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Marker-Free Transplastomic Plants by Excision of Plastid Marker Genes Using Directly Repeated DNA Sequences. Methods Mol Biol 2021. [PMID: 34028764 DOI: 10.1007/978-1-0716-1472-3_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Excision of marker genes using DNA direct repeats makes use of the efficient native homologous recombination pathway present in the plastids of algae and plants. The method is simple, efficient, and widely applicable to plants and green algae. Marker excision frequency is dependent on the length and number of directly repeated sequences. When two repeats are used a repeat size of greater than 600 bp promotes efficient excision of the marker gene. A wide variety of sequences can be used to make the direct repeats. Only a single round of transformation is required and there is no requirement to introduce site-specific recombinases by retransformation or sexual crosses. Selection is used to maintain the marker and ensure homoplasmy of transgenic plastid genomes (plastomes). Release of selection allows the accumulation of marker-free plastomes generated by marker excision, which is a spontaneous and unidirectional process. Cytoplasmic sorting allows the segregation of cells with marker-free transgenic plastids. The marker-free shoots resulting from direct repeat mediated excision of marker genes have been isolated by vegetative propagation of shoots in the T0 generation. Alternatively, accumulation of marker-free plastomes during growth, development and flowering of T0 plants allows for the collection of seeds that give rise to a high proportion of marker-free T1 seedlings. The procedure enables precise plastome engineering involving insertion of transgenes, point mutations and deletion of genes without the inclusion of any extraneous DNA. The simplicity and convenience of direct repeat excision facilitates its widespread use to isolate marker-free crops.
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Abstract
Plastids (chloroplasts) are the defining organelles of plants and eukaryotic algae. In addition to performing photosynthesis, plastids harbor numerous other metabolic pathways and therefore are often referred to as the biosynthetic center of the plant cell. The chloroplasts of seed plants possess dozens of copies of a circular genome of ∼150 kb that contains a conserved set of 120 to 130 genes. The engineering of this genome by genetic transformation is technically challenging and currently only possible in a small number of species. In this article, we describe the methods involved in generating stable chloroplast-transformed (transplastomic) plants in the model species Arabidopsis (Arabidopsis thaliana). The protocols presented here can be applied to (1) target genes in the Arabidopsis chloroplast genome by reverse genetics and (2) express reporter genes or other foreign genes of interest in plastids of Arabidopsis plants. © 2021 The Authors. Basic Protocol 1: Generation of root-derived microcallus material for biolistic transformation Basic Protocol 2: Chloroplast transformation by biolistic bombardment of root-derived microcalli Basic Protocol 3: Regeneration of transplastomic lines and seed production.
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Affiliation(s)
- Stephanie Ruf
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Xenia Kroop
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
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Rascón-Cruz Q, González-Barriga CD, Iglesias-Figueroa BF, Trejo-Muñoz JC, Siqueiros-Cendón T, Sinagawa-García SR, Arévalo-Gallegos S, Espinoza-Sánchez EA. Plastid transformation: Advances and challenges for its implementation in agricultural crops. ELECTRON J BIOTECHN 2021. [DOI: 10.1016/j.ejbt.2021.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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4
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Li S, Chang L, Zhang J. Advancing organelle genome transformation and editing for crop improvement. PLANT COMMUNICATIONS 2021; 2:100141. [PMID: 33898977 PMCID: PMC8060728 DOI: 10.1016/j.xplc.2021.100141] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 12/15/2020] [Accepted: 01/01/2021] [Indexed: 05/05/2023]
Abstract
Plant cells contain three organelles that harbor DNA: the nucleus, plastids, and mitochondria. Plastid transformation has emerged as an attractive platform for the generation of transgenic plants, also referred to as transplastomic plants. Plastid genomes have been genetically engineered to improve crop yield, nutritional quality, and resistance to abiotic and biotic stresses, as well as for recombinant protein production. Despite many promising proof-of-concept applications, transplastomic plants have not been commercialized to date. Sequence-specific nuclease technologies are widely used to precisely modify nuclear genomes, but these tools have not been applied to edit organelle genomes because the efficient homologous recombination system in plastids facilitates plastid genome editing. Unlike plastid transformation, successful genetic transformation of higher plant mitochondrial genome transformation was tested in several research group, but not successful to date. However, stepwise progress has been made in modifying mitochondrial genes and their transcripts, thus enabling the study of their functions. Here, we provide an overview of advances in organelle transformation and genome editing for crop improvement, and we discuss the bottlenecks and future development of these technologies.
