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Schmid LM, Manavski N, Chi W, Meurer J. Chloroplast Ribosome Biogenesis Factors. PLANT & CELL PHYSIOLOGY 2024; 65:516-536. [PMID: 37498958 DOI: 10.1093/pcp/pcad082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/13/2023] [Accepted: 07/25/2023] [Indexed: 07/29/2023]
Abstract
The formation of chloroplasts can be traced back to an ancient event in which a eukaryotic host cell containing mitochondria ingested a cyanobacterium. Since then, chloroplasts have retained many characteristics of their bacterial ancestor, including their transcription and translation machinery. In this review, recent research on the maturation of rRNA and ribosome assembly in chloroplasts is explored, along with their crucial role in plant survival and their implications for plant acclimation to changing environments. A comparison is made between the ribosome composition and auxiliary factors of ancient and modern chloroplasts, providing insights into the evolution of ribosome assembly factors. Although the chloroplast contains ancient proteins with conserved functions in ribosome assembly, newly evolved factors have also emerged to help plants acclimate to changes in their environment and internal signals. Overall, this review offers a comprehensive analysis of the molecular mechanisms underlying chloroplast ribosome assembly and highlights the importance of this process in plant survival, acclimation and adaptation.
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Affiliation(s)
- Lisa-Marie Schmid
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Street 2-4, Planegg-Martinsried 82152, Germany
| | - Nikolay Manavski
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Street 2-4, Planegg-Martinsried 82152, Germany
| | - Wei Chi
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jörg Meurer
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Street 2-4, Planegg-Martinsried 82152, Germany
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Takahashi A, Sugita C, Ichinose M, Sugita M. Moss PPR-SMR protein PpPPR_64 influences the expression of a psaA-psaB-rps14 gene cluster and processing of the 23S-4.5S rRNA precursor in chloroplasts. PLANT MOLECULAR BIOLOGY 2021; 107:417-429. [PMID: 33128724 DOI: 10.1007/s11103-020-01090-z] [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: 07/14/2020] [Accepted: 10/22/2020] [Indexed: 06/11/2023]
Abstract
Moss PPR-SMR protein PpPPR_64 is a pTAC2 homolog but is functionally distinct from pTAC2. PpPPR_64 is required for psaA gene expression and its function may have evolved in mosses. The pentatricopeptide repeat (PPR) proteins are key regulatory factors responsible for the control of plant organellar gene expression. A small subset of PPR proteins possess a C-terminal small MutS-related (SMR) domain and have diverse roles in plant organellar biogenesis. However, the function of PPR-SMR proteins is not fully understood. Here, we report the function of PPR-SMR protein PpPPR_64 in the moss Physcomitrium patens. Phylogenetic analysis indicated that PpPPR_64 belongs to the same clade as the Arabidopsis PPR-SMR protein pTAC2. PpPPR_64 knockout (KO) mutants grew autotrophically but with reduced protonemata growth and the poor formation of photosystems' antenna complexes. Quantitative reverse transcription-polymerase chain reaction and RNA gel blot hybridization analyses revealed a significant reduction in transcript levels of the psaA-psaB-rps14 gene cluster but no alteration to transcript levels of most photosynthesis- and non-photosynthesis-related genes. In addition, RNA processing of 23S-4.5S rRNA precursor was impaired in the PpPPR_64 KO mutants. This suggests that PpPPR_64 is specifically involved in the expression level of the psaA-psaB-rps14 gene and in processing of the 23S-4.5S rRNA precursor. Our results indicate that PpPPR_64 is functionally distinct from pTAC2 and is a novel PPR-SMR protein required for proper chloroplast biogenesis in P. patens.
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Affiliation(s)
- Ayumu Takahashi
- Center for Gene Research, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Chieko Sugita
- Center for Gene Research, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Mizuho Ichinose
- Center for Gene Research, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, 464-8601, Japan
- Faculty of Agriculture, Kyushu University, Fukuoka, 819-0395, Japan
| | - Mamoru Sugita
- Center for Gene Research, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan.
- Graduate School of Informatics, Nagoya University, Chikusa-ku, Nagoya, 464-8601, Japan.
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Chen J, Wang L, Jin X, Wan J, Zhang L, Je BI, Zhao K, Kong F, Huang J, Tian M. Oryza sativa ObgC1 Acts as a Key Regulator of DNA Replication and Ribosome Biogenesis in Chloroplast Nucleoids. RICE (NEW YORK, N.Y.) 2021; 14:65. [PMID: 34251486 PMCID: PMC8275814 DOI: 10.1186/s12284-021-00498-5] [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: 10/04/2020] [Accepted: 05/30/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND The Spo0B-associated GTP-binding protein (Obg) GTPase, has diverse and important functions in bacteria, including morphological development, DNA replication and ribosome maturation. Homologs of the Bacillus subtilis Obg have been also found in chloroplast of Oryza sativa, but their primary roles remain unknown. RESULTS We clarify that OsObgC1 is a functional homolog of AtObgC. The mutant obgc1-d1 exhibited hypersensitivity to the DNA replication inhibitor hydroxyurea. Quantitative PCR results showed that the ratio of chloroplast DNA to nuclear DNA in the mutants was higher than that of the wild-type plants. After DAPI staining, OsObgC1 mutants showed abnormal nucleoid architectures. The specific punctate staining pattern of OsObgC1-GFP signal suggests that this protein localizes to the chloroplast nucleoids. Furthermore, loss-of-function mutation in OsObgC1 led to a severe suppression of protein biosynthesis by affecting plastid rRNA processing. It was also demonstrated through rRNA profiling that plastid rRNA processing was decreased in obgc1-d mutants, which resulted in impaired ribosome biogenesis. The sucrose density gradient profiles revealed a defective chloroplast ribosome maturation of obgc1-d1 mutants. CONCLUSION Our findings here indicate that the OsObgC1 retains the evolutionarily biological conserved roles of prokaryotic Obg, which acts as a signaling hub that regulates DNA replication and ribosome biogenesis in chloroplast nucleoids.
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Affiliation(s)
- Ji Chen
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
- Division of Applied Life Sciences (BK21+), Graduate School of Gyeongsang National University, Jinju, 660-701, Republic of Korea
| | - Li Wang
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Xiaowan Jin
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Jian Wan
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Lang Zhang
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Byoung Il Je
- College of Ecology and Environment, Chengdu University of Technology, Chengdu, 61005, China
| | - Ke Zhao
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Fanlei Kong
- College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China
| | - Jin Huang
- Division of Applied Life Sciences (BK21+), Graduate School of Gyeongsang National University, Jinju, 660-701, Republic of Korea.
- College of Ecology and Environment, Chengdu University of Technology, Chengdu, 61005, China.
| | - Mengliang Tian
- Institute for New Rural Development, Sichuan Agricultural University, Yaan, 625000, China.
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Zhang Y, Huang X, Zou J, Liao X, Liu Y, Lian T, Nian H. Major contribution of transcription initiation to 5'-end formation of mitochondrial steady-state transcripts in maize. RNA Biol 2018; 16:104-117. [PMID: 30585757 DOI: 10.1080/15476286.2018.1561604] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In plant mitochondria, some steady-state transcripts contain primary 5' ends derived from transcription initiation, while the others have processed 5' termini generated by post-transcriptional processing. Differentiation and mapping of the primary and processed transcripts are important for unraveling the molecular mechanism(s) underlying transcription and transcript end maturation. However, previous efforts to systematically differentiate these two types of transcripts in plant mitochondria failed. At present, it is considered that the majority of mature mRNAs may have processed 5' ends in Arabidopsis. Here, by combination of circular RT-PCR, quantitative RT-PCR, RNA 5'-polyphosphatase treatment and Northern blot, we successfully discriminated and mapped the primary and processed transcripts in maize mitochondria. Among the thirty-five mature and eight precursor RNAs analyzed in this study, about one half (21/43) were found to have multiple isoforms. In total, seventy-seven steady-state transcripts were determined, and forty-seven of them had primary 5' ends. Most transcription initiation sites (126/167) were downstream of a crTA-motif. These data suggested a major contribution of transcription initiation to 5'-end formation of steady-state transcripts in maize mitochondria. Moreover, the mapping results revealed that mature RNA termini had largely been formed before trans-splicing, and C→U RNA editing was accompanied with trans-splicing and transcript end formation in maize mitochondria.
