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Kindgren P, Strand Å. Chloroplast transcription, untangling the Gordian Knot. THE NEW PHYTOLOGIST 2015; 206:889-891. [PMID: 25865165 DOI: 10.1111/nph.13388] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Affiliation(s)
- Peter Kindgren
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, S-90187, Umeå, Sweden
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, 6009, WA, Australia
| | - Åsa Strand
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, S-90187, Umeå, Sweden
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52
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Pfalz J, Holtzegel U, Barkan A, Weisheit W, Mittag M, Pfannschmidt T. ZmpTAC12 binds single-stranded nucleic acids and is essential for accumulation of the plastid-encoded polymerase complex in maize. THE NEW PHYTOLOGIST 2015; 206:1024-1037. [PMID: 25599833 PMCID: PMC6680207 DOI: 10.1111/nph.13248] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 11/19/2014] [Indexed: 05/04/2023]
Abstract
The plastid-encoded plastid RNA polymerase (PEP) represents the major transcription machinery in mature chloroplasts. Proteomic studies identified four plastome- and at least ten nuclear-encoded proteins making up this multimeric enzyme. Depletion of single subunits is known to result in strongly diminished PEP activity causing severe defects in chloroplast biogenesis. Here, we characterized one PEP subunit in maize, ZmpTAC12, and investigated the molecular basis underlying PEP-deficiency in Zmptac12 mutants. We show that the ZmpTAC12 gene encodes two different protein isoforms, both of which localize dually in chloroplasts and nuclei. Moreover, both variants assemble into the PEP-complex. Analysis of PEP-complex assembly in various maize mutants lacking different PEP-complex components demonstrates that ZmpTAC12, ZmpTAC2, ZmpTAC10 and ZmMurE are each required to accumulate a fully assembled PEP-complex. Antibodies to ZmpTAC12 coimmunoprecipitate a subset of plastid RNAs that are synthesized by PEP-dependent transcription. Gel mobility shift analyses with recombinant ZmpTAC12 revealed binding capabilities with ssRNA and ssDNA, but not dsDNA. Collectively these data demonstrate that ZmpTAC12 is required for the proper build-up of the PEP-complex and that it interacts with single-stranded nucleic acids.
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Affiliation(s)
- Jeannette Pfalz
- Department of Plant PhysiologyInstitute of General Botany and Plant PhysiologyFriedrich‐Schiller‐University JenaD‐07743JenaGermany
| | - Ute Holtzegel
- Department of Plant PhysiologyInstitute of General Botany and Plant PhysiologyFriedrich‐Schiller‐University JenaD‐07743JenaGermany
| | - Alice Barkan
- Institute of Molecular BiologyUniversity of OregonEugeneOR97403USA
| | - Wolfram Weisheit
- Department of General BotanyInstitute of General Botany and Plant PhysiologyFriedrich‐Schiller‐University JenaD‐07743JenaGermany
| | - Maria Mittag
- Department of General BotanyInstitute of General Botany and Plant PhysiologyFriedrich‐Schiller‐University JenaD‐07743JenaGermany
| | - Thomas Pfannschmidt
- Department of Plant PhysiologyInstitute of General Botany and Plant PhysiologyFriedrich‐Schiller‐University JenaD‐07743JenaGermany
- University Grenoble‐AlpesF‐38000GrenobleFrance
- CNRSUMR5168F‐38054GrenobleFrance
- CEAiRTSVLaboratoire de Physiologie Cellulaire & VégétaleF‐38054GrenobleFrance
- INRAUSC1359F‐38054GrenobleFrance
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53
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Belcher S, Williams-Carrier R, Stiffler N, Barkan A. Large-scale genetic analysis of chloroplast biogenesis in maize. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1004-16. [PMID: 25725436 DOI: 10.1016/j.bbabio.2015.02.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 02/16/2015] [Indexed: 01/09/2023]
Abstract
BACKGROUND Chloroplast biogenesis involves a collaboration between several thousand nuclear genes and ~100 genes in the chloroplast. Many of the nuclear genes are of cyanobacterial ancestry and continue to perform their ancestral function. However, many others evolved subsequently and comprise a diverse set of proteins found specifically in photosynthetic eucaryotes. Genetic approaches have been key to the discovery of nuclear genes that participate in chloroplast biogenesis, especially those lacking close homologs outside the plant kingdom. SCOPE OF REVIEW This article summarizes contributions from a genetic resource in maize, the Photosynthetic Mutant Library (PML). The PML collection consists of ~2000 non-photosynthetic mutants induced by Mu transposons. We include a summary of mutant phenotypes for 20 previously unstudied maize genes, including genes encoding chloroplast ribosomal proteins, a PPR protein, tRNA synthetases, proteins involved in plastid transcription, a putative ribosome assembly factor, a chaperonin 60 isoform, and a NifU-domain protein required for Photosystem I biogenesis. MAJOR CONCLUSIONS Insertions in 94 maize genes have been linked thus far to visible and molecular phenotypes with the PML collection. The spectrum of chloroplast biogenesis genes that have been genetically characterized in maize is discussed in the context of related efforts in other organisms. This comparison shows how distinct organismal attributes facilitate the discovery of different gene classes, and reveals examples of functional divergence between monocot and dicot plants. GENERAL SIGNIFICANCE These findings elucidate the biology of an organelle whose activities are fundamental to agriculture and the biosphere. This article is part of a Special Issue entitled: Chloroplast Biogenesis.
