251
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Gao S, Wang G. The enhancement of cyclic electron flow around photosystem I improves the recovery of severely desiccated Porphyra yezoensis (Bangiales, Rhodophyta). JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:4349-4358. [PMID: 22438301 DOI: 10.1093/jxb/ers082] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Porphyra yezoensis, a representative species of intertidal macro-algae, is able to withstand periodic desiccation at low tide but is submerged in seawater at high tide. In this study, changes in photosynthetic electron flow in P. yezoensis during desiccation and re-hydration were investigated. The results suggested that the cyclic electron flow around photosystem I (PSI) increased significantly during desiccation, continued to operate at times of severe desiccation, and showed greater tolerance to desiccation than the electron flow around PSII. In addition, PSI activity in desiccated blades recovered faster than PSII activity during re-hydration. Even though linear electron flow was suppressed by DCMU [3-(3',4'-dichlorophenyl)-1,1-dimethylurea], cyclic electron flow could still be restored. This process was insensitive to antimycin A and could be suppressed by dibromothymoquinone (DBMIB). The prolonged dark treatment of blades reduced the speed in which the cyclic electron flow around PSI recovered, suggesting that stromal reductants, including NAD(P)H, played an important role in the donation of electrons to PSI and were the main cause of the rapid recovery of cyclic electron flow in desiccated blades during re-hydration. These results suggested that cyclic electron flow in P. yezoensis played a significant physiological role during desiccation and re-hydration and may be one of the most important factors allowing P. yezoensis blades to adapt to intertidal environments.
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Affiliation(s)
- Shan Gao
- Institute of Oceanology, Chinese Academy of Sciences (IOCAS), Qingdao 266071, China
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252
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Control of electron transport routes through redox-regulated redistribution of respiratory complexes. Proc Natl Acad Sci U S A 2012; 109:11431-6. [PMID: 22733774 DOI: 10.1073/pnas.1120960109] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In cyanobacteria, respiratory electron transport takes place in close proximity to photosynthetic electron transport, because the complexes required for both processes are located within the thylakoid membranes. The balance of electron transport routes is crucial for cell physiology, yet the factors that control the predominance of particular pathways are poorly understood. Here we use a combination of tagging with green fluorescent protein and confocal fluorescence microscopy in live cells of the cyanobacterium Synechococcus elongatus PCC 7942 to investigate the distribution on submicron scales of two key respiratory electron donors, type-I NAD(P)H dehydrogenase (NDH-1) and succinate dehydrogenase (SDH). When cells are grown under low light, both complexes are concentrated in discrete patches in the thylakoid membranes, about 100-300 nm in diameter and containing tens to hundreds of complexes. Exposure to moderate light leads to redistribution of both NDH-1 and SDH such that they become evenly distributed within the thylakoid membranes. The effects of electron transport inhibitors indicate that redistribution of respiratory complexes is triggered by changes in the redox state of an electron carrier close to plastoquinone. Redistribution does not depend on de novo protein synthesis, and it is accompanied by a major increase in the probability that respiratory electrons are transferred to photosystem I rather than to a terminal oxidase. These results indicate that the distribution of complexes on the scale of 100-300 nm controls the partitioning of reducing power and that redistribution of electron transport complexes on these scales is a physiological mechanism to regulate the pathways of electron flow.
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253
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Lintala M, Lehtimäki N, Benz JP, Jungfer A, Soll J, Aro EM, Bölter B, Mulo P. Depletion of leaf-type ferredoxin-NADP(+) oxidoreductase results in the permanent induction of photoprotective mechanisms in Arabidopsis chloroplasts. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 70:809-17. [PMID: 22300243 DOI: 10.1111/j.1365-313x.2012.04930.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Arabidopsis thaliana contains two photosynthetically competent chloroplast-targeted ferredoxin-NADP(+) oxidoreductase (FNR) isoforms that are largely redundant in their function. Nevertheless, the FNR isoforms also display distinct molecular phenotypes, as only the FNR1 is able to directly bind to the thylakoid membrane. We report the consequences of depletion of FNR in the F(1) (fnr1 × fnr2) and F(2) (fnr1 fnr2) generation plants of the fnr1 and fnr2 single mutant crossings. The fnr1 × fnr2 plants, with a decreased total content of FNR, showed a small and pale green phenotype, accompanied with a marked downregulation of photosynthetic pigment-protein complexes. Specifically, when compared with the wild type (WT), the quantum yield of photosystem II (PSII) electron transport was lower, non-photochemical quenching (NPQ) was higher and the rate of P700(+) re-reduction was faster in the mutant plants. The slight over-reduction of the plastoquinone pool detected in the mutants resulted in the adjustment of the reactive oxygen species (ROS) scavenging systems, as both the content and de-epoxidation state of xanthophylls, as well as the content of α-tocopherol, were higher in the leaves of the mutant plants when compared with the WT. The fnr1 fnr2 double mutant plants, which had no detectable FNR and possessed an extremely downregulated photosynthetic machinery, survived only when grown heterotrophically in the presence of sucrose. Intriguingly, the fnr1 fnr2 plants were still capable of sustaining the biogenesis of a few malformed chloroplasts.
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Affiliation(s)
- Minna Lintala
- Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku, FI-20014 Turku, Finland
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254
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Porcar-Castell A, Garcia-Plazaola JI, Nichol CJ, Kolari P, Olascoaga B, Kuusinen N, Fernández-Marín B, Pulkkinen M, Juurola E, Nikinmaa E. Physiology of the seasonal relationship between the photochemical reflectance index and photosynthetic light use efficiency. Oecologia 2012; 170:313-23. [DOI: 10.1007/s00442-012-2317-9] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 03/21/2012] [Indexed: 11/24/2022]
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255
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Vu TT, Stolyar SM, Pinchuk GE, Hill EA, Kucek LA, Brown RN, Lipton MS, Osterman A, Fredrickson JK, Konopka AE, Beliaev AS, Reed JL. Genome-scale modeling of light-driven reductant partitioning and carbon fluxes in diazotrophic unicellular cyanobacterium Cyanothece sp. ATCC 51142. PLoS Comput Biol 2012; 8:e1002460. [PMID: 22529767 PMCID: PMC3329150 DOI: 10.1371/journal.pcbi.1002460] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 02/20/2012] [Indexed: 11/22/2022] Open
Abstract
Genome-scale metabolic models have proven useful for answering fundamental questions about metabolic capabilities of a variety of microorganisms, as well as informing their metabolic engineering. However, only a few models are available for oxygenic photosynthetic microorganisms, particularly in cyanobacteria in which photosynthetic and respiratory electron transport chains (ETC) share components. We addressed the complexity of cyanobacterial ETC by developing a genome-scale model for the diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142. The resulting metabolic reconstruction, iCce806, consists of 806 genes associated with 667 metabolic reactions and includes a detailed representation of the ETC and a biomass equation based on experimental measurements. Both computational and experimental approaches were used to investigate light-driven metabolism in Cyanothece sp. ATCC 51142, with a particular focus on reductant production and partitioning within the ETC. The simulation results suggest that growth and metabolic flux distributions are substantially impacted by the relative amounts of light going into the individual photosystems. When growth is limited by the flux through photosystem I, terminal respiratory oxidases are predicted to be an important mechanism for removing excess reductant. Similarly, under photosystem II flux limitation, excess electron carriers must be removed via cyclic electron transport. Furthermore, in silico calculations were in good quantitative agreement with the measured growth rates whereas predictions of reaction usage were qualitatively consistent with protein and mRNA expression data, which we used to further improve the resolution of intracellular flux values. Cyanobacteria have been promoted as platforms for biofuel production due to their useful physiological properties such as photosynthesis, relatively rapid growth rates, ability to accumulate high amounts of intracellular compounds and tolerance to extreme environments. However, development of a computational model is an important step to synthesize biochemical, physiological and regulatory understanding of photoautotrophic metabolism (either qualitatively or quantitatively) at a systems level, to make metabolic engineering of these organisms tractable. When integrated with other genome-scale data (e.g., expression data), numerical simulations can provide experimentally testable predictions of carbon fluxes and reductant partitioning to different biosynthetic pathways and macromolecular synthesis. This work is the first to computationally explore the interactions between components of photosynthetic and respiratory systems in detail. In silico predictions obtained from model analysis provided insights into the effects of light quantity and quality upon fluxes through electron transport pathways, alternative pathways for reductant consumption and carbon metabolism. The model will not only serve as a platform to develop genome-scale metabolic models for other cyanobacteria, but also as an engineering tool for manipulation of photosynthetic microorganisms to improve biofuel production.
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Affiliation(s)
- Trang T. Vu
- Department of Chemical and Biological Engineering, University of Wisconsin- Madison, Madison, Wisconsin, United States of America
| | - Sergey M. Stolyar
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Grigoriy E. Pinchuk
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Eric A. Hill
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Leo A. Kucek
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Roslyn N. Brown
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Mary S. Lipton
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Andrei Osterman
- Burnham Institute for Medical Research, La Jolla, California, United States of America
| | - Jim K. Fredrickson
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Allan E. Konopka
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Alexander S. Beliaev
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
- * E-mail: (ASB); (JLR)
| | - Jennifer L. Reed
- Department of Chemical and Biological Engineering, University of Wisconsin- Madison, Madison, Wisconsin, United States of America
- * E-mail: (ASB); (JLR)
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256
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Nevo R, Charuvi D, Tsabari O, Reich Z. Composition, architecture and dynamics of the photosynthetic apparatus in higher plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 70:157-76. [PMID: 22449050 DOI: 10.1111/j.1365-313x.2011.04876.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The process of oxygenic photosynthesis enabled and still sustains aerobic life on Earth. The most elaborate form of the apparatus that carries out the primary steps of this vital process is the one present in higher plants. Here, we review the overall composition and supramolecular organization of this apparatus, as well as the complex architecture of the lamellar system within which it is harbored. Along the way, we refer to the genetic, biochemical, spectroscopic and, in particular, microscopic studies that have been employed to elucidate the structure and working of this remarkable molecular energy conversion device. As an example of the highly dynamic nature of the apparatus, we discuss the molecular and structural events that enable it to maintain high photosynthetic yields under fluctuating light conditions. We conclude the review with a summary of the hypotheses made over the years about the driving forces that underlie the partition of the lamellar system of higher plants and certain green algae into appressed and non-appressed membrane domains and the segregation of the photosynthetic protein complexes within these domains.
