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Fages‐Lartaud M, Hundvin K, Hohmann‐Marriott MF. Mechanisms governing codon usage bias and the implications for protein expression in the chloroplast of Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 112:919-945. [PMID: 36071273 PMCID: PMC9828097 DOI: 10.1111/tpj.15970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 08/29/2022] [Accepted: 09/01/2022] [Indexed: 05/30/2023]
Abstract
Chloroplasts possess a considerably reduced genome that is decoded via an almost minimal set of tRNAs. These features make an excellent platform for gaining insights into fundamental mechanisms that govern protein expression. Here, we present a comprehensive and revised perspective of the mechanisms that drive codon selection in the chloroplast of Chlamydomonas reinhardtii and the functional consequences for protein expression. In order to extract this information, we applied several codon usage descriptors to genes with different expression levels. We show that highly expressed genes strongly favor translationally optimal codons, while genes with lower functional importance are rather affected by directional mutational bias. We demonstrate that codon optimality can be deduced from codon-anticodon pairing affinity and, for a small number of amino acids (leucine, arginine, serine, and isoleucine), tRNA concentrations. Finally, we review, analyze, and expand on the impact of codon usage on protein yield, secondary structures of mRNA, translation initiation and termination, and amino acid composition of proteins, as well as cotranslational protein folding. The comprehensive analysis of codon choice provides crucial insights into heterologous gene expression in the chloroplast of C. reinhardtii, which may also be applicable to other chloroplast-containing organisms and bacteria.
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Affiliation(s)
- Maxime Fages‐Lartaud
- Department of BiotechnologyNorwegian University of Science and TechnologyTrondheimN‐7491Norway
| | - Kristoffer Hundvin
- Department of BiotechnologyNorwegian University of Science and TechnologyTrondheimN‐7491Norway
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Bayro-Kaiser V, Nelson N. Temperature Sensitive Photosynthesis: Point Mutated CEF-G, PRK, or PsbO Act as Temperature-Controlled Switches for Essential Photosynthetic Processes. FRONTIERS IN PLANT SCIENCE 2020; 11:562985. [PMID: 33101332 PMCID: PMC7545824 DOI: 10.3389/fpls.2020.562985] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 09/04/2020] [Indexed: 05/30/2023]
Abstract
Temperature sensitive mutants have been widely used to study structure, biogenesis and function of a large variety of essential proteins. However, this method has not yet been exploited for the study of photosynthesis. We used negative selection to isolate temperature-sensitive-photoautotrophic (TSP) mutants in Chlamydomonas reinhardtii. From a population of randomly mutagenized cells (n=12,000), a significant number of TSP mutants (n=157) were isolated. They were able to grow photoautotrophically at 25°C, but lacked this ability at 37°C. Further phenotypic characterization of these mutants enabled the identification of three unique and highly interesting mutant strains. Following, the selected strains were genetically characterized by extensive crossing and whole genome sequencing. Correspondingly, the single amino acid changes P628F in the Chloroplast-Elongation-Factor-G (CEF-G), P129L in Phosphoribulokinase (PRK), and P101H in an essential subunit of Photosystem II (PsbO) were identified. These key changes alter the proteins in such way that they were functional at the permissive temperature, however, defective at the restrictive temperature. These mutants are presented here as superb and novel tools for the study of a wide range of aspects relevant to photosynthesis research, tackling three distinct and crucial photosynthetic processes: Chloroplast translation, PET-chain, and CBB-cycle.
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Dehghani J, Adibkia K, Movafeghi A, Pourseif MM, Omidi Y. Designing a new generation of expression toolkits for engineering of green microalgae; robust production of human interleukin-2. ACTA ACUST UNITED AC 2020; 10:259-268. [PMID: 32983942 PMCID: PMC7502910 DOI: 10.34172/bi.2020.33] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/17/2020] [Accepted: 06/29/2020] [Indexed: 02/06/2023]
Abstract
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Introduction: Attributable to some critical features especially the similarity of the protein synthesis machinery between humans and microalgae, these microorganisms can be utilized for the expression of many recombinant proteins. However, low and unstable gene expression levels prevent the further development of microalgae biotechnology towards protein production.
Methods: Here, we designed a novel "Gained Agrobacterium -2A plasmid for microalgae expression" (named GAME plasmid) for the production of the human interleukin-2 using three model microalgae, including Chlamydomonas reinhardtii, Chlorella vulgaris , and Dunaliella salina . The GAME plasmid harbors a native chimeric hsp70/Int-1/rbcS2 promoter, the microalgae specific Kozak sequence, a novel hybrid 2A peptide, and Int-1 and Int-3 of the rbcS2 gene in its expression cassette.
Results: The obtained data confirmed that the GAME plasmid can transform the microalgae with high transformation frequency. Molecular and proteomic analyses revealed the stable and robust production of the hIL-2 by the GAME plasmid in the microalgae. According to the densimetric analysis, the microalgae can accumulate the produced protein about 0.94% of the total soluble protein content. The ELISA data confirmed that the produced hIL-2 possesses the same conformation pattern with the acceptable biological activity found naturally in humans.
Conclusion: Most therapeutic proteins need post-translational modifications for their correct conformation, biological function, and half-life. Accordingly, microalgae could be considered as a cost-effective and more powerful platform for the production of a wide range of recombinant proteins such as antibodies, enzymes, hormones, and vaccines.
