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Nellaepalli S, Lau AS, Jarvis RP. Chloroplast protein translocation pathways and ubiquitin-dependent regulation at a glance. J Cell Sci 2023; 136:jcs241125. [PMID: 37732520 PMCID: PMC10546890 DOI: 10.1242/jcs.241125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023] Open
Abstract
Chloroplasts conduct photosynthesis and numerous metabolic and signalling processes that enable plant growth and development. Most of the ∼3000 proteins in chloroplasts are nucleus encoded and must be imported from the cytosol. Thus, the protein import machinery of the organelle (the TOC-TIC apparatus) is of fundamental importance for chloroplast biogenesis and operation. Cytosolic factors target chloroplast precursor proteins to the TOC-TIC apparatus, which drives protein import across the envelope membranes into the organelle, before various internal systems mediate downstream routing to different suborganellar compartments. The protein import system is proteolytically regulated by the ubiquitin-proteasome system (UPS), enabling centralized control over the organellar proteome. In addition, the UPS targets a range of chloroplast proteins directly. In this Cell Science at a Glance article and the accompanying poster, we present mechanistic details of these different chloroplast protein targeting and translocation events, and of the UPS systems that regulate chloroplast proteins.
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Affiliation(s)
- Sreedhar Nellaepalli
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Anne Sophie Lau
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
- Department of Plant Physiology, Faculty of Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R. Paul Jarvis
- Section of Molecular Plant Biology, Department of Biology, University of Oxford, Oxford OX1 3RB, UK
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2
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Chang CY, Chen LJ, Li HM. Chloroplast import motor subunits FtsHi1 and FtsHi2 are located on opposite sides of the inner envelope membrane. Proc Natl Acad Sci U S A 2023; 120:e2307747120. [PMID: 37669373 PMCID: PMC10500165 DOI: 10.1073/pnas.2307747120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/07/2023] [Indexed: 09/07/2023] Open
Abstract
Protein import into chloroplasts is powered by ATP hydrolysis in the stroma. Establishing the identity and functional mechanism of the stromal ATPase motor that drives import is critical for understanding chloroplast biogenesis. Recently, a complex consisting of Ycf2, FtsHi1, FtsHi2, FtsHi4, FtsHi5, FtsH12, and malate dehydrogenase was shown to be important for chloroplast protein import, and it has been proposed to act as the motor driving protein translocation across the chloroplast envelope into the stroma. To gain further mechanistic understanding of how the motor functions, we performed membrane association and topology analyses on two of its subunits, FtsHi1 and FtsHi2. We isolated cDNA clones encoding FtsHi1 and FtsHi2 preproteins to perform in vitro import experiments in order to determine the exact size of each mature protein. We also generated antibodies against the C-termini of the proteins, i.e., where their ATPase domains reside. Protease treatments and alkaline and high-salt extractions of chloroplasts with imported and endogenous proteins revealed that FtsHi1 is an integral membrane protein with its C-terminal portion located in the intermembrane space of the envelope, not the stroma, whereas FtsHi2 is a soluble protein in the stroma. We further complemented an FtsHi1-knockout mutant with a C-terminally tagged FtsHi1 and obtained identical results for topological analyses. Our data indicate that the model of a single membrane-anchored pulling motor at the stromal side of the inner membrane needs to be revised and suggest that the Ycf2-FtsHi complex may have additional functions.
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Affiliation(s)
- Chia-Yun Chang
- Institute of Molecular Biology, Academia Sinica, Taipei11529, Taiwan
| | - Lih-Jen Chen
- Institute of Molecular Biology, Academia Sinica, Taipei11529, Taiwan
| | - Hsou-min Li
- Institute of Molecular Biology, Academia Sinica, Taipei11529, Taiwan
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3
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Kizmaz B, Herrmann JM. Membrane insertases at a glance. J Cell Sci 2023; 136:jcs261219. [PMID: 37417332 DOI: 10.1242/jcs.261219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023] Open
Abstract
Protein translocases, such as the bacterial SecY complex, the Sec61 complex of the endoplasmic reticulum (ER) and the mitochondrial translocases, facilitate the transport of proteins across membranes. In addition, they catalyze the insertion of integral membrane proteins into the lipid bilayer. Several membrane insertases cooperate with these translocases, thereby promoting the topogenesis, folding and assembly of membrane proteins. Oxa1 and BamA family members serve as core components in the two major classes of membrane insertases. They facilitate the integration of proteins with α-helical transmembrane domains and of β-barrel proteins into lipid bilayers, respectively. Members of the Oxa1 family were initially found in the internal membranes of bacteria, mitochondria and chloroplasts. Recent studies, however, also identified several Oxa1-type insertases in the ER, where they serve as catalytically active core subunits in the ER membrane protein complex (EMC), the guided entry of tail-anchored (GET) and the GET- and EMC-like (GEL) complex. The outer membrane of bacteria, mitochondria and chloroplasts contain β-barrel proteins, which are inserted by members of the BamA family. In this Cell Science at a Glance article and the accompanying poster, we provide an overview of these different types of membrane insertases and discuss their function.