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Affiliation(s)
- Reinat Nevo
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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257
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The mechanism of photoinhibition in vivo: re-evaluation of the roles of catalase, α-tocopherol, non-photochemical quenching, and electron transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1127-33. [PMID: 22387427 DOI: 10.1016/j.bbabio.2012.02.020] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 02/11/2012] [Accepted: 02/17/2012] [Indexed: 11/24/2022]
Abstract
Photoinhibition of photosystem II (PSII) occurs when the rate of light-induced inactivation (photodamage) of PSII exceeds the rate of repair of the photodamaged PSII. For the quantitative analysis of the mechanism of photoinhibition of PSII, it is essential to monitor the rate of photodamage and the rate of repair separately and, also, to examine the respective effects of various perturbations on the two processes. This strategy has allowed the re-evaluation of the results of previous studies of photoinhibition and has provided insight into the roles of factors and mechanisms that protect PSII from photoinhibition, such as catalases and peroxidases, which are efficient scavengers of H(2)O(2); α-tocopherol, which is an efficient scavenger of singlet oxygen; non-photochemical quenching, which dissipates excess light energy that has been absorbed by PSII; and the cyclic and non-cyclic transport of electrons. Early studies of photoinhibition suggested that all of these factors and mechanisms protect PSII against photodamage. However, re-evaluation by the strategy mentioned above has indicated that, rather than protecting PSII from photodamage, they stimulate protein synthesis, with resultant repair of PSII and mitigation of photoinhibition. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
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258
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259
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Foyer CH, Neukermans J, Queval G, Noctor G, Harbinson J. Photosynthetic control of electron transport and the regulation of gene expression. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1637-61. [PMID: 22371324 DOI: 10.1093/jxb/ers013] [Citation(s) in RCA: 264] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The term 'photosynthetic control' describes the short- and long-term mechanisms that regulate reactions in the photosynthetic electron transport (PET) chain so that the rate of production of ATP and NADPH is coordinated with the rate of their utilization in metabolism. At low irradiances these mechanisms serve to optimize light use efficiency, while at high irradiances they operate to dissipate excess excitation energy as heat. Similarly, the production of ATP and NADPH in ratios tailored to meet demand is finely tuned by a sophisticated series of controls that prevents the accumulation of high NAD(P)H/NAD(P) ratios and ATP/ADP ratios that would lead to potentially harmful over-reduction and inactivation of PET chain components. In recent years, photosynthetic control has also been extrapolated to the regulation of gene expression because mechanisms that are identical or similar to those that serve to regulate electron flow through the PET chain also coordinate the regulated expression of genes encoding photosynthetic proteins. This requires coordinated gene expression in the chloroplasts, mitochondria, and nuclei, involving complex networks of forward and retrograde signalling pathways. Photosynthetic control operates to control photosynthetic gene expression in response to environmental and metabolic changes. Mining literature data on transcriptome profiles of C(3) and C(4) leaves from plants grown under high atmospheric carbon dioxide (CO(2)) levels compared with those grown with ambient CO(2) reveals that the transition to higher photorespiratory conditions in C(3) plants enhances the expression of genes associated with cyclic electron flow pathways in Arabidopsis thaliana, consistent with the higher ATP requirement (relative to NADPH) of photorespiration.
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Affiliation(s)
- Christine H Foyer
- Centre for Plant Sciences, Faculty of Biology, University of Leeds, Leeds LS2 9JT, UK.
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260
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Eugeni Piller L, Abraham M, Dörmann P, Kessler F, Besagni C. Plastid lipid droplets at the crossroads of prenylquinone metabolism. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1609-18. [PMID: 22371323 DOI: 10.1093/jxb/ers016] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Lipid droplets called plastoglobules (PGs) exist in most plant tissues and plastid types. In chloroplasts, the polar lipid monolayer surrounding these low-density lipoprotein particles is continuous with the outer lipid leaflet of the thylakoid membrane. Often small clusters of two or three PGs, only one of them directly connected to thylakoids, are present. Structural proteins (known as plastid-lipid associated proteins/fibrillins or plastoglobulins) together with lipid metabolic enzymes coat the PGs. The hydrophobic core of PGs contains a range of neutral lipids including the prenylquinones [tocopherols (vitamin E), phylloquinone (vitamin K(1)), and plastoquinone (PQ-9)]. In this review the function of PGs and their associated enzymes in prenylquinone metabolism will be discussed.
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Affiliation(s)
- Lucia Eugeni Piller
- Laboratoire de Physiologie Végétale, Université de Neuchâtel, 2000 Neuchâtel, Switzerland
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261
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Peng L, Fukao Y, Fujiwara M, Shikanai T. Multistep assembly of chloroplast NADH dehydrogenase-like subcomplex A requires several nucleus-encoded proteins, including CRR41 and CRR42, in Arabidopsis. THE PLANT CELL 2012; 24:202-14. [PMID: 22274627 PMCID: PMC3289569 DOI: 10.1105/tpc.111.090597] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Chloroplast NADH dehydrogenase-like complex (NDH) mediates photosystem I cyclic electron transport and chlororespiration in thylakoids. Recently, substantial progress has been made in understanding the structure of NDH, but our knowledge of its assembly has been limited. In this study, a series of interactive proteomic analyses identified several stroma-localized factors required for the assembly of a stroma-protruding arm of NDH (subcomplex A). In addition to further characterization of the previously identified CHLORORESPIRATORY REDUCTION1 (CRR1), CRR6, and CRR7, two novel stromal proteins, CRR41 and CRR42, were discovered. Arabidopsis thaliana mutants lacking these proteins are specifically defective in the accumulation of subcomplex A. A total of 10 mutants lacking subcomplex A, including crr27/cpn60β4, which is specifically defective in the folding of NdhH, and four mutants lacking NdhL-NdhO subunits, were extensively characterized. We propose a model for subcomplex A assembly: CRR41, NdhO, and native NdhH, as well as unknown factors, are first assembled to form an NDH subcomplex A assembly intermediate (NAI500). Subsequently, NdhJ, NdhM, NdhK, and NdhI are incorporated into NAI500 to form NAI400. CRR1, CRR6, and CRR42 are involved in this process. CRR7 is likely to be involved in the final step, in which the fully assembled NAI, including NdhN, is inserted into thylakoids.
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Affiliation(s)
- Lianwei Peng
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yoichiro Fukao
- Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama, Ikoma, Nara 630-0101, Japan
| | - Masayuki Fujiwara
- Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama, Ikoma, Nara 630-0101, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Address correspondence to
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262
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Roose JL, Frankel LK, Bricker TM. Developmental defects in mutants of the PsbP domain protein 5 in Arabidopsis thaliana. PLoS One 2011; 6:e28624. [PMID: 22174848 PMCID: PMC3235149 DOI: 10.1371/journal.pone.0028624] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 11/11/2011] [Indexed: 11/25/2022] Open
Abstract
Plants contain an extensive family of PsbP-related proteins termed PsbP-like (PPL) and PsbP domain (PPD) proteins, which are localized to the thylakoid lumen. The founding member of this family, PsbP, is an established component of the Photosystem II (PS II) enzyme, and the PPL proteins have also been functionally linked to other photosynthetic processes. However, the functions of the remaining seven PPD proteins are unknown. To elucidate the function of the PPD5 protein (At5g11450) in Arabidopsis, we have characterized a mutant T-DNA insertion line (SALK_061118) as well as several RNAi lines designed to suppress the expression of this gene. The functions of the photosynthetic electron transfer reactions are largely unaltered in the ppd5 mutants, except for a modest though significant decrease in NADPH dehydrogenase (NDH) activity. Interestingly, these mutants show striking plant developmental and morphological defects. Relative to the wild-type Col-0 plants, the ppd5 mutants exhibit both increased lateral root branching and defects associated with axillary bud formation. These defects include the formation of additional rosettes originating from axils at the base of the plant as well as aerial rosettes formed at the axils of the first few nodes of the shoot. The root-branching phenotype is chemically complemented by treatment with the synthetic strigolactone, GR24. We propose that the developmental defects observed in the ppd5 mutants are related to a deficiency in strigolactone biosynthesis.
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Affiliation(s)
- Johnna L Roose
- Department of Biological Sciences, Biochemistry and Molecular Biology Section, Louisiana State University, Baton Rouge, Louisiana, United States of America.
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263
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Yamori W, Sakata N, Suzuki Y, Shikanai T, Makino A. Cyclic electron flow around photosystem I via chloroplast NAD(P)H dehydrogenase (NDH) complex performs a significant physiological role during photosynthesis and plant growth at low temperature in rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:966-76. [PMID: 21848656 DOI: 10.1111/j.1365-313x.2011.04747.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The role of NAD(P)H dehydrogenase (NDH)-dependent cyclic electron flow around photosystem I in photosynthetic regulation and plant growth at several temperatures was examined in rice (Oryza sativa) that is defective in CHLORORESPIRATORY REDUCTION 6 (CRR6), which is required for accumulation of sub-complex A of the chloroplast NDH complex (crr6). NdhK was not detected by Western blot analysis in crr6 mutants, resulting in lack of a transient post-illumination increase in chlorophyll fluorescence, and confirming that crr6 mutants lack NDH activity. When plants were grown at 28 or 35°C, all examined photosynthetic parameters, including the CO(2) assimilation rate and the electron transport rate around photosystems I and II, at each growth temperature at light intensities above growth light (i.e. 800 μmol photons m(-2) sec(-1)), were similar between crr6 mutants and control plants. However, when plants were grown at 20°C, all the examined photosynthetic parameters were significantly lower in crr6 mutants than control plants, and this effect on photosynthesis caused a corresponding reduction in plant biomass. The F(v)/F(m) ratio was only slightly lower in crr6 mutants than in control plants after short-term strong light treatment at 20°C. However, after long-term acclimation to the low temperature, impairment of cyclic electron flow suppressed non-photochemical quenching and promoted reduction of the plastoquinone pool in crr6 mutants. Taken together, our experiments show that NDH-dependent cyclic electron flow plays a significant physiological role in rice during photosynthesis and plant growth at low temperature.
