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Liu J, Yang J, Bi H, Zhang P. Why mosaic? Gene expression profiling of African cassava mosaic virus-infected cassava reveals the effect of chlorophyll degradation on symptom development. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2014; 56:122-32. [PMID: 24237761 DOI: 10.1111/jipb.12133] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 11/11/2013] [Indexed: 05/18/2023]
Abstract
Cassava mosaic disease, caused by cassava begomoviruses, is the most serious disease for cassava in Africa. However, the pathogenesis of this disease is poorly understood. We employed high throughput digital gene expression profiling based on the Illumina Solexa sequencing technology to investigate the global transcriptional response of cassava to African cassava mosaic virus infection. We found that 3,210 genes were differentially expressed in virus-infected cassava leaves. Gene ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that genes implicated in photosynthesis were most affected, consistent with the chlorotic symptoms observed in infected leaves. The upregulation of chlorophyll degradation genes, including the genes encoding chlorophyllase, pheophytinase, and pheophorbide a oxygenase, and downregulation of genes encoding the major apoproteins in light-harvesting complex II were confirmed by qRT-PCR. These findings, together with the reduction of chlorophyll b content and fewer grana stacks in the infected leaf cells, reveal that the degradation of chlorophyll plays an important role in African cassava mosaic virus symptom development. This study will provide a road map for future investigations into viral pathogenesis.
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Affiliation(s)
- Jiao Liu
- Shanghai Chenshan Plant Science Research Center, the Chinese Academy of Sciences, Chenshan Botanical Garden, Shanghai, 201602, China; National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, the Chinese Academy of Science, Shanghai, 200032, China
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Shpilyov AV, Zinchenko VV, Grimm B, Lokstein H. Chlorophyll a phytylation is required for the stability of photosystems I and II in the cyanobacterium Synechocystis sp. PCC 6803. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:336-346. [PMID: 23039123 DOI: 10.1111/tpj.12044] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 09/28/2012] [Accepted: 10/02/2012] [Indexed: 06/01/2023]
Abstract
In oxygenic phototrophic organisms, the phytyl 'tail' of chlorophyll a is formed from a geranylgeranyl residue by the enzyme geranylgeranyl reductase. Additionally, in oxygenic phototrophs, phytyl residues are the tail moieties of tocopherols and phylloquinone. A mutant of the cyanobacterium Synechocystis sp. PCC 6803 lacking geranylgeranyl reductase, ΔchlP, was compared to strains with specific deficiencies in either tocopherols or phylloquinone to assess the role of chlorophyll a phytylatation (versus geranylgeranylation). The tocopherol-less Δhpt strain grows indistinguishably from the wild-type under 'standard' light photoautotrophic conditions, and exhibited only a slightly enhanced rate of photosystem I degradation under strong irradiation. The phylloquinone-less ΔmenA mutant also grows photoautotrophically, albeit rather slowly and only at low light intensities. Under strong irradiation, ΔmenA retained its chlorophyll content, indicative of stable photosystems. ΔchlP may only be cultured photomixotrophically (due to the instability of both photosystems I and II). The increased accumulation of myxoxanthophyll in ΔchlP cells indicates photo-oxidative stress even under moderate illumination. Under high-light conditions, ΔchlP exhibited rapid degradation of photosystems I and II. In conclusion, the results demonstrate that chlorophyll a phytylation is important for the (photo)stability of photosystems I and II, which, in turn, is necessary for photoautotrophic growth and tolerance of high light in an oxygenic environment.
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Affiliation(s)
- Alexey V Shpilyov
- Biology Division, Genetics Department, Lomonosov Moscow State University, Moscow, 119899, Russia
- Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany
| | - Vladislav V Zinchenko
- Biology Division, Genetics Department, Lomonosov Moscow State University, Moscow, 119899, Russia
| | - Bernhard Grimm
- Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany
| | - Heiko Lokstein
- Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany
- Institut für Biologie III, Albert-Ludwigs-Universität Freiburg, Schänzlestraße 1, D-79104, Freiburg, Germany
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Hoober JK, Eggink LL, Chen M, Larkum AWD. Chapter 15 The Chemistry and Biology of Light-Harvesting Complex II and Thylakoid Biogenesis: raison d’etre of Chlorophylls b and c. ACTA ACUST UNITED AC 2010. [DOI: 10.1007/978-90-481-8531-3_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
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Masuda T. Recent overview of the Mg branch of the tetrapyrrole biosynthesis leading to chlorophylls. PHOTOSYNTHESIS RESEARCH 2008; 96:121-43. [PMID: 18273690 DOI: 10.1007/s11120-008-9291-4] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Accepted: 01/29/2008] [Indexed: 05/20/2023]
Abstract
In plants, chlorophylls (chlorophyll a and chlorophyll b) are the most abundant tetrapyrrole molecules and are essential for photosynthesis. The first committed step of chlorophyll biosynthesis is the insertion of Mg(2+) into protoporphyrin IX, and thus subsequent steps of the biosynthesis are called the Mg branch. As the Mg branch in higher plants is complex, it was not until the last decade--after many years of intensive research--that most of the genes encoding the enzymes for the pathway were identified. Biochemical and molecular genetic analyses have certainly modified the classic metabolic map of tetrapyrrole biosynthesis, and only recently have the molecular mechanisms of regulatory pathways governing chlorophyll metabolism been elucidated. As a result, novel functions of tetrapyrroles and biosynthetic enzymes have been proposed. In this review, I summarize the recent findings on enzymes involved in the Mg branch, mainly in higher plants.
