1
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Pang Y, Liao Q, Peng H, Qian C, Wang F. CO 2 mesophyll conductance regulated by light: a review. PLANTA 2023; 258:11. [PMID: 37289402 DOI: 10.1007/s00425-023-04157-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 04/17/2023] [Indexed: 06/09/2023]
Abstract
MAIN CONCLUSION Light quality and intensity regulate plant mesophyll conductance, which has played an essential role in photosynthesis by controlling leaf structural and biochemical properties. Mesophyll conductance (gm), a crucial physiological factor influencing the photosynthetic rate of leaves, is used to describe the resistance of CO2 from the sub-stomatal cavity into the chloroplast up to the carboxylation site. Leaf structural and biochemical components, as well as external environmental factors such as light, temperature, and water, all impact gm. As an essential factor of plant photosynthesis, light affects plant growth and development and plays a vital role in regulating gm as well as determining photosynthesis and yield. This review aimed to summarize the mechanisms of gm response to light. Both structural and biochemical perspectives were combined to reveal the effects of light quality and intensity on the gm, providing a guide for selecting the optimal conditions for intensifying photosynthesis in plants.
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Affiliation(s)
- Yadan Pang
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, 610213, China
- College of Horticulture and Landscape Architecture, Southwest University, Chongqing, 400712, China
| | - Qiuhong Liao
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, 610213, China
| | - Honggui Peng
- College of Horticulture and Landscape Architecture, Southwest University, Chongqing, 400712, China
| | - Chun Qian
- College of Horticulture and Landscape Architecture, Southwest University, Chongqing, 400712, China
| | - Fang Wang
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, 610213, China.
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2
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Griffin JHC, Prado K, Sutton P, Toledo-Ortiz G. Coordinating light responses between the nucleus and the chloroplast, a role for plant cryptochromes and phytochromes. PHYSIOLOGIA PLANTARUM 2020; 169:515-528. [PMID: 32519399 DOI: 10.1111/ppl.13148] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 06/04/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
To promote photomorphogenesis, including plastid development and metabolism, the phytochrome (phy) and the cryptochrome (cry) photoreceptors orchestrate genome-wide changes in gene expression in response to Red (R)- and Blue (B)-light cues. While phys and crys have a clear role in modulating photosynthesis, their role in the coordination of the nuclear genome and the plastome, essential for functional chloroplasts, remains underexplored. Using publicly available genome datasets for WT and phyABCDE or cry1cry2 Arabidopsis seedlings, grown, respectively, under R- or B-light, we bioinformatically analyzed the influence of light inputs and photoreceptors in the control of nuclear genes with a function in the chloroplast, and evaluated the role of phyB in the modulation of plastome-encoded genes. We show gene co-induction by R-phys and B-crys for genes with a chloroplastic function, and also apparent photoreceptor-driven preferential responses. Evidence from phyB in Arabidopsis together with published evidence from CRY2 in tomato also supports the participation of both photoreceptor families in the global modulation of the plastome genes. To begin addressing how these light-sensors orchestrate changes in an organellar genome, we evaluated their effect over genes with potential functions in plastid gene-expression regulation based on their TAIR annotation. Results indicate that both crys and phys modulate 'plastome-regulatory genes' with enrichment in the contribution of crys to all processes and of phys to post-transcription and transcription. Furthermore, we identified a new role for HY5 as a relevant light-signaling component in photoreceptor-based anterograde signaling leading to plastome gene regulation.
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Affiliation(s)
| | - Karine Prado
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California, 94305, USA
| | - Phoebe Sutton
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
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3
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Seo SY, Wi SJ, Park KY. Functional switching of NPR1 between chloroplast and nucleus for adaptive response to salt stress. Sci Rep 2020; 10:4339. [PMID: 32152424 PMCID: PMC7062895 DOI: 10.1038/s41598-020-61379-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 02/13/2020] [Indexed: 02/02/2023] Open
Abstract
Salt stress causes rapid accumulation of nonexpressor of pathogenesis-related genes 1 (NPR1) protein, known as the redox-sensitive transcription coactivator, which in turn elicits many adaptive responses. The NPR1 protein transiently accumulates in chloroplast stroma under salt stress, which attenuates stress-triggered down-regulation of photosynthetic capability. We observed that oligomeric NPR1 in chloroplasts and cytoplasm had chaperone activity, whereas monomeric NPR1 in the nucleus did not. Additionally, NPR1 overexpression resulted in reinforcement of morning-phased and evening-phased circadian clock. NPR1 overexpression also enhanced antioxidant activity and reduced stress-induced reactive oxygen species (ROS) generation at early stage, followed with transcription levels for ROS detoxification. These results suggest a functional switch from a molecular chaperone to a transcriptional coactivator, which is dependent on subcellular localization. Our findings imply that dual localization of NPR1 is related to proteostasis and redox homeostasis in chloroplasts for emergency restoration as well as transcriptional coactivator in the nucleus for adaptation to stress.