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Affiliation(s)
- Yafeng Zhang
- a State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources , South China Agricultural University , Guangzhou , China.,b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China
| | - Xiaoyu Huang
- b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China
| | - Jingyun Zou
- b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China
| | - Xun Liao
- b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China
| | - Yujun Liu
- c Institute of Crop Science, College of Agriculture and Biotechnology , Zhejiang University , Hangzhou , China
| | - Tengxiang Lian
- a State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources , South China Agricultural University , Guangzhou , China.,b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China.,d Guangdong Subcenter of the National Center for Soybean Improvement, College of Agriculture , South China Agricultural University , Guangzhou , China
| | - Hai Nian
- a State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources , South China Agricultural University , Guangzhou , China.,b Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture , South China Agricultural University , Guangzhou , China.,d Guangdong Subcenter of the National Center for Soybean Improvement, College of Agriculture , South China Agricultural University , Guangzhou , China
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Jayaswall K, Mahajan P, Singh G, Parmar R, Seth R, Raina A, Swarnkar MK, Singh AK, Shankar R, Sharma RK. Transcriptome Analysis Reveals Candidate Genes involved in Blister Blight defense in Tea (Camellia sinensis (L) Kuntze). Sci Rep 2016; 6:30412. [PMID: 27465480 PMCID: PMC4964330 DOI: 10.1038/srep30412] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 07/05/2016] [Indexed: 02/01/2023] Open
Abstract
To unravel the molecular mechanism of defense against blister blight (BB) disease caused by an obligate biotrophic fungus, Exobasidium vexans, transcriptome of BB interaction with resistance and susceptible tea genotypes was analysed through RNA-seq using Illumina GAIIx at four different stages during ~20-day disease cycle. Approximately 69 million high quality reads were assembled de novo, yielding 37,790 unique transcripts with more than 55% being functionally annotated. Differentially expressed, 149 defense related transcripts/genes, namely defense related enzymes, resistance genes, multidrug resistant transporters, transcription factors, retrotransposons, metacaspases and chaperons were observed in RG, suggesting their role in defending against BB. Being present in the major hub, putative master regulators among these candidates were identified from predetermined protein-protein interaction network of Arabidopsis thaliana. Further, confirmation of abundant expression of well-known RPM1, RPS2 and RPP13 in quantitative Real Time PCR indicates salicylic acid and jasmonic acid, possibly induce synthesis of antimicrobial compounds, required to overcome the virulence of E. vexans. Compendiously, the current study provides a comprehensive gene expression and insights into the molecular mechanism of tea defense against BB to serve as a resource for unravelling the possible regulatory mechanism of immunity against various biotic stresses in tea and other crops.
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Affiliation(s)
- Kuldip Jayaswall
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Pallavi Mahajan
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Gagandeep Singh
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Rajni Parmar
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Romit Seth
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Aparnashree Raina
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Mohit Kumar Swarnkar
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Anil Kumar Singh
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Ravi Shankar
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
| | - Ram Kumar Sharma
- Biotechnology Department, CSIR-Institute of Himalayan Bioresource Technology, Palampur, Himachal Pradesh, India, 176061
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Endo T, Uebayashi N, Ishida S, Ikeuchi M, Sato F. Light energy allocation at PSII under field light conditions: how much energy is lost in NPQ-associated dissipation? PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 81:115-120. [PMID: 24726274 DOI: 10.1016/j.plaphy.2014.03.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 03/18/2014] [Indexed: 06/03/2023]
Abstract
In the field, plants are exposed to fluctuating light, where photosynthesis occurs under conditions far from a steady state. Excess energy dissipation associated with energy quenching of chlorophyll fluorescence (qE) functions as an efficient photo-protection mechanism in photosystem II. PsbS is an important regulator of qE, especially for the induction phase of qE. Beside the regulatory energy dissipation, some part of energy is lost through relaxation of excited chlorophyll molecules. To date, several models to quantify energy loss through these dissipative pathways in PSII have been proposed. In this short review, we compare and evaluate these models for PSII energy allocation when they are applied to non-steady state photosynthesis. As a case study, an investigation on energy allocation to qE-associated dissipation at PSII under non-steady state photosynthesis using PsbS-deficient rice transformants is introduced. Diurnal and seasonal changes in PSII energy allocation in rice under natural light are also presented. Future perspective of studies on PSII energy allocation is discussed.
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Affiliation(s)
- Tsuyoshi Endo
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
| | - Nozomu Uebayashi
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Satoshi Ishida
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Masahiro Ikeuchi
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Fumihiko Sato
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
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Germain A, Hotto AM, Barkan A, Stern DB. RNA processing and decay in plastids. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 4:295-316. [PMID: 23536311 DOI: 10.1002/wrna.1161] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Plastids were derived through endosymbiosis from a cyanobacterial ancestor, whose uptake was followed by massive gene transfer to the nucleus, resulting in the compact size and modest coding capacity of the extant plastid genome. Plastid gene expression is essential for plant development, but depends on nucleus-encoded proteins recruited from cyanobacterial or host-cell origins. The plastid genome is heavily transcribed from numerous promoters, giving posttranscriptional events a critical role in determining the quantity and sizes of accumulating RNA species. The major events reviewed here are RNA editing, which restores protein conservation or creates correct open reading frames by converting C residues to U, RNA splicing, which occurs both in cis and trans, and RNA cleavage, which relies on a variety of exoribonucleases and endoribonucleases. Because the RNases have little sequence specificity, they are collectively able to remove extraneous RNAs whose ends are not protected by RNA secondary structures or sequence-specific RNA-binding proteins (RBPs). Other plastid RBPs, largely members of the helical-repeat superfamily, confer specificity to editing and splicing reactions. The enzymes that catalyze RNA processing are also the main actors in RNA decay, implying that these antagonistic roles are optimally balanced. We place the actions of RBPs and RNases in the context of a recent proteomic analysis that identifies components of the plastid nucleoid, a protein-DNA complex with multiple roles in gene expression. These results suggest that sublocalization and/or concentration gradients of plastid proteins could underpin the regulation of RNA maturation and degradation.
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Germain A, Kim SH, Gutierrez R, Stern DB. Ribonuclease II preserves chloroplast RNA homeostasis by increasing mRNA decay rates, and cooperates with polynucleotide phosphorylase in 3' end maturation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:960-971. [PMID: 23061883 DOI: 10.1111/tpj.12006] [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: 06/01/2023]
Abstract
Ribonuclease R (RNR1) and polynucleotide phosphorylase (cpPNPase) are the two known 3'→5' exoribonucleases in Arabidopsis chloroplasts, and are involved in several aspects of rRNA and mRNA metabolism. In this work, we show that mutants lacking both RNR1 and cpPNPase exhibit embryo lethality, akin to the non-viability of the analogous double mutant in Escherichia coli. We were successful, however, in combining an rnr1 null mutation with weak pnp mutant alleles, and show that the resulting chlorotic plants display a global reduction in RNA abundance. Such a counterintuitive outcome following the loss of RNA degradation activity suggests a major importance of RNA maturation as a determinant of RNA stability. Detailed analysis of the double mutant demonstrates that the enzymes catalyze a two-step maturation of mRNA 3' ends, with RNR1 polishing 3' termini created by cpPNPase. The bulky quaternary structure of cpPNPase compared with RNR1 could explain this activity split between the two enzymes. In contrast to the double mutants, the rnr1 single mutant overaccumulates most mRNA species when compared with the wild type. The excess mRNAs in rnr1 are often present in non-polysomal fractions, and half-life measurements demonstrate a substantial increase in the stability of most mRNA species tested. Together, our data reveal the cooperative activity of two 3'→5' exoribonucleases in chloroplast mRNA 3' end maturation, and support the hypothesis that RNR1 plays a significant role in the destabilization of mRNAs unprotected by ribosomes.