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Affiliation(s)
- Tatsuru Masuda
- Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
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Eggink LL, LoBrutto R, Brune DC, Brusslan J, Yamasato A, Tanaka A, Hoober JK. Synthesis of chlorophyll b: localization of chlorophyllide a oxygenase and discovery of a stable radical in the catalytic subunit. BMC PLANT BIOLOGY 2004; 4:5. [PMID: 15086960 PMCID: PMC406501 DOI: 10.1186/1471-2229-4-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Accepted: 04/15/2004] [Indexed: 05/24/2023]
Abstract
BACKGROUND Assembly of stable light-harvesting complexes (LHCs) in the chloroplast of green algae and plants requires synthesis of chlorophyll (Chl) b, a reaction that involves oxygenation of the 7-methyl group of Chl a to a formyl group. This reaction uses molecular oxygen and is catalyzed by chlorophyllide a oxygenase (CAO). The amino acid sequence of CAO predicts mononuclear iron and Rieske iron-sulfur centers in the protein. The mechanism of synthesis of Chl b and localization of this reaction in the chloroplast are essential steps toward understanding LHC assembly. RESULTS Fluorescence of a CAO-GFP fusion protein, transiently expressed in young pea leaves, was found at the periphery of mature chloroplasts and on thylakoid membranes by confocal fluorescence microscopy. However, when membranes from partially degreened cells of Chlamydomonas reinhardtii cw15 were resolved on sucrose gradients, full-length CAO was detected by immunoblot analysis only on the chloroplast envelope inner membrane. The electron paramagnetic resonance spectrum of CAO included a resonance at g = 4.3, assigned to the predicted mononuclear iron center. Instead of a spectrum of the predicted Rieske iron-sulfur center, a nearly symmetrical, approximately 100 Gauss peak-to-trough signal was observed at g = 2.057, with a sensitivity to temperature characteristic of an iron-sulfur center. A remarkably stable radical in the protein was revealed by an isotropic, 9 Gauss peak-to-trough signal at g = 2.0042. Fragmentation of the protein after incorporation of 125I- identified a conserved tyrosine residue (Tyr-422 in Chlamydomonas and Tyr-518 in Arabidopsis) as the radical species. The radical was quenched by chlorophyll a, an indication that it may be involved in the enzymatic reaction. CONCLUSION CAO was found on the chloroplast envelope and thylakoid membranes in mature chloroplasts but only on the envelope inner membrane in dark-grown C. reinhardtii cells. Such localization provides further support for the envelope membranes as the initial site of Chl b synthesis and assembly of LHCs during chloroplast development. Identification of a tyrosine radical in the protein provides insight into the mechanism of Chl b synthesis.
