301
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Shikanai T, Shimizu K, Ueda K, Nishimura Y, Kuroiwa T, Hashimoto T. The chloroplast clpP gene, encoding a proteolytic subunit of ATP-dependent protease, is indispensable for chloroplast development in tobacco. PLANT & CELL PHYSIOLOGY 2001; 42:264-73. [PMID: 11266577 DOI: 10.1093/pcp/pce031] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
ClpP is a proteolytic subunit of the ATP-dependent Clp protease, which is found in chloroplasts in higher plants. Proteolytic subunits are encoded both by the chloroplast gene, clpP, and a nuclear multi gene family. We insertionally disrupted clpP by chloroplast transformation in tobacco. However, complete segregation was impossible, indicating that the chloroplast-encoded clpP gene has an indispensable function for cell survival. In the heteroplasmic clpP disruptant, the leaf surface was rough by clumping, and the lateral leaf expansion was irregularly arrested, which led to an asymmetric, slender leaf shape. Chloroplasts consisted of two populations: chloroplasts that were similar to the wild type, and small chloroplasts that emitted high chl fluorescence. Ultrastructural analysis of chloroplast development suggested that clpP disruption also induced swelling of the thylakoid lumen in the meristem plastids and inhibition of etioplast development in the dark. In mature leaves, thylakoid membranes of the smaller chloroplast population consisted exclusively of large stacks of tightly appressed membranes. These results indicate that chloroplast-encoded ClpP is involved in multiple processes of chloroplast development, including a housekeeping function that is indispensable for cell survival.
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Affiliation(s)
- T Shikanai
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-0101 Japan.
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302
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Sasaki Y, Kozaki A, Ohmori A, Iguchi H, Nagano Y. Chloroplast RNA editing required for functional acetyl-CoA carboxylase in plants. J Biol Chem 2001; 276:3937-40. [PMID: 11078738 DOI: 10.1074/jbc.m008166200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNA editing is an important post-transcriptional process in chloroplasts and is thought to be functionally significant. Here we show a requirement of RNA editing for a functional enzyme. In peas, acetyl-CoA carboxylase (ACCase), a key enzyme of fatty acid synthesis, is composed of biotin carboxylase with the biotin carboxyl carrier protein and carboxyltransferase (CT). CT is composed of the nuclear-encoded alpha polypeptide and the chloroplast-encoded beta polypeptide in peas. One nucleotide of the beta polypeptide mRNA, which is edited in pea chloroplasts, converts the serine codon to the leucine codon. We show that this RNA editing is required for functional CT by comparing the unedited and edited recombinant enzymes. In plants not having a leucine codon at the same position, editing was shown to take place so as to create the leucine codon, indicating that editing is needed for in vivo CT activity and therefore for ACCase. To our knowledge, ACCase is an essential enzyme, suggesting that the chloroplast RNA editing is necessary for these plants.
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Affiliation(s)
- Y Sasaki
- Laboratory of Plant Molecular Biology, Graduate School of Agricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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303
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Bukhov N, Carpentier R, Samson G. Heterogeneity of Photosystem I reaction centers in barley leaves as related to the donation from stromal reductants. PHOTOSYNTHESIS RESEARCH 2001; 70:273-9. [PMID: 16252172 DOI: 10.1023/a:1014741814581] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The light-response curves of P700 oxidation and time-resolved kinetics of P700(+) dark re-reduction were studied in barley leaves using absorbance changes at 820 nm. Leaves were exposed to 45 degrees C and treated with either diuron or diuron plus methyl viologen (MV) to prevent linear electron flow from PS II to PS I and ferredoxin-dependent cyclic electron flow around PS I. Under those conditions, P700(+) could accept electrons solely from soluble stromal reductants. P700 was oxidized under weak far-red light in leaves treated with diuron plus MV, while identical illumination was nearly ineffective in diuron-treated leaves in the absence of MV. When heat-exposed leaves were briefly illuminated with strong far-red light, which completely oxidized P700, the kinetics of P700(+) dark reduction was fitted by a single exponential term with half-time of about 40 ms. However, two first-order kinetic components of electron flow to P700(+) (fast and slow) were found after prolonged leaf irradiation. The light-induced modulation of the kinetics of P700(+) dark reduction was reversed following dark adaptation. The fast component (half time of 80-90 ms) was 1.5 larger than the slow one (half time of about 1 s). No kinetic competition occurred between two pathways of electron donation to P700(+) from stromal reductants. This suggests the presence of two different populations of PS I.