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Affiliation(s)
- Arnaud Germain
- Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA
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9
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Kim BH, Malec P, Waloszek A, von Arnim AG. Arabidopsis BPG2: a phytochrome-regulated gene whose protein product binds to plastid ribosomal RNAs. PLANTA 2012; 236:677-90. [PMID: 22526496 DOI: 10.1007/s00425-012-1638-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 03/22/2012] [Indexed: 05/08/2023]
Abstract
BPG2 (Brz-insensitive pale green 2) is a dark-repressible and light-inducible gene that is required for the greening process in Arabidopsis. Light pulse experiments suggested that light-regulated gene expression of BPG2 is mediated by phytochrome. The T-DNA insertion mutant bpg2-2 exhibited a reduced level of chlorophyll and carotenoid pigmentation in the plastids. Measurements of time resolved chlorophyll fluorescence and of fluorescence emission at 77 K indicated defective photosystem II and altered photosystem I functions in bpg2 mutants. Kinetic analysis of chlorophyll fluorescence induction suggested that the reduction of the primary acceptor (QA) is impaired in bpg2. The observed alterations resulted in reduced photosynthetic efficiency as measured by the electron transfer rate. BPG2 protein is localized in the plastid stroma fraction. Co-immunoprecipitation of a formaldehyde cross-linked RNA-protein complex indicated that BPG2 protein binds with specificity to chloroplast 16S and 23S ribosomal RNAs. The direct physical interaction with the plastid rRNAs supports an emerging model whereby BPG2 provides light-regulated ribosomal RNA processing functions, which are rate limiting for development of the plastid and its photosynthetic apparatus.
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Affiliation(s)
- Byung-Hoon Kim
- Department of Natural Sciences, Albany State University, 504 College Drive, Albany, GA 31705, USA.
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10
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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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Stoppel R, Meurer J. The cutting crew - ribonucleases are key players in the control of plastid gene expression. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1663-73. [PMID: 22140236 DOI: 10.1093/jxb/err401] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Chloroplast biogenesis requires constant adjustment of RNA homeostasis under conditions of on-going developmental and environmental change and its regulation is achieved mainly by post-transcriptional control mechanisms mediated by various nucleus-encoded ribonucleases. More than 180 ribonucleases are annotated in Arabidopsis, but only 17 are predicted to localize to the chloroplast. Although different ribonucleases act at different RNA target sites in vivo, most nucleases that attack RNA are thought to lack intrinsic cleavage specificity and show non-specific activity in vitro. In vivo, specificity is thought to be imposed by auxiliary RNA-binding proteins, including members of the huge pentatricopeptide repeat family, which protect RNAs from non-specific nucleolytic attack by masking otherwise vulnerable sites. RNA stability is also influenced by secondary structure, polyadenylation, and ribosome binding. Ribonucleases may cleave at internal sites (endonucleases) or digest successively from the 5' or 3' end of the polynucleotide chain (exonucleases). In bacteria, RNases act in the maturation of rRNA and tRNA precursors, as well as in initiating the degradation of mRNAs and small non-coding RNAs. Many ribonucleases in the chloroplasts of higher plants possess homologies to their bacterial counterparts, but their precise functions have rarely been described. However, many ribonucleases present in the chloroplast process polycistronic rRNAs, tRNAs, and mRNAs. The resulting production of monocistronic, translationally competent mRNAs may represent an adaptation to the eukaryotic cellular environment. This review provides a basic overview of the current knowledge of RNases in plastids and highlights gaps to stimulate future studies.
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Affiliation(s)
- Rhea Stoppel
- Biozentrum der Ludwig-Maximilians-Universität, Plant Molecular Biology/Botany, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany
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12
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Chi W, He B, Mao J, Li Q, Ma J, Ji D, Zou M, Zhang L. The function of RH22, a DEAD RNA helicase, in the biogenesis of the 50S ribosomal subunits of Arabidopsis chloroplasts. PLANT PHYSIOLOGY 2012; 158:693-707. [PMID: 22170977 PMCID: PMC3271760 DOI: 10.1104/pp.111.186775] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 12/12/2011] [Indexed: 05/18/2023]
Abstract
The chloroplast ribosome is a large and dynamic ribonucleoprotein machine that is composed of the 30S and 50S subunits. Although the components of the chloroplast ribosome have been identified in the last decade, the molecular mechanisms driving chloroplast ribosome biogenesis remain largely elusive. Here, we show that RNA helicase 22 (RH22), a putative DEAD RNA helicase, is involved in chloroplast ribosome assembly in Arabidopsis (Arabidopsis thaliana). A loss of RH22 was lethal, whereas a knockdown of RH22 expression resulted in virescent seedlings with clear defects in chloroplast ribosomal RNA (rRNA) accumulation. The precursors of 23S and 4.5S, but not 16S, rRNA accumulated in rh22 mutants. Further analysis showed that RH22 was associated with the precursors of 50S ribosomal subunits. These results suggest that RH22 may function in the assembly of 50S ribosomal subunits in chloroplasts. In addition, RH22 interacted with the 50S ribosomal protein RPL24 through yeast two-hybrid and pull-down assays, and it was also bound to a small 23S rRNA fragment encompassing RPL24-binding sites. This action of RH22 may be similar to, but distinct from, that of SrmB, a DEAD RNA helicase that is involved in the ribosomal assembly in Escherichia coli, which suggests that DEAD RNA helicases and rRNA structures may have coevolved with respect to ribosomal assembly and function.
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Affiliation(s)
| | | | | | | | | | | | | | - Lixin Zhang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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Sharwood RE, Halpert M, Luro S, Schuster G, Stern DB. Chloroplast RNase J compensates for inefficient transcription termination by removal of antisense RNA. RNA (NEW YORK, N.Y.) 2011; 17:2165-76. [PMID: 22033332 PMCID: PMC3222129 DOI: 10.1261/rna.028043.111] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 09/13/2011] [Indexed: 05/20/2023]
Abstract
Ribonuclease J is an essential enzyme, and the Bacillus subtilis ortholog possesses both endoribonuclease and 5' → 3' exoribonuclease activities. Chloroplasts also contain RNase J, which has been postulated to participate, as both an exo- and endonuclease, in the maturation of polycistronic mRNAs. Here we have examined recombinant Arabidopsis RNase J and found both 5' → 3' exoribonuclease and endonucleolytic activities. Virus-induced gene silencing was used to reduce RNase J expression in Arabidopsis and Nicotiana benthamiana, leading to chlorosis but surprisingly few disruptions in the cleavage of polycistronic rRNA and mRNA precursors. In contrast, antisense RNAs accumulated massively, suggesting that the failure of chloroplast RNA polymerase to terminate effectively leads to extensive symmetric transcription products that are normally eliminated by RNase J. Mung bean nuclease digestion and polysome analysis revealed that this antisense RNA forms duplexes with sense strand transcripts and prevents their translation. We conclude that a major role of chloroplast RNase J is RNA surveillance to prevent overaccumulation of antisense RNA, which would otherwise exert deleterious effects on chloroplast gene expression.
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Affiliation(s)
- Robert E. Sharwood
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
| | - Michal Halpert
- Department of Biology, Technion–Israel Institute of Technology, Haifa 32000, Israel
| | - Scott Luro
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
| | - Gadi Schuster
- Department of Biology, Technion–Israel Institute of Technology, Haifa 32000, Israel
| | - David B. Stern
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
- Corresponding author.E-mail .