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Affiliation(s)
- Laura L Eggink
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501, USA
- Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, USA
| | - Russell LoBrutto
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501, USA
- Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, USA
| | - Daniel C Brune
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA
- Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, USA
| | - Judy Brusslan
- Department of Biological Science, California State University, Long Beach, California 90840-3702, USA
| | - Akihiro Yamasato
- The Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
| | - Ayumi Tanaka
- The Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
| | - J Kenneth Hoober
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501, USA
- Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1604, USA
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Xu H, Vavilin D, Vermaas W. Chlorophyll b can serve as the major pigment in functional photosystem II complexes of cyanobacteria. Proc Natl Acad Sci U S A 2001; 98:14168-73. [PMID: 11717469 PMCID: PMC61186 DOI: 10.1073/pnas.251530298] [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: 11/18/2022] Open
Abstract
An Arabidopsis thaliana chlorophyll(ide) a oxygenase gene (cao), which is responsible for chlorophyll b synthesis from chlorophyll a, was introduced and expressed in a photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, most chlorophyll is associated with the photosystem II complex. In line with observations by Satoh et al. [Satoh, S., Ikeuchi, M., Mimuro, M. & Tanaka, A. (2001) J. Biol. Chem. 276, 4293-4297], chlorophyll b was made but accounted for less than 10% of total chlorophyll. However, when lhcb encoding light-harvesting complex (LHC)II from pea was present in the same strain (lhcb(+)/cao(+)), chlorophyll b accumulated in the cell to levels exceeding those of chlorophyll a, although LHCII did not accumulate. In the lhcb(+)/cao(+) strain, the total amount of chlorophyll, the number of chlorophylls per photosystem II center, and the oxygen-evolving activity on a per-chlorophyll basis were similar to those in the photosystem I-less strain. Furthermore, the chlorophyll a/b ratio of photosystem II core particles (retaining CP47 and CP43) and of whole cells of the lhcb(+)/cao(+) strain was essentially identical, and PS II activity could be obtained efficiently by chlorophyll b excitation. These data indicate that chlorophyll b functionally substitutes for chlorophyll a in photosystem II. Therefore, the availability of chlorophylls, rather than their binding specificity, may determine which chlorophyll is incorporated at many positions of photosystem II. We propose that the transient presence of a LHCII/chlorophyll(ide) a oxygenase complex in the lhcb(+)/cao(+) strain leads to a high abundance of available chlorophyll b that is subsequently incorporated into photosystem II complexes. The apparent LHCII requirement for high chlorophyll(ide) a oxygenase activity may be instrumental to limit the occurrence of chlorophyll b in plants to LHC proteins.
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Affiliation(s)
- H Xu
- Department of Plant Biology and Center of the Study of Early Events in Photosynthesis, Arizona State University, Box 871601, Tempe, AZ 85287-1601, USA
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Nakamura A, Tanaka S, Watanabe T. Normal-phase HPLC separation of possible biosynthetic intermediates of pheophytin a and chlorophyll a'. ANAL SCI 2001; 17:509-13. [PMID: 11990567 DOI: 10.2116/analsci.17.509] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Normal-phase HPLC conditions have been developed for separating the C17(3) isoprenoid isomers, which are expected to be formed as biosynthetic intermediates of chlorophyll (Chl) a, Chl a' (C13(2)-epimer of Chl a), pheophytin (Pheo) a and protochlorophyll (PChl). The application of these conditions to pigment composition analysis of greening etiolated barley leaves allowed us to detect, for the first time, the C17(3) isomers of Chl a', a possible constituent of the primary electron donor of photosystem (PS) I, P700, and those of Pheo a, the primary electron acceptor of PS II, in the very early stage of greening. The C17(3) isomer distribution patterns were approximately the same between Chl a and Chl a', but significantly different between Pheo a and Chl a', probably reflecting the similarity and difference, respectively, in the biosynthetic pathways of these pigment pairs.
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Affiliation(s)
- A Nakamura
- Institute of Industrial Science, The University of Tokyo, Komaba, Meguro, Japan.
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Abstract
Chlorophyll (Chl)-containing light-harvesting complexes (LHCs) in chloroplasts of plant and algal cells usually include an oxidized Chl (Chl b or c) in addition to Chl a. Oxidation of peripheral groups on the tetrapyrrole structure increases the Lewis acid strength of the central Mg atom. We propose that the resulting stronger coordination bonds between oxidized Chls and ligands in LHC apoproteins (LHCPs) stabilize the initial intermediates and thus promote assembly of LHCs within the chloroplast envelope.
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Affiliation(s)
- J K Hoober
- Department of Plant Biology and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, AZ 85287-1601, USA.
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Eggink LL, Park H, Hoober JK. The role of chlorophyll b in photosynthesis: hypothesis. BMC PLANT BIOLOGY 2001; 1:2. [PMID: 11710960 PMCID: PMC59834 DOI: 10.1186/1471-2229-1-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2001] [Accepted: 10/17/2001] [Indexed: 05/22/2023]
Abstract
BACKGROUND The physico-chemical properties of chlorophylls b and c have been known for decades. Yet the mechanisms by which these secondary chlorophylls support assembly and accumulation of light-harvesting complexes in vivo have not been resolved. PRESENTATION Biosynthetic modifications that introduce electronegative groups on the periphery of the chlorophyll molecule withdraw electrons from the pyrrole nitrogens and thus reduce their basicity. Consequently, the tendency of the central Mg to form coordination bonds with electron pairs in exogenous ligands, a reflection of its Lewis acid properties, is increased. Our hypothesis states that the stronger coordination bonds between the Mg atom in chlorophyll b and chlorophyll c and amino acid sidechain ligands in chlorophyll a/b- and a/c-binding apoproteins, respectively, enhance their import into the chloroplast and assembly of light-harvesting complexes. TESTING Several apoproteins of light-harvesting complexes, in particular, the major protein Lhcb1, are not detectable in leaves of chlorophyll b-less plants. A direct test of the hypothesis--with positive selection--is expression, in mutant plants that synthesize only chlorophyll a, of forms of Lhcb1 in which weak ligands are replaced with stronger Lewis bases. IMPLICATIONS The mechanistic explanation for the effects of deficiencies in chlorophyll b or c points to the need for further research on manipulation of coordination bonds between these chlorophylls and chlorophyll-binding proteins. Understanding these interactions will possibly lead to engineering plants to expand their light-harvesting antenna and ultimately their productivity.
