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Anderson SA, Satyanarayan MB, Wessendorf RL, Lu Y, Fernandez DE. A homolog of GuidedEntry of Tail-anchored proteins3 functions in membrane-specific protein targeting in chloroplasts of Arabidopsis. THE PLANT CELL 2021; 33:2812-2833. [PMID: 34021351 PMCID: PMC8408437 DOI: 10.1093/plcell/koab145] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/18/2021] [Indexed: 05/12/2023]
Abstract
The chloroplasts and mitochondria of photosynthetic eukaryotes contain proteins that are closely related to cytosolic Guided Entry of Tail-anchored proteins3 (Get3). Get3 is a targeting factor that efficiently escorts tail-anchored (TA) proteins to the ER. Because other components of the cytosolic-targeting pathway appear to be absent in organelles, previous investigators have asserted that organellar Get3 homologs are unlikely to act as targeting factors. However, we show here both that the Arabidopsis thaliana chloroplast homolog designated as GET3B is structurally similar to cytosolic Get3 proteins and that it selectively binds a thylakoid-localized TA protein. Based on genetic interactions between a get3b mutation and mutations affecting the chloroplast signal recognition particle-targeting pathway, as well as changes in the abundance of photosynthesis-related proteins in mutant plants, we propose that GET3B acts primarily to direct proteins to the thylakoids. Furthermore, through molecular complementation experiments, we show that function of GET3B depends on its ability to hydrolyze ATP, and this is consistent with action as a targeting factor. We propose that GET3B and related organellar Get3 homologs play a role that is analogous to that of cytosolic Get3 proteins, and that GET3B acts as a targeting factor in the chloroplast stroma to deliver TA proteins in a membrane-specific manner.
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Affiliation(s)
- Stacy A. Anderson
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Manasa B. Satyanarayan
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - Ryan L. Wessendorf
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - Yan Lu
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - Donna E. Fernandez
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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2
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Nymark M, Grønbech Hafskjold MC, Volpe C, Fonseca DDM, Sharma A, Tsirvouli E, Serif M, Winge P, Finazzi G, Bones AM. Functional studies of CpSRP54 in diatoms show that the mechanism of thylakoid protein insertion differs from that in plants and green algae. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 106:113-132. [PMID: 33372269 DOI: 10.1111/tpj.15149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 06/12/2023]
Abstract
The chloroplast signal recognition particle 54 kDa (CpSRP54) protein is a member of the CpSRP pathway known to target proteins to thylakoid membranes in plants and green algae. Loss of CpSRP54 in the marine diatom Phaeodactylum tricornutum lowers the accumulation of a selection of chloroplast-encoded subunits of photosynthetic complexes, indicating a role in the co-translational part of the CpSRP pathway. In contrast to plants and green algae, absence of CpSRP54 does not have a negative effect on the content of light-harvesting antenna complex proteins and pigments in P. tricornutum, indicating that the diatom CpSRP54 protein has not evolved to function in the post-translational part of the CpSRP pathway. Cpsrp54 KO mutants display altered photophysiological responses, with a stronger induction of photoprotective mechanisms and lower growth rates compared to wild type when exposed to increased light intensities. Nonetheless, their phenotype is relatively mild, thanks to the activation of mechanisms alleviating the loss of CpSRP54, involving upregulation of chaperones. We conclude that plants, green algae, and diatoms have evolved differences in the pathways for co-translational and post-translational insertion of proteins into the thylakoid membranes.
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Affiliation(s)
- Marianne Nymark
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Marthe Caroline Grønbech Hafskjold
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Charlotte Volpe
- Department of Biotechnology and Food Science, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Davi de Miranda Fonseca
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, NTNU, Trondheim, N-7491, Norway
- Proteomics and Modomics Experimental Core Facility (PROMEC), NTNU and Central Administration, St Olavs Hospital, The University Hospital in Trondheim, Trondheim, Norway
| | - Animesh Sharma
- Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, NTNU, Trondheim, N-7491, Norway
- Proteomics and Modomics Experimental Core Facility (PROMEC), NTNU and Central Administration, St Olavs Hospital, The University Hospital in Trondheim, Trondheim, Norway
| | - Eirini Tsirvouli
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Manuel Serif
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Per Winge
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
| | - Giovanni Finazzi
- Université Grenoble Alpes (UGA), Laboratoire de Physiologie Cellulaire et Végétale, UMR 5168, Centre National de la Recherche Scientifique (CNRS), Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Interdisciplinary Research Institute of Grenoble (IRIG), CEA-Grenoble, Grenoble, 38000, France
| | - Atle Magnar Bones
- Department of Biology, Norwegian University of Science and Technology, Trondheim, N-7491, Norway
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Xu X, Ouyang M, Lu D, Zheng C, Zhang L. Protein Sorting within Chloroplasts. Trends Cell Biol 2020; 31:9-16. [PMID: 33121860 DOI: 10.1016/j.tcb.2020.09.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/22/2020] [Accepted: 09/30/2020] [Indexed: 12/11/2022]
Abstract
Chloroplasts have multiple suborganellar membranes. Correct and efficient translocation of chloroplast proteins from their site of synthesis into or across membranes to their functional compartments are fundamental processes. In recent years, several new components and regulatory mechanisms involved in chloroplast protein import and sorting have been explored. Moreover, the formation of liquid-liquid phase transition (LLPT) has been recently reported as a novel mechanism for regulating chloroplast protein sorting. Here, we overview the recent advances of both nuclear- and chloroplast-encoded protein trafficking to their final destination within chloroplasts, and discuss the novel components and regulatory mechanisms of intrachloroplast sorting. Furthermore, we propose that LLPT may be a universal and conserved mechanism for driving organelle protein trafficking and organelle biogenesis.