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Affiliation(s)
- Wataru Yamori
- Department of Applied Plant Science, Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.
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264
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Adamski JM, Peters JA, Danieloski R, Bacarin MA. Excess iron-induced changes in the photosynthetic characteristics of sweet potato. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:2056-62. [PMID: 21752489 DOI: 10.1016/j.jplph.2011.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 05/18/2011] [Accepted: 06/14/2011] [Indexed: 05/13/2023]
Abstract
Iron (Fe) is an essential nutrient for plant growth and development. In plant tissues, approximately 80% of Fe is found in photosynthetic cells. This study was carried out to determine the effect of different iron concentrations on the photosynthetic characteristics of sweet potato plants. The fluorescence transient of chlorophyll a (OJIP), chlorophyll index and gas exchange were measured in plants grown for seven days in Hoagland solution containing an iron concentration of 0.45, 0.90, 4.50 or 9.00 mM Fe (as Fe-EDTA). The initial and maximum fluorescence increased in the plants receiving 9.00 mM Fe. In the analysis of the fluorescence kinetic difference, L- and K-bands appeared in all of the treatments, but the amplitude was higher in plants receiving 4.50 or 9.00 mM Fe. In plants grown in 9.00 mM Fe, the parameters of the JIP-Test indicated a better efficiency in the capture, absorption and use of light energy, and although the chlorophyll index was higher, the net photosynthesis was lower. The overall data showed that sweet potato plants subjected to high iron concentrations may not exhibit the toxicity symptoms, but the light reactions of photosynthesis can be affect, which may result in a declining net assimilation rate.
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Affiliation(s)
- Janete M Adamski
- Laboratório de Cultura de Células e Tecidos Vegetais, UFPel, Instituto de Biologia, Depto. Botânica, Campus Universitário S/N., CEP 96160-000, Capão do Leão, RS, Brazil
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265
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Yoshida K, Watanabe CK, Terashima I, Noguchi K. Physiological impact of mitochondrial alternative oxidase on photosynthesis and growth in Arabidopsis thaliana. PLANT, CELL & ENVIRONMENT 2011; 34:1890-9. [PMID: 21707657 DOI: 10.1111/j.1365-3040.2011.02384.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The mitochondrial alternative oxidase (AOX) has been suggested to have a beneficial role in illuminated leaves, but its function has not yet been fully elucidated. In this study, we investigated the effects of a knockout of the AOX1a gene on photosynthesis and growth under several light conditions in Arabidopsis thaliana. The AOX-deficient aox1a mutant showed a lowered operating efficiency of photosystem II and an enhanced activity of cyclic electron transport around photosystem I (CET-PSI) at high irradiance. To further address the physiological association of AOX with CET-PSI, we crossed aox1a with the pgr5 mutant, which is impaired in CET-PSI activity. In the pgr5 mutant background, AOX deficiency did not affect the apparent photosynthetic efficiency, indicating that the direct contribution of AOX to photosynthesis is not so large compared with CET-PSI. Nevertheless, the growth of the aox1a pgr5 double mutant was significantly impaired depending on the light intensity under growth conditions. The possibility of a synergistic function of AOX with CET-PSI in supporting plant growth is discussed.
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Affiliation(s)
- Keisuke Yoshida
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
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266
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Wu Y, Zheng F, Ma W, Han Z, Gu Q, Shen Y, Mi H. Regulation of NAD(P)H dehydrogenase-dependent cyclic electron transport around PSI by NaHSO₃ at low concentrations in tobacco chloroplasts. PLANT & CELL PHYSIOLOGY 2011; 52:1734-43. [PMID: 21828103 DOI: 10.1093/pcp/pcr109] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Although bisulfite at low concentrations (L-NaHSO₃) has been found to increase the cyclic electron transport around PSI (CET), its regulative mechanism remains unknown. In this work, the role of L-NaHSO₃ (0.1-500 μM) in NAD(P)H dehydrogenase-dependent CET (the NDH pathway) was investigated. After treatment of tobacco leaves with L-NaHSO₃, the NDH pathway, as reflected by a transient post-illumination increase in Chl fluorescence, the dark reduction of P700+ after far-red light and the amount of NDH, was increased after the light-dark-light transition, but was slightly lowered under continuous light. Meanwhile, the linear electron transport (LET) was accelerated by L-NaHSO₃ under both the light regimes. Experiments in thylakoids further demonstrated that both LET, monitored by light-dependent oxygen uptake, and CET, as determined from the NADPH-dependent oxygen uptake and dark reduction of P700+, were enhanced by L-NaHSO₃ and the enhancements were abolished by superoxide dismutase. Furthermore, L-NaHSO₃-induced CET was partially impaired in thylakoids of the ΔndhCKJ mutant, while L-NaHSO₃-induced LET was not affected. Based on these results, we propose that the photooxidation of L-NaHSO₃ initiated by superoxide anions in PSI regulates NDH pathway to maintain efficient photosynthesis.
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Affiliation(s)
- Yanxia Wu
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, PR China
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267
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Bolychevtseva YV, Elanskaya IV, Karapetyan NV. Regulation of cyclic electron transport through photosystem I in cyanobacterium Synechocystis sp. PCC 6803 mutants deficient in respiratory dehydrogenases. BIOCHEMISTRY (MOSCOW) 2011; 76:427-37. [PMID: 21585318 DOI: 10.1134/s0006297911040055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The rate of PSI mediated cyclic electron transport was studied in wild type and mutant cells of Synechocystis sp. PCC 6803 deficient in NDH-1 (M55) or succinate dehydrogenase (SDH(-)) that are responsible for the dark reduction of the plastoquinone pool. Kinetics of P700 photooxidation and P700(+) dark reduction in the presence of 5·10(-5) M 3-(3,4-dichlorophenyl)-1,1-dimethylurea have been registered as light induced absorbance changes at 810 nm resulting from illumination of cells with 730-nm actinic light for 1 sec. It is shown that in the absence of dehydrogenases the rate of dark reduction of P700(+) in both mutants did not decrease but even increased in NDH-1-less mutant cells as compared with the rate in wild type cells. Dibromothymoquinone drastically reduced the rate of P700(+) dark reduction both in wild type and in mutant cells. Thus, the cyclic electron transfer from ferredoxin through the plastoquinone pool to P700(+), which is independent from dehydrogenases, takes place in all the types of cells. Preillumination of cells of wild type and both mutants for 30 min or anaerobic conditions resulted in delay of P700 photooxidation and acceleration of P700(+) dark reduction, while the level of photosynthesis and respiration terminal acceptors (NAD(P)(+) and oxygen) decreased. It appears that the rate of P700 photooxidation and P700(+) dark reduction in cyclic electron transport in Synechocystis wild type and mutant cells is determined by the level of NADP+ and oxygen in stroma. A possible approach to evaluation of the levels of these acceptors in vivo is proposed, based on kinetic curve parameters of P700 photoconversions induced by 730-nm light with 1-sec duration.
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Affiliation(s)
- Yu V Bolychevtseva
- Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia.
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268
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Higuchi-Takeuchi M, Ichikawa T, Kondou Y, Matsui K, Hasegawa Y, Kawashima M, Sonoike K, Mori M, Hirochika H, Matsui M. Functional analysis of two isoforms of leaf-type ferredoxin-NADP(+)-oxidoreductase in rice using the heterologous expression system of Arabidopsis. PLANT PHYSIOLOGY 2011; 157:96-108. [PMID: 21734114 PMCID: PMC3165901 DOI: 10.1104/pp.111.181248] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Ferredoxin-NADP(+)-oxidoreductase (FNR) mediates electron transfer between ferredoxin (Fd) and NADP(+); therefore, it is a key enzyme that provides the reducing power used in the Calvin cycle. Other than FNR, nitrite reductase, sulfite reductase, glutamate synthase, and Fd-thioredoxin reductase also accept electrons from Fd, an electron carrier protein in the stroma. Therefore, the regulation of electron partitioning in the chloroplast is important for photosynthesis and other metabolic pathways. The regulatory mechanism of electron partitioning, however, remains to be elucidated. We found, by taking advantage of a gain-of-function approach, that expression of two rice (Oryza sativa) full-length cDNAs of leaf-type FNRs (OsLFNR1 and OsLFNR2) led to altered chlorophyll fluorescence and growth in Arabidopsis (Arabidopsis thaliana) and rice. We revealed that overexpression of the OsLFNR1 and OsLFNR2 full-length cDNAs resulted in distinct phenotypes despite the high sequence similarity between them. Expression of OsLFNR1 affected the nitrogen assimilation pathway without inhibition of photosynthesis under normal conditions. On the other hand, OsLFNR2 expression led to the impairment of photosynthetic linear electron transport as well as Fd-dependent cyclic electron flow around photosystem I. The endogenous protein level of OsLFNR was found to be suppressed in both OsLFNR1- and OsLFNR2-overexpressing rice plants, leading to changes in the stoichiometry of the two LFNR isoforms within the thylakoid and soluble fractions. Thus, we propose that the stoichiometry of two LFNR isoforms plays an important role in electron partitioning between carbon fixation and nitrogen assimilation.