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Affiliation(s)
- Laura L Eggink
- Department of Plant Biology Center for the Study of Early Events in Photosynthesis Arizona State University Tempe, AZ, USA
| | - Hyoungshin Park
- Department of Plant Biology Center for the Study of Early Events in Photosynthesis Arizona State University Tempe, AZ, USA
- E25-342, Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge, MA, USA
| | - J Kenneth Hoober
- Department of Plant Biology Center for the Study of Early Events in Photosynthesis Arizona State University Tempe, AZ, USA
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Schoefs B, Bertrand M. The formation of chlorophyll from chlorophyllide in leaves containing proplastids is a four-step process. FEBS Lett 2000; 486:243-6. [PMID: 11119711 DOI: 10.1016/s0014-5793(00)02309-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The time course of the different esters of chlorophyllide (Chlide) during the formation of chlorophyll a (Chl) in embryonic bean leaves containing proplastids was investigated by HPLC. After the reduction of photoactive Pchlide (Pchlide) to Chlide, three intermediates, i.e. Chlide geranylgeraniol, Chlide dihydrogeranylgeraniol and Chlide tetrahydrogeranylgeraniol were detected before the formation of Chlide phytol, i.e. authentic Chl. The transformation of Chlide to Chl was found to be much faster in leaves containing proplastids than in etiolated leaves with etioplasts.
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Affiliation(s)
- B Schoefs
- Laboratory of Biomembranes, University of South Bohemia at Ceske Budejovice, Czech Republic
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Eggink LL, Hoober JK. Chlorophyll binding to peptide maquettes containing a retention motif. J Biol Chem 2000; 275:9087-90. [PMID: 10734037 DOI: 10.1074/jbc.275.13.9087] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The motif Glu-X-X-His/Asn-X-Arg is conserved in the first and third membrane-spanning domains of all light-harvesting chlorophyll a/b- and a/c-binding proteins in chloroplasts. Molecular modeling of synthetic peptides containing the sequence Glu-Ile-Val-His-Ser-Arg, a motif found in the apoprotein of the major light-harvesting complex in plants, generated a loop structure formed by intrapeptide, electrostatic attraction between Glu and Arg. His, Asn, and charge-compensated Glu-Arg pairs are known ligands of the magnesium atom in chlorophyll. The prediction that this structure should bind two molecules of chlorophyll was confirmed experimentally with an assay based on fluorescence resonance energy transfer between peptides and chlorophyll a. Motifs with both potential ligands bound approximately two times the amount of chlorophyll as one in which His was replaced by Ala. These results support the conclusion that formation of this intermediate, within membranes of the envelope, is a crucial step in assembly of light-harvesting complexes and a mechanism that regulates import of the apoproteins into the chloroplast.
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Affiliation(s)
- L L Eggink
- Department of Plant Biology and The Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1601, USA
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12
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Nakamura A, Watanabe T. HPLC determination of photosynthetic pigments during greening of etiolated barley leaves. Evidence for the biosynthesis of chlorophyll a'. FEBS Lett 1998; 426:201-4. [PMID: 9599008 DOI: 10.1016/s0014-5793(98)00344-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The temporal evolution of pigment composition during greening of etiolated barley leaves was investigated by reversed-phase HPLC with particular attention to chlorophyll (Chl) a' (C13(2) epimer of Chl a), which had been detected by ourselves in photosystem (PS) I particles. At early stages of greening, the Chl a'/Chl a molar ratio rapidly increased to a level more than twice that in mature leaves, then gradually leveled off, accompanied by a growth of the Chl b/Chl a ratio, to the mature level. After 3 h of illumination, the temporal evolution of the Chl a'/Chl a molar ratio nearly paralleled that of the P700/Chl a ratio with a stoichiometry Chl a'/P700 approximately equal to 2: this strongly suggests that Chl a' is biosynthesized as a constituent of the PS I reaction center complex.