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Affiliation(s)
- Büsra Kizmaz
- Cell Biology, University of Kaiserslautern, Kaiserslautern 67663, Germany
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4
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Ballabani G, Forough M, Kessler F, Shanmugabalaji V. The journey of preproteins across the chloroplast membrane systems. Front Physiol 2023; 14:1213866. [PMID: 37324391 PMCID: PMC10267391 DOI: 10.3389/fphys.2023.1213866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/22/2023] [Indexed: 06/17/2023] Open
Abstract
The photosynthetic capacity of chloroplasts is vital for autotrophic growth in algae and plants. The origin of the chloroplast has been explained by the endosymbiotic theory that proposes the engulfment of a cyanobacterium by an ancestral eukaryotic cell followed by the transfer of many cyanobacterial genes to the host nucleus. As a result of the gene transfer, the now nuclear-encoded proteins acquired chloroplast targeting peptides (known as transit peptides; transit peptide) and are translated as preproteins in the cytosol. Transit peptides contain specific motifs and domains initially recognized by cytosolic factors followed by the chloroplast import components at the outer and inner envelope of the chloroplast membrane. Once the preprotein emerges on the stromal side of the chloroplast protein import machinery, the transit peptide is cleaved by stromal processing peptidase. In the case of thylakoid-localized proteins, cleavage of the transit peptides may expose a second targeting signal guiding the protein to the thylakoid lumen or allow insertion into the thylakoid membrane by internal sequence information. This review summarizes the common features of targeting sequences and describes their role in routing preproteins to and across the chloroplast envelope as well as the thylakoid membrane and lumen.
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Affiliation(s)
| | | | - Felix Kessler
- *Correspondence: Felix Kessler, ; Venkatasalam Shanmugabalaji,
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Zheng C, Xu X, Zhang L, Lu D. Liquid-Liquid Phase Separation Phenomenon on Protein Sorting Within Chloroplasts. Front Physiol 2022; 12:801212. [PMID: 35002776 PMCID: PMC8740050 DOI: 10.3389/fphys.2021.801212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 12/09/2021] [Indexed: 12/13/2022] Open
Abstract
In higher plants, chloroplasts are vital organelles possessing highly complex compartmentalization. As most chloroplast-located proteins are encoded in the nucleus and synthesized in the cytosol, the correct sorting of these proteins to appropriate compartments is critical for the proper functions of chloroplasts as well as plant survival. Nuclear-encoded chloroplast proteins are imported into stroma and further sorted to distinct compartments via different pathways. The proteins predicted to be sorted to the thylakoid lumen by the chloroplast twin arginine transport (cpTAT) pathway are shown to be facilitated by STT1/2 driven liquid-liquid phase separation (LLPS). Liquid-liquid phase separation is a novel mechanism to facilitate the formation of membrane-less sub-cellular compartments and accelerate biochemical reactions temporally and spatially. In this review, we introduce the sorting mechanisms within chloroplasts, and briefly summarize the properties and significance of LLPS, with an emphasis on the novel function of LLPS in the sorting of cpTAT substrate proteins. We conclude with perspectives for the future research on chloroplast protein sorting and targeting mechanisms.
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Affiliation(s)
- Canhui Zheng
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Xiumei Xu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Lixin Zhang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Dandan Lu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
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Petrů M, Dohnálek V, Füssy Z, Doležal P. Fates of Sec, Tat, and YidC Translocases in Mitochondria and Other Eukaryotic Compartments. Mol Biol Evol 2021; 38:5241-5254. [PMID: 34436602 PMCID: PMC8662606 DOI: 10.1093/molbev/msab253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Formation of mitochondria by the conversion of a bacterial endosymbiont was a key moment in the evolution of eukaryotes. It was made possible by outsourcing the endosymbiont's genetic control to the host nucleus, while developing the import machinery for proteins synthesized on cytosolic ribosomes. The original protein export machines of the nascent organelle remained to be repurposed or were completely abandoned. This review follows the evolutionary fates of three prokaryotic inner membrane translocases Sec, Tat, and YidC. Homologs of all three translocases can still be found in current mitochondria, but with different importance for mitochondrial function. Although the mitochondrial YidC homolog, Oxa1, became an omnipresent independent insertase, the other two remained only sporadically present in mitochondria. Only a single substrate is known for the mitochondrial Tat and no function has yet been assigned for the mitochondrial Sec. Finally, this review compares these ancestral mitochondrial proteins with their paralogs operating in the plastids and the endomembrane system.
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Affiliation(s)
- Markéta Petrů
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vít Dohnálek
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Zoltán Füssy
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Pavel Doležal
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
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7
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Xie N, Zhang C, Zhou P, Gao X, Wang M, Tian S, Lu C, Wang K, Shen C. Transcriptomic analyses reveal variegation-induced metabolic changes leading to high L-theanine levels in albino sectors of variegated tea (Camellia sinensis). PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 169:29-39. [PMID: 34749269 DOI: 10.1016/j.plaphy.2021.10.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/17/2021] [Accepted: 10/21/2021] [Indexed: 06/13/2023]
Abstract
Camellia sinensis cv. 'Yanling Huayecha' (YHC) is an albino-green chimaeric tea mutant with stable genetic traits. Here, we analysed the cell ultrastructure, photosynthetic pigments, amino acids, and transcriptomes of the albino, mosaic, and green zones of YHC. Well-organized thylakoids were found in chloroplasts in mesophyll cells of the green zone but not the albino zone. The albino zone of the leaves contained almost no photosynthetic pigment. However, the levels of total amino acids and theanine were higher in the albino zone than in the mosaic and green zones. A transcriptomic analysis showed that carbon metabolism, nitrogen metabolism and amino acid biosynthesis showed differences among the different zones. Metabolite and transcriptomic analyses revealed that (1) downregulation of CsPPOX1 and damage to thylakoids in the albino zone may block chlorophyll synthesis; (2) downregulation of CsLHCB6, CsFdC2 and CsSCY1 influences chloroplast biogenesis and thylakoid membrane formation, which may contribute to the appearance of variegated tea leaves; and (3) tea plant variegation disrupts the balance between carbon and nitrogen metabolism and promotes the accumulation of amino acids, and upregulation of CsTSⅠ and CsAlaDC may enhance L-theanine synthesis. In summary, our study provides a theoretical basis and valuable insights for elucidating the molecular mechanisms and promoting the economic utilization of variegation in tea.