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Affiliation(s)
- Jaber Dehghani
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Plant Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Khosro Adibkia
- Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Ali Movafeghi
- Department of Plant Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Mohammad M Pourseif
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yadollah Omidi
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, Florida 33328, USA
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4
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Wu W, Yan Y. Chloroplast proteome analysis of Nicotiana tabacum overexpressing TERF1 under drought stress condition. BOTANICAL STUDIES 2018; 59:26. [PMID: 30374844 PMCID: PMC6206318 DOI: 10.1186/s40529-018-0239-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/17/2018] [Indexed: 05/11/2023]
Abstract
BACKGROUND Chloroplast is indispensable for plant response to environmental stresses, growth and development, whose function is regulated by different plant hormones. The chloroplast proteome is encoded by chloroplast genome and nuclear genome, which play essential roles in plant photosynthesis, metabolism and other biological processes. Ethylene response factors (ERFs) are key transcription factors in activating the ethylene signaling pathway and plant response to abiotic stress. But we know little about how ethylene regulates plastid function under drought stress condition. In this study we utilized tobacco overexpressing tomato ethylene responsive factor 1 (TERF1), an ERF transcription factor isolated from tomato, to investigate its effects on the plastid proteome under drought stress condition by method of iTRAQ technology. RESULTS Results show that TERF1 represses the genes encoding the photosynthetic apparatus at both transcriptional and translational level, but the genes involved in carbon fixation are significantly induced by TERF1. TERF1 regulates multiple retrograde signaling pathways, providing a new mechanism for regulating nuclear gene expression. TERF1 also regulates plant utilization of phosphorus (Pi) and nitrogen (N). We find that several metabolic and signaling pathways related with Pi are significantly repressed and gene expression analysis shows that TERF1 significantly represses the Pi transport from root to shoot. However, the N metabolism is upregulated by TERF1 as shown by the activation of different amino acids biosynthesis pathways due to the induction of glutamine synthetase and stabilization of nitrate reductase although the root-to-shoot N transport is also reduced. TERF1 also regulates other core metabolic pathways and secondary metabolic pathways that are important for plant growth, development and response to environmental stresses. Gene set linkage analysis was applied for the upregulated proteins by TERF1, showing some new potential for regulating plant response to drought stress by TERF1. CONCLUSIONS Our research reveals effects of ethylene signaling on plastid proteome related with two key biological processes, including photosynthesis and nutrition utilization. We also provide a new mechanism to regulate nuclear gene expression by ERF1 transcription factor through retrograde signals in chloroplast. These results can enrich our knowledge about ERF1 transcription factor and function of ethylene signaling pathway.
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Affiliation(s)
- Wei Wu
- Graduate School of Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South St., Haidian District, Beijing, 100081 People’s Republic of China
| | - Yanchun Yan
- Graduate School of Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South St., Haidian District, Beijing, 100081 People’s Republic of China
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5
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Zhang Y, Cui YL, Zhang XL, Yu QB, Wang X, Yuan XB, Qin XM, He XF, Huang C, Yang ZN. A nuclear-encoded protein, mTERF6, mediates transcription termination of rpoA polycistron for plastid-encoded RNA polymerase-dependent chloroplast gene expression and chloroplast development. Sci Rep 2018; 8:11929. [PMID: 30093718 PMCID: PMC6085346 DOI: 10.1038/s41598-018-30166-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 04/20/2018] [Indexed: 12/13/2022] Open
Abstract
The expression of plastid genes is regulated by two types of DNA-dependent RNA polymerases, plastid-encoded RNA polymerase (PEP) and nuclear-encoded RNA polymerase (NEP). The plastid rpoA polycistron encodes a series of essential chloroplast ribosome subunits and a core subunit of PEP. Despite the functional importance, little is known about the regulation of rpoA polycistron. In this work, we show that mTERF6 directly associates with a 3′-end sequence of rpoA polycistron in vitro and in vivo, and that absence of mTERF6 promotes read-through transcription at this site, indicating that mTERF6 acts as a factor required for termination of plastid genes’ transcription in vivo. In addition, the transcriptions of some essential ribosome subunits encoded by rpoA polycistron and PEP-dependent plastid genes are reduced in the mterf6 knockout mutant. RpoA, a PEP core subunit, accumulates to about 50% that of the wild type in the mutant, where early chloroplast development is impaired. Overall, our functional analyses of mTERF6 provide evidence that it is more likely a factor required for transcription termination of rpoA polycistron, which is essential for chloroplast gene expression and chloroplast development.
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Affiliation(s)
- Yi Zhang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China.,Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai, 201602, China
| | - Yong-Lan Cui
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Xiao-Lei Zhang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Qing-Bo Yu
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Xi Wang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Xin-Bo Yuan
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Xue-Mei Qin
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Xiao-Fang He
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Chao Huang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Zhong-Nan Yang
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, 200234, China.