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Affiliation(s)
- A Nakamura
- Institute of Industrial Science, University of Tokyo, Japan.
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Ohtsuka T, Ito H, Tanaka A. Conversion of Chlorophyll b to Chlorophyll a and the Assembly of Chlorophyll with Apoproteins by Isolated Chloroplasts. PLANT PHYSIOLOGY 1997; 113:137-147. [PMID: 12223596 PMCID: PMC158124 DOI: 10.1104/pp.113.1.137] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The photosynthetic apparatus is reorganized during acclimation to various light environments. During adaptation of plants grown under a low-light to high-light environment, the light-harvesting chlorophyll a/b-protein complexes decompose concomitantly with an increase in the core complex of photosystem II. To study the mechanisms for reorganization of photosystems, the assembly of chlorophyll with apoproteins was investigated using isolated chloroplasts. When [14C]chlorophyllide b was incubated with chloroplasts in the presence of phytyl pyrophosphate, it was esterified and some of the [14C]chlorophyll b was converted to [14C]chlorophyll a via 7-hydroxymethyl chlorophyll. [14C]Chlorophyll a and b were incorporated into chlorophyll-protein complexes. Light-harvesting chlorophyll a/b-protein complexes of PSII had a lower [14C]chlorophyll a to [14C]chlorophyll b ratio than P700-chlorophyll a-protein complexes, indicating the specific binding of chlorophyll to apoproteins in our systems. 7-Hydroxymethyl chlorophyll, an intermediate molecule from chlorophyll b to chlorophyll a, did not become assembled with any apoproteins. These results indicate that chlorophyll b is released from light-harvesting chlorophyll a/b-protein complexes of photosystem II and converted to chlorophyll a via 7-hydroxymethyl chlorophyll in the lipid bilayer and is then used for the formation of core complexes of photosystems. These mechanisms provide the fast, fine regulation of the photosynthetic apparatus during construction of photosystems.
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Affiliation(s)
- T. Ohtsuka
- Department of Botany, Faculty of Science, Kyoto University, Kyoto 606-01 Japan
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Komine Y, Park H, Wolfe GR, Hoober J. Secretory granules in the cytoplasm of a wall-less mutant of Chlamydomonas reinhardtii contain processed light-harvesting complex apoproteins and HSP70. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 1996. [DOI: 10.1016/s1011-1344(96)07386-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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White RA, Wolfe GR, Komine Y, Hoober JK. Localization of light-harvesting complex apoproteins in the chloroplast and cytoplasm during greening ofChlamydomonas reinhardtii at 38°C. PHOTOSYNTHESIS RESEARCH 1996; 47:267-280. [PMID: 24301993 DOI: 10.1007/bf02184287] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/1995] [Accepted: 02/26/1996] [Indexed: 06/02/2023]
Abstract
Assembly of the major light-harvesting complex (LHC II) and development of photosynthetic function were examined during the initial phase of thylakoid biogenesis inChlamydomonas reinhardtii cells at 38°C. Continuous monitoring of LHC II fluorescence showed that these processes were initiated immediately upon exposure of cells to light. However, mature-size apoproteins of LHC II (Lhcb) increased in amount in an alkali-soluble (non-membrane) fraction in parallel with the increase in the membrane fraction. Alkali-soluble Lhcb were not integrated into membranes when protein synthesis was inhibited, suggesting that they were not active intermediates in LHC II assembly, nor were they recovered in a purified chloroplast preparation. Immunocytochemical analysis of greening cells revealed Lhcb inside the chloroplast near the envelope and in clusters deeper in the organelle. Antibody binding also detected Lhcb in granules within vacuoles in the cytosol, and Lhcb were recovered in granules purified from greening cells. Our results suggest that the cytosolic granules serve as receptacles of Lhcb synthesized in excess of the amount that can be accommodated by thylakoid membrane formation within the plastid envelope.