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14
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Hsu SC, Belmonte MF, Harada JJ, Inoue K. Indispensable Roles of Plastids in Arabidopsis thaliana Embryogenesis. Curr Genomics 2011; 11:338-49. [PMID: 21286311 PMCID: PMC2944999 DOI: 10.2174/138920210791616716] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 05/18/2010] [Accepted: 05/25/2010] [Indexed: 11/22/2022] Open
Abstract
The plastid is an organelle vital to all photosynthetic and some non-photosynthetic eukaryotes. In the model plant Arabidopsis thaliana, a number of nuclear genes encoding plastid proteins have been found to be necessary for embryo development. However, the exact roles of plastids in this process remain largely unknown. Here we use publicly available datasets to obtain insights into the relevance of plastid activities to A. thaliana embryogenesis. By searching the SeedGenes database (http://www.seedgenes.org) and recent literature, we found that, of the 339 non-redundant genes required for proper embryo formation, 108 genes likely encode plastid-targeted proteins. Nineteen of these genes are necessary for development of preglobular embryos and/or their conversion to globular embryos, of which 13 genes encode proteins involved in non-photosynthetic metabolism. By contrast, among 38 genes which are dispensable for globular embryo formation but necessary for further development, only one codes for a protein involved in metabolism. Products of 21 of the 38 genes play roles in plastid gene expression and maintenance. Examination of RNA profiles of embryos at distinct growth stages obtained in laser-capture microdissection coupled with DNA microarray experiments revealed that most of the identified genes are expressed throughout embryo morphogenesis and maturation. These findings suggest that metabolic activities are required at preglobular and throughout all stages of embryo development, whereas plastid gene expression becomes necessary during and/or after the globular stage to sustain various activities of the organelle including photosynthetic electron transport.
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Affiliation(s)
- Shih-Chi Hsu
- Department of Plant Sciences, University of California, Davis, CA, USA
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15
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Mechanism of RNA stabilization and translational activation by a pentatricopeptide repeat protein. Proc Natl Acad Sci U S A 2010; 108:415-20. [PMID: 21173259 DOI: 10.1073/pnas.1012076108] [Citation(s) in RCA: 211] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pentatricopeptide repeat (PPR) proteins comprise a large family of helical repeat proteins that bind RNA and modulate organellar RNA metabolism. The mechanisms underlying the functions attributed to PPR proteins are unknown. We describe in vitro studies of the maize protein PPR10 that clarify how PPR10 modulates the stability and translation of specific chloroplast mRNAs. We show that recombinant PPR10 bound to its native binding site in the chloroplast atpI-atpH intergenic region (i) blocks both 5'→3' and 3'→ 5 exoribonucleases in vitro; (ii) is sufficient to define the native processed atpH mRNA 5'-terminus in conjunction with a generic 5'→3' exoribonuclease; and (iii) remodels the structure of the atpH ribosome-binding site in a manner that can account for PPR10's ability to enhance atpH translation. In addition, we show that the minimal PPR10-binding site spans 17 nt. We propose that the site-specific barrier and RNA remodeling activities of PPR10 are a consequence of its unusually long, high-affinity interface with single-stranded RNA, that this interface provides a functional mimic to bacterial small RNAs, and that analogous activities underlie many of the biological functions that have been attributed to PPR proteins.
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16
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Liu X, Yu F, Rodermel S. An Arabidopsis pentatricopeptide repeat protein, SUPPRESSOR OF VARIEGATION7, is required for FtsH-mediated chloroplast biogenesis. PLANT PHYSIOLOGY 2010; 154:1588-601. [PMID: 20935174 PMCID: PMC2996016 DOI: 10.1104/pp.110.164111] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 10/04/2010] [Indexed: 05/18/2023]
Abstract
The Arabidopsis (Arabidopsis thaliana) yellow variegated2 (var2) mutant has green- and white-sectored leaves due to loss of VAR2, a subunit of the chloroplast FtsH protease/chaperone complex. Suppressor screens are a valuable tool to gain insight into VAR2 function and the mechanism of var2 variegation. Here, we report the molecular characterization of 004-003, a line in which var2 variegation is suppressed. We found that the suppression phenotype in this line is caused by lack of a chloroplast pentatricopeptide repeat (PPR) protein that we named SUPPRESSOR OF VARIEGATION7 (SVR7). PPR proteins contain tandemly repeated PPR motifs that bind specific RNAs, and they are thought to be central regulators of chloroplast and mitochondrial nucleic acid metabolism in plants. The svr7 mutant has defects in chloroplast ribosomal RNA (rRNA) processing that are different from those in other svr mutants, and these defects are correlated with reductions in the accumulation of some chloroplast proteins, directly or indirectly. We also found that whereas var2 displays a leaf variegation phenotype at 22°C, it has a pronounced chlorosis phenotype at 8°C that is correlated with defects in chloroplast rRNA processing and a drastic reduction in chloroplast protein accumulation. Surprisingly, the cold-induced phenotype of var2 cannot be suppressed by svr7. Our results strengthen the previously established linkage between var2 variegation and chloroplast rRNA processing/chloroplast translation, and they also point toward the possibility that VAR2 mediates different activities in chloroplast biogenesis at normal and chilling temperatures.
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Affiliation(s)
| | | | - Steve Rodermel
- Department of Genetics, Development, and Cell Biology (X.L., S.R.) and Interdepartmental Genetics Graduate Program (X.L.), Iowa State University, Ames, Iowa 50011; and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, People's Republic of China (F.Y.)
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17
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Nishimura K, Ashida H, Ogawa T, Yokota A. A DEAD box protein is required for formation of a hidden break in Arabidopsis chloroplast 23S rRNA. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 63:766-77. [PMID: 20561259 DOI: 10.1111/j.1365-313x.2010.04276.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In plant chloroplasts, the ribosomal RNA (rRNA) of the large subunit of the ribosome undergoes post-maturation fragmentation processing. This processing consists of site-specific cleavage that generates gapped, discontinuous rRNA molecules. However, the molecular mechanism underlying introduction of the gap structure (the 'hidden break') is poorly understood. Here, we found that the DEAD box protein RH39 plays a key role in introduction of the hidden break into the 23S rRNA in Arabidopsis chloroplasts. Genetic screening for an Arabidopsis plant with a drastically reduced level of ribulose-1,5-bisphosphate carboxylase/oxygenase identified an RH39 mutant. The levels of other chloroplast-encoded photosynthetic proteins were also severely reduced. The reductions were not due to a failure of transcription, but rather inefficiency in translation. RNA gel blotting revealed incomplete fragmentation of 23S rRNA in chloroplasts during maturation. In vitro analysis with recombinant RH39 suggested that the protein binds to the adjacent sequence upstream of the hidden break site to exert its function. We propose a molecular mechanism for the RH39-mediated fragmentation processing of 23S rRNA in chloroplasts.
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MESH Headings
- Amino Acid Sequence
- Arabidopsis/genetics
- Arabidopsis/metabolism
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Blotting, Northern
- Blotting, Western
- Chloroplasts/metabolism
- DEAD-box RNA Helicases/genetics
- DEAD-box RNA Helicases/metabolism
- Genes, Essential/genetics
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- Molecular Sequence Data
- Mutation
- Protein Binding
- RNA, Chloroplast/genetics
- RNA, Chloroplast/metabolism
- RNA, Ribosomal, 23S/genetics
- RNA, Ribosomal, 23S/metabolism
- Recombinant Proteins/metabolism
- Ribulose-Bisphosphate Carboxylase/genetics
- Ribulose-Bisphosphate Carboxylase/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- Kenji Nishimura
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan
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18
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Tseng CC, Sung TY, Li YC, Hsu SJ, Lin CL, Hsieh MH. Editing of accD and ndhF chloroplast transcripts is partially affected in the Arabidopsis vanilla cream1 mutant. PLANT MOLECULAR BIOLOGY 2010; 73:309-23. [PMID: 20143129 DOI: 10.1007/s11103-010-9616-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 01/30/2010] [Indexed: 05/04/2023]
Abstract
The vanilla cream1 (vac1) albino mutant is defective in a gene encoding a chloroplast-localized pentatricopeptide repeat protein of the DYW subgroup. However, the carboxyl-terminal DYW motif is truncated in VAC1. To identify vac1-specific phenotypes, we compared 34 chloroplast RNA editing sites and approximately 90 chloroplast gene expression patterns among wild type, vac1 and another albino mutant ispH, which is defective in the plastid isoprenoid biosynthesis pathway. We found that the editing of accD and ndhF transcripts is partially affected in vac1. In addition, steady-state levels of chloroplast rRNAs are significantly decreased in vac1. The expression of plastid-encoded RNA polymerase transcribed genes is down-regulated, whereas the expression of nucleus-encoded RNA polymerase transcribed genes is up-regulated in vac1. Although the development and function of mutant chloroplasts are severely impaired, steady-state mRNA levels of nucleus-encoded photosynthetic genes are not affected or are only slightly decreased in vac1. The ZAT10 gene encodes a transcription factor and its expression is down-regulated by norflurazon treatment in wild type. This norflurazon effect was not observed in vac1. These results suggest that the VAC1 protein may be involved in plastid-to-nucleus retrograde signaling in addition to its role in chloroplast RNA editing and gene expression. A defect in a key biosynthetic pathway can have many indirect effects on chloroplast gene expression as is seen in the ispH mutant. Similarly, the vac1 mutant has pleiotropic molecular phenotypes and most of which may be indirect effects.