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Affiliation(s)
- So Yeon Seo
- Department of Biology, Sunchon National University, Sunchon, Chonnam, Republic of Korea
| | - Soo Jin Wi
- Department of Biology, Sunchon National University, Sunchon, Chonnam, Republic of Korea
| | - Ky Young Park
- Department of Biology, Sunchon National University, Sunchon, Chonnam, Republic of Korea.
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4
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Lin D, Zhang L, Mei J, Chen J, Piao Z, Lee G, Dong Y. Mutation of the rice TCM12 gene encoding 2,3-bisphosphoglycerate-independent phosphoglycerate mutase affects chlorophyll synthesis, photosynthesis and chloroplast development at seedling stage at low temperatures. PLANT BIOLOGY (STUTTGART, GERMANY) 2019; 21:585-594. [PMID: 30803106 DOI: 10.1111/plb.12978] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
Glycolysis is a central metabolic pathway that provides energy and products of primary metabolites. 2,3-Biphosphoglycerate-independent phosphoglycerate mutase (iPGAM) is a key enzyme that catalyses the reversible interconversion of 3-phosphoglycerate (3-PGA) to 2-phosphoglycerate (2-PGA) in glycolysis. Low temperature is a common abiotic stress in rice production. However, the mechanism for rice iPGAM genes is not fully understood at low temperature. In this study, the rice mutant tcm12, with chlorosis, malformed chloroplasts and impaired photosynthesis, was grown at a low temperature (<20 °C) to the three-leaf stage, while the normal phenotype at 32 °C was used. Chlorophyll fluorescence analysis and transmission electron microscopy were used to examine features of the tcm12 mutant. The inheritance behaviour and function of TCM12 were then analysed thorough map-based cloning, transgenic complementation and subcellular localisation. The thermo-sensitive chlorosis phenotype was caused by a single nucleotide mutation (T→C) on the fifth exon of TCM12 (LOC_Os12g35040) encoding iPGAM, localised to both nucleus and membranes. In addition, TCM12 was constitutively expressed, and its disruption resulted in down-regulation of some genes associated with chlorophyll biosynthesis and photosynthesis at low temperatures (20 °C). This is the first report of the involvement of rice iPGAM gene in chlorophyll synthesis, photosynthesis and chloroplast development, providing new insights into the mechanisms underlying early growth of rice at low temperatures.