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269
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Ifuku K, Endo T, Shikanai T, Aro EM. Structure of the chloroplast NADH dehydrogenase-like complex: nomenclature for nuclear-encoded subunits. PLANT & CELL PHYSIOLOGY 2011; 52:1560-8. [PMID: 21785130 DOI: 10.1093/pcp/pcr098] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The chloroplast NADH dehydrogenase-like complex (NDH) was first discovered based on its similarity to complex I in respiratory electron transport, and is involved in electron transport from photoproduced stromal reductants such as NADPH and ferredoxin to the intersystem plastoqunone pool. However, a recent study suggested that it is a ferredoxin-dependent plastoquinone reductase rather than an NAD(P)H dehydrogenase. Furthermore, recent advances in subunit analysis of NDH have revealed the presence of a novel hydrophilic subcomplex on the stromal side of the thylakoid membrane, as well as an unexpected lumenal subcomplex. This review discusses these new studies on the structure of NDH, and proposes a unified nomenclature for newly discovered NDH subunits.
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Affiliation(s)
- Kentaro Ifuku
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Sakyo, Kyoto, 606-8502 Japan
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270
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Chloroplast lipid droplet type II NAD(P)H quinone oxidoreductase is essential for prenylquinone metabolism and vitamin K1 accumulation. Proc Natl Acad Sci U S A 2011; 108:14354-9. [PMID: 21844348 DOI: 10.1073/pnas.1104790108] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lipid droplets are ubiquitous cellular structures in eukaryotes and are required for lipid metabolism. Little is currently known about plant lipid droplets other than oil bodies. Here, we define dual roles for chloroplast lipid droplets (plastoglobules) in energy and prenylquinone metabolism. The prenylquinones--plastoquinone, plastochromanol-8, phylloquinone (vitamin K(1)), and tocopherol (vitamin E)--are partly stored in plastoglobules. This work shows that NAD(P)H dehydrogenase C1 (NDC1) (At5g08740), a type II NAD(P)H quinone oxidoreductase, associates with plastoglobules. NDC1 reduces a plastoquinone analog in vitro and affects the overall redox state of the total plastoquinone pool in vivo by reducing the plastoquinone reservoir of plastoglobules. Finally, NDC1 is required for normal plastochromanol-8 accumulation and is essential for vitamin K(1) production.
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271
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Stein H, Honig A, Miller G, Erster O, Eilenberg H, Csonka LN, Szabados L, Koncz C, Zilberstein A. Elevation of free proline and proline-rich protein levels by simultaneous manipulations of proline biosynthesis and degradation in plants. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 181:140-50. [PMID: 21683879 DOI: 10.1016/j.plantsci.2011.04.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 04/22/2011] [Accepted: 04/22/2011] [Indexed: 05/08/2023]
Abstract
Proline-rich proteins (PRP) are cell wall and plasma membrane-anchored factors involved in cell wall maintenance and its stress-induced fortification. Here we compare the synthesis of P5C as the proline (Pro) precursor in the cytosol and chloroplast by an introduced alien system and evaluate correlation between PRP synthesis and free Pro accumulation in plants. We developed a Pro over-producing system by generating transgenic tobacco plants overexpressing E. coli P5C biosynthetic enzymes; Pro-indifferent gamma-glutamyl kinase 74 (GK74) and gamma-glutamylphosphate reductase (GPR), as well as antisensing proline dehydrogenase (ProDH) transcription. GK74 and GPR enzymes were targeted either to the cytosol or plastids. Molecular analyses indicated that the two bacterial enzymes are efficiently expressed in plant cells, correctly targeted to the cytosol or chloroplasts, and processed to active enzymatic complexes in the two compartments. Maximal Pro increase is obtained when GK74 and GPR are active in chloroplasts, and ProDH mRNA level is reduced by anti-sense silencing, resulting in more than 50-fold higher Pro content compared to that of wild type tobacco plants. The Pro over-producing system efficiently works in tobacco and Arabidopsis. The elevation of Pro levels promotes accumulation of ectopically expressed Cell Wall Linker Protein (AtCWLP), a membrane protein with an external Pro-rich domain. These results suggest that the Pro-generating system can support endogenous or alien PRP production in plants.
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Affiliation(s)
- Hanan Stein
- Department of Plant Sciences, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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272
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Suzuki K, Ohmori Y, Ratel E. High Root Temperature Blocks Both Linear and Cyclic Electron Transport in the Dark During Chilling of the Leaves of Rice Seedlings. ACTA ACUST UNITED AC 2011; 52:1697-707. [DOI: 10.1093/pcp/pcr104] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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273
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Johnson MP, Ruban AV. Restoration of rapidly reversible photoprotective energy dissipation in the absence of PsbS protein by enhanced DeltapH. J Biol Chem 2011; 286:19973-81. [PMID: 21474447 PMCID: PMC3103371 DOI: 10.1074/jbc.m111.237255] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 04/05/2011] [Indexed: 11/06/2022] Open
Abstract
Variations in the light environment require higher plants to regulate the light harvesting process. Under high light a mechanism known as non-photochemical quenching (NPQ) is triggered to dissipate excess absorbed light energy within the photosystem II (PSII) antenna as heat, preventing photodamage to the reaction center. The major component of NPQ, known as qE, is rapidly reversible in the dark and dependent upon the transmembrane proton gradient (ΔpH), formed as a result of photosynthetic electron transport. Using diaminodurene and phenazine metasulfate, mediators of cyclic electron flow around photosystem I, to enhance ΔpH, it is demonstrated that rapidly reversible qE-type quenching can be observed in intact chloroplasts from Arabidopsis plants lacking the PsbS protein, previously believed to be indispensible for the process. The qE in chloroplasts lacking PsbS significantly quenched the level of fluorescence when all PSII reaction centers were in the open state (F(o) state), protected PSII reaction centers from photoinhibition, was modulated by zeaxanthin and was accompanied by the qE-typical absorption spectral changes, known as ΔA(535). Titrations of the ΔpH dependence of qE in the absence of PsbS reveal that this protein affects the cooperativity and sensitivity of the photoprotective process to protons. The roles of PsbS and zeaxanthin are discussed in light of their involvement in the control of the proton-antenna association constant, pK, via regulation of the interconnected phenomena of PSII antenna reorganization/aggregation and hydrophobicity.
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Affiliation(s)
- Matthew P. Johnson
- From the School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Alexander V. Ruban
- From the School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
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274
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Batista-Santos P, Lidon FC, Fortunato A, Leitão AE, Lopes E, Partelli F, Ribeiro AI, Ramalho JC. The impact of cold on photosynthesis in genotypes of Coffea spp.--photosystem sensitivity, photoprotective mechanisms and gene expression. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:792-806. [PMID: 21247660 DOI: 10.1016/j.jplph.2010.11.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Revised: 11/03/2010] [Accepted: 11/04/2010] [Indexed: 05/19/2023]
Abstract
Environmental constraints disturb plant metabolism and are often associated with photosynthetic impairments and yield reductions. Among them, low positive temperatures are of up most importance in tropical plant species, namely in Coffea spp. in which some acclimation ability has been reported. To further explain cold tolerance, the impacts on photosynthetic functioning and the expression of photosynthetic-related genes were analyzed. The experiments were carried out along a period of slow cold imposition (to allow acclimation), after chilling (4°C) exposure and in the following rewarming period, using 1.5-year-old coffee seedlings of 5 genotypes with different cold sensitivity: Coffea canephora cv. Apoatã, Coffea arabica cv. Catuaí, Coffea dewevrei and 2 hybrids, Icatu (C. arabica×C. canephora) and Piatã (C. dewevrei×C. arabica). All genotypes suffered a significant leaf area loss only after chilling exposure, with Icatu showing the lowest impact, a first indication of a higher cold tolerance, contrasting with Apoatã and C. dewevrei. During cold exposure, net photosynthesis and Chl a fluorescence parameters were strongly affected in all genotypes, but stomatal limitations were not detected. However, the extent of mesophyll limitation, reflecting regulatory mechanisms and/or damage, was genotype dependent. Overnight retention of zeaxanthin was common to Coffea genotypes, but the accumulation of photoprotective pigments was highest in Icatu. That down-regulated photochemical events but efficiently protected the photosynthetic structures, as shown, e.g., by the lowest impacts on A(max) and PSI activity and the strongest reinforcement of PSII activity, the latter possibly reflecting the presence of a photoprotective cycle around PSII in Icatu (and Catuaí). Concomitant to these protection mechanisms, Icatu was the sole genotype to present simultaneous upregulation of caCP22, caPI and caCytf, related to, respectively, PSII, PSI and to the complex Cytb(6)/f, which could promote better repair ability, contributing to the maintenance of efficient thylakoid functioning. We conclude that Icatu showed the best acclimation ability among the studied genotypes, mostly due to a better upregulation of photoprotection and repair mechanisms. We confirmed the presence of important variability in Coffea spp. that could be exploited in breeding programs, which should be assisted by useful markers of cold tolerance, namely the upregulation of antioxidative molecules, the expression of selected genes and PSI sensitivity.
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Affiliation(s)
- P Batista-Santos
- Centro de Ecofisiologia, Bioquímica e Biotecnologia Vegetal/Inst. Inv. Científica Tropical, Quinta do Marquês, 2784-505 Oeiras, Portugal
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275
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Magnuson A, Krassen H, Stensjö K, Ho FM, Styring S. Modeling Photosystem I with the alternative reaction center protein PsaB2 in the nitrogen fixing cyanobacterium Nostoc punctiforme. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1152-61. [PMID: 21605545 DOI: 10.1016/j.bbabio.2011.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 04/21/2011] [Accepted: 05/07/2011] [Indexed: 11/18/2022]
Abstract
Five nitrogen fixing cyanobacterial strains have been found to contain PsaB2, an additional and divergent gene copy for the Photosystem I reaction center protein PsaB. In all five species the divergent gene, psaB2, is located separately from the normal psaAB operon in the genome. The protein, PsaB2, was recently identified in heterocysts of Nostoc punctiforme sp. strain PCC 73102. 12 conserved amino acid replacements and one insertion, were identified by a multiple sequence alignment of several PsaB2 and PsaB1 sequences. Several, including an inserted glutamine, are located close to the iron-sulfur cluster F(X) in the electron transfer chain. By homology modeling, using the Photosystem I crystal structure as template, we have found that the amino acid composition in PsaB2 will introduce changes in critical parts of the Photosystem I protein structure. The changes are close to F(X) and the phylloquinone (PhQ) in the B-branch, indicating that the electron transfer properties most likely will be affected. We suggest that the divergent PsaB2 protein produces an alternative Photosystem I reaction center with different structural and electron transfer properties. Some interesting physiologcial consequences that this can have for the function of Photosystem I in heterocysts, are discussed.