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6
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Zhang Y, Launay H, Schramm A, Lebrun R, Gontero B. Exploring intrinsically disordered proteins in Chlamydomonas reinhardtii. Sci Rep 2018; 8:6805. [PMID: 29717210 PMCID: PMC5931566 DOI: 10.1038/s41598-018-24772-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 03/26/2018] [Indexed: 11/14/2022] Open
Abstract
The content of intrinsically disordered protein (IDP) is related to organism complexity, evolution, and regulation. In the Plantae, despite their high complexity, experimental investigation of IDP content is lacking. We identified by mass spectrometry 682 heat-resistant proteins from the green alga, Chlamydomonas reinhardtii. Using a phosphoproteome database, we found that 331 of these proteins are targets of phosphorylation. We analyzed the flexibility propensity of the heat-resistant proteins and their specific features as well as those of predicted IDPs from the same organism. Their mean percentage of disorder was about 20%. Most of the IDPs (~70%) were addressed to other compartments than mitochondrion and chloroplast. Their amino acid composition was biased compared to other classic IDPs. Their molecular functions were diverse; the predominant ones were nucleic acid binding and unfolded protein binding and the less abundant one was catalytic activity. The most represented proteins were ribosomal proteins, proteins associated to flagella, chaperones and histones. We also found CP12, the only experimental IDP from C. reinhardtii that is referenced in disordered protein database. This is the first experimental investigation of IDPs in C. reinhardtii that also combines in silico analysis.
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Affiliation(s)
- Yizhi Zhang
- Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13402, Marseille, Cedex 20, France
| | - Hélène Launay
- Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13402, Marseille, Cedex 20, France
| | | | - Régine Lebrun
- Plate-forme Protéomique, Marseille Protéomique (MaP), IBiSA labeled, IMM, FR 3479, CNRS, B.P. 71, 13402, Marseille, Cedex 20, France
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, 31 Chemin J. Aiguier, 13402, Marseille, Cedex 20, France.
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7
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Ahmed T, Shi J, Bhushan S. Unique localization of the plastid-specific ribosomal proteins in the chloroplast ribosome small subunit provides mechanistic insights into the chloroplastic translation. Nucleic Acids Res 2017; 45:8581-8595. [PMID: 28582576 PMCID: PMC5737520 DOI: 10.1093/nar/gkx499] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 05/26/2017] [Indexed: 12/30/2022] Open
Abstract
Chloroplastic translation is mediated by a bacterial-type 70S chloroplast ribosome. During the evolution, chloroplast ribosomes have acquired five plastid-specific ribosomal proteins or PSRPs (cS22, cS23, bTHXc, cL37 and cL38) which have been suggested to play important regulatory roles in translation. However, their exact locations on the chloroplast ribosome remain elusive due to lack of a high-resolution structure, hindering our progress to understand their possible roles. Here we present a cryo-EM structure of the 70S chloroplast ribosome from spinach resolved to 3.4 Å and focus our discussion mainly on the architecture of the 30S small subunit (SSU) which is resolved to 3.7 Å. cS22 localizes at the SSU foot where it seems to compensate for the deletions in 16S rRNA. The mRNA exit site is highly remodeled due to the presence of cS23 suggesting an alternative mode of translation initiation. bTHXc is positioned at the SSU head and appears to stabilize the intersubunit bridge B1b during thermal fluctuations. The translation factor plastid pY binds to the SSU on the intersubunit side and interacts with the conserved nucleotide bases involved in decoding. Most of the intersubunit bridges are conserved compared to the bacteria, except for a new bridge involving uL2c and bS6c.
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Affiliation(s)
- Tofayel Ahmed
- School of Biological Sciences, Nanyang Technological University, 637551, Singapore
| | - Jian Shi
- Center for BioImaging Sciences, National University of Singapore, 117546, Singapore
| | - Shashi Bhushan
- School of Biological Sciences, Nanyang Technological University, 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 639798, Singapore
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8
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Isolation of Plastid Ribosomes. Methods Mol Biol 2016. [PMID: 27730617 DOI: 10.1007/978-1-4939-6533-5_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Plastid ribosomes are responsible for a large part of the protein synthesis in plant leaves, green algal cells, and the vast majority in the thalli of red algae. Plastid translation is necessary not only for photosynthesis but also for development/differentiation of plants and algae. While some isolated plastid ribosomes from a few green lineages have been characterized by biochemical and proteomic approaches, in-depth proteomics including analyses of posttranslational modifications and processing, comparative proteomics of plastid ribosomes isolated from the cells grown under different conditions, and those from different taxa are still to be carried out. Establishment of isolation methods for pure plastid ribosomes from a wider range of species would be beneficial to study the relationship between structure, function, and evolution of plastid ribosomes. Here I describe methodologies and provide example protocols for extraction and isolation of plastid ribosomes from a unicellular green alga (Chlamydomonas reinhardtii), a land plant (Arabidopsis thaliana), and a marine red macroalga (Pyropia yezoensis).
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9
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Siniauskaya MG, Danilenko NG, Lukhanina NV, Shymkevich AM, Davydenko OG. Expression of the chloroplast genome: Modern concepts and experimental approaches. ACTA ACUST UNITED AC 2016. [DOI: 10.1134/s2079059716050117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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10
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He B, Mu Y, Chi W. Effects of inefficient transcription termination of rbcL on the expression of accD in plastids of Arabidopsis thaliana. PHOTOSYNTHESIS RESEARCH 2015; 126:323-330. [PMID: 26003009 DOI: 10.1007/s11120-015-0159-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/16/2015] [Indexed: 06/04/2023]
Abstract
The plastid accD gene encodes one subunit of a multimeric acetyl-CoA carboxylase that is required for fatty acid biosynthesis. In Arabidopsis thaliana, the accD gene is transcribed by the nuclear-encoded phage-type RNA polymerase, and the accumulation of accD transcripts is subjected to a dynamic pattern during chloroplast development. However, the mechanisms underlying the regulation of accD expression remain unknown. Here, we showed that the inefficient transcription termination of rbcL due to the absence of RHON1 impaired the developmental profile of accD, resulting in the constitutive expression of accD during chloroplast development. Moreover, the accumulation of accD transcripts accordingly resulted in an increase in accD protein levels, suggesting that transcript abundance is critical for accD gene production. Our study demonstrates that the interplay between accD and upstream rbcL regulates the expression of accD and highlights the significance of transcriptional regulation in plastid gene expression in higher plants.