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Affiliation(s)
- D Lin
- College of Life Sciences, Shanghai Normal University, Shanghai, China
| | - L Zhang
- College of Life Sciences, Shanghai Normal University, Shanghai, China
| | - J Mei
- College of Life Sciences, Shanghai Normal University, Shanghai, China
| | - J Chen
- College of Life Sciences, Shanghai Normal University, Shanghai, China
- Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Z Piao
- Crop Breeding and Cultivation Research Institute, Shanghai Academy of Agricultural Sciences, Fengxian District, Shanghai 3, China
| | - G Lee
- National Institute of Agricultural Science, Jeon Ju, Korea
| | - Y Dong
- College of Life Sciences, Shanghai Normal University, Shanghai, China
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5
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Chotewutmontri P, Barkan A. Multilevel effects of light on ribosome dynamics in chloroplasts program genome-wide and psbA-specific changes in translation. PLoS Genet 2018; 14:e1007555. [PMID: 30080854 PMCID: PMC6095610 DOI: 10.1371/journal.pgen.1007555] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/16/2018] [Accepted: 07/11/2018] [Indexed: 11/22/2022] Open
Abstract
Plants and algae adapt to fluctuating light conditions to optimize photosynthesis, minimize photodamage, and prioritize energy investments. Changes in the translation of chloroplast mRNAs are known to contribute to these adaptations, but the scope and magnitude of these responses are unclear. To clarify the phenomenology, we used ribosome profiling to analyze chloroplast translation in maize seedlings following dark-to-light and light-to-dark shifts. The results resolved several layers of regulation. (i) The psbA mRNA exhibits a dramatic gain of ribosomes within minutes after shifting plants to the light and reverts to low ribosome occupancy within one hour in the dark, correlating with the need to replace damaged PsbA in Photosystem II. (ii) Ribosome occupancy on all other chloroplast mRNAs remains similar to that at midday even after 12 hours in the dark. (iii) Analysis of ribosome dynamics in the presence of lincomycin revealed a global decrease in the translation elongation rate shortly after shifting plants to the dark. The pausing of chloroplast ribosomes at specific sites changed very little during these light-shift regimes. A similar but less comprehensive analysis in Arabidopsis gave similar results excepting a trend toward reduced ribosome occupancy at the end of the night. Our results show that all chloroplast mRNAs except psbA maintain similar ribosome occupancy following short-term light shifts, but are nonetheless translated at higher rates in the light due to a plastome-wide increase in elongation rate. A light-induced recruitment of ribosomes to psbA mRNA is superimposed on this global response, producing a rapid and massive increase in PsbA synthesis. These findings highlight the unique translational response of psbA in mature chloroplasts, clarify which steps in psbA translation are light-regulated in the context of Photosystem II repair, and provide a foundation on which to explore mechanisms underlying the psbA-specific and global effects of light on chloroplast translation.
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Affiliation(s)
| | - Alice Barkan
- Institute of Molecular Biology, University of Oregon, Eugene, OR, United States of America
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6
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Sun Y, Zerges W. Translational regulation in chloroplasts for development and homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:809-20. [PMID: 25988717 DOI: 10.1016/j.bbabio.2015.05.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 04/13/2015] [Accepted: 05/10/2015] [Indexed: 11/16/2022]
Abstract
Chloroplast genomes encode 100-200 proteins which function in photosynthesis, the organellar genetic system, and other pathways and processes. These proteins are synthesized by a complete translation system within the chloroplast, with bacterial-type ribosomes and translation factors. Here, we review translational regulation in chloroplasts, focusing on changes in translation rates which occur in response to requirements for proteins encoded by the chloroplast genome for development and homeostasis. In addition, we delineate the developmental and physiological contexts and model organisms in which translational regulation in chloroplasts has been studied. This article is part of a Special Issue entitled: Chloroplast biogenesis.
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Affiliation(s)
- Yi Sun
- Biology Department and Center for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke W., Montreal, Quebec H4B 1R6, Canada
| | - William Zerges
- Biology Department and Center for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke W., Montreal, Quebec H4B 1R6, Canada.
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7
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Recuenco-Muñoz L, Offre P, Valledor L, Lyon D, Weckwerth W, Wienkoop S. Targeted quantitative analysis of a diurnal RuBisCO subunit expression and translation profile in Chlamydomonas reinhardtii introducing a novel Mass Western approach. J Proteomics 2014; 113:143-53. [PMID: 25301535 DOI: 10.1016/j.jprot.2014.09.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 08/26/2014] [Accepted: 09/26/2014] [Indexed: 01/12/2023]
Abstract
UNLABELLED RuBisCO catalyzes the rate-limiting step of CO2 fixation in photosynthesis. Hypothetical mechanisms for the regulation of rbcL and rbcS gene expression assume that both large (LSU) and small (SSU) RuBisCO subunit proteins (RSUs) are present in equimolar amounts to fit the 1:1 subunit stoichiometry of the holoenzyme. However, the actual quantities of the RSUs have never been determined in any photosynthetic organism. In this study the absolute amount of rbc transcripts and RSUs was quantified in Chlamydomonas reinhardtii grown during a diurnal light/dark cycle. A novel approach utilizing more reliable protein stoichiometry quantification is introduced. The rbcL:rbcS transcript and protein ratios were both 5:1 on average during the diurnal time course, indicating that SSU is the limiting factor for the assembly of the holoenzyme. The oscillation of the RSUs was 9h out of phase relative to the transcripts. The amount of rbc transcripts was at its maximum in the dark while that of RSUs was at its maximum in the light phase suggesting that translation of the rbc transcripts is activated by light as previously hypothesized. A possible post-translational regulation that might be involved in the accumulation of a 37-kDa N-terminal LSU fragment during the light phase is discussed. BIOLOGICAL SIGNIFICANCE A novel MS based approach enabling the exact stoichiometric analysis and absolute quantification of protein complexes is presented in this article. The application of this method revealed new insights in RuBisCO subunit dynamics.