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Affiliation(s)
- Nianci Xie
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - Chenyu Zhang
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - Pinqian Zhou
- Tea Research Institute of Hunan Academy of Agricultural Sciences, Changsha, Hunan, 410125, China
| | - Xizhi Gao
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - Minghan Wang
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - Shuanghong Tian
- Xiangxi Academy of Agricultural Sciences, Jishou, Hunan, 416000, China
| | - Cui Lu
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China
| | - Kunbo Wang
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China.
| | - Chengwen Shen
- Key Laboratory of Tea Science of Ministry of Education, Hunan Agricultural University, Changsha, Hunan, 410128, China; National Research Center of Engineering and Technology for Utilization of Botanical Functional Ingredients, Hunan Agricultural University, Changsha, Hunan, 410128, China.
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8
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Lavell A, Smith M, Xu Y, Froehlich JE, De La Mora C, Benning C. Proteins associated with the Arabidopsis thaliana plastid rhomboid-like protein RBL10. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1332-1345. [PMID: 34582071 PMCID: PMC9219029 DOI: 10.1111/tpj.15514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 09/10/2021] [Accepted: 09/21/2021] [Indexed: 05/07/2023]
Abstract
Rhomboid-like proteins are intramembrane proteases with a variety of regulatory roles in cells. Though many rhomboid-like proteins are predicted in plants, their detailed molecular mechanisms or cellular functions are not yet known. Of the 13 predicted rhomboids in Arabidopsis thaliana, one, RBL10, affects lipid metabolism in the chloroplast, because in the respective rbl10 mutant the transfer of phosphatidic acid through the inner envelope membrane is disrupted. Here we show that RBL10 is part of a high-molecular-weight complex of 250 kDa or greater in size. Nine likely components of this complex are identified by two independent methods and include Acyl Carrier Protein 4 (ACP4) and Carboxyltransferase Interactor1 (CTI1), which have known roles in chloroplast lipid metabolism. The acp4 mutant has decreased C16:3 fatty acid content of monogalactosyldiacylglycerol, similar to the rbl10 mutant, prompting us to offer a mechanistic model of how an interaction between ACP4 and RBL10 might affect chloroplast lipid assembly. We also demonstrate the presence of a seventh transmembrane domain in RBL10, refining the currently accepted topology of this protein. Taken together, the identity of possible RBL10 complex components as well as insights into RBL10 topology and distribution in the membrane provide a stepping-stone towards a deeper understanding of RBL10 function in Arabidopsis lipid metabolism.
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Affiliation(s)
- Anastasiya Lavell
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - Montgomery Smith
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
| | - Yang Xu
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - John E. Froehlich
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - Cameron De La Mora
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
- Dept. of Molecular & Cellular Biology, Illinois State University, Normal, IL 61761
| | - Christoph Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
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9
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Rottet S, Förster B, Hee WY, Rourke LM, Price GD, Long BM. Engineered Accumulation of Bicarbonate in Plant Chloroplasts: Known Knowns and Known Unknowns. FRONTIERS IN PLANT SCIENCE 2021; 12:727118. [PMID: 34531888 PMCID: PMC8438413 DOI: 10.3389/fpls.2021.727118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 08/06/2021] [Indexed: 05/10/2023]
Abstract
Heterologous synthesis of a biophysical CO2-concentrating mechanism (CCM) in plant chloroplasts offers significant potential to improve the photosynthetic efficiency of C3 plants and could translate into substantial increases in crop yield. In organisms utilizing a biophysical CCM, this mechanism efficiently surrounds a high turnover rate Rubisco with elevated CO2 concentrations to maximize carboxylation rates. A critical feature of both native biophysical CCMs and one engineered into a C3 plant chloroplast is functional bicarbonate (HCO3 -) transporters and vectorial CO2-to-HCO3 - converters. Engineering strategies aim to locate these transporters and conversion systems to the C3 chloroplast, enabling elevation of HCO3 - concentrations within the chloroplast stroma. Several CCM components have been identified in proteobacteria, cyanobacteria, and microalgae as likely candidates for this approach, yet their successful functional expression in C3 plant chloroplasts remains elusive. Here, we discuss the challenges in expressing and regulating functional HCO3 - transporter, and CO2-to-HCO3 - converter candidates in chloroplast membranes as an essential step in engineering a biophysical CCM within plant chloroplasts. We highlight the broad technical and physiological concerns which must be considered in proposed engineering strategies, and present our current status of both knowledge and knowledge-gaps which will affect successful engineering outcomes.