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Affiliation(s)
- Baoye He
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ying Mu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wei Chi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing, 100093, China.
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11
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Nesbit AD, Whippo C, Hangarter RP, Kehoe DM. Translation initiation factor 3 families: what are their roles in regulating cyanobacterial and chloroplast gene expression? PHOTOSYNTHESIS RESEARCH 2015; 126:147-59. [PMID: 25630975 DOI: 10.1007/s11120-015-0074-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 01/02/2015] [Indexed: 05/09/2023]
Abstract
Initiation is a key control point for the regulation of translation in prokaryotes and prokaryotic-like translation systems such as those in plant chloroplasts. Genome sequencing and biochemical studies are increasingly demonstrating differences in many aspects of translation between well-studied microbes such as Escherichia coli and lesser studied groups such as cyanobacteria. Analyses of chloroplast translation have revealed its prokaryotic origin but also uncovered many unique aspects that do not exist in E. coli. Recently, a novel form of posttranscriptional regulation by light color was discovered in the filamentous cyanobacterium Fremyella diplosiphon that requires a putative stem-loop and involves the use of two different prokaryotic translation initiation factor 3s (IF3s). Multiple (up to five) putative IF3s have now been found to be encoded in 22 % of sequenced cyanobacterial genomes and 26 % of plant nuclear genomes. The lack of similar light-color regulation of gene expression in most of these species suggests that IF3s play roles in regulating gene expression in response to other environmental and developmental cues. In the plant Arabidopsis, two nuclear-encoded IF3s have been shown to localize to the chloroplasts, and the mRNA levels encoding these vary significantly in certain organ and tissue types and during several phases of development. Collectively, the accumulated data suggest that in about one quarter of photosynthetic prokaryotes and eukaryotes, IF3 gene families are used to regulate gene expression in addition to their traditional roles in translation initiation. Models for how this might be accomplished in prokaryotes versus eukaryotic plastids are presented.
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Affiliation(s)
- April D Nesbit
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
- Department of Biology/Chemistry, Purdue University North Central, 1401 S. US 421, Westville, IN, 46391, USA
| | - Craig Whippo
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
- Department of Natural Science, Dickinson State University, Dickinson, ND, 58601, USA
| | - Roger P Hangarter
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
| | - David M Kehoe
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
- Indiana Molecular Biology Institute, Indiana University, Bloomington, IN, 47405, USA.
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12
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Rasala BA, Mayfield SP. Photosynthetic biomanufacturing in green algae; production of recombinant proteins for industrial, nutritional, and medical uses. PHOTOSYNTHESIS RESEARCH 2015; 123:227-39. [PMID: 24659086 DOI: 10.1007/s11120-014-9994-7] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 03/03/2014] [Indexed: 05/18/2023]
Abstract
Recombinant proteins are widely used for industrial, nutritional, and medical applications. Green microalgae have attracted considerable attention recently as a biomanufacturing platform for the production of recombinant proteins for a number of reasons. These photosynthetic eukaryotic microorganisms are safe, scalable, easy to genetically modify through transformation, mutagenesis, or breeding, and inexpensive to grow. Many microalgae species are genetically transformable, but the green alga Chlamydomonas reinhardtii is the most widely used host for recombinant protein expression. An extensive suite of molecular genetic tools has been developed for C. reinhardtii over the last 25 years, including a fully sequenced genome, well-established methods for transformation, mutagenesis and breeding, and transformation vectors for high levels of recombinant protein accumulation and secretion. Here, we review recent successes in the development of C. reinhardtii as a biomanufacturing host for recombinant proteins, including antibodies and immunotoxins, hormones, industrial enzymes, an orally-active colostral protein for gastrointestinal health, and subunit vaccines. In addition, we review the biomanufacturing potential of other green algae from the genera Dunaliella and Chlorella.
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Affiliation(s)
- Beth A Rasala
- California Center for Algae Biotechnology and Division of Biological Sciences, University of California, 9500 Gilman Dr, La Jolla, San Diego, CA, 92093-0368, USA
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13
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Tiller N, Bock R. The translational apparatus of plastids and its role in plant development. MOLECULAR PLANT 2014; 7:1105-20. [PMID: 24589494 PMCID: PMC4086613 DOI: 10.1093/mp/ssu022] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 02/26/2014] [Indexed: 05/18/2023]
Abstract
Chloroplasts (plastids) possess a genome and their own machinery to express it. Translation in plastids occurs on bacterial-type 70S ribosomes utilizing a set of tRNAs that is entirely encoded in the plastid genome. In recent years, the components of the chloroplast translational apparatus have been intensely studied by proteomic approaches and by reverse genetics in the model systems tobacco (plastid-encoded components) and Arabidopsis (nucleus-encoded components). This work has provided important new insights into the structure, function, and biogenesis of chloroplast ribosomes, and also has shed fresh light on the molecular mechanisms of the translation process in plastids. In addition, mutants affected in plastid translation have yielded strong genetic evidence for chloroplast genes and gene products influencing plant development at various levels, presumably via retrograde signaling pathway(s). In this review, we describe recent progress with the functional analysis of components of the chloroplast translational machinery and discuss the currently available evidence that supports a significant impact of plastid translational activity on plant anatomy and morphology.