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Affiliation(s)
- Ann Magnuson
- Department of Photochemistryand Molecular Science, Uppsala University, Sweden.
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276
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Johnson GN. Reprint of: physiology of PSI cyclic electron transport in higher plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:906-11. [PMID: 21620796 DOI: 10.1016/j.bbabio.2011.05.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 11/12/2010] [Accepted: 11/13/2010] [Indexed: 11/17/2022]
Abstract
Having long been debated, it is only in the last few years that a concensus has emerged that the cyclic flow of electrons around Photosystem I plays an important and general role in the photosynthesis of higher plants. Two major pathways of cyclic flow have been identified, involving either a complex termed NDH or mediated via a pathway involving a protein PGR5 and two functions have been described-to generate ATP and to provide a pH gradient inducing non-photochemical quenching. The best evidence for the occurrence of the two pathways comes from measurements under stress conditions-high light, drought and extreme temperatures. In this review, the possible relative functions and importance of the two pathways is discussed as well as evidence as to how the flow through these pathways is regulated. Our growing knowledge of the proteins involved in cyclic electron flow will, in the future, enable us to understand better the occurrence and diversity of cyclic electron transport pathways. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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277
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Rochaix JD. Reprint of: Regulation of photosynthetic electron transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:878-86. [PMID: 21605544 DOI: 10.1016/j.bbabio.2011.05.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 11/11/2010] [Accepted: 11/13/2010] [Indexed: 11/28/2022]
Abstract
The photosynthetic electron transport chain consists of photosystem II, the cytochrome b(6)f complex, photosystem I, and the free electron carriers plastoquinone and plastocyanin. Light-driven charge separation events occur at the level of photosystem II and photosystem I, which are associated at one end of the chain with the oxidation of water followed by electron flow along the electron transport chain and concomitant pumping of protons into the thylakoid lumen, which is used by the ATP synthase to generate ATP. At the other end of the chain reducing power is generated, which together with ATP is used for CO(2) assimilation. A remarkable feature of the photosynthetic apparatus is its ability to adapt to changes in environmental conditions by sensing light quality and quantity, CO(2) levels, temperature, and nutrient availability. These acclimation responses involve a complex signaling network in the chloroplasts comprising the thylakoid protein kinases Stt7/STN7 and Stl1/STN7 and the phosphatase PPH1/TAP38, which play important roles in state transitions and in the regulation of electron flow as well as in thylakoid membrane folding. The activity of some of these enzymes is closely connected to the redox state of the plastoquinone pool, and they appear to be involved both in short-term and long-term acclimation. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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278
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Savitch LV, Ivanov AG, Gudynaite-Savitch L, Huner NPA, Simmonds J. Cold Stress Effects on PSI Photochemistry in Zea mays: Differential Increase of FQR-Dependent Cyclic Electron Flow and Functional Implications. ACTA ACUST UNITED AC 2011; 52:1042-54. [DOI: 10.1093/pcp/pcr056] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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279
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Nishiyama Y, Allakhverdiev SI, Murata N. Protein synthesis is the primary target of reactive oxygen species in the photoinhibition of photosystem II. PHYSIOLOGIA PLANTARUM 2011; 142:35-46. [PMID: 21320129 DOI: 10.1111/j.1399-3054.2011.01457.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Photoinhibition of photosystem II (PSII) occurs when the rate of photodamage to PSII exceeds the rate of the repair of photodamaged PSII. Recent examination of photoinhibition by separate determinations of photodamage and repair has revealed that the rate of photodamage to PSII is directly proportional to the intensity of incident light and that the repair of PSII is particularly sensitive to the inactivation by reactive oxygen species (ROS). The ROS-induced inactivation of repair is attributable to the suppression of the synthesis de novo of proteins, such as the D1 protein, that are required for the repair of PSII at the level of translational elongation. Furthermore, molecular analysis has revealed that the ROS-induced suppression of protein synthesis is associated with the specific inactivation of elongation factor G via the formation of an intramolecular disulfide bond. Impairment of various mechanisms that protect PSII against photoinhibition, including photorespiration, thermal dissipation of excitation energy, and the cyclic transport of electrons, decreases the rate of repair of PSII via the suppression of protein synthesis. In this review, we present a newly established model of the mechanism and the physiological significance of repair in the regulation of the photoinhibition of PSII.
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Affiliation(s)
- Yoshitaka Nishiyama
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering and Institute for Environmental Science and Technology, Saitama University, Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
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280
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Hammani K, des Francs-Small CC, Takenaka M, Tanz SK, Okuda K, Shikanai T, Brennicke A, Small I. The pentatricopeptide repeat protein OTP87 is essential for RNA editing of nad7 and atp1 transcripts in Arabidopsis mitochondria. J Biol Chem 2011; 286:21361-71. [PMID: 21504904 DOI: 10.1074/jbc.m111.230516] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In plant organelles, RNA editing is a post-transcriptional mechanism that converts specific cytidines to uridines in RNA of both mitochondria and plastids, altering the information encoded by the gene. The cytidine to be edited is determined by a cis-element surrounding the editing site that is specifically recognized and bound by a trans-acting factor. All the trans-acting editing factors identified so far in plant organelles are members of a large protein family, the pentatricopeptide repeat (PPR) proteins. We have identified the Organelle Transcript Processing 87 (OTP87) gene, which is required for RNA editing of the nad7-C24 and atp1-C1178 sites in Arabidopsis mitochondria. OTP87 encodes an E-subclass PPR protein with an unusually short E-domain. The recombinant protein expressed in Escherichia coli specifically binds to RNAs comprising 30 nucleotides upstream and 10 nucleotides downstream of the nad7-C24 and atp1-C1178 editing sites. The loss-of-function of OTP87 results in small plants with growth and developmental delays. In the otp87 mutant, the amount of assembled respiratory complex V (ATP synthase) is highly reduced compared with the wild type suggesting that the amino acid alteration in ATP1 caused by loss of editing at the atp1-C1178 site affects complex V assembly in mitochondria.
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Affiliation(s)
- Kamel Hammani
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 Western Australia, Australia.
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281
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A chaperonin subunit with unique structures is essential for folding of a specific substrate. PLoS Biol 2011; 9:e1001040. [PMID: 21483722 PMCID: PMC3071376 DOI: 10.1371/journal.pbio.1001040] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 02/23/2011] [Indexed: 01/01/2023] Open
Abstract
Type I chaperonins are large, double-ring complexes present in bacteria (GroEL),
mitochondria (Hsp60), and chloroplasts (Cpn60), which are involved in mediating
the folding of newly synthesized, translocated, or stress-denatured proteins. In
Escherichia coli, GroEL comprises 14 identical subunits and
has been exquisitely optimized to fold its broad range of substrates. However,
multiple Cpn60 subunits with different expression profiles have evolved in
chloroplasts. Here, we show that, in Arabidopsis thaliana, the
minor subunit Cpn60β4 forms a heterooligomeric Cpn60 complex with
Cpn60α1 and Cpn60β1–β3 and is specifically required for the
folding of NdhH, a subunit of the chloroplast NADH dehydrogenase-like complex
(NDH). Other Cpn60β subunits cannot complement the function of Cpn60β4.
Furthermore, the unique C-terminus of Cpn60β4 is required for the full
activity of the unique Cpn60 complex containing Cpn60β4 for folding of NdhH.
Our findings suggest that this unusual kind of subunit enables the Cpn60 complex
to assist the folding of some particular substrates, whereas other dominant
Cpn60 subunits maintain a housekeeping chaperonin function by facilitating the
folding of other obligate substrates. Chaperonins assist the folding of some nascent and denatured proteins to their
native, functional forms. Each chaperonin consists of a pair of protein
complexes resembling two stacked toroids; folding occurs inside the toroid
cavity. Chaperonins are ubiquitous in both bacteria and more complex nucleated
cells, as well as in the intracellular organelles that have evolved from
bacteria by endosymbiosis: mitochondria and, in plants, chloroplasts. They are
indispensable for cellular function. Many different chaperonin subunits have
evolved in various species of bacteria as well as in most mitochondria and
chloroplasts. The physiological and functional relevance of these multiple
chaperonin subunits is poorly understood, however. In this study, we have
characterized the minor chaperonin subunit Cpn60β4 from
Arabidopsis chloroplasts, which differs in structure from
other chloroplast chaperonins. When the Cpn60β4 gene is
defective, the plants fail to accumulate one protein complex in particular: the
chloroplast NADH dehydrogenase-like complex (NDH). We discovered that
Cpn60β4 forms a complex with other Cpn60 α and β
subunits and that this complex is essential for the folding of the NDH subunit
NdhH. Cpn60β4 has a unique protein “tail” that is required for
the efficient folding of NdhH. Our findings suggest that Cpn60β4 has evolved
with distinctive structural features that facilitate the folding of one specific
substrate and that this strategy is used by plants to satisfy their conflicting
requirements for chaperonins with both specialized and general functions.