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Affiliation(s)
- Shengchun Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Ling Chang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Jiang Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, China
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Yu Q, Tungsuchat-Huang T, Verma K, Radler MR, Maliga P. Independent translation of ORFs in dicistronic operons, synthetic building blocks for polycistronic chloroplast gene expression. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:2318-2329. [PMID: 32497322 DOI: 10.1111/tpj.14864] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 05/13/2020] [Accepted: 05/21/2020] [Indexed: 06/11/2023]
Abstract
We designed a dicistronic plastid marker system that relies on the plastid's ability to translate polycistronic mRNAs. The identification of transplastomic clones is based on selection for antibiotic resistance encoded in the first open reading frame (ORF) and accumulation of the reporter gene product in tobacco chloroplasts encoded in the second ORF. The antibiotic resistance gene may encode spectinomycin or kanamycin resistance based on the expression of aadA or neo genes, respectively. The reporter gene used in the study is the green fluorescent protein (GFP). The mRNA level depends on the 5'-untranslated region of the first ORF. The protein output depends on the strengths of the ribosome binding, and is proportional with the level of translatable mRNA. Because the dicistronic mRNA is not processed, we could show that protein output from the second ORF is independent from the first ORF. High-level GFP accumulation from the second ORF facilitates identification of transplastomic events under ultraviolet light. Expression of multiple proteins from an unprocessed mRNA is an experimental design that enables predictable protein output from polycistronic mRNAs, expanding the toolkit of plant synthetic biology.
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Affiliation(s)
- Qiguo Yu
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
| | | | - Kanak Verma
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
| | - Megan R Radler
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
| | - Pal Maliga
- Waksman Institute of Microbiology, Rutgers University, Piscataway, NJ, 08854, USA
- Department of Plant Biology, Rutgers University, New Brunswick, NJ, 08901, USA
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6
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Evangelisti E, Yunusov T, Shenhav L, Schornack S. N-acetyltransferase AAC(3)-I confers gentamicin resistance to Phytophthora palmivora and Phytophthora infestans. BMC Microbiol 2019; 19:265. [PMID: 31775609 PMCID: PMC6882347 DOI: 10.1186/s12866-019-1642-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 11/14/2019] [Indexed: 12/12/2022] Open
Abstract
Background Oomycetes are pathogens of mammals, fish, insects and plants, and the potato late blight agent Phytophthora infestans and the oil palm and cocoa infecting pathogen Phytophthora palmivora cause economically impacting diseases on a wide range of crop plants. Increasing genomic and transcriptomic resources and recent advances in oomycete biology demand new strategies for genetic modification of oomycetes. Most oomycete transformation procedures rely on geneticin-based selection of transgenic strains. Results We established N-acetyltransferase AAC(3)-I as a gentamicin-based selectable marker for oomycete transformation without interference with existing geneticin resistance. Strains carrying gentamicin resistance are fully infectious in plants. We further demonstrate the usefulness of this new antibiotic selection to super-transform well-characterized, already fluorescently-labelled P. palmivora strains and provide a comprehensive protocol for maintenance and zoospore electro-transformation of Phytophthora strains to aid in plant-pathogen research. Conclusions N-acetyltransferase AAC(3)-I is functional in Phytophthora oomycetes. In addition, the substrate specificity of the AAC(3)-I enzyme allows for re-transformation of geneticin-resistant strains. Our findings and resources widen the possibilities to study oomycete cell biology and plant-oomycete interactions.
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Affiliation(s)
| | - Temur Yunusov
- Sainsbury Laboratory Cambridge University (SLCU), Cambridge, UK
| | - Liron Shenhav
- Sainsbury Laboratory Cambridge University (SLCU), Cambridge, UK
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Sandoval-Vargas JM, Jiménez-Clemente LA, Macedo-Osorio KS, Oliver-Salvador MC, Fernández-Linares LC, Durán-Figueroa NV, Badillo-Corona JA. Use of the ptxD gene as a portable selectable marker for chloroplast transformation in Chlamydomonas reinhardtii. Mol Biotechnol 2019; 61:461-468. [PMID: 30997667 DOI: 10.1007/s12033-019-00177-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synthetic biology and genetic engineering in algae offer an unprecedented opportunity to develop species with traits that can help solve the problems associated with food and energy supply in the 21st century. In the green alga Chlamydomonas reinhardtii, foreign genes can be expressed from the chloroplast genome for molecular farming and metabolic engineering to obtain commodities and high-value molecules. To introduce these genes, selectable markers, which rely mostly on the use of antibiotics, are needed. This has risen social concern associated with the potential risk of horizontal gene transfer across life kingdoms, which has led to a quest for antibiotic-free selectable markers. Phosphorus (P) is a scarce nutrient element that most organisms can only assimilate in its most oxidized form as phosphate (Pi); however, some organisms are able to oxidize phosphite (Phi) to Pi prior to incorporation into the central metabolism of P. As an alternative to the use of the two positive selectable makers already available for chloroplast transformation in C. reinhardtii, the aadA and the aphA-6 genes, that require the use of antibiotics, we investigated if a phosphite-based selection method could be used for the direct recovery of chloroplast transformed lines in this alga. Here we show that following bombardment with a vector carrying the ptxD gene from Pseudomonas stutzeri WM88, only cells that integrate and express the gene proliferate and form colonies using Phi as the sole P source. Our results demonstrate that a selectable marker based on the assimilation of Phi can be used for chloroplasts transformation in a biotechnologically relevant organism. The portable selectable marker we have developed is, in more than 18 years, the latest addition to the markers available for selection of chloroplast transformed cells in C. reinhardtii. The ptxD gene will contribute to the repertoire of tools available for synthetic biology and genetic engineering in the chloroplast of C. reinhardtii.