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Affiliation(s)
- Nadine Tiller
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
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14
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Schröter Y, Steiner S, Weisheit W, Mittag M, Pfannschmidt T. A purification strategy for analysis of the DNA/RNA-associated sub-proteome from chloroplasts of mustard cotyledons. FRONTIERS IN PLANT SCIENCE 2014; 5:557. [PMID: 25400643 PMCID: PMC4212876 DOI: 10.3389/fpls.2014.00557] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 09/29/2014] [Indexed: 05/20/2023]
Abstract
Plant cotyledons are a tissue that is particularly active in plastid gene expression in order to develop functional chloroplasts from pro-plastids, the plastid precursor stage in plant embryos. Cotyledons, therefore, represent a material being ideal for the study of composition, function and regulation of protein complexes involved in plastid gene expression. Here, we present a pilot study that uses heparin-Sepharose and phospho-cellulose chromatography in combination with isoelectric focussing and denaturing SDS gel electrophoresis (two-dimensional gel electrophoresis) for investigating the nucleic acids binding sub-proteome of mustard chloroplasts purified from cotyledons. We describe the technical requirements for a highly resolved biochemical purification of several hundreds of protein spots obtained from such samples. Subsequent mass spectrometry of peptides isolated out of cut spots that had been treated with trypsin identified 58 different proteins within 180 distinct spots. Our analyses indicate a high enrichment of proteins involved in transcription and translation and, in addition, the presence of massive post-translational modification of this plastid protein sub-fraction. The study provides an extended catalog of plastid proteins from mustard being involved in gene expression and its regulation and describes a suitable purification strategy for further analysis of low abundant gene expression related proteins.
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Affiliation(s)
- Yvonne Schröter
- Lehrstuhl für Pflanzenphysiologie, Institut für Allgemeine Botanik und Pflanzenphysiologie, Friedrich-Schiller-Universität JenaJena, Germany
| | - Sebastian Steiner
- Lehrstuhl für Pflanzenphysiologie, Institut für Allgemeine Botanik und Pflanzenphysiologie, Friedrich-Schiller-Universität JenaJena, Germany
- KWS SAAT AGEinbeck, Germany
| | - Wolfram Weisheit
- Lehrstuhl für Pflanzenphysiologie, Institut für Allgemeine Botanik und Pflanzenphysiologie, Friedrich-Schiller-Universität JenaJena, Germany
- Department of General Botany, Institute of General Botany and Plant Physiology, Friedrich Schiller University JenaJena, Germany
| | - Maria Mittag
- Lehrstuhl für Pflanzenphysiologie, Institut für Allgemeine Botanik und Pflanzenphysiologie, Friedrich-Schiller-Universität JenaJena, Germany
- Department of General Botany, Institute of General Botany and Plant Physiology, Friedrich Schiller University JenaJena, Germany
| | - Thomas Pfannschmidt
- Lehrstuhl für Pflanzenphysiologie, Institut für Allgemeine Botanik und Pflanzenphysiologie, Friedrich-Schiller-Universität JenaJena, Germany
- University of Grenoble-AlpesGrenoble, France
- CNRS, UMR5168Grenoble, France
- Commissariat a L'energie Atomique (CEA), iRTSV, Laboratoire de Physiologie Cellulaire & VégétaleGrenoble, France
- INRA, USC1359Grenoble, France
- *Correspondence: Thomas Pfannschmidt, Commissariat a L'energie Atomique (CEA), iRTSV, Laboratoire de Physiologie Cellulaire & Végétale, 17 Rue des Martyrs, 38000 Grenoble, France e-mail:
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15
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Lyska D, Meierhoff K, Westhoff P. How to build functional thylakoid membranes: from plastid transcription to protein complex assembly. PLANTA 2013; 237:413-28. [PMID: 22976450 PMCID: PMC3555230 DOI: 10.1007/s00425-012-1752-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 08/10/2012] [Indexed: 05/06/2023]
Abstract
Chloroplasts are the endosymbiotic descendants of cyanobacterium-like prokaryotes. Present genomes of plant and green algae chloroplasts (plastomes) contain ~100 genes mainly encoding for their transcription-/translation-machinery, subunits of the thylakoid membrane complexes (photosystems II and I, cytochrome b (6) f, ATP synthase), and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Nevertheless, proteomic studies have identified several thousand proteins in chloroplasts indicating that the majority of the plastid proteome is not encoded by the plastome. Indeed, plastid and host cell genomes have been massively rearranged in the course of their co-evolution, mainly through gene loss, horizontal gene transfer from the cyanobacterium/chloroplast to the nucleus of the host cell, and the emergence of new nuclear genes. Besides structural components of thylakoid membrane complexes and other (enzymatic) complexes, the nucleus provides essential factors that are involved in a variety of processes inside the chloroplast, like gene expression (transcription, RNA-maturation and translation), complex assembly, and protein import. Here, we provide an overview on regulatory factors that have been described and characterized in the past years, putting emphasis on mechanisms regulating the expression and assembly of the photosynthetic thylakoid membrane complexes.
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Affiliation(s)
- Dagmar Lyska
- Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, Düsseldorf, Germany.