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Affiliation(s)
- N Bukhov
- Groupe de Recherche en Energie et Information Biomoléculaires, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, G9A 5H7, Canada,
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304
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Carol P, Kuntz M. A plastid terminal oxidase comes to light: implications for carotenoid biosynthesis and chlororespiration. TRENDS IN PLANT SCIENCE 2001; 6:31-36. [PMID: 11164375 DOI: 10.1016/s1360-1385(00)01811-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Inactivation of a plastid located quinone-oxygen oxidoreductase gene in the immutans Arabidopsis mutant leads to a photobleached phenotype because of a lack of photoprotective carotenoids. Inactivation of the corresponding gene in the ghost tomato mutant leads to a similar phenotype in leaves and to carotenoid deficiency in petals and ripe fruits. This plastid terminal oxidase (the first to be cloned and biochemically characterized) resembles the mitochondrial cyanide-insensitive alternative oxidase. Here, we propose a model integrating this novel oxidase as a component of an electron transport chain associated to carotenoid desaturation, as well as to a respiratory activity within plastids.
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Affiliation(s)
- P Carol
- Laboratoire de Génétique Moléculaire des Plantes, UMR5575, CNRS, Université Joseph Fourier, BP53X, Grenoble 9, Cedex, France
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305
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Wakasugi T, Tsudzuki T, Sugiura M. The genomics of land plant chloroplasts: Gene content and alteration of genomic information by RNA editing. PHOTOSYNTHESIS RESEARCH 2001; 70:107-18. [PMID: 16228365 DOI: 10.1023/a:1013892009589] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The entire nucleotide sequence of the chloroplast genome has been determined from 12 land plants. The gene content and arrangement are relatively uniform from species to species, and the genome contains an average of 111 identified gene species (except Epifagus). Chloroplast genes can be classified into three main categories: Genes for the photosynthetic apparatus, those for the transcription/translation system, and those related to biosyntheses. The genes encoding components of the photosynthesis apparatus have been identified by protein chemical analyses from higher plants, Chlamydomonas and cyanobacteria, and then by chloroplast transformation techniques using tobacco and Chlamydomonas. The genes for subunits of RNA polymerases and of ribosomes were initially deduced similarity to those in E. coli, and later confirmed by protein analyses. Coding information is often modified at the level of transcripts by RNA editing (mostly C-U changes), resulting in amino acid substitutions and creation of novel reading frames. Perspectives of chloroplast genomics are discussed.
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Affiliation(s)
- T Wakasugi
- Department of Biology, Toyama University, Toyama, 930-8555, Japan
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306
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Mi H, Deng Y, Tanaka Y, Hibino T, Takabe T. Photo-induction of an NADPH dehydrogenase which functions as a mediator of electron transport to the intersystem chain in the cyanobacterium Synechocystis PCC6803. PHOTOSYNTHESIS RESEARCH 2001; 70:167-73. [PMID: 16228350 DOI: 10.1023/a:1017946524199] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Illumination of the dark-incubated cells of Synechocystis PCC6803 caused recovery of both respiratory activity of oxygen uptake and PS I-cyclic electron flow, which was monitored by the dark reduction of P700(+) in the presence of DCMU after a 50 ms pulse light (MT) under background far-red light, but the effects were much smaller in those of the mutant M55, which has an ndh-B defective gene. Activity of an NADPH-NBT oxidoreductase with a higher molecular mass (around 380 kDa), which was only found in wild type but not in M55, became evident after the dark-incubated cells were exposed to the light. Immuno-blotting analysis indicated that the NADPH-NBT oxidoreductase contains the NdhB subunit of NDH. The expression of NdhB decreased in dark-incubated cells and increased upon transfer of the cells back to light. These results indicate that an NADPH-specific NDH participates in the light-regulated cyclic electron transport around Photosystem I as well as in respiratory electron transport to the intersystem chain in Synechocystis 6803.