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Affiliation(s)
- Ching-Chih Tseng
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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19
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Komatsu T, Kawaide H, Saito C, Yamagami A, Shimada S, Nakazawa M, Matsui M, Nakano A, Tsujimoto M, Natsume M, Abe H, Asami T, Nakano T. The chloroplast protein BPG2 functions in brassinosteroid-mediated post-transcriptional accumulation of chloroplast rRNA. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:409-22. [PMID: 19919572 DOI: 10.1111/j.1365-313x.2009.04077.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Brassinazole (Brz) is a specific inhibitor of the biosynthesis of brassinosteroids (BRs), which regulate plant organ and chloroplast development. We identified a recessive pale green Arabidopsis mutant, bpg2-1 (Brz-insensitive-pale green 2-1) that showed reduced sensitivity to chlorophyll accumulation promoted by Brz in the light. BPG2 encodes a chloroplast-localized protein with a zinc finger motif and four GTP-binding domains that are necessary for normal chloroplast biogenesis. BPG2-homologous genes are evolutionally conserved in plants, green algae and bacteria. Expression of BPG2 is induced by light and Brz. Chloroplasts of the bpg2-1 mutant have a decreased number of stacked grana thylakoids. In bpg2-1 and bpg2-2 mutants, there was no reduction in expression of rbcL and psbA, but there was abnormal accumulation of precursors of chloroplast 16S and 23S rRNA. Chloroplast protein accumulation induced by Brz was suppressed by the bpg2 mutation. These results indicate that BPG2 plays an important role in post-transcriptional and translational regulation in the chloroplast, and is a component of BR signaling.
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Affiliation(s)
- Tomoyuki Komatsu
- Plant Chemical Biology Research Unit, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan
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20
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Zybailov B, Friso G, Kim J, Rudella A, Rodríguez VR, Asakura Y, Sun Q, van Wijk KJ. Large scale comparative proteomics of a chloroplast Clp protease mutant reveals folding stress, altered protein homeostasis, and feedback regulation of metabolism. Mol Cell Proteomics 2010; 8:1789-1810. [PMID: 19423572 DOI: 10.1074/mcp.m900104-mcp200] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The clpr2-1 mutant is delayed in development due to reduction of the chloroplast ClpPR protease complex. To understand the role of Clp proteases in plastid biogenesis and homeostasis, leaf proteomes of young seedlings of clpr2-1 and wild type were compared using large scale mass spectrometry-based quantification using an LTQ-Orbitrap and spectral counting with significance determined by G-tests. Virtually only chloroplast-localized proteins were significantly affected, indicating that the molecular phenotype was confined to the chloroplast. A comparative chloroplast stromal proteome analysis of fully developed plants was used to complement the data set. Chloroplast unfoldase ClpB3 was strongly up-regulated in both young and mature leaves, suggesting widespread and persistent protein folding stress. The importance of ClpB3 in the clp2-1 mutant was demonstrated by the observation that a CLPR2 and CLPB3 double mutant was seedling-lethal. The observed up-regulation of chloroplast chaperones and protein sorting components further illustrated destabilization of protein homeostasis. Delayed rRNA processing and up-regulation of a chloroplast DEAD box RNA helicase and polynucleotide phosphorylase, but no significant change in accumulation of ribosomal subunits, suggested a bottleneck in ribosome assembly or RNA metabolism. Strong up-regulation of a chloroplast translational regulator TypA/BipA GTPase suggested a specific response in plastid gene expression to the distorted homeostasis. The stromal proteases PreP1,2 were up-regulated, likely constituting compensation for reduced Clp protease activity and possibly shared substrates between the ClpP and PreP protease systems. The thylakoid photosynthetic apparatus was decreased in the seedlings, whereas several structural thylakoid-associated plastoglobular proteins were strongly up-regulated. Two thylakoid-associated reductases involved in isoprenoid and chlorophyll synthesis were up-regulated reflecting feedback from rate-limiting photosynthetic electron transport. We discuss the quantitative proteomics data and the role of Clp proteolysis using a "systems view" of chloroplast homeostasis and metabolism and provide testable hypotheses and putative substrates to further determine the significance of Clp-driven proteolysis.
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Affiliation(s)
- Boris Zybailov
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
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21
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Abstract
The chloroplast genome encodes proteins required for photosynthesis, gene expression, and other essential organellar functions. Derived from a cyanobacterial ancestor, the chloroplast combines prokaryotic and eukaryotic features of gene expression and is regulated by many nucleus-encoded proteins. This review covers four major chloroplast posttranscriptional processes: RNA processing, editing, splicing, and turnover. RNA processing includes the generation of transcript 5' and 3' termini, as well as the cleavage of polycistronic transcripts. Editing converts specific C residues to U and often changes the amino acid that is specified by the edited codon. Chloroplasts feature introns of groups I and II, which undergo protein-facilitated cis- or trans-splicing in vivo. Each of these RNA-based processes involves proteins of the pentatricopeptide motif-containing family, which does not occur in prokaryotes. Plant-specific RNA-binding proteins may underpin the adaptation of the chloroplast to the eukaryotic context.
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Affiliation(s)
- David B Stern
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA.
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22
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Kim J, Rudella A, Ramirez Rodriguez V, Zybailov B, Olinares PDB, van Wijk KJ. Subunits of the plastid ClpPR protease complex have differential contributions to embryogenesis, plastid biogenesis, and plant development in Arabidopsis. THE PLANT CELL 2009; 21:1669-92. [PMID: 19525416 PMCID: PMC2714938 DOI: 10.1105/tpc.108.063784] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 05/06/2009] [Accepted: 05/18/2009] [Indexed: 05/21/2023]
Abstract
The plastid ClpPR protease complex in Arabidopsis thaliana consists of five catalytic ClpP and four noncatalytic ClpR subunits. An extensive analysis of the CLPR family and CLPP5 is presented to address this complexity. Null alleles for CLPR2 and CLPR4 showed delayed embryogenesis and albino embryos, with seedling development blocked in the cotyledon stage; this developmental block was overcome under heterotrophic conditions, and seedlings developed into small albino to virescent seedlings. By contrast, null alleles for CLPP5 were embryo lethal. Thus, the ClpPR proteins make different functional contributions. To further test for redundancies and functional differences between the ClpR proteins, we overexpressed full-length cDNAs for ClpR1, R2, R3, R4 in clpr1, clpr2 and clpr4 mutants. This showed that overexpression of ClpR3 can complement for the loss of ClpR1, but not for the loss of ClpR2 or ClpR4, indicating that ClpR3 can functionally substitute ClpR1. By contrast, ClpR1, R2 and R4 could not substitute each other. Double mutants of weak CLPR1 and 2 alleles were seedling lethal, showing that a minimum concentration of different ClpR proteins is essential for Clp function. Microscopy and large-scale comparative leaf proteome analyses of a CLPR4 null allele demonstrate a central role of Clp protease in chloroplast biogenesis and protein homeostasis; substrates are discussed. Lack of transcriptional and translational feedback regulation within the CLPPR gene family indicates that regulation of Clp activity occurs through Clp complex assembly and substrate delivery.