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16
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Luo L, Herrin DL. A novel rhodanese is required to maintain chloroplast translation in Chlamydomonas. PLANT MOLECULAR BIOLOGY 2012; 79:495-508. [PMID: 22644440 DOI: 10.1007/s11103-012-9926-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 05/11/2012] [Indexed: 06/01/2023]
Abstract
Rhodanese-domain proteins (RDPs) are widespread in plants and other organisms, but their biological roles are mostly unknown. Here we report on a novel RDP from Chlamydomonas that has a single rhodanese domain, and a predicted chloroplast transit peptide. The protein was produced in Escherichia coli with a His-tag, but lacking most of the N-terminal transit peptide, and after purification was found to have rhodanese activity in vitro. It was also used to elicit antibodies for western blot analysis, which showed that the native Chlamydomonas protein migrated slower on SDS gels (apparent M(r) =34 kDa) than its predicted size (27 kDa), and co-fractionated with chloroplasts. To assess function in vivo, the tandem-RNAi approach was used to generate Chlamydomonas strains that had reductions of 30-70% for the mRNA and ~20-40% for the 34-kDa protein. These strains showed reduced growth under all trophic conditions, and were sensitive to even moderate light; properties reminiscent of chloroplast translation mutants. Pulse-labeling in the presence of cycloheximide indicated that chloroplast protein synthesis was broadly reduced in the RNAi strains, and transcript analysis (by RT-PCR and northern blotting) indicated the effect was mainly translational. These results identify a novel rhodanese-like protein that we have named CRLT, because it is required to maintain chloroplast translation.
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Affiliation(s)
- Liming Luo
- Section of Molecular Cell and Developmental Biology, School of Biological Sciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
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17
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Barkan A. Expression of plastid genes: organelle-specific elaborations on a prokaryotic scaffold. PLANT PHYSIOLOGY 2011; 155:1520-32. [PMID: 21346173 PMCID: PMC3091090 DOI: 10.1104/pp.110.171231] [Citation(s) in RCA: 219] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 01/29/2011] [Indexed: 05/19/2023]
Affiliation(s)
- Alice Barkan
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
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18
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Drechsel O, Bock R. Selection of Shine-Dalgarno sequences in plastids. Nucleic Acids Res 2011; 39:1427-38. [PMID: 20965967 PMCID: PMC3045613 DOI: 10.1093/nar/gkq978] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/16/2010] [Accepted: 10/04/2010] [Indexed: 11/29/2022] Open
Abstract
Like bacterial genes, most plastid (chloroplast) genes are arranged in operons and transcribed as polycistronic mRNAs. Plastid protein biosynthesis occurs on bacterial-type 70S ribosomes and translation initiation of many (but not all) mRNAs is mediated by Shine-Dalgarno (SD) sequences. To study the mechanisms of SD sequence recognition, we have analyzed translation initiation from mRNAs containing multiple SD sequences. Comparing translational efficiencies of identical transgenic mRNAs in Escherichia coli and plastids, we find surprising differences between the two systems. Most importantly, while internal SD sequences are efficiently recognized in E. coli, plastids exhibit a bias toward utilizing predominantly the 5'-most SD sequence. We propose that inefficient recognition of internal SD sequences provides the raison d'être for most plastid polycistronic transcripts undergoing post-transcriptional cleavage into monocistronic mRNAs.
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Affiliation(s)
| | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
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19
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Abstract
Proteomics of chloroplast ribosomes in spinach and Chlamydomonas revealed unique protein composition and structures of plastid ribosomes. These studies have suggested the presence of some ribosomal proteins unique to plastid ribosomes which may be involved in plastid-unique translation regulation. Considering the strong background of genetic analysis and molecular biology in Arabidopsis, the in-depth proteomic characterization of Arabidopsis plastid ribosomes would facilitate further understanding of plastid translation in higher plants. Here, I describe simple and rapid methods for the preparation of plastid ribosomes from Chlamydomonas and Arabidopsis using sucrose gradients. I also describe purity criteria and methods for yield estimation of the purified plastid ribosomes and subunits, methods for the preparation of plastid ribosomal proteins, as well as the identification of some Arabidopsis plastid ribosomal proteins by matrix-assisted laser desorption/ionization mass spectrometry.
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20
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Abstract
Despite recent elucidation of the three-dimensional structure of major photosynthetic complexes, our understanding of light energy conversion in plant chloroplasts and microalgae under physiological conditions requires exploring the dynamics of photosynthesis. The photosynthetic apparatus is a flexible molecular machine that can acclimate to metabolic and light fluctuations in a matter of seconds and minutes. On a longer time scale, changes in environmental cues trigger acclimation responses that elicit intracellular signaling between the nucleo-cytosol and chloroplast resulting in modification of the biogenesis of the photosynthetic machinery. Here we attempt to integrate well-established knowledge on the functional flexibility of light-harvesting and electron transfer processes, which has greatly benefited from genetic approaches, with data derived from the wealth of recent transcriptomic and proteomic studies of acclimation responses in photosynthetic eukaroytes.