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282
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Yamamoto H, Peng L, Fukao Y, Shikanai T. An Src homology 3 domain-like fold protein forms a ferredoxin binding site for the chloroplast NADH dehydrogenase-like complex in Arabidopsis. THE PLANT CELL 2011; 23:1480-93. [PMID: 21505067 PMCID: PMC3101538 DOI: 10.1105/tpc.110.080291] [Citation(s) in RCA: 167] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 03/07/2011] [Accepted: 04/05/2011] [Indexed: 05/18/2023]
Abstract
Some subunits of chloroplast NAD(P)H dehydrogenase (NDH) are related to those of the respiratory complex I, and NDH mediates photosystem I (PSI) cyclic electron flow. Despite extensive surveys, the electron donor and its binding subunits have not been identified. Here, we identified three novel components required for NDH activity. CRRJ and CRRL are J- and J-like proteins, respectively, and are components of NDH subcomplex A. CRR31 is an Src homology 3 domain-like fold protein, and its C-terminal region may form a tertiary structure similar to that of PsaE, a ferredoxin (Fd) binding subunit of PSI, although the sequences are not conserved between CRR31 and PsaE. Although CRR31 can accumulate in thylakoids independently of NDH, its accumulation requires CRRJ, and CRRL accumulation depends on CRRJ and NDH. CRR31 was essential for the efficient operation of Fd-dependent plastoquinone reduction in vitro. The phenotype of crr31 pgr5 suggested that CRR31 is required for NDH activity in vivo. We propose that NDH functions as a PGR5-PGRL1 complex-independent Fd:plastoquinone oxidoreductase in chloroplasts and rename it the NADH dehydrogenase-like complex.
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Affiliation(s)
- Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Lianwei Peng
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yoichiro Fukao
- Plant Global Educational Project, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma 630-0101, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Address correspondence to
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283
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Peng L, Shikanai T. Supercomplex formation with photosystem I is required for the stabilization of the chloroplast NADH dehydrogenase-like complex in Arabidopsis. PLANT PHYSIOLOGY 2011; 155:1629-39. [PMID: 21278308 PMCID: PMC3091109 DOI: 10.1104/pp.110.171264] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 01/23/2011] [Indexed: 05/18/2023]
Abstract
In higher plants, the chloroplast NADH dehydrogenase-like complex (NDH) interacts with photosystem I (PSI) to form the NDH-PSI supercomplex via two minor light-harvesting complex I (LHCI) proteins, Lhca5 and Lhca6. Previously, we showed that in lhca5 and lhca6, NDH still associates with PSI to form smaller versions of the NDH-PSI supercomplex, although their molecular masses are far smaller than that of the full-size NDH-PSI supercomplex. In this study, we show that the NDH complex is present in the monomeric form in Arabidopsis (Arabidopsis thaliana) lhca5 lhca6, implying that NDH interacts with multiple copies of PSI. NDH subunit levels were slightly reduced in immature leaves and more drastically (approximately 50%) in mature leaves of the lhca5 lhca6 double mutant compared with the wild type. Chlorophyll fluorescence analyses detected NDH activity of lhca5 lhca6, suggesting that the supercomplex formation is not essential for NDH activity. However, the severe phenotypes of the lhca5 lhca6 proton gradient regulation5 triple mutant in both plant growth rate and photosynthesis suggest that the function of NDH was impaired in this mutant in vivo. Accumulation of NDH subunits was drastically reduced in lhca5 lhca6 when the light intensity was shifted from 50 to 500 μmol photons m(-2) s(-1). Furthermore, the half-life of NDH subunits, especially that of NDH18, was shorter in monomeric NDH than in the NDH-PSI supercomplex under the high-light conditions. We propose that NDH-PSI supercomplex formation stabilizes NDH and that the process is especially required under stress conditions.
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284
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Ducruet JM, Serrano A, Roncel M, Ortega JM. Peculiar properties of chlorophyll thermoluminescence emission of autotrophically or mixotrophically grown Chlamydomonas reinhardtii. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:301-7. [PMID: 21402481 DOI: 10.1016/j.jphotobiol.2011.02.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 02/14/2011] [Accepted: 02/15/2011] [Indexed: 10/18/2022]
Abstract
The microalgae Chlamydomonas reinhardtii and Chlorella sp. CCAP 211/84 were grown autotrophically and mixotrophically and their thermoluminescence emissions were recorded above 0 °C after excitation by 1, 2 or 3 xenon flashes or by continuous far-red light. An oscillation of the B band intensity according to the number of flashes was always observed, with a maximum after 2 flashes, accompanied by a downshift of the B band temperature maximum in mixotrophic compared to autotrophic grown cells, indicative of a dark stable pH gradient. Moreover, new flash-induced bands emerged in mixotrophic Chlamydomonas grown cells, at temperatures higher than that of the B band. In contrast to the afterglow band observed in higher plants, in Chlamydomonas these bands were not inducible by far-red light, were fully suppressed by 2 μM antimycin A, and peaked at different temperatures depending on the flash number and growth stage, with higher temperature maxima in cells at a stationary compared to an exponential growth stage. These differences are discussed according to the particular properties of cyclic electron transfer pathways in C. reinhardtii.
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Affiliation(s)
- Jean-Marc Ducruet
- Groupe de Biospectroscopie Végétale, Ecophysiologie Végétale, ESE, Bât. 362, Université Paris-Sud-Orsay, 91400 Orsay, France.
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285
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Alternative photosynthetic electron transport pathways during anaerobiosis in the green alga Chlamydomonas reinhardtii. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:919-26. [PMID: 21376011 DOI: 10.1016/j.bbabio.2011.02.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 02/21/2011] [Accepted: 02/23/2011] [Indexed: 12/29/2022]
Abstract
Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or "substrate" in a number of biosynthetic pathways. Though photosynthesis of higher plants, algae and cyanobacteria produces oxygen, there are conditions under which this type of photosynthesis operates under hypoxic or anaerobic conditions. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. This review summarizes the recent knowledge about various electron sources and sinks of oxygenic photosynthesis besides water and NADP(+) in the context of their contribution to hydrogen photoproduction by C. reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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286
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Cramer WA, Hasan SS, Yamashita E. The Q cycle of cytochrome bc complexes: a structure perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:788-802. [PMID: 21352799 DOI: 10.1016/j.bbabio.2011.02.006] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 02/08/2011] [Accepted: 02/13/2011] [Indexed: 12/01/2022]
Abstract
Aspects of the crystal structures of the hetero-oligomeric cytochrome bc(1) and b(6)f ("bc") complexes relevant to their electron/proton transfer function and the associated redox reactions of the lipophilic quinones are discussed. Differences between the b(6)f and bc(1) complexes are emphasized. The cytochrome bc(1) and b(6)f dimeric complexes diverge in structure from a core of subunits that coordinate redox groups consisting of two bis-histidine coordinated hemes, a heme b(n) and b(p) on the electrochemically negative (n) and positive (p) sides of the complex, the high potential [2Fe-2S] cluster and c-type heme at the p-side aqueous interface and aqueous phase, respectively, and quinone/quinol binding sites on the n- and p-sides of the complex. The bc(1) and b(6)f complexes diverge in subunit composition and structure away from this core. b(6)f Also contains additional prosthetic groups including a c-type heme c(n) on the n-side, and a chlorophyll a and β-carotene. Common structure aspects; functions of the symmetric dimer. (I) Quinone exchange with the bilayer. An inter-monomer protein-free cavity of approximately 30Å along the membrane normal×25Å (central inter-monomer distance)×15Å (depth in the center), is common to both bc(1) and b(6)f complexes, providing a niche in which the lipophilic quinone/quinol (Q/QH(2)) can be exchanged with the membrane bilayer. (II) Electron transfer. The dimeric structure and the proximity of the two hemes b(p) on the electrochemically positive side of the complex in the two monomer units allow the possibility of two alternate routes of electron transfer across the complex from heme b(p) to b(n): intra-monomer and inter-monomer involving electron cross-over between the two hemes b(p). A structure-based summary of inter-heme distances in seven bc complexes, representing mitochondrial, chromatophore, cyanobacterial, and algal sources, indicates that, based on the distance parameter, the intra-monomer pathway would be favored kinetically. (III) Separation of quinone binding sites. A consequence of the dimer structure and the position of the Q/QH(2) binding sites is that the p-side QH(2) oxidation and n-side Q reduction sites are each well separated. Therefore, in the event of an overlap in residence time by QH(2) or Q molecules at the two oxidation or reduction sites, their spatial separation would result in minimal steric interference between extended Q or QH(2) isoprenoid chains. (IV) Trans-membrane QH(2)/Q transfer. (i) n/p-side QH(2)/Q transfer may be hindered by lipid acyl chains; (ii) the shorter less hindered inter-monomer pathway across the complex would not pass through the center of the cavity, as inferred from the n-side antimycin site on one monomer and the p-side stigmatellin site on the other residing on the same surface of the complex. (V) Narrow p-side portal for QH(2)/Q passage. The [2Fe-2S] cluster that serves as oxidant, and whose histidine ligand serves as a H(+) acceptor in the oxidation of QH(2), is connected to the inter-monomer cavity by a narrow extended portal, which is also occupied in the b(6)f complex by the 20 carbon phytyl chain of the bound chlorophyll.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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287
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Abstract
Hydrogenases catalyze the reversible reaction 2H(+) + 2e(-) ↔ H(2) with an equilibrium constant that is dependent on the reducing potential of electrons carried by their redox partner. To examine the possibility of increasing the photobiological production of hydrogen within cyanobacterial cultures, we expressed the [FeFe] hydrogenase, HydA, from Clostridium acetobutylicum in the non-nitrogen-fixing cyanobacterium Synechococcus elongatus sp. 7942. We demonstrate that the heterologously expressed hydrogenase is functional in vitro and in vivo, and that the in vivo hydrogenase activity is connected to the light-dependent reactions of the electron transport chain. Under anoxic conditions, HydA activity is capable of supporting light-dependent hydrogen evolution at a rate > 500-fold greater than that supported by the endogenous [NiFe] hydrogenase. Furthermore, HydA can support limited growth solely using H(2) and light as the source of reducing equivalents under conditions where Photosystem II is inactivated. Finally, we demonstrate that the addition of exogenous ferredoxins can modulate redox flux in the hydrogenase-expressing strain, allowing for greater hydrogen yields and for dark fermentation of internal energy stores into hydrogen gas.