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Affiliation(s)
- Xiumei Xu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Jinming Avenue, Kaifeng 475004, China
| | - Min Ouyang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, China
| | - Dandan Lu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Jinming Avenue, Kaifeng 475004, China
| | - Canhui Zheng
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Jinming Avenue, Kaifeng 475004, China
| | - Lixin Zhang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Jinming Avenue, Kaifeng 475004, China.
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Shi Y, He Y, Lv X, Wei Y, Zhang X, Xu X, Li L, Wu JL. Chloroplast SRP54s are Essential for Chloroplast Development in Rice. RICE (NEW YORK, N.Y.) 2020; 13:54. [PMID: 32761436 PMCID: PMC7410889 DOI: 10.1186/s12284-020-00415-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/29/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND The chloroplast signal recognition particle 54 (cpSRP54) is known for targeting the light-harvesting complex proteins to thylakoids and plays a critical role for chloroplast development in Arabidopsis, but little is known in rice. Here, we reported two homologous cpSRP54s that affect chloroplast development and plant survival in rice. RESULTS Two rice cpSRP54 homologues, OscpSRP54a and OscpSRP54b, were identified in present study. The defective OscpSRP54a (LOC_Os11g05552) was responsible for the pale green leaf phenotype of the viable pale green leaf 14 (pgl14) mutant. A single nucleotide substitution from G to A at the position 278, the first intron splicing site, was detected in LOC_Os11g05552 in pgl14. The wild type allele could rescue the mutant phenotype. Knockout lines of OscpSRP54b (LOC_Os11g05556) exhibited similar pale green phenotype to pgl14 with reduced chlorophyll contents and impaired chloroplast development, but showed apparently arrested-growth and died within 3 weeks. Both OscpSRP54a and OscpSRP54b were constitutively expressed mainly in shoots and leaves at the vegetative growth stage. Subcellular location indicated that both OscpSRP54a and OscpSRP54b were chloroplast-localized. Both OscpSRP54a and OscpSRP54b were able to interact with OscpSRP43, respectively. The transcript level of OscpSRP43 was significantly reduced while the transcript level of OscpSRP54b was apparently increased in pgl14. In contrast, the transcript levels of OscpSRP54a, OscpSRP43 and OscpSRP54b were all significantly decreased in OscpSRP54b knockout lines. CONCLUSION Our study demonstrated that both OscpSRP54a and OscpSRP54b were essential for normal chloroplast development by interacting with OscpSRP43 in rice. OscpSRP54a and OscpSRP54b might play distinct roles in transporting different chloroplast proteins into thylakoids through cpSRP-mediated pathway.
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Affiliation(s)
- Yongfeng Shi
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Yan He
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xiangguang Lv
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100081 China
| | - Yanlin Wei
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xiaobo Zhang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Xia Xu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Liangjian Li
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
| | - Jian-li Wu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China
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Co-Translational Protein Folding and Sorting in Chloroplasts. PLANTS 2020; 9:plants9020214. [PMID: 32045984 PMCID: PMC7076657 DOI: 10.3390/plants9020214] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 01/22/2023]
Abstract
Cells depend on the continuous renewal of their proteome composition during the cell cycle and in order to replace aberrant proteins or to react to changing environmental conditions. In higher eukaryotes, protein synthesis is achieved by up to five million ribosomes per cell. With the fast kinetics of translation, the large number of newly made proteins generates a substantial burden for protein homeostasis and requires a highly orchestrated cascade of factors promoting folding, sorting and final maturation. Several of the involved factors directly bind to translating ribosomes for the early processing of emerging nascent polypeptides and the translocation of ribosome nascent chain complexes to target membranes. In plant cells, protein synthesis also occurs in chloroplasts serving the expression of a relatively small set of 60–100 protein-coding genes. However, most of these proteins, together with nucleus-derived subunits, form central complexes majorly involved in the essential processes of photosynthetic light reaction, carbon fixation, metabolism and gene expression. Biogenesis of these heterogenic complexes adds an additional level of complexity for protein biogenesis. In this review, we summarize the current knowledge about co-translationally binding factors in chloroplasts and discuss their role in protein folding and ribosome translocation to thylakoid membranes.
