results demonstrate the efficacy in tomato of a selection strategy which avoids the integration of a dominant bacterial antibiotic resistance gene.
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Affiliation(s)
- G D Nugent
- Biology Department, National University of Ireland, Maynooth, County Kildare, Ireland
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Rumeau D, Bécuwe-Linka N, Beyly A, Louwagie M, Garin J, Peltier G. New subunits NDH-M, -N, and -O, encoded by nuclear genes, are essential for plastid Ndh complex functioning in higher plants. THE PLANT CELL 2005; 17:219-32. [PMID: 15608332 PMCID: PMC544500 DOI: 10.1105/tpc.104.028282] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Accepted: 11/09/2004] [Indexed: 05/18/2023]
Abstract
In higher plants, the Ndh complex reduces plastoquinones and is involved in cyclic electron flow around photosystem I, supplying extra-ATP for photosynthesis, particularly under environmental stress conditions. Based on plastid genome sequences, the Ndh complex would contain 11 subunits (NDH-A to -K), but homologies with bacterial complex indicate the probable existence of additional subunits. To identify missing subunits, tobacco (Nicotiana tabacum) NDH-H was His tagged at its N terminus using plastid transformation. A functional Ndh subcomplex was purified by Ni(2+) affinity chromatography and its subunit composition analyzed by mass spectrometry. Five plastid encoded subunits (NDH-A, -H, -I, -J, and -K) were identified as well as three new subunits (NDH-M, -N, and -O) homologous to cyanobacterial and higher plant proteins. Arabidopsis thaliana mutants missing one of these new subunits lack a functional Ndh complex, and NDH-M and NDH-N are not detected in a tobacco transformant lacking the Ndh complex. We discuss the involvement of these three nuclear-encoded subunits in the functional integrity of the plastidial complex.
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Affiliation(s)
- Dominique Rumeau
- Département d'Ecophysiologie Végétale et de Microbiologie, Laboratoire d'Ecophysiologie de la Photosynthèse, Centre National de la Recherche Scientifique, Université de la Méditerranée, Saint-Paul-lez-Durance, France.
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