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Affiliation(s)
- Susan Belcher
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | | | - Nicholas Stiffler
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Alice Barkan
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
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Lu X, Zhang D, Li S, Su Y, Liang Q, Meng H, Shen S, Fan Y, Liu C, Zhang C. FtsHi4 is essential for embryogenesis due to its influence on chloroplast development in Arabidopsis. PLoS One 2014; 9:e99741. [PMID: 24964212 PMCID: PMC4070914 DOI: 10.1371/journal.pone.0099741] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 05/17/2014] [Indexed: 12/31/2022] Open
Abstract
Chloroplast formation is associated with embryo development and seedling growth. However, the relationship between chloroplast differentiation and embryo development remains unclear. Five FtsHi genes that encode proteins with high similarity to FtsH proteins, but lack Zn2+-binding motifs, are present in the Arabidopsis genome. In this study, we showed that T-DNA insertion mutations in the Arabidopsis FtsHi4 gene resulted in embryo arrest at the globular-to-heart-shaped transition stage. Transmission electron microscopic analyses revealed abnormal plastid differentiation with a severe defect in thylakoid formation in the mutant embryos. Immunocytological studies demonstrated that FtsHi4 localized in chloroplasts as a thylakoid membrane-associated protein, supporting its essential role in thylakoid membrane formation. We further showed that FtsHi4 forms protein complexes, and that there was a significant reduction in the accumulation of D2 and PsbO (two photosystem II proteins) in mutant ovules. The role of FtsHi4 in chloroplast development was confirmed using an RNA-interfering approach. Additionally, mutations in other FtsHi genes including FtsHi1, FtsHi2, and FtsHi5 caused phenotypic abnormalities similar to ftshi4 with respect to plastid differentiation during embryogenesis. Taken together, our data suggest that FtsHi4, together with FtsHi1, FtsHi2, and FtsHi5 are essential for chloroplast development in Arabidopsis.
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Affiliation(s)
- Xiaoduo Lu
- Department of Life Sciences, Qilu Normal University, Jinan, China
| | - Dongyuan Zhang
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
| | - Shipeng Li
- Department of Life Sciences, Qilu Normal University, Jinan, China
| | - Yanping Su
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, China
| | - Qiuju Liang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
- National Key Facility for Crop Gene Resources and Genetic Improvement (NFCRI), Beijing, China
| | - Hongyan Meng
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Songdong Shen
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, China
| | - Yunliu Fan
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
- National Key Facility for Crop Gene Resources and Genetic Improvement (NFCRI), Beijing, China
| | - Chunming Liu
- Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Chunyi Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China
- National Key Facility for Crop Gene Resources and Genetic Improvement (NFCRI), Beijing, China
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55
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Casanova-Sáez R, Mateo-Bonmatí E, Kangasjärvi S, Candela H, Micol JL. Arabidopsis ANGULATA10 is required for thylakoid biogenesis and mesophyll development. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:2391-404. [PMID: 24663344 PMCID: PMC4036511 DOI: 10.1093/jxb/eru131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The chloroplasts of land plants contain internal membrane systems, the thylakoids, which are arranged in stacks called grana. Because grana have not been found in Cyanobacteria, the evolutionary origin of genes controlling the structural and functional diversification of thylakoidal membranes in land plants remains unclear. The angulata10-1 (anu10-1) mutant, which exhibits pale-green rosettes, reduced growth, and deficient leaf lateral expansion, resulting in the presence of prominent marginal teeth, was isolated. Palisade cells in anu10-1 are larger and less packed than in the wild type, giving rise to large intercellular spaces. The ANU10 gene encodes a protein of unknown function that localizes to both chloroplasts and amyloplasts. In chloroplasts, ANU10 associates with thylakoidal membranes. Mutant anu10-1 chloroplasts accumulate H2O2, and have reduced levels of chlorophyll and carotenoids. Moreover, these chloroplasts are small and abnormally shaped, thylakoidal membranes are less abundant, and their grana are absent due to impaired thylakoid stacking in the anu10-1 mutant. Because the trimeric light-harvesting complex II (LHCII) has been reported to be required for thylakoid stacking, its levels were determined in anu10-1 thylakoids and they were found to be reduced. Together, the data point to a requirement for ANU10 for chloroplast and mesophyll development.
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Affiliation(s)
- Rubén Casanova-Sáez
- Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain
| | - Eduardo Mateo-Bonmatí
- Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain
| | - Saijaliisa Kangasjärvi
- Department of Biochemistry and Food Chemistry, University of Turku, FI-20014 Turku, Finland
| | - Héctor Candela
- Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain
| | - José Luis Micol
- Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain
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John CR, Smith-Unna RD, Woodfield H, Covshoff S, Hibberd JM. Evolutionary convergence of cell-specific gene expression in independent lineages of C4 grasses. PLANT PHYSIOLOGY 2014; 165:62-75. [PMID: 24676859 PMCID: PMC4012605 DOI: 10.1104/pp.114.238667] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/20/2014] [Indexed: 05/04/2023]
Abstract
Leaves of almost all C4 lineages separate the reactions of photosynthesis into the mesophyll (M) and bundle sheath (BS). The extent to which messenger RNA profiles of M and BS cells from independent C4 lineages resemble each other is not known. To address this, we conducted deep sequencing of RNA isolated from the M and BS of Setaria viridis and compared these data with publicly available information from maize (Zea mays). This revealed a high correlation (r=0.89) between the relative abundance of transcripts encoding proteins of the core C4 pathway in M and BS cells in these species, indicating significant convergence in transcript accumulation in these evolutionarily independent C4 lineages. We also found that the vast majority of genes encoding proteins of the C4 cycle in S. viridis are syntenic to homologs used by maize. In both lineages, 122 and 212 homologous transcription factors were preferentially expressed in the M and BS, respectively. Sixteen shared regulators of chloroplast biogenesis were identified, 14 of which were syntenic homologs in maize and S. viridis. In sorghum (Sorghum bicolor), a third C4 grass, we found that 82% of these trans-factors were also differentially expressed in either M or BS cells. Taken together, these data provide, to our knowledge, the first quantification of convergence in transcript abundance in the M and BS cells from independent lineages of C4 grasses. Furthermore, the repeated recruitment of syntenic homologs from large gene families strongly implies that parallel evolution of both structural genes and trans-factors underpins the polyphyletic evolution of this highly complex trait in the monocotyledons.