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Hristou A, Gerlach I, Stolle DS, Neumann J, Bischoff A, Dünschede B, Nowaczyk MM, Zoschke R, Schünemann D. Ribosome-Associated Chloroplast SRP54 Enables Efficient Cotranslational Membrane Insertion of Key Photosynthetic Proteins. THE PLANT CELL 2019; 31:2734-2750. [PMID: 31444312 PMCID: PMC6881123 DOI: 10.1105/tpc.19.00169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/12/2019] [Accepted: 08/22/2019] [Indexed: 05/20/2023]
Abstract
Key proteins of the photosynthetic complexes are encoded in the chloroplast genome and cotranslationally inserted into the thylakoid membrane. However, the molecular details of this process are largely unknown. Here, we demonstrate by ribosome profiling that the conserved chloroplast signal recognition particle subunit (cpSRP54) is required for efficient cotranslational targeting of several central photosynthetic proteins, such as the PSII PsbA (D1) subunit, in Arabidopsis (Arabidopsis thaliana). High-resolution analysis of membrane-associated and soluble ribosome footprints revealed that the SRP-dependent membrane targeting of PsbA is already initiated at an early translation step before exposure of the nascent chain from the ribosome. In contrast to cytosolic SRP, which contacts the ribosome close to the peptide tunnel exit site, analysis of the cpSRP54/ribosome binding interface revealed a direct interaction of cpSRP54 and the ribosomal subunit uL4, which is not located at the tunnel exit site but forms a part of the internal peptide tunnel wall by a loop domain. The plastid-specific C-terminal tail region of cpSRP54 plays a crucial role in uL4 binding. Our data indicate a novel mechanism of SRP-dependent membrane protein transport with the cpSRP54/uL4 interaction as a central element in early initiation of cotranslational membrane targeting.
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Affiliation(s)
- Athina Hristou
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Ines Gerlach
- Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany
| | - Dominique S Stolle
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Jennifer Neumann
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Annika Bischoff
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Beatrix Dünschede
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Marc M Nowaczyk
- Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
| | - Reimo Zoschke
- Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany
| | - Danja Schünemann
- Molecular Biology of Plant Organelles, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany
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Ma Y, Wang J, Wang C, Zhang Q, Xu Y, Liu H, Xiang X, Ma J. DPP-4 inhibitor anagliptin protects against hypoxia-induced cytotoxicity in cardiac H9C2 cells. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2019; 47:3823-3831. [PMID: 31556325 DOI: 10.1080/21691401.2019.1652624] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yunxiang Ma
- Southern Medical University Affiliated Fengxian Hospital, Shanghai, Shanghai, P.R. China
- Tengzhou Central People's Hospital, Tengzhou, Shandong Province, P.R. China
| | - Junkai Wang
- Tengzhou Central People's Hospital, Tengzhou, Shandong Province, P.R. China
| | - Changhua Wang
- Tengzhou Central People's Hospital, Tengzhou, Shandong Province, P.R. China
| | - Qiong Zhang
- Southern Medical University Affiliated Fengxian Hospital, Shanghai, Shanghai, P.R. China
| | - Yannan Xu
- Southern Medical University Affiliated Fengxian Hospital, Shanghai, Shanghai, P.R. China
| | - Huajin Liu
- Southern Medical University Affiliated Fengxian Hospital, Shanghai, Shanghai, P.R. China
| | - Xia Xiang
- Shanghai University of Medicine & Health Sciences, Shanghai, P.R. China
| | - Jiangwei Ma
- Southern Medical University Affiliated Fengxian Hospital, Shanghai, Shanghai, P.R. China
- Shanghai University of Medicine & Health Sciences, Shanghai, P.R. China
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Króliczewski J, Bartoszewski R, Króliczewska B. Chloroplast PetD protein: evidence for SRP/Alb3-dependent insertion into the thylakoid membrane. BMC PLANT BIOLOGY 2017; 17:213. [PMID: 29162052 PMCID: PMC5697057 DOI: 10.1186/s12870-017-1176-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 11/13/2017] [Indexed: 05/24/2023]
Abstract
BACKGROUND In thylakoid membrane, each monomer of the dimeric complex of cytochrome b 6 f is comprised of eight subunits that are both nucleus- and plastid-encoded. Proper cytochrome b 6 f complex integration into the thylakoid membrane requires numerous regulatory factors for coordinated transport, insertion and assembly of the subunits. Although, the chloroplast-encoded cytochrome b 6 f subunit IV (PetD) consists of three transmembrane helices, the signal and the mechanism of protein integration into the thylakoid membrane have not been identified. RESULTS Here, we demonstrate that the native PetD subunit cannot incorporate into the thylakoid membranes spontaneously, but that proper integration occurs through the post-translational signal recognition particle (SRP) pathway. Furthermore, we show that PetD insertion into thylakoid membrane involves the coordinated action of cpFTSY, cpSRP54 and ALB3 insertase. CONCLUSIONS PetD subunit integration into the thylakoid membrane is a post-translational and an SRP-dependent process that requires the formation of the cpSRP-cpFtsY-ALB3-PetD complex. This data provides a new insight into the molecular mechanisms by which membrane proteins integration into the thylakoid membrane is accomplished and is not limited to PetD.