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Affiliation(s)
- H Mi
- Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China,
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307
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Pieulle L, Guedeney G, Cassier-Chauvat C, Jeanjean R, Chauvat F, Peltier G. The gene encoding the NdhH subunit of type 1 NAD(P)H dehydrogenase is essential to survival of synechocystis PCC6803. FEBS Lett 2000; 487:272-6. [PMID: 11150523 DOI: 10.1016/s0014-5793(00)02369-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The physiological function of the type 1 NAD(P)H dehydrogenase (Ndh-1) of Synechocystis sp. PCC6803 has been investigated by inactivating the gene ndhH encoding a subunit of the complex. Molecular analysis of independent transformants revealed that all clones were heteroploid, containing both wild-type and mutant ndhH copies, whatever the metabolic conditions used during genome segregation, including high CO(2) concentration. By replacing the chromosomal copy of the ndhH gene by a plasmidial copy under the control of a temperature-controlled promoter, we induce a conditional phenotype, growth being only possible at high temperature. This clearly shows for the first time that an ndh gene is indispensable to the survival of Synechocystis sp. PCC6803.
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Affiliation(s)
- L Pieulle
- CEA/Cadarache, DSV-DEVM, Laboratoire d'Ecophysiologie de la Photosynthèse, Saint-Paul-lez-Durance, France
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308
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Abstract
Recent studies have provided new insights into the ways that plants may dissipate excess photons and electrons, thereby protecting the photosynthetic apparatus against light-induced damage. These 'safety valves' include nonphotochemical mechanisms for quenching excited chlorophylls, as well as alternative electron acceptors such as oxygen.
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Affiliation(s)
- K K Niyogi
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA.
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309
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Abstract
The term 'chlororespiration' is used to describe the activity of a putative respiratory electron transler chain within the thylakoid membrane of chloroplasts and was originally proposed by Bennouon in 1982 to explain effects on the redox state of the plastoquinone pool in green algae in the absence of photosynthetic plastoquinone electrontransfer. In his original model, Bennoun suggested that the pool could be reduced through the action of a NAD(P) H dehydrogenase and could be oxidized by oxygen at an oxidase. At the same time an electrochemical gradient would be generated across the membrane. This review describes the current status of the chlororespiration model in light of the recent discoveries of novel respiratory components chloroplast thylakoid membrane.
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Affiliation(s)
- P J Nixon
- Deparlment of Biochemistry, Imperial College of Science, Technology and Medicine, London, UK.
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310
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Cournac L, Josse EM, Joët T, Rumeau D, Redding K, Kuntz M, Peltier G. Flexibility in photosynthetic electron transport: a newly identified chloroplast oxidase involved in chlororespiration. Philos Trans R Soc Lond B Biol Sci 2000; 355:1447-54. [PMID: 11127998 PMCID: PMC1692870 DOI: 10.1098/rstb.2000.0705] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Besides electron transfer reactions involved in the 'Z' scheme of photosynthesis, alternative electron transfer pathways have been characterized in chloroplasts. These include cyclic electron flow around photosystem I (PS I) or a respiratory chain called chlororespiration. Recent work has supplied new information concerning the molecular nature of the electron carriers involved in the non-photochemical reduction of the plastoquinone (PQ) pool. However, until now little is known concerning the nature of the electron carriers involved in PQ oxidation. By using mass spectrometric measurement of oxygen exchange performed in the presence of 18O-enriched O2 and Chlamydomonas mutants deficient in PS I, we show that electrons can be directed to a quinol oxidase sensitive to propyl gallate but insensitive to salicyl hydroxamic acid. This oxidase has immunological and pharmacological similarities with a plastid protein involved in carotenoid biosynthesis.
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Affiliation(s)
- L Cournac
- CEA/Cadarache, DSV, DEVM, Laboratoire d'Ecophysiologie de la Photosynthèse, Saint-Paul-lez-Durance, France.