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Affiliation(s)
- Sarah Rottet
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - Britta Förster
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Wei Yih Hee
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - Loraine M. Rourke
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
| | - G. Dean Price
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Benedict M. Long
- Realizing Increased Photosynthetic Efficiency (RIPE), The Australian National University, Canberra, ACT, Australia
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Canberra, ACT, Australia
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10
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Chu X, Gugger PF, Li L, Zhao J, Li Q. Responses of an endemic species (
Roscoea humeana
) in the Hengduan Mountains to climate change. DIVERS DISTRIB 2021. [DOI: 10.1111/ddi.13397] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Xue Chu
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology Yunnan University Kunming China
- Laboratory of Ecology and Evolutionary Biology State Key Laboratory for Conservation and Utilization of Bio‐Resources in Yunnan Yunnan University Kunming China
- School of Ecology and Environmental Science Yunnan University Kunming China
| | - Paul F. Gugger
- Appalachian Laboratory University of Maryland Center for Environmental Science Frostburg MD USA
- Ronin Institute Montclair NJ USA
| | - Li Li
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology Yunnan University Kunming China
- Laboratory of Ecology and Evolutionary Biology State Key Laboratory for Conservation and Utilization of Bio‐Resources in Yunnan Yunnan University Kunming China
- School of Ecology and Environmental Science Yunnan University Kunming China
| | - Jian‐Li Zhao
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology Yunnan University Kunming China
- Laboratory of Ecology and Evolutionary Biology State Key Laboratory for Conservation and Utilization of Bio‐Resources in Yunnan Yunnan University Kunming China
- School of Ecology and Environmental Science Yunnan University Kunming China
| | - Qing‐Jun Li
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology Yunnan University Kunming China
- Laboratory of Ecology and Evolutionary Biology State Key Laboratory for Conservation and Utilization of Bio‐Resources in Yunnan Yunnan University Kunming China
- School of Ecology and Environmental Science Yunnan University Kunming China
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11
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Mielke K, Wagner R, Mishra LS, Demir F, Perrar A, Huesgen PF, Funk C. Abundance of metalloprotease FtsH12 modulates chloroplast development in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:3455-3473. [PMID: 33216923 PMCID: PMC8042743 DOI: 10.1093/jxb/eraa550] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/19/2020] [Indexed: 05/11/2023]
Abstract
The ATP-dependent metalloprotease FtsH12 (filamentation temperature sensitive protein H 12) has been suggested to participate in a heteromeric motor complex, driving protein translocation into the chloroplast. FtsH12 was immuno-detected in proplastids, seedlings, leaves, and roots. Expression of Myc-tagged FtsH12 under its native promotor allowed identification of FtsHi1, 2, 4, and 5, and plastidic NAD-malate dehydrogenase, five of the six interaction partners in the suggested import motor complex. Arabidopsis thaliana mutant seedlings with reduced FTSH12 abundance exhibited pale cotyledons and small, deformed chloroplasts with altered thylakoid structure. Mature plants retained these chloroplast defects, resulting in slightly variegated leaves and lower chlorophyll content. Label-free proteomics revealed strong changes in the proteome composition of FTSH12 knock-down seedlings, reflecting impaired plastid development. The composition of the translocon on the inner chloroplast membrane (TIC) protein import complex was altered, with coordinated reduction of the FtsH12-FtsHi complex subunits and accumulation of the 1 MDa TIC complex subunits TIC56, TIC214 and TIC22-III. FTSH12 overexpressor lines showed no obvious phenotype, but still displayed distinct differences in their proteome. N-terminome analyses further demonstrated normal proteolytic maturation of plastid-imported proteins irrespective of FTSH12 abundance. Together, our data suggest that FtsH12 has highest impact during seedling development; its abundance alters the plastid import machinery and impairs chloroplast development.
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Affiliation(s)
- Kati Mielke
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - Raik Wagner
- Department of Chemistry, Umeå University, Umeå, Sweden
| | | | - Fatih Demir
- Central Institute for Engineering, Electronics and Analytics, Jülich, Germany
| | - Andreas Perrar
- Central Institute for Engineering, Electronics and Analytics, Jülich, Germany
| | - Pitter F Huesgen
- Central Institute for Engineering, Electronics and Analytics, Jülich, Germany
- CECAD, Medical Faculty and University Hospital, University of Cologne, Cologne, Germany
- Institute of Biochemistry, University of Cologne, Cologne, Germany
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12
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Wojcik S, Kriechbaumer V. Go your own way: membrane-targeting sequences. PLANT PHYSIOLOGY 2021; 185:608-618. [PMID: 33822216 PMCID: PMC8133554 DOI: 10.1093/plphys/kiaa058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/19/2020] [Indexed: 05/05/2023]
Abstract
Membrane-targeting sequences, connected targeting mechanisms, and co-factors orchestrate primary targeting of proteins to membranes.
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Affiliation(s)
- Stefan Wojcik
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Verena Kriechbaumer
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
- Author for communication: (V.K.)