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Affiliation(s)
- Stephan Eberhard
- Université Pierre et Marie Curie, Institut de Biologie Physico-Chimique, F-75005 Paris, France
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21
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Uniacke J, Zerges W. Stress induces the assembly of RNA granules in the chloroplast of Chlamydomonas reinhardtii. ACTA ACUST UNITED AC 2008; 182:641-6. [PMID: 18710928 PMCID: PMC2518703 DOI: 10.1083/jcb.200805125] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Eukaryotic cells under stress repress translation and localize these messenger RNAs (mRNAs) to cytoplasmic RNA granules. We show that specific stress stimuli induce the assembly of RNA granules in an organelle with bacterial ancestry, the chloroplast of Chlamydomonas reinhardtii. These chloroplast stress granules (cpSGs) form during oxidative stress and disassemble during recovery from stress. Like mammalian stress granules, cpSGs contain poly(A)-binding protein and the small, but not the large, ribosomal subunit. In addition, mRNAs are in continuous flux between polysomes and cpSGs during stress. Localization of cpSGs within the pyrenoid reveals that this chloroplast compartment functions in this stress response. The large subunit of ribulosebisphosphate carboxylase/oxygenase also assembles into cpSGs and is known to bind mRNAs during oxidative stress, raising the possibility that it plays a role in cpSG assembly. This discovery within such an organelle suggests that mRNA localization to granules during stress is a more general phenomenon than currently realized.
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Affiliation(s)
- James Uniacke
- Biology Department, Concordia University, Montreal, Quebec, Canada
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22
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Beligni MV, Mayfield SP. Arabidopsis thaliana mutants reveal a role for CSP41a and CSP41b, two ribosome-associated endonucleases, in chloroplast ribosomal RNA metabolism. PLANT MOLECULAR BIOLOGY 2008; 67:389-401. [PMID: 18398686 DOI: 10.1007/s11103-008-9328-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Accepted: 03/19/2008] [Indexed: 05/04/2023]
Abstract
A proteomic analysis of Chlamydomonas reinhardtii 70S ribosomes identified two proteins, RAP38 and RAP41, which associate in stoichiometric amounts with intact ribosomes. In this work we show results that suggest the Arabidopsis thaliana homologs, CSP41b and CSP41a, participate in ribosomal RNA metabolism. Csp41a-1 and csp41b-1 single mutants show little phenotype, while the loss of both proteins is lethal. Plants homozygous for the csp41b-1 mutation and heterozygous for the csp41a-1 mutation (csp41b-1/csp41a-1*) fail to accumulate CSP41b and show a marked reduction in the levels of CSP41a. These mutants have reduced chlorophyll content, grow slower and over-accumulate 23S precursor rRNAs compared to their wild-type (WT) siblings, whereas other rRNAs or mRNAs are unaffected. Chloroplast polysome assembly is reduced in csp41b-1/csp41a-1* mutants, which also contain increased amounts of pre-ribosomal particles compared to mature 70S ribosomes. Our results also indicate that CSP41b associates with pre-ribosomal particles in vivo. In vitro, the pattern of 23S precursors and mature rRNAs is altered upon incubation with recombinant CSP41a and CSP41b. Taken together, these results suggest that CSP41a and CSP41b have a role in chloroplast ribosomal RNA metabolism, most likely acting in the final steps of 23S rRNA maturation.
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Affiliation(s)
- María Verónica Beligni
- Department of Cell Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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23
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Manuell AL, Quispe J, Mayfield SP. Structure of the chloroplast ribosome: novel domains for translation regulation. PLoS Biol 2008; 5:e209. [PMID: 17683199 PMCID: PMC1939882 DOI: 10.1371/journal.pbio.0050209] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Accepted: 06/01/2007] [Indexed: 02/05/2023] Open
Abstract
Gene expression in chloroplasts is controlled primarily through the regulation of translation. This regulation allows coordinate expression between the plastid and nuclear genomes, and is responsive to environmental conditions. Despite common ancestry with bacterial translation, chloroplast translation is more complex and involves positive regulatory mRNA elements and a host of requisite protein translation factors that do not have counterparts in bacteria. Previous proteomic analyses of the chloroplast ribosome identified a significant number of chloroplast-unique ribosomal proteins that expand upon a basic bacterial 70S-like composition. In this study, cryo-electron microscopy and single-particle reconstruction were used to calculate the structure of the chloroplast ribosome to a resolution of 15.5 Å. Chloroplast-unique proteins are visualized as novel structural additions to a basic bacterial ribosome core. These structures are located at optimal positions on the chloroplast ribosome for interaction with mRNAs during translation initiation. Visualization of these chloroplast-unique structures on the ribosome, combined with mRNA cross-linking, allows us to propose a model for translation initiation in chloroplasts in which chloroplast-unique ribosomal proteins interact with plastid-specific translation factors and RNA elements to facilitate regulated translation of chloroplast mRNAs. Translation of mRNA into protein is the main step for the regulation of gene expression in the chloroplast, the photosynthetic organelle of plant cells. Translation is conducted by the ribosome, a large macromolecular machine composed of RNA and protein. Studies have shown that the composition of the chloroplast ribosome is similar to that of bacterial ribosomes, but also that chloroplast ribosomes contain a number of unique proteins. We present the three-dimensional structure of the chloroplast ribosome, as calculated using cryo-electron microscopy and single-particle reconstruction. Chloroplast-unique structures are clearly visible on our ribosome map, and expand upon a basic bacterial ribosome-like core. The role of these chloroplast-unique ribosomal proteins in regulating translation of chloroplast mRNAs, including light-regulated translation, is suggested by the location of these structures on the ribosome. Biochemical data confirm a predicted function in chloroplast translation for some of the unique proteins. Our model for translation in the chloroplast incorporates decades of biochemical and genetic studies with the structure presented here, and should help guide future studies to understand the molecular mechanisms of translation regulation in the chloroplast. Cryo-electron microscopy and single-particle reconstruction were used to calculate the structure of the chloroplast ribosome. Chloroplast-unique proteins are visualized as novel structural additions to a basic bacterial ribosome core.