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Affiliation(s)
- Luis Recuenco-Muñoz
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Pierre Offre
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Luis Valledor
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - David Lyon
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Wolfram Weckwerth
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Stefanie Wienkoop
- Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria.
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8
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Abstract
Overall translational machinery in plastids is similar to that of E. coli. Initiation is the crucial step for translation and this step in plastids is somewhat different from that of E. coli. Unlike the Shine-Dalgarno sequence in E. coli, cis-elements for translation initiation are not well conserved in plastid mRNAs. Specific trans-acting factors are generally required for translation initiation and its regulation in plastids. During translation elongation, ribosomes pause sometimes on photosynthesis-related mRNAs due probably to proper insertion of nascent polypeptides into membrane complexes. Codon usage of plastid mRNAs is different from that of E. coli and mammalian cells. Plastid mRNAs do not have the so-called rare codons. Translation efficiencies of several synonymous codons are not always correlated with codon usage in plastid mRNAs.
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9
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Hu X, Wu X, Li C, Lu M, Liu T, Wang Y, Wang W. Abscisic acid refines the synthesis of chloroplast proteins in maize (Zea mays) in response to drought and light. PLoS One 2012; 7:e49500. [PMID: 23152915 PMCID: PMC3496715 DOI: 10.1371/journal.pone.0049500] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/09/2012] [Indexed: 12/18/2022] Open
Abstract
To better understand abscisic acid (ABA) regulation of the synthesis of chloroplast proteins in maize (Zea mays L.) in response to drought and light, we compared leaf proteome differences between maize ABA-deficient mutant vp5 and corresponding wild-type Vp5 green and etiolated seedlings exposed to drought stress. Proteins extracted from the leaves of Vp5 and vp5 seedlings were used for two-dimensional electrophoresis (2-DE) and subsequent matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). After Coomassie brilliant blue staining, approximately 450 protein spots were reproducibly detected on 2-DE gels. A total of 36 differentially expressed protein spots in response to drought and light were identified using MALDI-TOF MS and their subcellular localization was determined based on the annotation of reviewed accession in UniProt Knowledgebase and the software prediction. As a result, corresponding 13 proteins of the 24 differentially expressed protein spots were definitely localized in chloroplasts and their expression was in an ABA-dependent way, including 6 up-regulated by both drought and light, 5 up-regulated by drought but down-regulated by light, 5 up-regulated by light but down-regulated by drought; 5 proteins down-regulated by drought were mainly those involved in photosynthesis and ATP synthesis. Thus, the results in the present study supported the vital role of ABA in regulating the synthesis of drought- and/or light-induced proteins in maize chloroplasts and would facilitate the functional characterization of ABA-induced chloroplast proteins in C(4) plants.
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Affiliation(s)
- Xiuli Hu
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, Henan Agricultural University, Zhengzhou, China
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Xiaolin Wu
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Chaohai Li
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, Henan Agricultural University, Zhengzhou, China
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Minghui Lu
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Tianxue Liu
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, Henan Agricultural University, Zhengzhou, China
- College of Agronomy, Henan Agricultural University, Zhengzhou, China
| | - Ying Wang
- College of Life Science, Henan Agricultural University, Zhengzhou, China
| | - Wei Wang
- Key Laboratory of Physiological Ecology and Genetic Improvement of Food Crops in Henan Province, Henan Agricultural University, Zhengzhou, China
- College of Life Science, Henan Agricultural University, Zhengzhou, China
- * E-mail:
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10
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Payne TM, Payne AJ, Knoll LJ. A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection. Mol Microbiol 2011; 82:1204-16. [PMID: 22059956 DOI: 10.1111/j.1365-2958.2011.07879.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite of all warm-blooded animals. We previously described a forward genetic screen to identify T. gondii mutants defective in the establishment of a chronic infection. One of the mutants isolated was disrupted in the 3' untranslated region (3'UTR) of an orthologue of bacterial translation elongation factor G (EFG). The mutant does not have a growth defect in tissue culture. Genetic complementation of this mutant with the genomic locus of TgEFG restores virulence in an acute infection mouse model. Epitope tagged TgEFG localized to the apicoplast, via a non-canonical targeting signal, where it functions as an elongation factor for translation in the apicoplast. Comparisons of TgEFG expression constructs with wild-type or mutant 3'UTRs showed that a wild-type 3'UTR is necessary for translation of TgEFG. In tissue culture, the TgEFG transcript is equally abundant in wild-type and mutant parasites; however, during an animal infection, the TgEFG transcript is increased more than threefold in the mutant. These results highlight that in tissue culture, translation in the apicoplast can be diminished, but during an animal infection, translation in the apicoplast must be fully functional.