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311
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Kimata-Ariga Y, Matsumura T, Kada S, Fujimoto H, Fujita Y, Endo T, Mano J, Sato F, Hase T. Differential electron flow around photosystem I by two C(4)-photosynthetic-cell-specific ferredoxins. EMBO J 2000; 19:5041-50. [PMID: 11013207 PMCID: PMC302093 DOI: 10.1038/sj.emboj.7593319] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2000] [Revised: 07/06/2000] [Accepted: 08/03/2000] [Indexed: 11/09/2022] Open
Abstract
In the C(4) plant maize (Zea mays L.), two ferredoxin isoproteins, Fd I and Fd II, are expressed specifically in mesophyll and bundle-sheath cells, respectively. cDNAs for these ferredoxins were introduced separately into the cyanobacterium Plectonema boryanum with a disrupted endogenous ferredoxin gene, yielding TM202 and KM2-9 strains expressing Fd I and Fd II. The growth of TM202 was retarded under high light (130 micromol/m(2)/s), whereas KM2-9 grew at a normal rate but exhibited a nitrogen-deficient phenotype. Measurement of photosynthetic O(2) evolution revealed that the reducing power was not efficiently partitioned into nitrogen assimilation in KM2-9. After starvation of the cells in darkness, the P700 oxidation level under far-red illumination increased significantly in TM202. However, it remained low in KM2-9, indicating an active cyclic electron flow. In accordance with this, the cellular ratio of ATP/ADP increased and that of NADPH/NADP(+) decreased in KM2-9 as compared with TM202. These results demonstrated that the two cell type-specific ferredoxins differentially modulate electron flow around photosystem I.
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Affiliation(s)
- Y Kimata-Ariga
- Division of Enzymology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
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312
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Horváth EM, Peter SO, Joët T, Rumeau D, Cournac L, Horváth GV, Kavanagh TA, Schäfer C, Peltier G, Medgyesy P. Targeted inactivation of the plastid ndhB gene in tobacco results in an enhanced sensitivity of photosynthesis to moderate stomatal closure. PLANT PHYSIOLOGY 2000; 123:1337-50. [PMID: 10938352 PMCID: PMC59092 DOI: 10.1104/pp.123.4.1337] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/1999] [Accepted: 04/17/2000] [Indexed: 05/18/2023]
Abstract
The ndh genes encoding for the subunits of NAD(P)H dehydrogenase complex represent the largest family of plastid genes without a clearly defined function. Tobacco (Nicotiana tabacum) plastid transformants were produced in which the ndhB gene was inactivated by replacing it with a mutant version possessing translational stops in the coding region. Western-blot analysis indicated that no functional NAD(P)H dehydrogenase complex can be assembled in the plastid transformants. Chlorophyll fluorescence measurements showed that dark reduction of the plastoquinone pool by stromal reductants was impaired in ndhB-inactivated plants. Both the phenotype and photosynthetic performance of the plastid transformants was completely normal under favorable conditions. However, an enhanced growth retardation of ndhB-inactivated plants was revealed under humidity stress conditions causing a moderate decline in photosynthesis via stomatal closure. This distinctive phenotype was mimicked under normal humidity by spraying plants with abscisic acid. Measurements of CO(2) fixation demonstrated an enhanced decline in photosynthesis in the mutant plants under humidity stress, which could be restored to wild-type levels by elevating the external CO(2) concentration. These results suggest that the plastid NAD(P)H:plastoquinone oxidoreductase in tobacco performs a significant physiological role by facilitating photosynthesis at moderate CO(2) limitation.
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Affiliation(s)
- E M Horváth
- Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary
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313
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Abstract
Transformation of the plastid genome has a number of inherent advantages for the engineering of gene expression in plants. These advantages include: 10-50 times higher transgene expression levels; the absence of gene silencing and position effect variation; the ability to express polycistronic messages from a single promoter; uniparental plastid gene inheritance in most crop plants that prevents pollen transmission of foreign DNA; integration via a homologous recombination process that facilitates targeted gene replacement and precise transgene control; and sequestration of foreign proteins in the organelle which prevents adverse interactions with the cytoplasmic environment. It is now 12 years since the first conclusive demonstration of stable introduction of cloned DNA into the Chlamydomonas chloroplast by the Boynton and Gillham laboratory, and 10 years since the laboratory of Pal Maliga successfully extended these approaches to tobacco. Since then, technical developments in plastid transformation and advances in our understanding of the rules of plastid gene expression have facilitated tremendous progress towards the goal of establishing the chloroplast as a feasible platform for genetic modification of plants.