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Affiliation(s)
- Jitae Kim
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
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23
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Schuster G, Stern D. RNA polyadenylation and decay in mitochondria and chloroplasts. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 85:393-422. [PMID: 19215778 DOI: 10.1016/s0079-6603(08)00810-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Mitochondria and chloroplasts were originally acquired by eukaryotic cells through endosymbiotic events and retain their own gene expression machinery. One hallmark of gene regulation in these two organelles is the predominance of posttranscriptional control, which is exerted both at the gene-specific and global levels. This review focuses on their mechanisms of RNA degradation, and therefore mainly on the polyadenylation-stimulated degradation pathway. Overall, mitochondria and chloroplasts have retained the prokaryotic RNA decay system, despite evolution in the number and character of the enzymes involved. However, several significant differences exist, of which the presence of stable poly(A) tails, and the location of PNPase in the intermembrane space in animal mitochondria, are perhaps the most remarkable. The known and predicted proteins taking part in polyadenylation-stimulated degradation pathways are described, both in chloroplasts and four mitochondrial types: plant, yeast, trypanosome, and animal.
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Affiliation(s)
- Gadi Schuster
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
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24
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Yu F, Liu X, Alsheikh M, Park S, Rodermel S. Mutations in SUPPRESSOR OF VARIEGATION1, a factor required for normal chloroplast translation, suppress var2-mediated leaf variegation in Arabidopsis. THE PLANT CELL 2008; 20:1786-804. [PMID: 18599582 PMCID: PMC2518225 DOI: 10.1105/tpc.107.054965] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 05/13/2008] [Accepted: 05/28/2008] [Indexed: 05/18/2023]
Abstract
The Arabidopsis thaliana yellow variegated2 (var2) mutant is variegated due to lack of a chloroplast FtsH-like metalloprotease (FtsH2/VAR2). We have generated suppressors of var2 variegation to gain insight into factors and pathways that interact with VAR2 during chloroplast biogenesis. Here, we describe two such suppressors. Suppression of variegation in the first line, TAG-FN, was caused by disruption of the nuclear gene (SUPPRESSOR OF VARIEGATION1 [SVR1]) for a chloroplast-localized homolog of pseudouridine (Psi) synthase, which isomerizes uridine to Psi in noncoding RNAs. svr1 single mutants were epistatic to var2, and they displayed a phenotypic syndrome that included defects in chloroplast rRNA processing, reduced chloroplast translation, reduced chloroplast protein accumulation, and elevated chloroplast mRNA levels. In the second line (TAG-IE), suppression of variegation was caused by a lesion in SVR2, the gene for the ClpR1 subunit of the chloroplast ClpP/R protease. Like svr1, svr2 was epistatic to var2, and clpR1 mutants had a phenotype that resembled svr1. We propose that an impairment of chloroplast translation in TAG-FN and TAG-IE decreased the demand for VAR2 activity during chloroplast biogenesis and that this resulted in the suppression of var2 variegation. Consistent with this hypothesis, var2 variegation was repressed by chemical inhibitors of chloroplast translation. In planta mutagenesis revealed that SVR1 not only played a role in uridine isomerization but that its physical presence was necessary for proper chloroplast rRNA processing. Our data indicate that defects in chloroplast rRNA processing are a common, but not universal, molecular phenotype associated with suppression of var2 variegation.
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Affiliation(s)
- Fei Yu
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50011, USA
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25
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Beligni MV, Mayfield SP. Arabidopsis thaliana mutants reveal a role for CSP41a and CSP41b, two ribosome-associated endonucleases, in chloroplast ribosomal RNA metabolism. PLANT MOLECULAR BIOLOGY 2008; 67:389-401. [PMID: 18398686 DOI: 10.1007/s11103-008-9328-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Accepted: 03/19/2008] [Indexed: 05/04/2023]
Abstract
A proteomic analysis of Chlamydomonas reinhardtii 70S ribosomes identified two proteins, RAP38 and RAP41, which associate in stoichiometric amounts with intact ribosomes. In this work we show results that suggest the Arabidopsis thaliana homologs, CSP41b and CSP41a, participate in ribosomal RNA metabolism. Csp41a-1 and csp41b-1 single mutants show little phenotype, while the loss of both proteins is lethal. Plants homozygous for the csp41b-1 mutation and heterozygous for the csp41a-1 mutation (csp41b-1/csp41a-1*) fail to accumulate CSP41b and show a marked reduction in the levels of CSP41a. These mutants have reduced chlorophyll content, grow slower and over-accumulate 23S precursor rRNAs compared to their wild-type (WT) siblings, whereas other rRNAs or mRNAs are unaffected. Chloroplast polysome assembly is reduced in csp41b-1/csp41a-1* mutants, which also contain increased amounts of pre-ribosomal particles compared to mature 70S ribosomes. Our results also indicate that CSP41b associates with pre-ribosomal particles in vivo. In vitro, the pattern of 23S precursors and mature rRNAs is altered upon incubation with recombinant CSP41a and CSP41b. Taken together, these results suggest that CSP41a and CSP41b have a role in chloroplast ribosomal RNA metabolism, most likely acting in the final steps of 23S rRNA maturation.
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Affiliation(s)
- María Verónica Beligni
- Department of Cell Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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26
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Sakamoto W, Miyagishima SY, Jarvis P. Chloroplast biogenesis: control of plastid development, protein import, division and inheritance. THE ARABIDOPSIS BOOK 2008; 6:e0110. [PMID: 22303235 PMCID: PMC3243408 DOI: 10.1199/tab.0110] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The chloroplast is a multi-copy cellular organelle that not only performs photosynthesis but also synthesizes amino acids, lipids and phytohormones. The plastid also responds to environmental stimuli such as gravitropism. Biogenesis of chloroplasts is initiated from proplastids in shoot meristems, and involves a series of important events. In the last decade, considerable progress has been made towards understanding various aspects of chloroplast biogenesis at the molecular level, via studies in model systems such as Arabidopsis. This review focuses on two important aspects of chloroplast biogenesis, synthesis/assembly and division/transmission. Chloroplasts originated through endosymbiosis from an ancestor of extant cyanobacteria, and thus contain their own genomes. DNA in chloroplasts is organized into complexes with proteins, and these are called nucleoids. The synthesis of chloroplast proteins is regulated at various steps. However, a majority of proteins are synthesized in the cytosol, and their proper import into chloroplast compartments is a prerequisite for chloroplast development. Fundamental aspects of plastid gene expression/regulation and chloroplast protein transport are described, together with recent proteome analyses of the organelle. Chloroplasts are not de novo synthesized, but instead are propagated from pre-existing plastids. In addition, plastids are transmitted from generation to generation with a unique mode of inheritance. Our current knowledge on the division machinery and the inheritance of plastids is described.
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Affiliation(s)
- Wataru Sakamoto
- Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
- Address correspondence to
| | | | - Paul Jarvis
- Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
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27
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Mudd EA, Sullivan S, Gisby MF, Mironov A, Kwon CS, Chung WI, Day A. A 125 kDa RNase E/G-like protein is present in plastids and is essential for chloroplast development and autotrophic growth in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:2597-610. [PMID: 18515828 PMCID: PMC2486463 DOI: 10.1093/jxb/ern126] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 03/28/2008] [Accepted: 03/31/2008] [Indexed: 05/20/2023]
Abstract
Endoribonuclease E (RNase E) is a regulator of global gene expression in Escherichia coli and is the best studied member of the RNase E/G ribonuclease family. Homologues are present in other bacteria but the roles of plant RNase E/G-like proteins are not known. Arabidopsis thaliana contains a single nuclear gene (At2g04270) encoding a product with the conserved catalytic domain of RNase E/G-like proteins. At2g04270 and the adjacent At2g04280 gene form converging transcription units with a approximately 40 base overlap at their 3' ends. Several translation products were predicted from the analyses of At2g04270 cDNAs. An antibody raised against a recombinant A. thaliana RNase E/G-like protein recognized a 125 kDa protein band in purified chloroplast preparations fractionated by SDS-PAGE. The 125 kDa RNase E/G-like protein was detected in cotyledons, rosette and cauline leaves. T-DNA insertions in exon 6 or intron 11 of At2g04270 result in loss of the 125 kDa band or truncation to a 110 kDa band. Loss of At2g04270 function resulted in the arrest of chloroplast development, loss of autotrophic growth, and reduced plastid ribosomal, psbA and rbcL RNA levels. Homozygous mutant plants were pale-green, contained smaller plastids with fewer thylakoids and shorter granal stacks than wild-type chloroplasts, and required sucrose at all growth stages following germination right up to flowering and setting seeds. Recombinant A. thaliana RNase E/G-like proteins rescued an E. coli RNase E mutant and cleaved an rbcL RNA substrate. Expression of At2g04270 was highly correlated with genes encoding plastid polyribonucleotide phosphorylase, S1 RNA-binding, and CRS1/YhbY domain proteins.