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Affiliation(s)
- Christopher R. John
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Richard D. Smith-Unna
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Helen Woodfield
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Julian M. Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
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57
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Williams-Carrier R, Zoschke R, Belcher S, Pfalz J, Barkan A. A major role for the plastid-encoded RNA polymerase complex in the expression of plastid transfer RNAs. PLANT PHYSIOLOGY 2014; 164:239-48. [PMID: 24246379 PMCID: PMC3875804 DOI: 10.1104/pp.113.228726] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 11/16/2013] [Indexed: 05/18/2023]
Abstract
Chloroplast transcription in land plants relies on collaboration between a plastid-encoded RNA polymerase (PEP) of cyanobacterial ancestry and a nucleus-encoded RNA polymerase of phage ancestry. PEP associates with additional proteins that are unrelated to bacterial transcription factors, many of which have been shown to be important for PEP activity in Arabidopsis (Arabidopsis thaliana). However, the biochemical roles of these PEP-associated proteins are not known. We describe phenotypes conditioned by transposon insertions in genes encoding the maize (Zea mays) orthologs of five such proteins: ZmPTAC2, ZmMurE, ZmPTAC10, ZmPTAC12, and ZmPRIN2. These mutants have similar ivory/virescent pigmentation and similar reductions in plastid ribosomes and photosynthetic complexes. RNA gel-blot and microarray hybridizations revealed numerous changes in plastid transcript populations, many of which resemble those reported for the orthologous mutants in Arabidopsis. However, unanticipated reductions in the abundance of numerous transfer RNAs (tRNAs) dominated the microarray data and were validated on RNA gel blots. The magnitude of the deficiencies for several tRNAs was similar to that of the most severely affected messenger RNAs, with the loss of trnL-UAA being particularly severe. These findings suggest that PEP and its associated proteins are critical for the robust transcription of numerous plastid tRNAs and that this function is essential for the prodigious translation of plastid-encoded proteins that is required during the installation of the photosynthetic apparatus.
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58
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Williams-Carrier R, Zoschke R, Belcher S, Pfalz J, Barkan A. A major role for the plastid-encoded RNA polymerase complex in the expression of plastid transfer RNAs. PLANT PHYSIOLOGY 2014. [PMID: 24246379 DOI: 10.1104/pp.113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Chloroplast transcription in land plants relies on collaboration between a plastid-encoded RNA polymerase (PEP) of cyanobacterial ancestry and a nucleus-encoded RNA polymerase of phage ancestry. PEP associates with additional proteins that are unrelated to bacterial transcription factors, many of which have been shown to be important for PEP activity in Arabidopsis (Arabidopsis thaliana). However, the biochemical roles of these PEP-associated proteins are not known. We describe phenotypes conditioned by transposon insertions in genes encoding the maize (Zea mays) orthologs of five such proteins: ZmPTAC2, ZmMurE, ZmPTAC10, ZmPTAC12, and ZmPRIN2. These mutants have similar ivory/virescent pigmentation and similar reductions in plastid ribosomes and photosynthetic complexes. RNA gel-blot and microarray hybridizations revealed numerous changes in plastid transcript populations, many of which resemble those reported for the orthologous mutants in Arabidopsis. However, unanticipated reductions in the abundance of numerous transfer RNAs (tRNAs) dominated the microarray data and were validated on RNA gel blots. The magnitude of the deficiencies for several tRNAs was similar to that of the most severely affected messenger RNAs, with the loss of trnL-UAA being particularly severe. These findings suggest that PEP and its associated proteins are critical for the robust transcription of numerous plastid tRNAs and that this function is essential for the prodigious translation of plastid-encoded proteins that is required during the installation of the photosynthetic apparatus.