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13
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Luo Y, Zhang L, Li W, Xu M, Zhang C, Wang L. HS1 Is Involved in Hygromycin Resistance Through Facilitating Hygromycin Phosphotransferase Transportation From Cytosol to Chloroplast. FRONTIERS IN PLANT SCIENCE 2020; 11:613. [PMID: 32528495 PMCID: PMC7266939 DOI: 10.3389/fpls.2020.00613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
The transportation of proteins encoded by nuclear genes from plant cytosol to chloroplast is essential for chloroplast functions. Proteins that have a chloroplast transit peptide (cTP) are imported into chloroplasts via translocases on the outer and inner chloroplast envelope. How proteins lacking transit sequence are imported into chloroplast remains largely unknown. During screening of an Arabidopsis population transformed with a hairpin RNA gene-silencing library, we identified some transgenic plants that had active expression of the selectable marker gene, hygromycin phosphotransferase (HPT), but were sensitive to the selection agent, hygromycin B (HyB). Mutant and complementation analysis showed that this HyB sensitivity of transgenic plants was due to silencing of the HS1 (Hygromycin-Sensitive 1) gene. HS1 is localized in the chloroplast and interacts physically with HPT in yeast cells and in planta. Fluorescence and immunoblotting analysis showed that HPT could not be transported effectively into chloroplasts in Aths1, which resulted in Aths1 is sensitivity to hygromycin on higher HyB-containing medium. These data revealed that HS1 is involved in HyB resistance in transgenic Arabidopsis through facilitating cytosol-chloroplast transportation of HPT. Our findings provide novel insights on transportation of chloroplast cTP-less proteins.
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Protein import into chloroplasts and its regulation by the ubiquitin-proteasome system. Biochem Soc Trans 2020; 48:71-82. [PMID: 31922184 PMCID: PMC7054747 DOI: 10.1042/bst20190274] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 02/08/2023]
Abstract
Chloroplasts are photosynthetic plant organelles descended from a bacterial ancestor. The vast majority of chloroplast proteins are synthesized in the cytosol and then imported into the chloroplast post-translationally. Translocation complexes exist in the organelle's outer and inner envelope membranes (termed TOC and TIC, respectively) to facilitate protein import. These systems recognize chloroplast precursor proteins and mediate their import in an energy-dependent manner. However, many unanswered questions remain regarding mechanistic details of the import process and the participation and functions of individual components; for example, the cytosolic events that mediate protein delivery to chloroplasts, the composition of the TIC apparatus, and the nature of the protein import motor all require resolution. The flux of proteins through TOC and TIC varies greatly throughout development and in response to specific environmental cues. The import process is, therefore, tightly regulated, and it has emerged that the ubiquitin-proteasome system (UPS) plays a key role in this regard, acting at several different steps in the process. The UPS is involved in: the selective degradation of transcription factors that co-ordinate the expression of chloroplast precursor proteins; the removal of unimported chloroplast precursor proteins in the cytosol; the inhibition of chloroplast biogenesis pre-germination; and the reconfiguration of the TOC apparatus in response to developmental and environmental signals in a process termed chloroplast-associated protein degradation. In this review, we highlight recent advances in our understanding of protein import into chloroplasts and how this process is regulated by the UPS.
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15
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Synthetic Protein Scaffolding at Biological Membranes. Trends Biotechnol 2019; 38:432-446. [PMID: 31718802 DOI: 10.1016/j.tibtech.2019.10.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 02/07/2023]
Abstract
Protein scaffolding is a natural phenomenon whereby proteins colocalize into macromolecular complexes via specific protein-protein interactions. In the case of metabolic enzymes, protein scaffolding drives metabolic flux through specific pathways by colocalizing enzyme active sites. Synthetic protein scaffolding is increasingly used as a mechanism to improve product specificity and yields in metabolic engineering projects. To date, synthetic scaffolding has focused primarily on soluble enzyme systems, but many metabolic pathways for high-value secondary metabolites depend on membrane-bound enzymes. The compositional diversity of biological membranes and general challenges associated with modifying membrane proteins complicate scaffolding with membrane-requiring enzymes. Several recent studies have introduced new approaches to protein scaffolding at membrane surfaces, with notable success in improving product yields from specific metabolic pathways.
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Lavell A, Froehlich J, Baylis O, Rotondo A, Benning C. A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 99:978-987. [PMID: 31062431 PMCID: PMC6711814 DOI: 10.1111/tpj.14377] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/22/2019] [Accepted: 05/01/2019] [Indexed: 05/23/2023]
Abstract
The thylakoid membranes of the chloroplast harbor the photosynthetic machinery that converts light into chemical energy. Chloroplast membranes are unique in their lipid makeup, which is dominated by the galactolipids mono- and digalactosyldiacylglycerol (MGDG and DGDG). The most abundant galactolipid, MGDG, is assembled through both plastid and endoplasmic reticulum (ER) pathways in Arabidopsis, resulting in distinguishable molecular lipid species. Phosphatidic acid (PA) is the first glycerolipid formed by the plastid galactolipid biosynthetic pathway. It is converted to substrate diacylglycerol (DAG) for MGDG Synthase (MGD1) which adds to it a galactose from UDP-Gal. The enzymatic reactions yielding these galactolipids have been well established. However, auxiliary or regulatory factors are largely unknown. We identified a predicted rhomboid-like protease 10 (RBL10), located in plastids of Arabidopsis thaliana, that affects galactolipid biosynthesis likely through intramembrane proteolysis. Plants with T-DNA disruptions in RBL10 have greatly decreased 16:3 (acyl carbons:double bonds) and increased 18:3 acyl chain abundance in MGDG of leaves. Additionally, rbl10-1 mutants show reduced [14 C]-acetate incorporation into MGDG during pulse-chase labeling, indicating a reduced flux through the plastid galactolipid biosynthesis pathway. While plastid MGDG biosynthesis is blocked in rbl10-1 mutants, they are capable of synthesizing PA, as well as producing normal amounts of MGDG by compensating with ER-derived lipid precursors. These findings link this predicted protease to the utilization of PA for plastid galactolipid biosynthesis potentially revealing a regulatory mechanism in chloroplasts.