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Affiliation(s)
- P B Heifetz
- Novartis Agribusiness Biotechnology Research, Inc., 3054 Cornwallis Road, Research Triangle Park, NC 27709-2257, USA.
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314
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Drescher A, Ruf S, Calsa T, Carrer H, Bock R. The two largest chloroplast genome-encoded open reading frames of higher plants are essential genes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2000; 22:97-104. [PMID: 10792825 DOI: 10.1046/j.1365-313x.2000.00722.x] [Citation(s) in RCA: 250] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The chloroplast genomes of most higher plants contain two giant open reading frames designated ycf1 and ycf2. In tobacco, ycf1 potentially specifies a protein of 1901 amino acids. The putative gene product of the ycf2 reading frame is a protein of 2280 amino acids. In an attempt to determine the functions of ycf1 and ycf2, we have constructed several mutant alleles for targeted disruption and/or deletion of these two reading frames. The mutant alleles were introduced into the tobacco plastid genome by biolistic chloroplast transformation to replace the corresponding wild-type alleles by homologous recombination. Chloroplast transformants were obtained for all constructs and tested for their homoplastomic state. We report here that all transformed lines remained heteroplastomic even after repeated cycles of regeneration under high selective pressure. A balanced selection was observed in the presence of the antibiotic spectinomycin, resulting in maintenance of a fairly constant ratio of wild-type versus transformed genome copies. Upon removal of the antibiotic and therewith release of the selective pressure, sorting out towards the wild-type plastid genome occurred in all transplastomic lines. These findings suggest that ycf1 and ycf2 are functional genes and encode products that are essential for cell survival. The two reading frames are thus the first higher plant chloroplast genes identified as being indispensable.
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Affiliation(s)
- A Drescher
- Institut für Biologie III, Universität Freiburg, Schänzlestrabetae 1, D-79104 Freiburg, Germany
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315
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Casano LM, Zapata JM, Martín M, Sabater B. Chlororespiration and poising of cyclic electron transport. Plastoquinone as electron transporter between thylakoid NADH dehydrogenase and peroxidase. J Biol Chem 2000; 275:942-8. [PMID: 10625631 DOI: 10.1074/jbc.275.2.942] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polypeptides encoded by plastid ndh genes form a complex (Ndh) which could reduce plastoquinone with NADH. Through a terminal oxidase, reduced plastoquinone would be oxidized in chlororespiration. However, isolated Ndh complex has low activity with plastoquinone and no terminal oxidase has been found in chloroplasts, thus the function of Ndh complex is unknown. Alternatively, thylakoid hydroquinone peroxidase could oxidize reduced plastoquinone with H(2)O(2). By immunoaffinity chromatography, we have purified the plastid Ndh complex of barley (Hordeum vulgare L.) to investigate the electron donor and acceptor specificity. A detergent-containing system was reconstructed with thylakoid Ndh complex and peroxidase which oxidized NADH with H(2)O(2) in a plastoquinone-dependent process. This system and the increases of thylakoid Ndh complex and peroxidase activities under photooxidative stress suggest that the chlororespiratory process consists of the sequence of reactions catalyzed by Ndh complex, peroxidase (acting on reduced plastoquinone), superoxide dismutase, and the non-enzymic one-electron transfer from reduced iron-sulfur protein (FeSP) to O(2). When FeSP is a component of cytochrome b(6).f complex or of the same Ndh complex, O(2) may be reduced with NADH, without requirement of light. Chlororespiration consumes reactive species of oxygen and, eventually, may decrease their production by lowering O(2) concentration in chloroplasts. The common plastoquinone pool with photosynthetic electron transport suggests that chlororespiratory reactions may poise reduced and oxidized forms of the intermediates of cyclic electron transport under highly fluctuating light intensities.