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59
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Yua QB, Ma Q, Kong MM, Zhao TT, Zhang XL, Zhou Q, Huang C, Chong K, Yang ZN. AtECB1/MRL7, a thioredoxin-like fold protein with disulfide reductase activity, regulates chloroplast gene expression and chloroplast biogenesis in Arabidopsis thaliana. MOLECULAR PLANT 2014; 7:206-17. [PMID: 23956074 DOI: 10.1093/mp/sst092] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Plastid-encoded RNA polymerase (PEP) is closely associated with numerous factors to form PEP complex for plastid gene expression and chloroplast development. However, it is not clear how PEP complex are regulated in chloroplast. Here, one thioredoxin-like fold protein, Arabidopsis early chloroplast biogenesis 1 (AtECB1), an allele of MRL7, was identified to regulate PEP function and chloroplast biogenesis. The knockout lines for AtECB1 displayed albino phenotype and impaired chloroplast development. The transcripts of PEP-dependent plastid genes were barely detected, suggesting that the PEP activity is almost lost in atecb1-1. Although AtECB1 was not identified in PEP complex, a yeast two-hybrid assay and pull-down experiments demonstrated that it can interact with Trx Z and FSD3, two intrinsic subunits of PEP complex, respectively. This indicates that AtECB1 may play a regulatory role for PEP-dependent plastid gene expression through these two subunits. AtECB1 contains a βαβαββα structure in the thioredoxin-like fold domain and lacks the typical C-X-X-C active site motif. Insulin assay demonstrated that AtECB1 harbors disulfide reductase activity in vitro using the purified recombinant AtECB1 protein. This showed that this thioredoxin-like fold protein, AtECB1 also has the thioredoxin activity. AtECB1 may play a role in thioredoxin signaling to regulate plastid gene expression and chloroplast development.
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Affiliation(s)
- Qing-Bo Yua
- Biology Department, Life and Environmental College, Shanghai Normal University, Shanghai 200234, China
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60
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Yu QB, Huang C, Yang ZN. Nuclear-encoded factors associated with the chloroplast transcription machinery of higher plants. FRONTIERS IN PLANT SCIENCE 2014; 5:316. [PMID: 25071799 PMCID: PMC4080259 DOI: 10.3389/fpls.2014.00316] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/14/2014] [Indexed: 05/02/2023]
Abstract
Plastid transcription is crucial for plant growth and development. There exist two types of RNA polymerases in plastids: a nuclear-encoded RNA polymerase (NEP) and plastid-encoded RNA polymerase (PEP). PEP is the major RNA polymerase activity in chloroplast. Its core subunits are encoded by the plastid genome, and these are embedded into a larger complex of nuclear-encoded subunits. Biochemical and genetics analysis identified at least 12 proteins are tightly associated with the core subunit, while about 34 further proteins are associated more loosely generating larger complexes such as the transcriptionally active chromosome (TAC) or a part of the nucleoid. Domain analyses and functional investigations suggested that these nuclear-encoded factors may form several functional modules that mediate regulation of plastid gene expression by light, redox, phosphorylation, and heat stress. Genetic analyses also identified that some nuclear-encoded proteins in the chloroplast that are important for plastid gene expression, although a physical association with the transcriptional machinery is not observed. This covers several PPR proteins including CLB19, PDM1/SEL1, OTP70, and YS1 which are involved in the processing of transcripts for PEP core subunit as well as AtECB2, Prin2, SVR4-Like, and NARA5 that are also important for plastid gene expression, although their functions are unclear.
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Affiliation(s)
- Qing-Bo Yu
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal UniversityShanghai, China
- Institute for Plant Gene Function, Department of Biology, Shanghai Normal UniversityShanghai, China
| | - Chao Huang
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal UniversityShanghai, China
- Institute for Plant Gene Function, Department of Biology, Shanghai Normal UniversityShanghai, China
| | - Zhong-Nan Yang
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal UniversityShanghai, China
- Institute for Plant Gene Function, Department of Biology, Shanghai Normal UniversityShanghai, China
- *Correspondence: Zhong-Nan Yang, Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, No.100, Rd. GuiLin, Shanghai 200234, China e-mail:
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61
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Pyo YJ, Kwon KC, Kim A, Cho MH. Seedling Lethal1, a pentatricopeptide repeat protein lacking an E/E+ or DYW domain in Arabidopsis, is involved in plastid gene expression and early chloroplast development. PLANT PHYSIOLOGY 2013; 163:1844-58. [PMID: 24144791 PMCID: PMC3850184 DOI: 10.1104/pp.113.227199] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Chloroplasts are the site of photosynthesis and the biosynthesis of essential metabolites, including amino acids, fatty acids, and secondary metabolites. It is known that many seedling-lethal mutants are impaired in chloroplast function or development, indicating the development of functional chloroplast is essential for plant growth and development. Here, we isolated a novel transfer DNA insertion mutant, dubbed sel1 (for seedling lethal1), that exhibited a pigment-defective and seedling-lethal phenotype with a disrupted pentatricopeptide repeat (PPR) gene. Sequence analysis revealed that SEL1 is a member of the PLS subgroup, which is lacking known E/E(+) or DYW domains at the C terminus, in the PLS subfamily of the PPR protein family containing a putative N-terminal transit peptide and 14 putative PPR or PPR-like motifs. Confocal microscopic analysis showed that the SEL1-green fluorescent protein fusion protein is localized in chloroplasts. Transmission electron microscopic analysis revealed that the sel1 mutant is impaired in the etioplast, as well as in chloroplast development. In sel1 mutants, plastid-encoded proteins involved in photosynthesis were rarely detected due to the lack of the corresponding transcripts. Furthermore, transcript profiles of plastid genes revealed that, in sel1 mutants, the transcript levels of plastid-encoded RNA polymerase-dependent genes were greatly reduced, but those of nuclear-encoded RNA polymerase-dependent genes were increased or not changed. Additionally, the RNA editing of two editing sites of the acetyl-CoA carboxylase beta subunit gene transcripts in the sel1 mutant was compromised, though it is not directly connected with the sel1 mutant phenotype. Our results demonstrate that SEL1 is involved in the regulation of plastid gene expression required for normal chloroplast development.