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Affiliation(s)
- Andrea L Manuell
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Joel Quispe
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
- National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, California, United States of America
| | - Stephen P Mayfield
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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24
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Uniacke J, Zerges W. Photosystem II assembly and repair are differentially localized in Chlamydomonas. THE PLANT CELL 2007; 19:3640-54. [PMID: 18055604 PMCID: PMC2174875 DOI: 10.1105/tpc.107.054882] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Revised: 11/07/2007] [Accepted: 11/08/2007] [Indexed: 05/19/2023]
Abstract
Many proteins of the photosynthesis complexes are encoded by the genome of the chloroplast and synthesized by bacterium-like ribosomes within this organelle. To determine where proteins are synthesized for the de novo assembly and repair of photosystem II (PSII) in the chloroplast of Chlamydomonas reinhardtii, we used fluorescence in situ hybridization, immunofluorescence staining, and confocal microscopy. These locations were defined as having colocalized chloroplast mRNAs encoding PSII subunits and proteins of the chloroplast translation machinery specifically under conditions of PSII subunit synthesis. The results revealed that the synthesis of the D1 subunit for the repair of photodamaged PSII complexes occurs in regions of the chloroplast with thylakoids, consistent with the current model. However, for de novo PSII assembly, PSII subunit synthesis was detected in discrete regions near the pyrenoid, termed T zones (for translation zones). In two PSII assembly mutants, unassembled D1 subunits and incompletely assembled PSII complexes localized around the pyrenoid, where we propose that they mark an intermediate compartment of PSII assembly. These results reveal a novel chloroplast compartment that houses de novo PSII biogenesis and the regulated transport of newly assembled PSII complexes to thylakoid membranes throughout the chloroplast.
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Affiliation(s)
- James Uniacke
- Biology Department, Concordia University, Montreal, Quebec, Canada H4B 1R6
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25
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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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26
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Wijnen H, Naef F, Boothroyd C, Claridge-Chang A, Young MW. Control of daily transcript oscillations in Drosophila by light and the circadian clock. PLoS Genet 2006; 2:e39. [PMID: 16565745 PMCID: PMC1413497 DOI: 10.1371/journal.pgen.0020039] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Accepted: 02/03/2006] [Indexed: 11/19/2022] Open
Abstract
The transcriptional circuits of circadian clocks control physiological and behavioral rhythms. Light may affect such overt rhythms in two ways: (1) by entraining the clock circuits and (2) via clock-independent molecular pathways. In this study we examine the relationship between autonomous transcript oscillations and light-driven transcript responses. Transcript profiles of wild-type and arrhythmic mutant Drosophila were recorded both in the presence of an environmental photocycle and in constant darkness. Systematic autonomous oscillations in the 12- to 48-h period range were detectable only in wild-type flies and occurred preferentially at the circadian period length. However, an extensive program of light-driven expression was confirmed in arrhythmic mutant flies. Many light-responsive transcripts are preferentially expressed in the compound eyes and the phospholipase C component of phototransduction, NORPA (no receptor potential), is required for their light-dependent regulation. Although there is evidence for the existence of multiple molecular clock circuits in cyanobacteria, protists, plants, and fungi, Drosophila appears to possess only one such system. The sustained photic expression responses identified here are partially coupled to the circadian clock and may reflect a mechanism for flies to modulate functions such as visual sensitivity and synaptic transmission in response to seasonal changes in photoperiod.
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Affiliation(s)
- Herman Wijnen
- Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Felix Naef
- Laboratory of Mathematical Physics, The Rockefeller University, New York, New York, United States of America
- Swiss Institute for Experimental Cancer Research (ISREC), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
| | - Catharine Boothroyd
- Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America
| | - Adam Claridge-Chang
- Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America
| | - Michael W Young
- Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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27
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Klinkert B, Elles I, Nickelsen J. Translation of chloroplast psbD mRNA in Chlamydomonas is controlled by a secondary RNA structure blocking the AUG start codon. Nucleic Acids Res 2006; 34:386-94. [PMID: 16410618 PMCID: PMC1331992 DOI: 10.1093/nar/gkj433] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 12/21/2005] [Accepted: 12/21/2005] [Indexed: 11/28/2022] Open
Abstract
Translation initiation represents a key step during regulation of gene expression in chloroplasts. Here, we report on the identification and characterization of three suppressor point mutations which overcome a translational defect caused by the deletion of a U-rich element in the 5'-untranslated region (5'-UTR) of the psbD mRNA in the green alga Chlamydomonas reinhardtii. All three suppressors affect a secondary RNA structure encompassing the psbD AUG initiation codon within a double-stranded region as judged by the analysis of site-directed chloroplast mutants as well as in vitro RNA mapping experiments using RNase H. In conclusion, the data suggest that these new element serves as a negative regulator which mediates a rapid shut-down of D2 synthesis.
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Affiliation(s)
- Birgit Klinkert
- Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstr. 150D-44780 Bochum, Germany
| | - Ingolf Elles
- Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstr. 150D-44780 Bochum, Germany
| | - Jörg Nickelsen
- Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstr. 150D-44780 Bochum, Germany
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