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Affiliation(s)
- Elisabeth A. Mudd
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Stuart Sullivan
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Martin F. Gisby
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Aleksandr Mironov
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Chang Seob Kwon
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejon, Republic of Korea 305-701
| | - Won-Il Chung
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejon, Republic of Korea 305-701
| | - Anil Day
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
- To whom correspondence should be addressed. E-mail:
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28
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Lalonde MS, Zuo Y, Zhang J, Gong X, Wu S, Malhotra A, Li Z. Exoribonuclease R in Mycoplasma genitalium can carry out both RNA processing and degradative functions and is sensitive to RNA ribose methylation. RNA (NEW YORK, N.Y.) 2007; 13:1957-68. [PMID: 17872508 PMCID: PMC2040080 DOI: 10.1261/rna.706207] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Mycoplasma genitalium, a small bacterium having minimal genome size, has only one identified exoribonuclease, RNase R (MgR). We have purified MgR to homogeneity, and compared its RNA degradative properties to those of its Escherichia coli homologs RNase R (EcR) and RNase II (EcII). MgR is active on a number of substrates including oligoribonucleotides, poly(A), rRNA, and precursors to tRNA. Unlike EcR, which degrades rRNA and pre-tRNA without formation of intermediate products, MgR appears sensitive to certain RNA structural features and forms specific products from these stable RNA substrates. The 3'-ends of two MgR degradation products of 23S rRNA were mapped by RT-PCR to positions 2499 and 2553, each being 1 nucleotide downstream of a 2'-O-methylation site. The sensitivity of MgR to ribose methylation is further demonstrated by the degradation patterns of 16S rRNA and a synthetic methylated oligoribonucleotide. Remarkably, MgR removes the 3'-trailer sequence from a pre-tRNA, generating product with the mature 3'-end more efficiently than EcII does. In contrast, EcR degrades this pre-tRNA without the formation of specific products. Our results suggest that MgR shares some properties of both EcR and EcII and can carry out a broad range of RNA processing and degradative functions.
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Affiliation(s)
- Maureen S Lalonde
- Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL 33431, USA
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29
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Sasaki K, Saito T, Lämsä M, Oksman-Caldentey KM, Suzuki M, Ohyama K, Muranaka T, Ohara K, Yazaki K. Plants utilize isoprene emission as a thermotolerance mechanism. PLANT & CELL PHYSIOLOGY 2007; 48:1254-62. [PMID: 17711876 DOI: 10.1093/pcp/pcm104] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Isoprene is a volatile compound emitted from leaves of many plant species in large quantities, which has an impact on atmospheric chemistry due to its massive global emission rate (5 x 10(14) carbon g year(-1)) and its high reactivity with the OH radical, resulting in an increase in the half-life of methane. Isoprene emission is strongly induced by the increase in isoprene synthase activity in plastids at high temperature in the day time, which is regulated at its gene expression level in leaves, while the physiological meaning of isoprene emission for plants has not been clearly demonstrated. In this study, we have functionally overexpressed Populus alba isoprene synthase in Arabidopsis to observe isoprene emission from transgenic plants. A striking difference was observed when both transgenic and wild-type plants were treated with heat at 60 degrees C for 2.5 h, i.e. transformants revealed clear heat tolerance compared with the wild type. High isoprene emission and a decrease in the leaf surface temperature were observed in transgenic plants under heat stress treatment. In contrast, neither strong light nor drought treatments showed an apparent difference. These data suggest that isoprene emission plays a crucial role in a heat protection mechanism in plants.
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Affiliation(s)
- Kanako Sasaki
- Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Japan
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30
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Zicker AA, Kadakia CS, Herrin DL. Distinct roles for the 5' and 3' untranslated regions in the degradation and accumulation of chloroplast tufA mRNA: identification of an early intermediate in the in vivo degradation pathway. PLANT MOLECULAR BIOLOGY 2007; 63:689-702. [PMID: 17180456 DOI: 10.1007/s11103-006-9117-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Accepted: 11/13/2006] [Indexed: 05/13/2023]
Abstract
Elongation factor Tu in Chlamydomonas reinhardtii is a chloroplast-encoded gene (tufA) whose 1.7-kb mRNA has a relatively short half-life. In the presence of chloramphenicol (CAP), which freezes translating chloroplast ribosomes, a 1.5-kb tufA RNA becomes prominent. Rifampicin-chase analysis indicates that the 1.5-kb RNA is a degradation intermediate, and mapping studies show that it is missing 176-180 nucleotides from the 5' end of tufA. The 5' terminus of the intermediate maps to a section of the untranslated region (UTR) predicted to be highly structured and to encode a small ORF. The intermediate could be detected in older cultures in the absence of CAP, indicating that it is not an artifact of drug treatment. Also, it did not overaccumulate in the chloroplast ribosome-deficient mutant, ac20 cr1, indicating its stabilization is specific to elongation-arrested ribosomes. To determine if the 5' UTR of tufA is destabilizing, the corresponding region of the atpA-aadA-rbcL gene was replaced with the tufA sequence, and introduced into the chloroplast genome; the 3' UTR was also substituted for comparison. Analysis of these transformants showed that the transcripts containing the tufA 3'-UTR accumulate to significantly lower levels. Data from constructs based on the vital reporter, Renilla luciferase, confirmed the importance of the tufA 3'-UTR in determining RNA levels, and suggested that the 5' UTR of tufA affects translation efficiency. These data indicate that the in vivo degradation of tufA mRNA begins in the 5' UTR, and is promoted by translation. The data also suggest, however, that the level of the mature RNA is determined more by the 3' UTR than the 5' UTR.
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Affiliation(s)
- Alicia A Zicker
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, School of Biological Sciences, University of Texas at Austin, 1 University Station A6700, Austin, TX 78712, USA
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31
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Koussevitzky S, Stanne TM, Peto CA, Giap T, Sjögren LLE, Zhao Y, Clarke AK, Chory J. An Arabidopsis thaliana virescent mutant reveals a role for ClpR1 in plastid development. PLANT MOLECULAR BIOLOGY 2007; 63:85-96. [PMID: 17009084 DOI: 10.1007/s11103-006-9074-2] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Accepted: 08/09/2006] [Indexed: 05/07/2023]
Abstract
The ATP-dependent Clp protease has been well-characterized in Escherichia coli, but knowledge of its function in higher plants is limited. In bacteria, this two-component protease consists of a Ser-type endopeptidase ClpP, which relies on the ATP-dependent unfolding activity from an Hsp100 molecular chaperone to initiate protein degradation. In the chloroplasts of higher plants, multiple isoforms of the proteolytic subunit exist, with Arabidopsis having five ClpPs and four ClpP-like proteins termed ClpR predicted in its genome. In this work we characterized an Arabidopsis mutant impaired in one subunit of the chloroplast-localized Clp protease core, ClpR1. clpR1-1, a virescent mutant, carries a pre-mature stop codon in the clpR1 gene, resulting in no detectable ClpR1 protein. The accumulation of several chloroplast proteins, as well as most of the chloroplast-localized Clp protease subunits, is inhibited in clpR1-1. Unexpectedly, some plastid-encoded proteins do not accumulate, although their transcripts accumulate to wild-type levels. Maturation of 23S and 4.5S chloroplast ribosomal RNA (cp-rRNA) is delayed in clpR1-1, and both RNAs accumulate as higher molecular weight precursors. Also, chloroplasts in clpR1-1 are smaller than in wild type and have fewer thylakoid membranes with smaller grana stacks. We propose that a ClpR1-containing activity is required for chloroplast development and differentiation and in its absence both are delayed.