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Affiliation(s)
- A. Lavell
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - J.E. Froehlich
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - O. Baylis
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - A. Rotondo
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - C. Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
- DOE-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
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17
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Bouchnak I, Brugière S, Moyet L, Le Gall S, Salvi D, Kuntz M, Tardif M, Rolland N. Unraveling Hidden Components of the Chloroplast Envelope Proteome: Opportunities and Limits of Better MS Sensitivity. Mol Cell Proteomics 2019; 18:1285-1306. [PMID: 30962257 PMCID: PMC6601204 DOI: 10.1074/mcp.ra118.000988] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 04/03/2019] [Indexed: 12/31/2022] Open
Abstract
The chloroplast is a major plant cell organelle that fulfills essential metabolic and biosynthetic functions. Located at the interface between the chloroplast and other cell compartments, the chloroplast envelope system is a strategic barrier controlling the exchange of ions, metabolites and proteins, thus regulating essential metabolic functions (synthesis of hormones precursors, amino acids, pigments, sugars, vitamins, lipids, nucleotides etc.) of the plant cell. However, unraveling the contents of the chloroplast envelope proteome remains a difficult challenge; many proteins constituting this functional double membrane system remain to be identified. Indeed, the envelope contains only 1% of the chloroplast proteins (i.e. 0.4% of the whole cell proteome). In other words, most envelope proteins are so rare at the cell, chloroplast, or even envelope level, that they remained undetectable using targeted MS studies. Cross-contamination of chloroplast subcompartments by each other and by other cell compartments during cell fractionation, impedes accurate localization of many envelope proteins. The aim of the present study was to take advantage of technologically improved MS sensitivity to better define the proteome of the chloroplast envelope (differentiate genuine envelope proteins from contaminants). This MS-based analysis relied on an enrichment factor that was calculated for each protein identified in purified envelope fractions as compared with the value obtained for the same protein in crude cell extracts. Using this approach, a total of 1269 proteins were detected in purified envelope fractions, of which, 462 could be assigned an envelope localization by combining MS-based spectral count analyses with manual annotation using data from the literature and prediction tools. Many of such proteins being previously unknown envelope components, these data constitute a new resource of significant value to the broader plant science community aiming to define principles and molecular mechanisms controlling fundamental aspects of plastid biogenesis and functions.
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Affiliation(s)
- Imen Bouchnak
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France
| | - Sabine Brugière
- §University Grenoble Alpes, CEA, Inserm, IRIG-BGE, 38000 Grenoble, France
| | - Lucas Moyet
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France
| | - Sophie Le Gall
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France
| | - Daniel Salvi
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France
| | - Marcel Kuntz
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France
| | - Marianne Tardif
- §University Grenoble Alpes, CEA, Inserm, IRIG-BGE, 38000 Grenoble, France
| | - Norbert Rolland
- From the ‡University Grenoble Alpes, INRA, CNRS, CEA, IRIG-LPCV, 38000 Grenoble, France;.
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18
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Bölter B. En route into chloroplasts: preproteins' way home. PHOTOSYNTHESIS RESEARCH 2018; 138:263-275. [PMID: 29943212 DOI: 10.1007/s11120-018-0542-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
Chloroplasts are the characteristic endosymbiotic organelles of plant cells which during the course of evolution lost most of their genetic information to the nucleus. Thus, they critically depend on the host cell for allocation of nearly their complete protein supply. This includes gene expression, translation, protein targeting, and transport-all of which need to be tightly regulated and perfectly coordinated to accommodate the cells' needs. To this end, multiple signaling pathways have been implemented that interchange information between the different cellular compartments. One of the most complex and energy consuming processes is the translocation of chloroplast-destined proteins into their target organelle. It is a concerted effort from chaperones, receptor proteins, channels, and regulatory elements to ensure correct targeting, efficient transport, and subsequent folding. Although we have discovered and learned a lot about protein import into chloroplasts in the last decades, there are still many open questions and debates about the roles of individual proteins as well as the mechanistic details. In this review, I will summarize and discuss the published data with a focus on the translocation complex in the chloroplast inner envelope membrane.
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Affiliation(s)
- Bettina Bölter
- Department Biologie I, Botanik, Ludwig-Maximilians-Universität, Planegg-Martinsried, Germany.