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MESH Headings
- Amino Acid Sequence
- Arabidopsis/genetics
- Arabidopsis/growth & development
- Arabidopsis/ultrastructure
- Arabidopsis Proteins/chemistry
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Base Sequence
- Blotting, Northern
- Chloroplast Proteins/chemistry
- Chloroplast Proteins/genetics
- Chloroplast Proteins/metabolism
- Chloroplasts/genetics
- Chloroplasts/ultrastructure
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Genes, Plant
- Molecular Sequence Data
- Molecular Weight
- Multiprotein Complexes/metabolism
- Mutation/genetics
- Photosynthesis
- Protein Structure, Tertiary
- RNA Editing/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Transfer/metabolism
- Repetitive Sequences, Amino Acid
- Ribosomes/metabolism
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62
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Qiao J, Li J, Chu W, Luo M. PRDA1, a novel chloroplast nucleoid protein, is required for early chloroplast development and is involved in the regulation of plastid gene expression in Arabidopsis. PLANT & CELL PHYSIOLOGY 2013; 54:2071-84. [PMID: 24132784 DOI: 10.1093/pcp/pct148] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Chloroplast development requires accurate spatio-temporal expression of plastid genes. The regulation of plastid genes mediated by plastid-encoded RNA polymerase (PEP) is rather complex, and its related mechanism remains largely unclear. Here, we report the identification of a novel protein that is essential for plant development, PEP-Related Development Arrested 1 (PRDA1). Knock-out of PRDA1 in Arabidopsis (prda1 mutant) caused a seedling-lethal, albino phenotype and arrested the development of leaf chloroplasts. Localization analysis showed that PRDA1 was specifically targeted to chloroplasts and co-localized with chloroplast nucleoids, revealing that PRDA1 is a chloroplast nucleoid-associated protein. Gene expression analyses revealed that the PEP-dependent plastid transcript levels were greatly reduced in prda1. PRDA1 was co-expressed with most of the PEP-associated proteins. Protein interaction assays showed that PRDA1 clearly interacts with MRL7 and FSD2, both of which have been verified as essential for PEP-related chloroplast development. Reactive oxygen species scavenging through dimethylthiourea markedly alleviated the cotyledon-albino phenotypes of PRDA1 and MRL7 RNA interference seedlings. These results demonstrate that PRDA1 is required for early chloroplast development and involved in the regulation of plastid gene expression.
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Affiliation(s)
- Jiangwei Qiao
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China
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63
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Huang C, Yu QB, Lv RH, Yin QQ, Chen GY, Xu L, Yang ZN. The reduced plastid-encoded polymerase-dependent plastid gene expression leads to the delayed greening of the Arabidopsis fln2 mutant. PLoS One 2013; 8:e73092. [PMID: 24019900 PMCID: PMC3760890 DOI: 10.1371/journal.pone.0073092] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 07/19/2013] [Indexed: 12/21/2022] Open
Abstract
In Arabidopsis leaf coloration mutants, the delayed greening phenomenon is common. Nonetheless, the mechanism remains largely elusive. Here, a delayed greening mutant fln2–4 of FLN2 (Fructokinase-Like Protein2) was studied. FLN2 is one component of Transcriptionally Active Chromosome (TAC) complex which is thought to contain the complete plastid-encoded polymerase (PEP). fln2–4 displayed albino phenotype on medium without sucrose. The PEP-dependent plastid gene expression and chloroplast development were inhibited in fln2–4. Besides interacting with thioredoxin z (TRX z), we identified that FLN2 interacted with another two members of TAC complex in yeast including its homologous protein FLN1 (Fructokinase-Like Protein1) and pTAC5. This indicates that FLN2 functions in regulation of PEP activity associated with these TAC components. fln2–4 exhibited delayed greening on sucrose-containing medium. Comparison of the PEP-dependent gene expression among two complete albino mutants (trx z and ptac14), two yellow mutants (ecb2–2 and ys1) and the fln2–4 showed that fln2–4 remains partial PEP activity. FLN2 and FLN1 are the target proteins of TRX z involved in affecting the PEP activity. Together with the data that FLN1 could interact with itself in yeast, FLN1 may form a homodimer to replace FLN1–FLN2 as the TRX z target in redox pathway for maintaining partial PEP activity in fln2–4. We proposed the partial PEP activity in the fln2 mutant allowed plastids to develop into fully functional chloroplasts when exogenous sucrose was supplied, and finally the mutants exhibited green phenotype.
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Affiliation(s)
- Chao Huang
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China
- Department of Biology, School of Life Sciences, East China Normal University, Shanghai, P.R. China
| | - Qing-Bo Yu
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China
| | - Ruo-Hong Lv
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China
| | - Qian-Qian Yin
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China
| | - Gen-Yun Chen
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, Shanghai, P.R. China
| | - Ling Xu
- Department of Biology, School of Life Sciences, East China Normal University, Shanghai, P.R. China
| | - Zhong-Nan Yang
- Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China
- * E-mail:
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Zhong L, Zhou W, Wang H, Ding S, Lu Q, Wen X, Peng L, Zhang L, Lu C. Chloroplast small heat shock protein HSP21 interacts with plastid nucleoid protein pTAC5 and is essential for chloroplast development in Arabidopsis under heat stress. THE PLANT CELL 2013; 25:2925-43. [PMID: 23922206 PMCID: PMC3784589 DOI: 10.1105/tpc.113.111229] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 07/04/2013] [Accepted: 07/18/2013] [Indexed: 05/18/2023]
Abstract
Compared with small heat shock proteins (sHSPs) in other organisms, those in plants are the most abundant and diverse. However, the molecular mechanisms by which sHSPs are involved in cell protection remain unknown. Here, we characterized the role of HSP21, a plastid nucleoid-localized sHSP, in chloroplast development under heat stress. We show that an Arabidopsis thaliana knockout mutant of HSP21 had an ivory phenotype under heat stress. Quantitative real-time RT-PCR, run-on transcription, RNA gel blot, and polysome association analyses demonstrated that HSP21 is involved in plastid-encoded RNA polymerase (PEP)-dependent transcription. We found that the plastid nucleoid protein pTAC5 was an HSP21 target. pTAC5 has a C4-type zinc finger similar to that of Escherichia coli DnaJ and zinc-dependent disulfide isomerase activity. Reduction of pTAC5 expression by RNA interference led to similar phenotypic effects as observed in hsp21. HSP21 and pTAC5 formed a complex that was associated mainly with the PEP complex. HSP21 and pTAC5 were associated with the PEP complex not only during transcription initiation, but also during elongation and termination. Our results suggest that HSP21 and pTAC5 are required for chloroplast development under heat stress by maintaining PEP function.