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Affiliation(s)
- T Matthew Payne
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
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11
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Marín-Navarro J, Manuell AL, Wu J, P Mayfield S. Chloroplast translation regulation. PHOTOSYNTHESIS RESEARCH 2007; 94:359-74. [PMID: 17661159 DOI: 10.1007/s11120-007-9183-z] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 04/19/2007] [Indexed: 05/16/2023]
Abstract
Chloroplast gene expression is primarily controlled during the translation of plastid mRNAs. Translation is regulated in response to a variety of biotic and abiotic factors, and requires a coordinate expression with the nuclear genome. The translational apparatus of chloroplasts is related to that of bacteria, but has adopted novel mechanisms in order to execute the specific roles that this organelle performs within a eukaryotic cell. Accordingly, plastid ribosomes contain a number of chloroplast-unique proteins and domains that may function in translational regulation. Chloroplast translation regulation involves cis-acting RNA elements (located in the mRNA 5' UTR) as well as a set of corresponding trans-acting protein factors. While regulation of chloroplast translation is primarily controlled at the initiation steps through these RNA-protein interactions, elongation steps are also targets for modulating chloroplast gene expression. Translation of chloroplast mRNAs is regulated in response to light, and the molecular mechanisms underlying this response involve changes in the redox state of key elements related to the photosynthetic electron chain, fluctuations of the ADP/ATP ratio and the generation of a proton gradient. Photosynthetic complexes also experience assembly-related autoinhibition of translation to coordinate the expression of different subunits of the same complex. Finally, the localization of all these molecular events among the different chloroplast subcompartments appear to be a crucial component of the regulatory mechanisms of chloroplast gene expression.
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Affiliation(s)
- Julia Marín-Navarro
- Department of Cell Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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12
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Motohashi R, Yamazaki T, Myouga F, Ito T, Ito K, Satou M, Kobayashi M, Nagata N, Yoshida S, Nagashima A, Tanaka K, Takahashi S, Shinozaki K. Chloroplast ribosome release factor 1 (AtcpRF1) is essential for chloroplast development. PLANT MOLECULAR BIOLOGY 2007; 64:481-97. [PMID: 17450416 DOI: 10.1007/s11103-007-9166-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Accepted: 03/20/2007] [Indexed: 05/08/2023]
Abstract
To study the functions of nuclear genes involved in chloroplast development, we systematically analyzed albino and pale green Arabidopsis thaliana mutants by use of the Activator/Dissociation (Ac/Ds) transposon tagging system. In this study, we focused on one of these albino mutants, designated apg3-1 (for a lbino or p ale g reen mutant 3). A gene encoding a ribosome release factor 1 (RF1) homologue was disrupted by the insertion of a Ds transposon into the APG3 gene; a T-DNA insertion into the same gene caused a similar phenotype (apg3-2). The APG3 gene (At3g62910) has 15 exons and encodes a protein (422-aa) with a transit peptide that functions in targeting the protein to chloroplasts. The amino acid sequence of APG3 showed 40.6% homology with an RF1 of Escherichia coli, and complementation analysis using the E. coli rf1 mutant revealed that APG3 functions as an RF1 in E. coli, although complementation was not successful in the RF2-deficient (rf2) mutants of E. coli. These results indicate that the APG3 protein is an orthologue of E. coli RF1, and is essential for chloroplast translation machinery; it was accordingly named AtcpRF1. Since the chloroplasts of apg3-1 plants contained few internal thylakoid membranes, and chloroplast proteins related to photosynthesis were not detected by immunoblot analysis, AtcpRF1 is thought to be essential for chloroplast development.