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288
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Huang W, Zhang SB, Cao KF. Cyclic electron flow plays an important role in photoprotection of tropical trees illuminated at temporal chilling temperature. PLANT & CELL PHYSIOLOGY 2011; 52:297-305. [PMID: 21062868 DOI: 10.1093/pcp/pcq166] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Our previous study indicated that PSII is more sensitive to chilling and light stress than PSI in tropical trees, and Erythrophleum guineense is more sensitive to chilling stress than Dalbergia odorifera and Khaya ivorensis, but the underlying physiological mechanisms are unclear. Although recent studies have reported that cyclic electron flow (CEF) plays an important role in photoprotection, the role of CEF in protecting PSI and PSII of tropical tree species remains unclear. We investigated the effect of temporal chilling temperature on energy distribution in PSII, the redox state of P700 and CEF in the above-mentioned tropical evergreen tree species grown in an open field. Our results indicated that the overclosure of PSII reaction centers at chilling temperature led to excess excitation pressure in PSII. At the temporal chilling temperature under low light, PSI acceptor side limitation [Y(NA)] was lower than those at 25°C for all species. Although the effective quantum yield of CEF [Y(CEF)] was not significantly stimulated in E. guineense and K. ivorensis under temporal chilling at low light levels, the ratio of Y(CEF) to the effective quantum yield of PSII [Y(II)] significantly increased. Under chilling conditions Y(CEF)/Y(II) was stimulated much more in K. ivorensis and D. odorifera compared with that in the chilling-sensitive E. guineense. These results suggested that stimulation of Y(CEF)/Y(II) plays an important role in protecting PSI and PSII from photoinhibition caused by chilling stress.
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Affiliation(s)
- Wei Huang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, PR China
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289
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Yamori W, Takahashi S, Makino A, Price GD, Badger MR, von Caemmerer S. The roles of ATP synthase and the cytochrome b6/f complexes in limiting chloroplast electron transport and determining photosynthetic capacity. PLANT PHYSIOLOGY 2011; 155:956-62. [PMID: 21177473 PMCID: PMC3032479 DOI: 10.1104/pp.110.168435] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 12/16/2010] [Indexed: 05/18/2023]
Abstract
In C(3) plants, CO(2) assimilation is limited by ribulose 1,5-bisphosphate (RuBP) regeneration rate at high CO(2). RuBP regeneration rate in turn is determined by either the chloroplast electron transport capacity to generate NADPH and ATP or the activity of Calvin cycle enzymes involved in regeneration of RuBP. Here, transgenic tobacco (Nicotiana tabacum 'W38') expressing an antisense gene directed at the transcript of either the Rieske iron-sulfur protein of the cytochrome (Cyt) b(6)/f complex or the δ-subunit of chloroplast ATP synthase have been used to investigate the effect of a reduction of these complexes on chloroplast electron transport rate (ETR). Reductions in δ-subunit of ATP synthase content did not alter chlorophyll, Cyt b(6)/f complex, or Rubisco content, but reduced ETR estimated either from measurements of chlorophyll fluorescence or CO(2) assimilation rates at high CO(2). Plants with low ATP synthase content exhibited higher nonphotochemical quenching and achieved higher ETR per ATP synthase than the wild type. The proportional increase in ETR per ATP synthase complex was greatest at 35°C, showing that the ATP synthase activity can vary in vivo. In comparison, there was no difference in the ETR per Cyt b(6)/f complex in plants with reduced Cyt b(6)/f content and the wild type. The ETR decreased more drastically with reductions in Cyt b(6)/f complex than ATP synthase content. This suggests that chloroplast ETR is more limited by Cyt b(6)/f than ATP synthase content and is a potential target for enhancing photosynthetic capacity in crops.
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Affiliation(s)
- Wataru Yamori
- Molecular Plant Physiology Cluster, Plant Science Division, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
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290
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Shikanai T, Okuda K. In vitro RNA-binding assay for studying trans-factors for RNA editing in chloroplasts. Methods Mol Biol 2011; 774:199-208. [PMID: 21822841 DOI: 10.1007/978-1-61779-234-2_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In plant organelles, specific C residues are modified to U by RNA editing. Short RNA sequences surrounding the target site (i.e., cis-elements) are recognized by trans-factors, which were recently shown to be pentatricopeptide repeat (PPR) proteins. PPR proteins consist of tandem arrays of a highly degenerate unit of 35 (pentatrico) amino acids, and PPR motifs are believed to recognize specific RNA sequences. In Arabidopsis thaliana, more than 450 sites are edited in mitochondria and plastids, and a similar number of PPR proteins are encoded in the nuclear genome. To study how the tandem array of a PPR motif facilitates the recognition of RNA sequences, an efficient biochemical strategy is an in vitro binding assay of recombinant PPR proteins with target RNA. This analysis is especially powerful with a combination of in vivo analyses based on the phenotypes of mutants and transgenic plants. In this chapter, we describe methods for the expression of recombinant PPR proteins in Escherichia coli, preparation of probe RNAs, and RNA gel shift assays. These methods can also be utilized for other RNA-binding proteins.
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Affiliation(s)
- Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, Japan.
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291
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Xu F, Yuan S, Lin HH. Response of mitochondrial alternative oxidase (AOX) to light signals. PLANT SIGNALING & BEHAVIOR 2011; 6:55-8. [PMID: 21270540 PMCID: PMC3122006 DOI: 10.4161/psb.6.1.14192] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 11/12/2010] [Indexed: 05/03/2023]
Abstract
Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes the energy wasteful cyanide (CN)-resistant respiration and plays a role in optimizing photosynthesis. Recent studies from our group indicated that AOX plays a crucial role in chloroplast protection under extreme environments, such as high light (HL). Genetic data suggest that AOX is upregulated by light that was mediated by photoreceptors (phytochromes, phototropins and cryptochromes), and it also might have a particular role in relieving the overreduction of chloroplasts. Physiological analyses further suggest that AOX is essential for the dark-to-light transition, especially in de-etiolation course. In this mini-review, we highlight recent progresses in understanding the beneficial interaction between photosynthesis and mitochondria metabolism and discuss the possible role and mechanism of AOX in dissipation of excess reduced equivalents for chloroplasts under high light condition.
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Affiliation(s)
- Fei Xu
- Ministry of Education Key Laboratory for Bio-Resource & Eco-Environment, College of Life Science, Sichuan University, Chengdu, China
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292
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Armbruster U, Pesaresi P, Pribil M, Hertle A, Leister D. Update on chloroplast research: new tools, new topics, and new trends. MOLECULAR PLANT 2011; 4:1-16. [PMID: 20924030 DOI: 10.1093/mp/ssq060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Chloroplasts, the green differentiation form of plastids, are the sites of photosynthesis and other important plant functions. Genetic and genomic technologies have greatly boosted the rate of discovery and functional characterization of chloroplast proteins during the past decade. Indeed, data obtained using high-throughput methodologies, in particular proteomics and transcriptomics, are now routinely used to assign functions to chloroplast proteins. Our knowledge of many chloroplast processes, notably photosynthesis and photorespiration, has reached such an advanced state that biotechnological approaches to crop improvement now seem feasible. Meanwhile, efforts to identify the entire complement of chloroplast proteins and their interactions are progressing rapidly, making the organelle a prime target for systems biology research in plants.
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Affiliation(s)
- Ute Armbruster
- Lehrstuhl für Molekularbiologie der Pflanzen (Botanik), Department Biologie I, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany
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293
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Cruz S, Goss R, Wilhelm C, Leegood R, Horton P, Jakob T. Impact of chlororespiration on non-photochemical quenching of chlorophyll fluorescence and on the regulation of the diadinoxanthin cycle in the diatom Thalassiosira pseudonana. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:509-19. [PMID: 20876335 PMCID: PMC3003802 DOI: 10.1093/jxb/erq284] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 08/23/2010] [Accepted: 08/23/2010] [Indexed: 05/20/2023]
Abstract
In diatoms, metabolic activity during long dark periods leads to a chlororespiratory electron flow, which is accompanied by the build-up of a proton gradient strong enough to activate the diadinoxanthin (Ddx) de-epoxidation reaction of the Ddx cycle. In the present study, the impact of chlororespiration on non-photochemical quenching (NPQ) of chlorophyll fluorescence and the regulation of the Ddx cycle in the diatom Thalassiosira pseudonana was investigated by manipulation of the redox state of the photosynthetic electron transport chain during darkness. The response of a transfer of T. pseudonana cells from growth light conditions to 60 min darkness was found to depend on oxygen: in its presence there was no significant reduction of the PQ pool and no de-epoxidation of Ddx to diatoxanthin (Dtx). Under anaerobic conditions a high reduction state of the electron transport chain and a slow but steady de-epoxidation of Ddx was observed, which resulted in a significant accumulation of Dtx after 60 min of anaerobiosis. Unexpectedly, this high concentration of Dtx did not induce a correspondingly high NPQ as it would have been observed with Dtx formed under high light conditions. However, the sensitivity of NPQ to Dtx in cells kept under dark anaerobic conditions increased during reoxygenation and far-red (FR) light illumination. The results are discussed with respect to the activation of the de-epoxidation reaction and the formation of NPQ and their dependence on the extent of the proton gradient across the thylakoid membrane.
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Affiliation(s)
- Sonia Cruz
- Animal and Plant Sciences Department, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Reimund Goss
- Institute of Biology I, Plant Physiology, University of Leipzig, Johannisallee 21-23, D-04103 Leipzig, Germany
| | - Christian Wilhelm
- Institute of Biology I, Plant Physiology, University of Leipzig, Johannisallee 21-23, D-04103 Leipzig, Germany
| | - Richard Leegood
- Animal and Plant Sciences Department, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Peter Horton
- Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Torsten Jakob
- Institute of Biology I, Plant Physiology, University of Leipzig, Johannisallee 21-23, D-04103 Leipzig, Germany
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294
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Kramer DM, Evans JR. The importance of energy balance in improving photosynthetic productivity. PLANT PHYSIOLOGY 2011; 155:70-8. [PMID: 21078862 PMCID: PMC3075755 DOI: 10.1104/pp.110.166652] [Citation(s) in RCA: 319] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 11/10/2010] [Indexed: 05/18/2023]
Affiliation(s)
- David M Kramer
- Biochemistry and Molecular Biology and Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
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295
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Murchie EH, Niyogi KK. Manipulation of photoprotection to improve plant photosynthesis. PLANT PHYSIOLOGY 2011; 155:86-92. [PMID: 21084435 PMCID: PMC3075776 DOI: 10.1104/pp.110.168831] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 11/15/2010] [Indexed: 05/18/2023]
Affiliation(s)
- Erik H Murchie
- Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington LE12 5RD, United Kingdom.