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Affiliation(s)
- Linlin Zhong
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wen Zhou
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haijun Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shunhua Ding
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Qingtao Lu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Xiaogang Wen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Lianwei Peng
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Lixin Zhang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- National Center for Plant Gene Research, Beijing 100093, China
| | - Congming Lu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- National Center for Plant Gene Research, Beijing 100093, China
- Address correspondence to
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Yu QB, Lu Y, Ma Q, Zhao TT, Huang C, Zhao HF, Zhang XL, Lv RH, Yang ZN. TAC7, an essential component of the plastid transcriptionally active chromosome complex, interacts with FLN1, TAC10, TAC12 and TAC14 to regulate chloroplast gene expression in Arabidopsis thaliana. PHYSIOLOGIA PLANTARUM 2013; 148:408-21. [PMID: 23082802 DOI: 10.1111/j.1399-3054.2012.01718.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 10/05/2012] [Accepted: 10/09/2012] [Indexed: 05/03/2023]
Abstract
Transcriptionally active chromosome (TAC) is a fraction of protein/DNA complexes with RNA polymerase activity in the plastid. However, the function of most TAC proteins remains unknown. Here, we isolated two allelic mutants of the gene for a TAC component, TAC7, and performed functional analysis in plastid gene expression and chloroplast development in Arabidopsis. tac7-1 is a mutant with a premature translation termination isolated from a population treated with ethyl methane sulfonate, and tac7-2 is a transfer-DNA tagging mutant. Both of them showed an albino phenotype when grown under normal light conditions, and a few appressed membranes were observed inside the defective chloroplasts. These data indicate that TAC7 is important for thylakoid biogenesis. The TAC7 gene encodes an uncharacterized 161 amino acids polypeptide localized in chloroplast. The transcriptional levels of plastid-encoded polymerase (PEP)-dependent genes were downregulated in tac7-2, suggesting that PEP activity was decreased in the mutant. Yeast two-hybrid assay shows that TAC7 can interact with the four TAC components including FLN1, TAC10, TAC12 and TAC14 which are involved in redox state changes, phosphorylation processes and phytochrome-dependent light signaling, respectively, These data indicate that TAC7 plays an important role for TAC to regulate PEP-dependent chloroplast gene expression and chloroplast development.
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Affiliation(s)
- Qing-Bo Yu
- College of Life and Environmental Sciences, Shanghai Normal University, Shanghai 200234, China
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66
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Guarnieri MT, Nag A, Yang S, Pienkos PT. Proteomic analysis of Chlorella vulgaris: potential targets for enhanced lipid accumulation. J Proteomics 2013; 93:245-53. [PMID: 23748020 DOI: 10.1016/j.jprot.2013.05.025] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 04/25/2013] [Accepted: 05/20/2013] [Indexed: 10/26/2022]
Abstract
UNLABELLED Oleaginous microalgae are capable of producing large quantities of fatty acids and triacylglycerides. As such, they are promising feedstocks for the production of biofuels and bioproducts. Genetic strain-engineering strategies offer a means to accelerate the commercialization of algal biofuels by improving the rate and total accumulation of microalgal lipids. However, the industrial potential of these organisms remains to be met, largely due to the incomplete knowledgebase surrounding the mechanisms governing the induction of algal lipid biosynthesis. Such strategies require further elucidation of genes and gene products controlling algal lipid accumulation. In this study, we have set out to examine these mechanisms and identify novel strain-engineering targets in the oleaginous microalga, Chlorella vulgaris. Comparative shotgun proteomic analyses have identified a number of novel targets, including previously unidentified transcription factors and proteins involved in cell signaling and cell cycle regulation. These results lay the foundation for strain-improvement strategies and demonstrate the power of translational proteomic analysis. BIOLOGICAL SIGNIFICANCE We have applied label-free, comparative shotgun proteomic analyses, via a transcriptome-to-proteome pipeline, in order to examine the nitrogen deprivation response in the oleaginous microalga, C. vulgaris. Herein, we identify potential targets for strain-engineering strategies targeting enhanced lipid accumulation for algal biofuels applications. Among the identified targets are proteins involved in transcriptional regulation, lipid biosynthesis, cell signaling and cell cycle progression. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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Affiliation(s)
- Michael T Guarnieri
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA.