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19
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Day PM, Theg SM. Evolution of protein transport to the chloroplast envelope membranes. PHOTOSYNTHESIS RESEARCH 2018; 138:315-326. [PMID: 30291507 DOI: 10.1007/s11120-018-0540-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/20/2018] [Indexed: 05/11/2023]
Abstract
Chloroplasts are descendants of an ancient endosymbiotic cyanobacterium that lived inside a eukaryotic cell. They inherited the prokaryotic double membrane envelope from cyanobacteria. This envelope contains prokaryotic protein sorting machineries including a Sec translocase and relatives of the central component of the bacterial outer membrane β-barrel assembly module. As the endosymbiont was integrated with the rest of the cell, the synthesis of most of its proteins shifted from the stroma to the host cytosol. This included nearly all the envelope proteins identified so far. Consequently, the overall biogenesis of the chloroplast envelope must be distinct from cyanobacteria. Envelope proteins initially approach their functional locations from the exterior rather than the interior. In many cases, they have been shown to use components of the general import pathway that also serves the stroma and thylakoids. If the ancient prokaryotic protein sorting machineries are still used for chloroplast envelope proteins, their activities must have been modified or combined with the general import pathway. In this review, we analyze the current knowledge pertaining to chloroplast envelope biogenesis and compare this to bacteria.
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Affiliation(s)
- Philip M Day
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA
| | - Steven M Theg
- Department of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, CA, USA.
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20
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Fernandez DE. Two paths diverged in the stroma: targeting to dual SEC translocase systems in chloroplasts. PHOTOSYNTHESIS RESEARCH 2018; 138:277-287. [PMID: 29951837 DOI: 10.1007/s11120-018-0541-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
Chloroplasts inherited systems and strategies for protein targeting, translocation, and integration from their cyanobacterial ancestor. Unlike cyanobacteria however, chloroplasts in green algae and plants contain two distinct SEC translocase/integrase systems: the SEC1 system in the thylakoid membrane and the SEC2 system in the inner envelope membrane. This review summarizes the mode of action of SEC translocases, identification of components of the SEC2 system, evolutionary history of SCY and SECA genes, and previous work on the co- and post-translational targeting of lumenal and thylakoid membrane proteins to the SEC1 system. Recent work identifying substrates for the SEC2 system and potential features that may contribute to inner envelope targeting are also discussed.
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Affiliation(s)
- Donna E Fernandez
- Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
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21
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Peculiar features of the plastids of the colourless alga Euglena longa and photosynthetic euglenophytes unveiled by transcriptome analyses. Sci Rep 2018; 8:17012. [PMID: 30451959 PMCID: PMC6242988 DOI: 10.1038/s41598-018-35389-1] [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: 07/26/2018] [Accepted: 11/02/2018] [Indexed: 12/17/2022] Open
Abstract
Euglenophytes are a familiar algal group with green alga-derived secondary plastids, but the knowledge of euglenophyte plastid function and evolution is still highly incomplete. With this in mind we sequenced and analysed the transcriptome of the non-photosynthetic species Euglena longa. The transcriptomic data confirmed the absence of genes for the photosynthetic machinery, but provided candidate plastid-localised proteins bearing N-terminal bipartite topogenic signals (BTSs) of the characteristic euglenophyte type. Further comparative analyses including transcriptome assemblies available for photosynthetic euglenophytes enabled us to unveil salient aspects of the basic euglenophyte plastid infrastructure, such as plastidial targeting of several proteins as C-terminal translational fusions with other BTS-bearing proteins or replacement of the conventional eubacteria-derived plastidial ribosomal protein L24 by homologs of archaeo-eukaryotic origin. Strikingly, no homologs of any key component of the TOC/TIC system and the plastid division apparatus are discernible in euglenophytes, and the machinery for intraplastidial protein targeting has been simplified by the loss of the cpSRP/cpFtsY system and the SEC2 translocon. Lastly, euglenophytes proved to encode a plastid-targeted homolog of the termination factor Rho horizontally acquired from a Lambdaproteobacteria-related donor. Our study thus further documents a substantial remodelling of the euglenophyte plastid compared to its green algal progenitor.
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22
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Luo Y, Qiu Y, Na R, Meerja F, Lu QS, Yang C, Tian L. A Golden Gate and Gateway double-compatible vector system for high throughput functional analysis of genes. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2018; 271:117-126. [PMID: 29650149 DOI: 10.1016/j.plantsci.2018.03.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 03/20/2018] [Accepted: 03/21/2018] [Indexed: 06/08/2023]
Abstract
A major research topic nowadays is to study and understand the functions of the increasing number of predicted genes that have been discovered through the complete genome sequencing of many plant species. With the aim of developing tools for rapid and convenient gene function analysis, we have developed a set of "pGate" vectors based on the principle of Golden gate and Gateway cloning approaches. These vectors combine the positive aspects of both Golden gate and Gateway cloning strategies. pGate vectors can not only be used as Golden gate recipient vectors to assemble multiple DNA fragments in a pre-defined order, but they can also work as an entry vector to transfer the assembled DNA fragment(s) to a large number of already-existing, functionally diverse, Gateway compatible destination vectors without adding additional nucleotides during cloning. We show the pGate vectors are effective and convenient in several major aspects of gene function analyses, including BiFC (Bimolecular fluorescence complementation) to analyze protein-protein interaction, amiRNA (artificial microRNA) candidate screening and as assembly of CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeats, CRISPR-associated protein-9 nuclease) system elements together for genome editing. The pGate system is a practical and flexible tool which can facilitate plant gene function research.