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Affiliation(s)
- R A White
- Department of Botany, Arizona State University, 85287-1601, Tempe, AZ, USA
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17
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Plumley GF, Schmidt GW. Light-Harvesting Chlorophyll a/b Complexes: Interdependent Pigment Synthesis and Protein Assembly. THE PLANT CELL 1995; 7:689-704. [PMID: 12242383 PMCID: PMC160816 DOI: 10.1105/tpc.7.6.689] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The biogenetic interdependence of light-harvesting chlorophyll (Chl) a/b proteins (LHCPs) and antenna pigments has been analyzed for two nuclear mutants of Chlamydomonas that have low levels of Chl b, neoxanthin, and loroxanthin. In mutant PA2.1, the apoprotein precursors (pLHCP II) of the major light-harvesting complex LHC II were synthesized at approximately wild-type rates, processed to their mature size, and rapidly degraded. Because the bulk of labile LHCP II in PA2.1 was soluble, a thylakoid integration factor apparently is defective in this strain. Chl a, Chl b, neoxanthin, and loroxanthin synthesis and accumulation were coordinately reduced in PA2.1, indicating that LHCP II play important regulatory or substrate roles in de novo synthesis of these pigments. Mutant GE2.27 is impaired principally in Chl b synthesis but nonetheless accumulated wild-type levels of all LHCPs. Topology studies of the GE2.27 LHCP II demonstrated that their insertion into thylakoids was incomplete even though they were not structurally altered. Thus, Chl b formation mediates conformational changes of LHCP II after thylakoid integration is initiated. GE2.27 also exhibited very low rates of neoxanthin synthesis and was unable to accumulate loroxanthin. Revertant GE2.27 strains with varying capacities for Chl b formation provided additional evidence that neoxanthin synthesis and accumulation are coupled with the final steps of LHCP II integration into thylakoids. We propose that biogenesis of LHC includes interdependent pigment synthesis/assembly events that occur during LHCP integration into the thylakoid membrane and that defects in these events account for the pleiotropic characteristics of many Chl b-deficient mutants.
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Affiliation(s)
- G. F. Plumley
- Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775
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18
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Webber AN, Bingham SE, Lee H. Genetic engineering of thylakoid protein complexes by chloroplast transformation in Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 1995; 44:191-205. [PMID: 24307038 DOI: 10.1007/bf00018309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/1994] [Accepted: 03/01/1995] [Indexed: 06/02/2023]
Abstract
Chloroplast transformation of Chlamydomonas reinhardtii has developed into a powerful tool for studying the structure, function and assembly of thylakoid protein complexes in a eukaryotic organism. In this article we review the progress that is being made in the development of procedures for efficient chloroplast transformation. This focuses on the development of selectable markers and the use of Chlamydomonas mutants, individually lacking thylakoid protein complexes, as recipients. Chloroplast transformation has now been used to engineer all four major thylakoid protein complexes, photosystem II, photosystem I, cytochrome b 6/f and ATP synthase. These results are discussed with an emphasis on new insights into assembly and function of these complexes in chloroplasts as compared with their prokaryotic counterparts.
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Affiliation(s)
- A N Webber
- Department of Botany and Center for the Study of Early Events in Photosynthesis, Arizona State University, Box 871601, 85287-1601, Tempe, AZ, USA
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White RA, Hoober JK. Biogenesis of Thylakoid Membranes in Chlamydomonas reinhardtii y1 (A Kinetic Study of Initial Greening). PLANT PHYSIOLOGY 1994; 106:583-590. [PMID: 12232351 PMCID: PMC159564 DOI: 10.1104/pp.106.2.583] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Initiation of thylakoid membrane assembly was examined in degreened cells of Chlamydomonas reinhardtii y1 cells depleted of thylakoid membranes and photosynthetic activity by growth in the dark for 3 to 4 d. Photoreductive activities of photosystem II (PSII) and photosystem I (PSI) increased with no apparent lag when degreened cells were exposed to light at 38[deg]C. However, fluorescence transients induced by actinic light, which reflect the functional state of PSII, changed only slightly during the first 2 h of greening. When these cells were treated with 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) or saturating light, fluorescence increased commensurate with the cellular content of chlorophyll. In similar experiments with greening cells of C. reinhardtii CC-2341 (ac-u-g-2.3), a PSI-minus strain, fluorescence increased with chlorophyll without treatment with DCMU. These data suggested that fluorescence of initial PSII centers in greening y1 cells was quenched by activity of PSI. Continuous monitoring of fluorescence in the presence or absence of DCMU showed that assembly of quenched PSII centers occurred within seconds after exposure of y1 cells to light. These results are consistent with initial assembly of PSI and PSII within localized domains, where their proximity allows efficient energy coupling.
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Affiliation(s)
- R. A. White
- Department of Botany and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287-1601
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Hoober JK, White RA, Marks DB, Gabriel JL. Biogenesis of thylakoid membranes with emphasis on the process in Chlamydomonas. PHOTOSYNTHESIS RESEARCH 1994; 39:15-31. [PMID: 24310997 DOI: 10.1007/bf00027139] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/1993] [Accepted: 11/10/1993] [Indexed: 06/02/2023]
Abstract
Recent results obtained by electron microscopic and biochemical analyses of greening Chlamydomonas reinhardtii y1 suggest that localized expansion of the plastid envelope is involved in thylakoid biogenesis. Kinetic analyses of the assembly of light-harvesting complexes and development of photosynthetic function when degreened cells of the alga are exposed to light suggest that proteins integrate into membrane at the level of the envelope. Current information, therefore, supports the earlier conclussion that the chloroplast envelope is a major biogenic structure, from which thylakoid membranes emerge. Chloroplast development in Chlamydomonas provides unique opportunities to examine in detail the biogenesis of thylakoids.