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296
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Baniulis D, Zhang H, Zakharova T, Hasan SS, Cramer WA. Purification and crystallization of the cyanobacterial cytochrome b6f complex. Methods Mol Biol 2011; 684:65-77. [PMID: 20960122 DOI: 10.1007/978-1-60761-925-3_7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The cytochrome b6f complex from the filamentous cyanobacteria (Mastigocladus laminosus, Nostoc sp. PCC 7120) and spinach chloroplasts has been purified as a homo-dimer. Electrospray ionization mass spectroscopy showed the monomer to contain eight and nine subunits, respectively, and dimeric masses of 217.1, 214.2, and 286.5 kDa for M. laminosus, Nostoc, and the complex from spinach. The core subunits containing or interacting with redox-active prosthetic groups are petA (cytochrome f), B (cytochrome b6, C (Rieske iron-sulfur protein), D (subunit IV), with protein molecular weights of 31.8-32.3, 24.7-24.9, 18.9-19.3, and 17.3-17.5 kDa, and four small 3.2-4.2 kDa polypeptides petG, L, M, and N. A ninth polypeptide, the 35 kDa petH (FNR) polypeptide in the spinach complex, was identified as ferredoxin:NADP reductase (FNR), which binds to the complex tightly at a stoichiometry of approx 0.8/cytf. The spinach complex contains diaphorase activity diagnostic of FNR and is active in facilitating ferredoxin-dependent electron transfer from NADPH to the cytochrome b6f complex. The purified cytochrome b6f complex contains stoichiometrically bound chlorophyll a and β-carotene at a ratio of approximately one molecule of each per cytochrome f. It also contains bound lipid and detergent, indicating seven lipid-binding sites per monomer. Highly purified complexes are active for approximately 1 week after isolation, transferring 200-300 electrons/cytf s. The M. laminosus complex was shown to be subject to proteolysis and associated loss of activity if incubated for more than 1 week at room temperature. The Nostoc complex is more resistant to proteolysis. Addition of pure synthetic lipid to the cyanobacterial complex, which is mostly delipidated by the isolation procedure, allows rapid formation of large (≥0.2 mm) crystals suitable for X-ray diffraction analysis and structure determination. The crystals made from the cyanobacterial complex diffract to 3.0 Å with R values of 0.222 and 0.230 for M. laminosus and Nostoc, respectively. It has not yet been possible to obtain crystals of the b6f complex from any plant source, specifically spinach or pea, perhaps because of incomplete binding of FNR or other peripheral polypeptides. Well diffracting crystals have been obtained from the green alga, Chlamydomonas reinhardtii (ref. 10).
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Affiliation(s)
- Danas Baniulis
- Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN, USA
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297
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Cardol P, Forti G, Finazzi G. Regulation of electron transport in microalgae. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:912-8. [PMID: 21167125 DOI: 10.1016/j.bbabio.2010.12.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 12/03/2010] [Accepted: 12/04/2010] [Indexed: 01/23/2023]
Abstract
Unicellular algae are characterized by an extreme flexibility with respect to their responses to environmental constraints. This flexibility probably explains why microalgae show a very high biomass yield, constitute one of the major contributors to primary productivity in the oceans and are considered a promising choice for biotechnological applications. Flexibility results from a combination of several factors including fast changes in the light-harvesting apparatus and a strong interaction between different metabolic processes (e.g. respiration and photosynthesis), which all take place within the same cell. Microalgae are also capable of modifying their photosynthetic electron flow capacity, by changing its maximum rate and/or by diverting photogenerated electrons towards different sinks depending on their growth status. In this review, we will focus on the occurrence and regulation of alternative electron flows in unicellular algae and compare data obtained in these systems with those available in vascular plants. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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Affiliation(s)
- Pierre Cardol
- Laboratoire de Génétique des Microorganismes, Institut de Botanique, Université de Liège, 27 bld du rectorat, B-4000 Liège, Belgium
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298
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de Oliveira Dal’Molin CG, Quek LE, Palfreyman RW, Brumbley SM, Nielsen LK. C4GEM, a genome-scale metabolic model to study C4 plant metabolism. PLANT PHYSIOLOGY 2010; 154:1871-85. [PMID: 20974891 PMCID: PMC2996019 DOI: 10.1104/pp.110.166488] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 10/25/2010] [Indexed: 05/17/2023]
Abstract
Leaves of C(4) grasses (such as maize [Zea mays], sugarcane [Saccharum officinarum], and sorghum [Sorghum bicolor]) form a classical Kranz leaf anatomy. Unlike C(3) plants, where photosynthetic CO(2) fixation proceeds in the mesophyll (M), the fixation process in C(4) plants is distributed between two cell types, the M cell and the bundle sheath (BS) cell. Here, we develop a C(4) genome-scale model (C4GEM) for the investigation of flux distribution in M and BS cells during C(4) photosynthesis. C4GEM, to our knowledge, is the first large-scale metabolic model that encapsulates metabolic interactions between two different cell types. C4GEM is based on the Arabidopsis (Arabidopsis thaliana) model (AraGEM) but has been extended by adding reactions and transporters responsible to represent three different C(4) subtypes (NADP-ME [for malic enzyme], NAD-ME, and phosphoenolpyruvate carboxykinase). C4GEM has been validated for its ability to synthesize 47 biomass components and consists of 1,588 unique reactions, 1,755 metabolites, 83 interorganelle transporters, and 29 external transporters (including transport through plasmodesmata). Reactions in the common C(4) model have been associated with well-annotated C(4) species (NADP-ME subtypes): 3,557 genes in sorghum, 11,623 genes in maize, and 3,881 genes in sugarcane. The number of essential reactions not assigned to genes is 131, 135, and 156 in sorghum, maize, and sugarcane, respectively. Flux balance analysis was used to assess the metabolic activity in M and BS cells during C(4) photosynthesis. Our simulations were consistent with chloroplast proteomic studies, and C4GEM predicted the classical C(4) photosynthesis pathway and its major effect in organelle function in M and BS. The model also highlights differences in metabolic activities around photosystem I and photosystem II for three different C(4) subtypes. Effects of CO(2) leakage were also explored. C4GEM is a viable framework for in silico analysis of cell cooperation between M and BS cells during photosynthesis and can be used to explore C(4) plant metabolism.
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Affiliation(s)
| | | | | | | | - Lars Keld Nielsen
- Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, Queensland 4072, Australia
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299
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Miyake C. Alternative electron flows (water-water cycle and cyclic electron flow around PSI) in photosynthesis: molecular mechanisms and physiological functions. PLANT & CELL PHYSIOLOGY 2010; 51:1951-63. [PMID: 21068108 DOI: 10.1093/pcp/pcq173] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
An electron flow in addition to the major electron sinks in C(3) plants [both photosynthetic carbon reduction (PCR) and photorespiratory carbon oxidation (PCO) cycles] is termed an alternative electron flow (AEF) and functions in the chloroplasts of leaves. The water-water cycle (WWC; Mehler-ascorbate peroxidase pathway) and cyclic electron flow around PSI (CEF-PSI) have been studied as the main AEFs in chloroplasts and are proposed to play a physiologically important role in both the regulation of photosynthesis and the alleviation of photoinhibition. In the present review, I discuss the molecular mechanisms of both AEFs and their functions in vivo. To determine their physiological function, accurate measurement of the electron flux of AEFs in vivo are required. Methods to assay electron flux in CEF-PSI have been developed recently and their problematic points are discussed. The common physiological function of both the WWC and CEF-PSI is the supply of ATP to drive net CO(2) assimilation. The requirement for ATP depends on the activities of both PCR and PCO cycles, and changes in both WWC and CEF-PSI were compared with the data obtained in intact leaves. Furthermore, the fact that CEF-PSI cannot function independently has been demonstrated. I propose a model for the regulation of CEF-PSI by WWC, in which WWC is indispensable as an electron sink for the expression of CEF-PSI activity.
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Affiliation(s)
- Chikahiro Miyake
- Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan.
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Rochaix JD. Regulation of photosynthetic electron transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:375-83. [PMID: 21118674 DOI: 10.1016/j.bbabio.2010.11.010] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 11/11/2010] [Accepted: 11/13/2010] [Indexed: 11/30/2022]
Abstract
The photosynthetic electron transport chain consists of photosystem II, the cytochrome b(6)f complex, photosystem I, and the free electron carriers plastoquinone and plastocyanin. Light-driven charge separation events occur at the level of photosystem II and photosystem I, which are associated at one end of the chain with the oxidation of water followed by electron flow along the electron transport chain and concomitant pumping of protons into the thylakoid lumen, which is used by the ATP synthase to generate ATP. At the other end of the chain reducing power is generated, which together with ATP is used for CO(2) assimilation. A remarkable feature of the photosynthetic apparatus is its ability to adapt to changes in environmental conditions by sensing light quality and quantity, CO(2) levels, temperature, and nutrient availability. These acclimation responses involve a complex signaling network in the chloroplasts comprising the thylakoid protein kinases Stt7/STN7 and Stl1/STN7 and the phosphatase PPH1/TAP38, which play important roles in state transitions and in the regulation of electron flow as well as in thylakoid membrane folding. The activity of some of these enzymes is closely connected to the redox state of the plastoquinone pool, and they appear to be involved both in short-term and long-term acclimation. This article is part of a Special Issue entitled "Regulation of Electron Transport in Chloroplasts".
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Affiliation(s)
- Jean-David Rochaix
- Department of Molecular Biology, University of Geneva, Geneva, Switzerland.
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