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Affiliation(s)
- Yanjie Luo
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON, N5V4T3, Canada
| | - Yang Qiu
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON, N5V4T3, Canada; Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Ren Na
- Institute of Cereal and Oil Crops, Hebei Academy of Agricultural and Forestry Sciences, Shijiazhuang, 050035, China
| | - Farida Meerja
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON, N5V4T3, Canada; Department of Biology, Western University, London, ON, N6A5B7, Canada
| | - Qing Shi Lu
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON, N5V4T3, Canada
| | - Chunyan Yang
- Institute of Cereal and Oil Crops, Hebei Academy of Agricultural and Forestry Sciences, Shijiazhuang, 050035, China
| | - Lining Tian
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, ON, N5V4T3, Canada.
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23
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Zoschke R, Bock R. Chloroplast Translation: Structural and Functional Organization, Operational Control, and Regulation. THE PLANT CELL 2018; 30:745-770. [PMID: 29610211 PMCID: PMC5969280 DOI: 10.1105/tpc.18.00016] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/26/2018] [Accepted: 04/01/2018] [Indexed: 05/20/2023]
Abstract
Chloroplast translation is essential for cellular viability and plant development. Its positioning at the intersection of organellar RNA and protein metabolism makes it a unique point for the regulation of gene expression in response to internal and external cues. Recently obtained high-resolution structures of plastid ribosomes, the development of approaches allowing genome-wide analyses of chloroplast translation (i.e., ribosome profiling), and the discovery of RNA binding proteins involved in the control of translational activity have greatly increased our understanding of the chloroplast translation process and its regulation. In this review, we provide an overview of the current knowledge of the chloroplast translation machinery, its structure, organization, and function. In addition, we summarize the techniques that are currently available to study chloroplast translation and describe how translational activity is controlled and which cis-elements and trans-factors are involved. Finally, we discuss how translational control contributes to the regulation of chloroplast gene expression in response to developmental, environmental, and physiological cues. We also illustrate the commonalities and the differences between the chloroplast and bacterial translation machineries and the mechanisms of protein biosynthesis in these two prokaryotic systems.
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Affiliation(s)
- Reimo Zoschke
- Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany
| | - Ralph Bock
- Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany
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24
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Abstract
The plastids, including chloroplasts, are a group of interrelated organelles that confer photoautotrophic growth and the unique metabolic capabilities that are characteristic of plant systems. Plastid biogenesis relies on the expression, import, and assembly of thousands of nuclear encoded preproteins. Plastid proteomes undergo rapid remodeling in response to developmental and environmental signals to generate functionally distinct plastid types in specific cells and tissues. In this review, we will highlight the central role of the plastid protein import system in regulating and coordinating the import of functionally related sets of preproteins that are required for plastid-type transitions and maintenance.
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25
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Lee DW, Lee J, Hwang I. Sorting of nuclear-encoded chloroplast membrane proteins. CURRENT OPINION IN PLANT BIOLOGY 2017; 40:1-7. [PMID: 28668581 DOI: 10.1016/j.pbi.2017.06.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 06/07/2017] [Accepted: 06/14/2017] [Indexed: 05/11/2023]
Abstract
Among the many organelles in eukaryotic cells, chloroplasts have the most complex structure, with multiple suborganellar membranes, making protein targeting to chloroplasts, particularly to various suborganellar membranes, highly challenging. Multiple mechanisms function in the biogenesis of chloroplast membrane proteins. Nuclear-encoded nascent proteins can be targeted to the outer envelope membrane directly from the cytosol after translation, but their targeting to the inner envelope and thylakoid membranes requires multiple steps, including cytosolic sorting, translocation across the envelope membranes, sorting in the stroma, and insertion into their target membranes. In this review, we discuss the current knowledge about the sorting mechanisms of proteins to the two envelope membranes and the thylakoid membrane, along with perspectives for future research.
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Affiliation(s)
- Dong Wook Lee
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Junho Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 37673, Republic of Korea; Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
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26
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Singhal R, Fernandez DE. Sorting of SEC translocase SCY components to different membranes in chloroplasts. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:5029-5043. [PMID: 28992187 PMCID: PMC5853536 DOI: 10.1093/jxb/erx318] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 08/15/2017] [Indexed: 05/20/2023]
Abstract
Membrane proteins that are imported into chloroplasts must be accurately routed in order to establish and maintain the highly differentiated membranes characteristic of these organelles. Little is known about the targeting information or pathways involved, especially in the case of proteins with multiple transmembrane domains. We have studied targeting of the SCY components of the two SEC translocases in chloroplasts. SCY1 and SCY2 share a similar, highly conserved structure with 10 transmembrane domains, but are targeted to different membranes: the thylakoids and inner envelope, respectively. We used protoplast transfections and a confocal microscopy imaging assay in combination with a domain-swapping approach to investigate sorting pathways and identify important targeting elements in these proteins. We show that the N-terminal region of SCY1 contains targeting determinants that allow SCY1 to be recruited to the signal-recognition particle pathway. In addition, substituting the N-terminal region of SCY1 for the N-terminal region of SCY2 causes SCY2 to be displaced out of the inner envelope. The region of SCY2 that contains transmembrane domains 3 and 4 is necessary for localization to the inner envelope and may serve as a membrane anchor, enhancing the integration of other transmembrane domains via either stop-transfer or post-import mechanisms.
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Affiliation(s)
- Rajneesh Singhal
- Department of Botany, University of Wisconsin-Madison, Madison, WI, USA
| | - Donna E Fernandez
- Department of Botany, University of Wisconsin-Madison, Madison, WI, USA
- Correspondence:
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