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Pfalz J, Pfannschmidt T. Essential nucleoid proteins in early chloroplast development. TRENDS IN PLANT SCIENCE 2013; 18:186-94. [PMID: 23246438 DOI: 10.1016/j.tplants.2012.11.003] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 11/01/2012] [Accepted: 11/12/2012] [Indexed: 05/04/2023]
Abstract
The plastid transcription machinery can be biochemically purified at different organisational levels as soluble RNA polymerase, transcriptionally active chromosome, or nucleoid. Recent proteomic studies have uncovered several novel proteins in these structures and functional genomic studies have indicated that a lack of many of these proteins results in chlorotic phenotypes of varying degree. The most severe cases exhibit complete albino phenotypes, which led to the conclusion that the proteins that were lacking had important regulatory roles in plastid gene expression and chloroplast development. In this opinion article, we propose an alternative model in which the structural establishment of a transcriptional subdomain within the nucleoid represents an early developmental bottleneck that leads to abortion of proper chloroplast biogenesis if disturbed.
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Affiliation(s)
- Jeannette Pfalz
- Department of Plant Physiology, Institute of General Botany and Plant Physiology, Friedrich-Schiller-University Jena, Dornburger Str. 159, D-07743 Jena, Germany
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Krupinska K, Melonek J, Krause K. New insights into plastid nucleoid structure and functionality. PLANTA 2013; 237:653-64. [PMID: 23212213 DOI: 10.1007/s00425-012-1817-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 11/09/2012] [Indexed: 05/04/2023]
Abstract
Investigations over many decades have revealed that nucleoids of higher plant plastids are highly dynamic with regard to their number, their structural organization and protein composition. Membrane attachment and environmental cues seem to determine the activity and functionality of the nucleoids and point to a highly regulated structure-function relationship. The heterogeneous composition and the many functions that are seemingly associated with the plastid nucleoids could be related to the high number of chromosomes per plastid. Recent proteomic studies have brought novel nucleoid-associated proteins into the spotlight and indicated that plastid nucleoids are an evolutionary hybrid possessing prokaryotic nucleoid features and eukaryotic (nuclear) chromatin components, several of which are dually targeted to the nucleus and chloroplasts. Future studies need to unravel if and how plastid-nucleus communication depends on nucleoid structure and plastid gene expression.
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Affiliation(s)
- Karin Krupinska
- Institute of Botany, University of Kiel, Olshausenstraße 40, 24098, Kiel, Germany.
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Huang XY, Niu J, Sun MX, Zhu J, Gao JF, Yang J, Zhou Q, Yang ZN. CYCLIN-DEPENDENT KINASE G1 is associated with the spliceosome to regulate CALLOSE SYNTHASE5 splicing and pollen wall formation in Arabidopsis. THE PLANT CELL 2013; 25:637-48. [PMID: 23404887 PMCID: PMC3608783 DOI: 10.1105/tpc.112.107896] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Arabidopsis thaliana CYCLIN-DEPEDENT KINASE G1 (CDKG1) belongs to the family of cyclin-dependent protein kinases that were originally characterized as cell cycle regulators in eukaryotes. Here, we report that CDKG1 regulates pre-mRNA splicing of CALLOSE SYNTHASE5 (CalS5) and, therefore, pollen wall formation. The knockout mutant cdkg1 exhibits reduced male fertility with impaired callose synthesis and abnormal pollen wall formation. The sixth intron in CalS5 pre-mRNA, a rare type of intron with a GC 5' splice site, is abnormally spliced in cdkg1. RNA immunoprecipitation analysis suggests that CDKG1 is associated with this intron. CDKG1 contains N-terminal Ser/Arg (RS) motifs and interacts with splicing factor Arginine/Serine-Rich Zinc Knuckle-Containing Protein33 (RSZ33) through its RS region to regulate proper splicing. CDKG1 and RS-containing Zinc Finger Protein22 (SRZ22), a splicing factor interacting with RSZ33 and U1 small nuclear ribonucleoprotein particle (snRNP) component U1-70k, colocalize in nuclear speckles and reside in the same complex. We propose that CDKG1 is recruited to U1 snRNP through RSZ33 to facilitate the splicing of the sixth intron of CalS5.
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Affiliation(s)
- Xue-Yong Huang
- College of Tourism, Shanghai Normal University, Shanghai 200234, China
| | - Jin Niu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Ming-Xi Sun
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Jun Zhu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Ju-Fang Gao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Jun Yang
- College of Tourism, Shanghai Normal University, Shanghai 200234, China
| | - Que Zhou
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Zhong-Nan Yang
- College of Tourism, Shanghai Normal University, Shanghai 200234, China
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
- Address correspondence to
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Gao ZP, Chen GX, Yang ZN. Regulatory role of Arabidopsis pTAC14 in chloroplast development and plastid gene expression. PLANT SIGNALING & BEHAVIOR 2012; 7:1354-6. [PMID: 22902688 PMCID: PMC3493425 DOI: 10.4161/psb.21618] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Transcriptionally active chromosome (TAC) is a fraction of protein/DNA complexes with RNA polymerase activity in the plastid. The function of most TAC proteins is not well known. We isolated a mutant gene encoding a plastid TAC component, pTAC14, and performed functional analysis of plastid gene expression and chloroplast development in Arabidopsis. We found that knockout of pTAC14 led to the blockage of thylakoid formation in the initial process of chloroplast development. Furthermore, the transcript levels of plastid-encoded polymerase (PEP)-dependent genes were downregulated in ptac14, suggesting that PEP activity was decreased in the mutant. On the basis of these results, we briefly review the available evidence and highlight the interaction between pTAC14 and pTAC12 that could help us understand the regulatory role of pTAC14 in chloroplast development and plastid gene expression.