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Affiliation(s)
- J K Hoober
- Department of Botany, Arizona State University, 85287-1601, Tempe, AZ, USA
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Cammarata KV, Gerald Plumley F, Schmidt GW. Pigment and protein composition of reconstituted light-harvesting complexes and effects of some protein modifications. PHOTOSYNTHESIS RESEARCH 1992; 33:235-250. [PMID: 24408667 DOI: 10.1007/bf00030034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/1992] [Accepted: 05/13/1992] [Indexed: 06/03/2023]
Abstract
The structure and heterogeneity of LHC II were studied by in vitro reconstitution of apoproteins with pigments (Plumley and Schmidt 1987, Proc Natl Acad Sci 84: 146-150). Reconstituted CP 2 complexes purified by LDS-PAGE were subsequently characterized and shown to have spectroscopic properties and pigment-protein compositions and stoichiometries similar to those of authentic complexes. Heterologous reconstitutions utilizing pigments and light-harvesting proteins from spinach, pea and Chlamydomonas reinhardtii reveal no evidence of specialized binding sites for the unique C. reinhardtii xanthophyll loroxanthin: lutein and loroxanthin are interchangeable for in vitro reconstitution. Proteins modified by the presence of a transit peptide, phosphorylation, or proteolytic removal of the NH2-terminus could be reconstituted. Evidence suggests that post-translational modification are not responsible for the presence of six electrophoretic variants of C. reinhardtii CP 2. Reconstitution is blocked by iodoacetamide pre-treatment of the apoproteins suggesting a role for cysteine in pigment ligation and/or proper folding of the pigment-protein complex. Finally, no effect of divalent cations on pigment reassembly could be detected.
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Affiliation(s)
- K V Cammarata
- Botany Department, University of Georgia, 30602, Athens, Georgia, USA
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Hoober JK, Hughes MJ. Purification and Characterization of a Membrane-Bound Protease from Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 1992; 99:932-7. [PMID: 16669021 PMCID: PMC1080566 DOI: 10.1104/pp.99.3.932] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
In Chlamydomonas reinhardtii y-1, newly synthesized chlorophyll a/b-binding apoproteins are degraded when chlorophylls are not present for assembly of stable light-harvesting complexes. A protease was purified from the membrane fraction of degreened y-1 cells, which digested chlorophyll a/b-binding proteins in membranes from C. reinhardtii pg-113, a protease-deficient strain. This protease was active with p-nitroanilides of nonpolar amino acids (Leu and Phe), but not of basic amino acids (Lys and Arg). The apparent molecular weight of the enzyme is 38,000 +/- 2,000 as determined by electrophoresis in the presence of sodium dodecyl sulfate. Typical inhibitors of the major classes of proteases were ineffective with this enzyme. Protease activity was constant from pH 7.5 to 9; a plot of log V versus pH suggested that deprotonation of an ionizable group with a pK value of 6.0 to 6.5 is required for activity. The protease was inactivated by diethylpyrocarbonate and by photooxidation sensitized by rose bengal. These results suggested that a histidyl residue is required for catalysis. Although very sensitive to photodynamic conditions in vitro, the enzyme was not inactivated in vivo when cells were exposed to light.
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Affiliation(s)
- J K Hoober
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
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Laroche J, Mortain-Bertrand A, Falkowski PG. Light Intensity-Induced Changes in cab mRNA and Light Harvesting Complex II Apoprotein Levels in the Unicellular Chlorophyte Dunaliella tertiolecta. PLANT PHYSIOLOGY 1991; 97:147-53. [PMID: 16668361 PMCID: PMC1080976 DOI: 10.1104/pp.97.1.147] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
During a transition from high growth irradiance (700 micromoles quanta per square meter per second) to low growth irradiance (70 micromoles quanta per square meter per second), the unicellular marine chlorophyte Dunaliella tertiolecta Butcher increases the cellular pool size of the light-harvesting complex of photosystem II (LHC II). We showed that the increase in LHC II apoproteins and in chlorophyll content per cell is preceded by an approximately fourfold increase in cab mRNA. The increase in cab mRNA is detectable within 1.5 hours following a shift from high to low light intensity. An increase in the relative abundance of cab mRNA was also found following a shift from high light to darkness and from high light to low light in the presence of gabaculine, a chlorophyll synthesis inhibitor. However, the LHC II apoproteins did not accumulate in the latter experiments, suggesting that LHC II apoprotein synthesis is coupled to chlorophyll synthesis at or beyond translation. We propose that changes in energy balance brought about by a change in light intensity may control a regulatory factor acting to repress cab mRNA expression in high light.