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Affiliation(s)
- L M Casano
- Department of Plant Biology, University of Alcalá, Alcalá de Henares, 28871 Madrid, Spain
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316
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Yamane Y, Shikanai T, Kashino Y, Koike H, Satoh K. Reduction of Q(A) in the dark: Another cause of fluorescence F(o) increases by high temperatures in higher plants. PHOTOSYNTHESIS RESEARCH 2000; 63:23-34. [PMID: 16252162 DOI: 10.1023/a:1006350706802] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Increases in the chlorophyll fluorescence F(o) (dark level fluorescence) during heat treatments were studied in various higher plants. Besides the dissociation of light-harvesting chlorophyll a/b protein complexes from the reaction center complex of PS II and inactivation of PS II, dark reduction of Q(A) via plastoquinone (PQ) seemed to be related to the F(o) increase at high temperatures. In potato leaves or green tobacco cultured cells, a part of the F(o) increase was quenched by light, reflecting light-induced oxidation of Q(A) (-) which had been reduced in the dark at high temperatures. Appearance of the F(o) increase due to Q(A) reduction depended on the plant species, and the mechanisms for this are proposed. The reductants seemed to be already present and formed by very brief illumination of the leaves at high temperatures. A ndhB-less mutant of tobacco showed that complex I type NAD(P)H dehydrogenase is not involved in the heat-induced reduction of Q(A). Quite strong inhibition of the Q(A) reduction by diphenyleneiodonium suggests that a flavoenzyme is one of the electron mediator to PQ from the reductant in the stroma. Reversibility of the heat-induced Q(A) reduction suggests that an enzyme(s) involved is activated at high temperatures and mostly returns to an inactive form at room temperature (25 degrees C).
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Affiliation(s)
- Y Yamane
- Department of Life Science, Faculty of Science, Himeji Institute of Technology, Harima Science Garden City, Hyogo, 678-1297, Japan
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317
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Turmel M, Otis C, Lemieux C. The complete chloroplast DNA sequence of the green alga Nephroselmis olivacea: insights into the architecture of ancestral chloroplast genomes. Proc Natl Acad Sci U S A 1999; 96:10248-53. [PMID: 10468594 PMCID: PMC17874 DOI: 10.1073/pnas.96.18.10248] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Green plants seem to form two sister lineages: Chlorophyta, comprising the green algal classes Prasinophyceae, Ulvophyceae, Trebouxiophyceae, and Chlorophyceae, and Streptophyta, comprising the Charophyceae and land plants. We have determined the complete chloroplast DNA (cpDNA) sequence (200,799 bp) of Nephroselmis olivacea, a member of the class (Prasinophyceae) thought to include descendants of the earliest-diverging green algae. The 127 genes identified in this genome represent the largest gene repertoire among the green algal and land plant cpDNAs completely sequenced to date. Of the Nephroselmis genes, 2 (ycf81 and ftsI, a gene involved in peptidoglycan synthesis) have not been identified in any previously investigated cpDNA; 5 genes [ftsW, rnE, ycf62, rnpB, and trnS(cga)] have been found only in cpDNAs of nongreen algae; and 10 others (ndh genes) have been described only in land plant cpDNAs. Nephroselmis and land plant cpDNAs share the same quadripartite structure-which is characterized by the presence of a large rRNA-encoding inverted repeat and two unequal single-copy regions-and very similar sets of genes in corresponding genomic regions. Given that our phylogenetic analyses place Nephroselmis within the Chlorophyta, these structural characteristics were most likely present in the cpDNA of the common ancestor of chlorophytes and streptophytes. Comparative analyses of chloroplast genomes indicate that the typical quadripartite architecture and gene-partitioning pattern of land plant cpDNAs are ancient features that may have been derived from the genome of the cyanobacterial progenitor of chloroplasts. Our phylogenetic data also offer insight into the chlorophyte ancestor of euglenophyte chloroplasts.
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Affiliation(s)
- M Turmel
- Canadian Institute for Advanced Research, Program in Evolutionary Biology and Département de Biochimie, Université Laval, Québec, QC, G1K 7P4, Canada.