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Affiliation(s)
- Reiko Motohashi
- Faculty of Agriculture, University of Shizuoka, 836 Ohya, Suruga-ku, Shizuoka, 422-8529, Japan.
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13
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Wostrikoff K, Stern D. Rubisco large-subunit translation is autoregulated in response to its assembly state in tobacco chloroplasts. Proc Natl Acad Sci U S A 2007; 104:6466-71. [PMID: 17404229 PMCID: PMC1851044 DOI: 10.1073/pnas.0610586104] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Indexed: 01/01/2023] Open
Abstract
Plants rely on ribulose bisphosphate carboxylase/oxygenase (Rubisco) for carbon fixation. Higher plant Rubisco possesses an L(8)S(8) structure, with the large subunit (LS) encoded in the chloroplast by rbcL and the small subunit encoded by the nuclear RBCS gene family. Because its components accumulate stoichiometrically but are encoded in two genetic compartments, rbcL and RBCS expression must be tightly coordinated. Although this coordination has been observed, the underlying mechanisms have not been defined. Here, we use tobacco to understand how LS translation is related to its assembly status. To do so, two transgenic lines deficient in LS biogenesis were created: a chloroplast transformant expressing a truncated and unstable LS polypeptide, and a line where a homolog of the maize Rubisco-specific chaperone, BSD2, was repressed by RNAi. We found that in both lines, LS translation is no longer regulated by the availability of small subunit (SS), indicating that LS translation is not activated by the presence of its assembly partner but, rather, undergoes an autoregulation of translation. Pulse labeling experiments indicate that LS is synthesized but not accumulated in the transgenic lines, suggesting that accumulation of a repressor motif is required for LS assembly-dependent translational regulation.
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Affiliation(s)
- Katia Wostrikoff
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
| | - David Stern
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
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14
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Translation and translational regulation in chloroplasts. CELL AND MOLECULAR BIOLOGY OF PLASTIDS 2007. [DOI: 10.1007/4735_2007_0234] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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15
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Cohen I, Knopf JA, Irihimovitch V, Shapira M. A proposed mechanism for the inhibitory effects of oxidative stress on Rubisco assembly and its subunit expression. PLANT PHYSIOLOGY 2005; 137:738-46. [PMID: 15681660 PMCID: PMC1065373 DOI: 10.1104/pp.104.056341] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Revised: 12/02/2004] [Accepted: 12/08/2004] [Indexed: 05/18/2023]
Abstract
In Chlamydomonas reinhardtii, a light-induced oxidative stress shifts the glutathione pool toward its oxidized form, resulting in a translational arrest of the large subunit (LSU) of Rubisco. We show here that the translational arrest of LSU is tightly coordinated with cessation of Rubisco assembly, and both processes take place after a threshold level of reactive oxygen species is reached. As a result, the small subunit is also eliminated by rapid degradation. We previously showed that the amino terminus of the LSU could bind RNA in a sequence-independent manner, as it shares a structural similarity with the RNA recognition motif. This domain becomes exposed only under oxidizing conditions, thus restricting the RNA-binding activity. Here we show that in vitro, thiol groups of both subunits become oxidized in the presence of oxidized glutathione. The structural changes are mediated by oxidized glutathione, whereas only very high concentrations of H2O2 confer similar results in vitro. Changes in the redox state of the LSU thiol groups are also observed in vivo, in response to a physiological light shock caused by transfer of cells from low light to high light. We propose that during a photooxidative stress, oxidation of thiol groups occurs already in nascent LSU chains, perhaps hindering their association with chaperones. As a result, their RNA recognition motif domain becomes exposed and will bind any RNA in its vicinity, including its own transcript. Due to this binding the ribosome stalls, preventing the assembly of additional ribosomes on the transcript. Polysome analysis using Suc gradients indeed shows that the rbcL RNA is associated with the polysomal fraction at all times but shifts toward fractions that contain smaller polysomes and monosomes during oxidative stress. Thus, translational arrest of the LSU most likely occurs at a postinitiation stage.
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Affiliation(s)
- Idan Cohen
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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