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Affiliation(s)
- Zhi-Ping Gao
- College of Life Sciences; Nanjing Normal University; Jiangsu, China
- School of Life Sciences; The Chinese University of HongKong; Shatin, Hong Kong, China
- College of Life and Environmental Sciences; Shanghai Normal University; Shanghai, China
| | - Guo-Xiang Chen
- College of Life Sciences; Nanjing Normal University; Jiangsu, China
- Correspondence to: Guo-Xiang Chen, and Zhong-Nan Yang,
| | - Zhong-Nan Yang
- College of Life and Environmental Sciences; Shanghai Normal University; Shanghai, China
- Correspondence to: Guo-Xiang Chen, and Zhong-Nan Yang,
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Gilkerson J, Perez-Ruiz JM, Chory J, Callis J. The plastid-localized pfkB-type carbohydrate kinases FRUCTOKINASE-LIKE 1 and 2 are essential for growth and development of Arabidopsis thaliana. BMC PLANT BIOLOGY 2012; 12:102. [PMID: 22770232 PMCID: PMC3409070 DOI: 10.1186/1471-2229-12-102] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 07/08/2012] [Indexed: 05/18/2023]
Abstract
BACKGROUND Transcription of plastid-encoded genes requires two different DNA-dependent RNA polymerases, a nuclear-encoded polymerase (NEP) and plastid-encoded polymerase (PEP). Recent studies identified two related pfkB-type carbohydrate kinases, named FRUCTOKINASE-LIKE PROTEIN (FLN1 and FLN2), as components of the thylakoid bound PEP complex in both Arabidopsis thaliana and Sinapis alba (mustard). Additional work demonstrated that RNAi-mediated reduction in FLN expression specifically diminished transcription of PEP-dependent genes. RESULTS Here, we report the characterization of Arabidopsis FLN knockout alleles to examine the contribution of each gene in plant growth, chloroplast development, and in mediating PEP-dependent transcription. We show that fln plants have severe phenotypes with fln1 resulting in an albino phenotype that is seedling lethal without a source of exogenous carbon. In contrast, fln2 plants display chlorosis prior to leaf expansion, but exhibit slow greening, remain autotrophic, can grow to maturity, and set viable seed. fln1 fln2 double mutant analysis reveals haplo-insufficiency, and fln1 fln2 plants have a similar, but more severe phenotype than either single mutant. Normal plastid development in both light and dark requires the FLNs, but surprisingly skotomorphogenesis is unaffected in fln seedlings. Seedlings genetically fln1-1 with dexamethasone-inducible FLN1-HA expression at germination are phenotypically indistinguishable from wild-type. Induction of FLN-HA after 24 hours of germination cannot rescue the mutant phenotype, indicating that the effects of loss of FLN are not always reversible. Examination of chloroplast gene expression in fln1-1 and fln2-1 by qRT-PCR reveals that transcripts of PEP-dependent genes were specifically reduced compared to NEP-dependent genes in both single mutants. CONCLUSIONS Our results demonstrate that each FLN protein contributes to wild type growth, and acting additively are absolutely essential for plant growth and development.
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Affiliation(s)
- Jonathan Gilkerson
- Department of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA
- Plant Biology Graduate Group, University of California, Davis, CA, 95616, USA
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Juan Manuel Perez-Ruiz
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Joanne Chory
- Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Judy Callis
- Department of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA
- Plant Biology Graduate Group, University of California, Davis, CA, 95616, USA
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Bang WY, Chen J, Jeong IS, Kim SW, Kim CW, Jung HS, Lee KH, Kweon HS, Yoko I, Shiina T, Bahk JD. Functional characterization of ObgC in ribosome biogenesis during chloroplast development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:122-34. [PMID: 22380942 DOI: 10.1111/j.1365-313x.2012.04976.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The Spo0B-associated GTP-binding protein (Obg) GTPase, essential for bacterial viability, is also conserved in eukaryotes, but its primary role in eukaryotes remains unknown. Here, our functional characterization of Arabidopsis and rice obgc mutants strongly underlines the evolutionarily conserved role of eukaryotic Obgs in organellar ribosome biogenesis. The mutants exhibited a chlorotic phenotype, caused by retarded chloroplast development. A plastid DNA macroarray revealed a plastid-encoded RNA polymerase (PEP) deficiency in an obgc mutant, caused by incompleteness of the PEP complex, as its western blot exhibited reduced levels of RpoA protein, a component of PEP. Plastid rRNA profiling indicated that plastid rRNA processing is defective in obgc mutants, probably resulting in impaired ribosome biogenesis and, in turn, in reduced levels of RpoA protein. RNA co-immunoprecipitation revealed that ObgC specifically co-precipitates with 23S rRNA in vivo. These findings indicate that ObgC functions primarily in plastid ribosome biogenesis during chloroplast development. Furthermore, complementation analysis can provide new insights into the functional modes of three ObgC domains, including the Obg fold, G domain and OCT.
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Affiliation(s)
- Woo Young Bang
- Swine Science and Technology Center, Gyeongnam National University of Science and Technology-GNTECH, Jinju 660-758, Korea
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The Arabidopsis pentatricopeptide repeat protein PDM1 is associated with the intergenic sequence of S11-rpoA for rpoA monocistronic RNA cleavage. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11434-012-5278-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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