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318
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Endo T, Shikanai T, Takabayashi A, Asada K, Sato F. The role of chloroplastic NAD(P)H dehydrogenase in photoprotection. FEBS Lett 1999; 457:5-8. [PMID: 10486552 DOI: 10.1016/s0014-5793(99)00989-8] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
After a brief exposure to supra-saturating light, leaves of a tobacco transformant, in which chloroplastic NAD(P)H dehydrogenase (NDH) was defective, showed more severe photoinhibition than the wild-type, when judged by the parameter of chlorophyll fluorescence Fv/Fm. Repeated application of supra-saturating light eventually resulted in chlorosis in the NDH-defective mutant, while the wild-type sustained less photodamage and was able to recover from it. The mechanism of the phenomena is discussed with respect to the potential role of NDH in photosynthesis.
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Affiliation(s)
- T Endo
- Division of Integrated Life Sciences, Graduate School of Biostudies, Kyoto University, Japan.
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319
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Asada K. THE WATER-WATER CYCLE IN CHLOROPLASTS: Scavenging of Active Oxygens and Dissipation of Excess Photons. ACTA ACUST UNITED AC 1999; 50:601-639. [PMID: 15012221 DOI: 10.1146/annurev.arplant.50.1.601] [Citation(s) in RCA: 1861] [Impact Index Per Article: 74.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Photoreduction of dioxygen in photosystem I (PSI) of chloroplasts generates superoxide radicals as the primary product. In intact chloroplasts, the superoxide and the hydrogen peroxide produced via the disproportionation of superoxide are so rapidly scavenged at the site of their generation that the active oxygens do not inactivate the PSI complex, the stromal enzymes, or the scavenging system itself. The overall reaction for scavenging of active oxygens is the photoreduction of dioxygen to water via superoxide and hydrogen peroxide in PSI by the electrons derived from water in PSII, and the water-water cycle is proposed for these sequences. An overview is given of the molecular mechanism of the water-water cycle and microcompartmentalization of the enzymes participating in it. Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress. The dual functions of the water-water cycle for protection from photoinihibition are discussed.
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Affiliation(s)
- Kozi Asada
- Department of Biotechnology, Faculty of Engineering, Fukuyama University, Gakuen-cho 1, Fukuyama, 729-0292, Japan; e-mail:
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320
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Abstract
The involvement of excited and highly reactive intermediates in oxygenic photosynthesis poses unique problems for algae and plants in terms of potential oxidative damage to the photosynthetic apparatus. Photoprotective processes prevent or minimize generation of oxidizing molecules, scavenge reactive oxygen species efficiently, and repair damage that inevitably occurs. This review summarizes several photoprotective mechanisms operating within chloroplasts of plants and green algae. The recent use of genetic and molecular biological approaches is providing new insights into photoprotection, especially with respect to thermal dissipation of excess absorbed light energy, alternative electron transport pathways, chloroplast antioxidant systems, and repair of photosystem II.
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Affiliation(s)
- Krishna K. Niyogi
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102; e-mail:
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321
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Wu D, Wright DA, Wetzel C, Voytas DF, Rodermel S. The IMMUTANS variegation locus of Arabidopsis defines a mitochondrial alternative oxidase homolog that functions during early chloroplast biogenesis. THE PLANT CELL 1999. [PMID: 9878631 DOI: 10.2307/3870837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Nuclear gene-induced variegation mutants provide a powerful system to dissect interactions between the genetic systems of the nucleus-cytoplasm, the chloroplast, and the mitochondrion. The immutans (im) variegation mutation of Arabidopsis is nuclear and recessive and results in the production of green- and white-sectored leaves. The green sectors contain cells with normal chloroplasts, whereas the white sectors are heteroplastidic and contain cells with abnormal, pigment-deficient plastids as well as some normal chloroplasts. White sector formation can be promoted by enhanced light intensities, but sectoring becomes irreversible early in leaf development. The white sectors accumulate the carotenoid precursor phytoene. We have positionally cloned IM and found that the gene encodes a 40.5-kD protein with sequence motifs characteristic of alternative oxidase, a mitochondrial protein that functions as a terminal oxidase in the respiratory chains of all plants. However, phylogenetic analyses revealed that the IM protein is only distantly related to these other alternative oxidases, suggesting that IM is a novel member of this protein class. We sequenced three alleles of im, and all are predicted to be null. Our data suggest a model of variegation in which the IM protein functions early in chloroplast biogenesis as a component of a redox chain responsible for phytoene desaturation but that a redundant electron transfer function is capable of compensating for IM activity in some plastids and cells.