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MESH Headings
- Arabidopsis/genetics
- Arabidopsis/physiology
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Arabidopsis Proteins/physiology
- Blotting, Northern
- Blotting, Western
- Chloroplasts/genetics
- Chloroplasts/physiology
- Chloroplasts/ultrastructure
- Endopeptidase Clp/genetics
- Endopeptidase Clp/metabolism
- Endopeptidase Clp/physiology
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Microscopy, Electron, Transmission
- Mutation
- Plant Leaves/growth & development
- Plant Leaves/metabolism
- Plants, Genetically Modified
- Plastids/genetics
- Plastids/physiology
- Plastids/ultrastructure
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Ribosomal, 23S/genetics
- RNA, Ribosomal, 23S/metabolism
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Affiliation(s)
- Shai Koussevitzky
- Plant Biology Laboratory, The Salk Institute, La Jolla, CA 92037, USA.
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32
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Processing, degradation, and polyadenylation of chloroplast transcripts. CELL AND MOLECULAR BIOLOGY OF PLASTIDS 2007. [DOI: 10.1007/4735_2007_0235] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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33
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Chakrabarti SK, Lutz KA, Lertwiriyawong B, Svab Z, Maliga P. Expression of the cry9Aa2 B.t. gene in tobacco chloroplasts confers resistance to potato tuber moth. Transgenic Res 2006; 15:481-8. [PMID: 16906448 DOI: 10.1007/s11248-006-0018-z] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2005] [Accepted: 03/22/2006] [Indexed: 10/24/2022]
Abstract
We report here the control of potato tuber moth (Phthorimaea operculella) by incorporating a truncated Bacillus thuringiensis cry9Aa2 gene in the plastid genome. Plasmids pSKC84 and pSKC85 are derivatives of a new polycistronic plastid transformation vector, pPRV312L, that carries spectinomycin resistance (aadA) as a selective marker and targets insertions in the trnI-trnA intergenic region. The Cry9Aa2 N-terminal region (82.1 kDa; 734 amino acids) was expressed in a cassette, which consists of 49 nucleotides of the cry9Aa2 leader and the 3'-untranslated region of the plastid rbcL gene (TrbcL), and relies on readthrough transcription from the plastid rRNA operon. In a tobacco leaf bioassay, expression of Cry9Aa2 conferred resistance to potato tuber moth. In accordance, the Cry9Aa2 insecticidal protein accumulated to high levels, approximately 10% of the total soluble cellular protein and approximately 20% in the membrane fraction. However, high-level Cry9Aa2 expression significantly delayed plant development. Thus, a practical system to control potato tuber moth by Cry9Aa2 expression calls for down-regulation of its expression.
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34
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Hricová A, Quesada V, Micol JL. The SCABRA3 nuclear gene encodes the plastid RpoTp RNA polymerase, which is required for chloroplast biogenesis and mesophyll cell proliferation in Arabidopsis. PLANT PHYSIOLOGY 2006; 141:942-56. [PMID: 16698900 PMCID: PMC1489898 DOI: 10.1104/pp.106.080069] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 05/03/2006] [Accepted: 05/04/2006] [Indexed: 05/09/2023]
Abstract
In many plant species, a subset of the genes of the chloroplast genome is transcribed by RpoTp, a nuclear-encoded plastid-targeted RNA polymerase. Here, we describe the positional cloning of the SCABRA3 (SCA3) gene, which was found to encode RpoTp in Arabidopsis (Arabidopsis thaliana). We studied one weak (sca3-1) and two strong (sca3-2 and sca3-3) alleles of the SCA3 gene, the latter two showing severely impaired plant growth and reduced pigmentation of the cotyledons, leaves, stem, and sepals, all of which were pale green. The leaf surface was extremely crumpled in the sca3 mutants, although epidermal cell size and morphology were not perturbed, whereas the mesophyll cells were less densely packed and more irregular in shape than in the wild type. A significant reduction in the size, morphology, and number of chloroplasts was observed in homozygous sca3-2 individuals whose photoautotrophic growth was consequently perturbed. Microarray analysis showed that several hundred nuclear genes were differentially expressed in sca3-2 and the wild type, about one-fourth of which encoded chloroplast-targeted proteins. Quantitative reverse transcription-PCR analyses showed that the sca3-2 mutation alters the expression of the rpoB, rpoC1, clpP, and accD plastid genes and the SCA3 paralogs RpoTm and RpoTmp, which respectively encode nuclear-encoded mitochondrion or dually targeted RNA polymerases. Double-mutant analysis indicated that RpoTmp and SCA3 play redundant functions in plant development. Our findings support a role for plastids in leaf morphogenesis and indicate that RpoTp is required for mesophyll cell proliferation.
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Affiliation(s)
- Andrea Hricová
- División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Spain
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35
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Bollenbach TJ, Lange H, Gutierrez R, Erhardt M, Stern DB, Gagliardi D. RNR1, a 3'-5' exoribonuclease belonging to the RNR superfamily, catalyzes 3' maturation of chloroplast ribosomal RNAs in Arabidopsis thaliana. Nucleic Acids Res 2005; 33:2751-63. [PMID: 15891117 PMCID: PMC1110743 DOI: 10.1093/nar/gki576] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Revised: 04/26/2005] [Accepted: 04/26/2005] [Indexed: 11/15/2022] Open
Abstract
Arabidopsis thaliana chloroplasts contain at least two 3' to 5' exoribonucleases, polynucleotide phosphorylase (PNPase) and an RNase R homolog (RNR1). PNPase has been implicated in both mRNA and 23S rRNA 3' processing. However, the observed maturation defects do not affect chloroplast translation, suggesting that the overall role of PNPase in maturation of chloroplast rRNA is not essential. Here, we show that this role can be largely ascribed to RNR1, for which homozygous mutants germinate only on sucrose-containing media, and have white cotyledons and pale green rosette leaves. Accumulation of chloroplast-encoded mRNAs and tRNAs is unaffected in such mutants, suggesting that RNR1 activity is either unnecessary or redundant for their processing and turnover. However, accumulation of several chloroplast rRNA species is severely affected. High-resolution RNA gel blot analysis, and mapping of 5' and 3' ends, revealed that RNR1 is involved in the maturation of 23S, 16S and 5S rRNAs. The 3' extensions of the accumulating 5S rRNA precursors can be efficiently removed in vitro by purified RNR1, consistent with this view. Our data suggest that decreased accumulation of mature chloroplast ribosomal RNAs leads to a reduction in the number of translating ribosomes, ultimately compromising chloroplast protein abundance and thus plant growth and development.
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Affiliation(s)
- Thomas J. Bollenbach
- Boyce Thompson Institute for Plant Research, Cornell UniversityTower Rd., Ithaca, NY 14853, USA
- Institut de Biologie Moléculaire des Plantes, CNRS UPR235712 rue du général Zimmer, 67084 Strasbourg cedex, France
| | - Heike Lange
- Institut de Biologie Moléculaire des Plantes, CNRS UPR235712 rue du général Zimmer, 67084 Strasbourg cedex, France
| | - Ryan Gutierrez
- Boyce Thompson Institute for Plant Research, Cornell UniversityTower Rd., Ithaca, NY 14853, USA
- Institut de Biologie Moléculaire des Plantes, CNRS UPR235712 rue du général Zimmer, 67084 Strasbourg cedex, France
| | - Mathieu Erhardt
- Institut de Biologie Moléculaire des Plantes, CNRS UPR235712 rue du général Zimmer, 67084 Strasbourg cedex, France
| | - David B. Stern
- To whom correspondence should be addressed. Tel: +1 607 254 1306; Fax: +1 607 254 6779;
| | - Dominique Gagliardi
- Institut de Biologie Moléculaire des Plantes, CNRS UPR235712 rue du général Zimmer, 67084 Strasbourg cedex, France
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