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Affiliation(s)
- J Laroche
- Oceanographic and Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, New York 11973
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Hoober JK, Boyd CO, Paavola LG. Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38 degrees C. PLANT PHYSIOLOGY 1991; 96:1321-8. [PMID: 16668337 PMCID: PMC1080933 DOI: 10.1104/pp.96.4.1321] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The origin of thylakoid membranes was studied in Chlamydomonas reinhardtii y-1 cells during greening at 38 degrees C. Previous studies showed that, when dark-grown cells are exposed to light under these conditions, the initial rates of accumulation of chlorophyll and the chlorophyll a/b-binding proteins in membranes are maximal (MA Maloney JK Hoober, DB Marks [1989] Plant Physiol 91: 1100-1106; JK Hoober MA Maloney, LR Asbury, DB Marks [1990] Plant Physiol 92: 419-426). As shown in this paper, photosystem II activity, which was nearly absent in dark-grown cells, also increased at a linear rate in parallel with chlorophyll. As compared with those made at 25 degrees C, photosystem II units assembled during greening at 38 degrees C were photochemically more efficient, as judged by saturation at a lower fluence of light and a negligible loss of excitation energy as fluorescence. Electron microscopy of cells in light for 5 or 15 minutes at 38 degrees C showed that these initial, functional thylakoid membranes developed in association with the chloroplast envelope.
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Affiliation(s)
- J K Hoober
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
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Huang L, Hoffman NE. Evidence that Isolated Developing Chloroplasts Are Capable of Synthesizing Chlorophyll b from 5-Aminolevulinic Acid. PLANT PHYSIOLOGY 1990; 94:375-9. [PMID: 16667712 PMCID: PMC1077235 DOI: 10.1104/pp.94.1.375] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Developing chloroplasts isolated from cucumber (Cucumis sativus L. var Beit Alpha) cotyledons are capable of incorporating [(14)C]5-aminolevulinic acid into chlorophyll (Chl) b and Chl a when incubated under photosynthetic illumination. Thin layer chromatography and high pressure liquid chromatography were employed to analyze the pigments. The specific radioactivity in Chl a was over three times higher than that found in Chl b. Both Chl a and b synthesizing activities in organello decayed rapidly at approximately the same rate. We conclude that concomitant synthesis of Chl a/b-binding apoprotein is not required for Chl b synthesis.
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Affiliation(s)
- L Huang
- Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305
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Hoober JK, Maloney MA, Asbury LR, Marks DB. Accumulation of Chlorophyll a/b-Binding Polypeptides in Chlamydomonas reinhardtii y-1 in the Light or Dark at 38 degrees C : Evidence for Proteolytic Control. PLANT PHYSIOLOGY 1990; 92:419-26. [PMID: 16667292 PMCID: PMC1062308 DOI: 10.1104/pp.92.2.419] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The kinetics of accumulation of light harvesting chlorophyll (Chl) a/b-binding polypeptides (LHCPs) in thylakoid membranes were analyzed during greening of Chlamydomonas reinhardtii y-1 at 38 degrees C. Initial accumulation of LHCPs in thylakoid membranes was linear; LHCP precursors or polypeptides in transit within the chloroplast stroma were not detected. The rate of accumulation in the light was at least five-fold greater than that in the dark. The relatively small amount of LHCPs that accumulated in the dark was integrated properly in the membrane, as judged by the pattern of cleavage in vitro by exogenous proteases, and did not turn over at a significant rate in vivo. The kinetic data suggested that in y-1 cells either translation of LHCP mRNA was inhibited in the dark or newly synthesized polypeptides were degraded concurrently with transport into the chloroplast unless rescued by Chl. LHCPs accumulated in cells of the Chl b-deficient strain pg-113 at the same rate in the dark or the light at 38 degrees C, an indication that light did not affect translation of LHCP mRNA. Membrane-associated LHCPs in pg-113 cells were completely degraded, in contrast to those in y-1 cells, by exogenous proteases, which suggested that pg-113 cells are deficient in a proteolytic activity. A peptidase was recovered from y-1 cells in a membrane fraction with a buoyant density slightly less than that of thylakoid membranes. Although a role for this activity in degradation of LHCPs has not been established, the specific activity of this peptidase in pg-113 cells was only 10 to 15% of the level in y-1 cells.
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Affiliation(s)
- J K Hoober
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
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