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Affiliation(s)
- D Wu
- Department of Botany, Iowa State University, Ames, Iowa 50011, USA
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Wu D, Wright DA, Wetzel C, Voytas DF, Rodermel S. The IMMUTANS variegation locus of Arabidopsis defines a mitochondrial alternative oxidase homolog that functions during early chloroplast biogenesis. THE PLANT CELL 1999; 11:43-55. [PMID: 9878631 PMCID: PMC144093 DOI: 10.1105/tpc.11.1.43] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Nuclear gene-induced variegation mutants provide a powerful system to dissect interactions between the genetic systems of the nucleus-cytoplasm, the chloroplast, and the mitochondrion. The immutans (im) variegation mutation of Arabidopsis is nuclear and recessive and results in the production of green- and white-sectored leaves. The green sectors contain cells with normal chloroplasts, whereas the white sectors are heteroplastidic and contain cells with abnormal, pigment-deficient plastids as well as some normal chloroplasts. White sector formation can be promoted by enhanced light intensities, but sectoring becomes irreversible early in leaf development. The white sectors accumulate the carotenoid precursor phytoene. We have positionally cloned IM and found that the gene encodes a 40.5-kD protein with sequence motifs characteristic of alternative oxidase, a mitochondrial protein that functions as a terminal oxidase in the respiratory chains of all plants. However, phylogenetic analyses revealed that the IM protein is only distantly related to these other alternative oxidases, suggesting that IM is a novel member of this protein class. We sequenced three alleles of im, and all are predicted to be null. Our data suggest a model of variegation in which the IM protein functions early in chloroplast biogenesis as a component of a redox chain responsible for phytoene desaturation but that a redundant electron transfer function is capable of compensating for IM activity in some plastids and cells.
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Affiliation(s)
- D Wu
- Department of Botany, Iowa State University, Ames, Iowa 50011, USA
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Shahak Y, Crowther D, Hind G. The involvement of ferredoxin-NADP+ reductase in cyclic electron transport in chloroplasts. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 170:1139-47. [PMID: 7284351 DOI: 10.1016/j.jplph.2013.03.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 03/15/2013] [Accepted: 03/15/2013] [Indexed: 05/16/2023]
Abstract
The sites of action, in spinach thylakoid, of known inhibitors of electron transport at the reducing end of photosystem I have been more accurately located by parallel investigation of effects on three partial reactions: photo-reduction (from water) of added NADP+, photoreduction of added cytochrome c, and dark reduction of cyto-chrome c by added NADPH. Comparison with inhibitory effects on cyclic electron flow (registered by the slow phase of the electrochromic response during repetitive flash excitation) permitted assessment of the role of ferredoxin and ferredoxin-NADP+ reductase (ferredoxin: NADP+ oxidoreductase, EC 1.18.1.3) in the cyclic electron transport pathway around photosystem I. Disulfodisalicylidenepropane-1,1-diamine inhibited all the above partial reactions except the ferredoxin-dependent photoreduction of cytochrome C. thereby indicating its interference with the reductase or the complexation between reductase and ferredoxin. Studies with purified ferredoxin-NADP+ reductase established it as the sensitive component. Cyclic flow is also sensitive to the above inhibitor and thus presumably involves the reductase. Supporting evidence for this came from studies of inhibition by substituted maleimides, which are inhibitors of electron transfer through the isolated reductase; these also inhibited the slow phase of the electrochromic response and all partial reactions except the photoreduction of cytochrome c. In contrast, an antiserum against the reductase affected only reactions involving NADP. The conclusion is drawn that the pathway of cyclic electron transport includes both ferredoxin and ferredoxin-NADP+ reductase, but not the NADP-binding site on the reductase.
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