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Affiliation(s)
- Jarosław Króliczewski
- Faculty of Biotechnology, University of Wrocław, Fryderyka Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Rafał Bartoszewski
- Department of Biology and Pharmaceutical Botany Medical University of Gdańsk, Hallera 107, 80-416 Gdansk, Poland
| | - Bożena Króliczewska
- Department of Animal Physiology and Biostructure, Faculty of Veterinary Medicine Wroclaw University of Environmental and Life Sciences, C.K Norwida 31, 50-375 Wrocław, Poland
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Króliczewski J, Piskozub M, Bartoszewski R, Króliczewska B. ALB3 Insertase Mediates Cytochrome b 6 Co-translational Import into the Thylakoid Membrane. Sci Rep 2016; 6:34557. [PMID: 27698412 PMCID: PMC5048292 DOI: 10.1038/srep34557] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 09/15/2016] [Indexed: 01/10/2023] Open
Abstract
The cytochrome b6 f complex occupies an electrochemically central position in the electron-transport chain bridging the photosynthetic reaction center of PS I and PS II. In plants, the subunits of these thylakoid membrane protein complexes are both chloroplast and nuclear encoded. How the chloroplast-encoded subunits of multi-spanning cytochrome b6 are targeted and inserted into the thylakoid membrane is not fully understood. Experimental approaches to evaluate the cytochrome b6 import mechanism in vivo have been limited to bacterial membranes and were not a part of the chloroplast environment. To evaluate the mechanism governing cytochrome b6 integration in vivo, we performed a comparative analysis of both native and synthetic cytochrome b6 insertion into purified thylakoids. Using biophysical and biochemical methods, we show that cytochrome b6 insertion into the thylakoid membrane is a non-spontaneous co-translational process that involves ALB3 insertase. Furthermore, we provided evidence that CSP41 (chloroplast stem-loop-binding protein of 41 kDa) interacts with RNC-cytochrome b6 complexes, and may be involved in cytochrome b6 (petB) transcript stabilization or processing.
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Affiliation(s)
- Jarosław Króliczewski
- Laboratory of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław Poland
| | - Małgorzata Piskozub
- Amplicon Sp. z o. o., Wrocław, Poland
- Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Rafał Bartoszewski
- Department of Biology and Pharmaceutical Botany, Medical University of Gdansk, Gdansk, Poland
| | - Bożena Króliczewska
- Department of Animal Physiology and Biostructure, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences, Wrocław, Poland
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Oryza sativa Chloroplast Signal Recognition Particle 43 (OscpSRP43) Is Required for Chloroplast Development and Photosynthesis. PLoS One 2015; 10:e0143249. [PMID: 26600124 PMCID: PMC4657901 DOI: 10.1371/journal.pone.0143249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/02/2015] [Indexed: 12/26/2022] Open
Abstract
A rice chlorophyll-deficient mutant w67 was isolated from an ethyl methane sulfonate (EMS)-induced IR64 (Oryza sativa L. ssp. indica) mutant bank. The mutant exhibited a distinct yellow-green leaf phenotype in the whole plant growth duration with significantly reduced levels of chlorophyll and carotenoid, impaired chloroplast development and lowered capacity of photosynthesis compared with the wild-type IR64. Expression of a number of genes associated with chlorophyll metabolism, chloroplast biogenesis and photosynthesis was significantly altered in the mutant. Genetic analysis indicated that the yellow-green phenotype was controlled by a single recessive nuclear gene located on the short arm of chromosome 3. Using map-based strategy, the mutation was isolated and predicted to encode a chloroplast signal recognition particle 43 KD protein (cpSRP43) with 388 amino acid residuals. A single base substitution from A to T at position 160 resulted in a premature stop codon. OscpSRP43 was constitutively expressed in various organs with the highest level in the leaf. Functional complementation could rescue the mutant phenotype and subcellular localization showed that the cpSRP43:GFP fusion protein was targeted to the chloroplast. The data suggested that Oryza sativa cpSRP43 (OscpSRP43) was required for the normal development of chloroplasts and photosynthesis in rice.
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