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Affiliation(s)
- José M Sandoval-Vargas
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - Luis A Jiménez-Clemente
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - Karla S Macedo-Osorio
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - María C Oliver-Salvador
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - Luis C Fernández-Linares
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - Noé V Durán-Figueroa
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico
| | - Jesús A Badillo-Corona
- Instituto Politécnico Nacional, Unidad Profesional Interdisciplinaria de Biotecnología, Av. Acueducto SN, Col. Barrio la Laguna Ticomán, 07340, Mexico City, Mexico.
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Kota S, Lakkam R, Kasula K, Narra M, Qiang H, Rao Allini V, Zanmin H, Abbagani S. Construction of a species-specific vector for improved plastid transformation efficiency in Capsicum annuum L. 3 Biotech 2019; 9:226. [PMID: 31139541 DOI: 10.1007/s13205-019-1747-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 05/08/2019] [Indexed: 11/26/2022] Open
Abstract
In the present study, we focused on designing a species-specific chloroplast vector for Capsicum annuum L. and finding out its transformation efficiency compared to a heterologous vector. The plastid transformation vector (CaIA) was designed to target homologous regions trnA and trnI of IR region. A selectable marker gene aadA, whose expression is controlled by psbA promoter and terminator, was cloned between two flanking regions. A heterologous vector pRB95, which targets trnfM and trnG of LSC region along with aadA driven by rrn promoter and psbA terminator, was also used for developing plastid transformation in Capsicum. Cotyledonary explants were bombarded with stabilized biolistic parameters: 900 psi pressure and 9 cm flight distance, and optimized regeneration protocol (0.7 mg/L TDZ + 0.2 mg/L IAA) was used to obtain transplastomic lines on selection medium (300 mg/L spectinomycin). The aadA integration and homoplasmy were confirmed by obtaining 1.2 and 3.7 kb amplicons in CaIA transformants and subsequently verified by Southern blotting, whereas in pRB95 transformants, integration was confirmed by PCR with 1.45 kb and 255 bp amplicons corresponding to aadA integration and flanks, respectively. The transformation efficiencies attained with two plastid vectors were found to be 20%, i.e., 10 transplastomic lines in 50 bombarded plates, with CaIA and 2%, i.e., 1 transplastomic line in 50 bombarded plates, with heterologous pRB95, respectively.
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Affiliation(s)
- Srinivas Kota
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
- 2Institute of Genetics and Developmental Biology, Beijing, China
| | - Raghuvardhan Lakkam
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
| | - Kirnamayee Kasula
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
- 3Department of Biotechnology, Telangana University, Nizamabad, Telangana 503322 India
| | - Muralikrishna Narra
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
| | - Hao Qiang
- 2Institute of Genetics and Developmental Biology, Beijing, China
| | - V Rao Allini
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
| | - Hu Zanmin
- 2Institute of Genetics and Developmental Biology, Beijing, China
| | - Sadanandam Abbagani
- 1Plant Biotechnology Research Unit, Department of Biotechnology, Kakatiya University, Warangal, Telangana 506009 India
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Occhialini A, Piatek AA, Pfotenhauer AC, Frazier TP, Stewart CN, Lenaghan SC. MoChlo: A Versatile, Modular Cloning Toolbox for Chloroplast Biotechnology. PLANT PHYSIOLOGY 2019; 179:943-957. [PMID: 30679266 PMCID: PMC6393787 DOI: 10.1104/pp.18.01220] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 01/16/2019] [Indexed: 05/19/2023]
Abstract
Plant synthetic biology is a rapidly evolving field with new tools constantly emerging to drive innovation. Of particular interest is the application of synthetic biology to chloroplast biotechnology to generate plants capable of producing new metabolites, vaccines, biofuels, and high-value chemicals. Progress made in the assembly of large DNA molecules, composing multiple transcriptional units, has significantly aided in the ability to rapidly construct novel vectors for genetic engineering. In particular, Golden Gate assembly has provided a facile molecular tool for standardized assembly of synthetic genetic elements into larger DNA constructs. In this work, a complete modular chloroplast cloning system, MoChlo, was developed and validated for fast and flexible chloroplast engineering in plants. A library of 128 standardized chloroplast-specific parts (47 promoters, 38 5' untranslated regions [5'UTRs], nine promoter:5'UTR fusions, 10 3'UTRs, 14 genes of interest, and 10 chloroplast-specific destination vectors) were mined from the literature and modified for use in MoChlo assembly, along with chloroplast-specific destination vectors. The strategy was validated by assembling synthetic operons of various sizes and determining the efficiency of assembly. This method was successfully used to generate chloroplast transformation vectors containing up to seven transcriptional units in a single vector (∼10.6-kb synthetic operon). To enable researchers with limited resources to engage in chloroplast biotechnology, and to accelerate progress in the field, the entire kit, as described, is available through Addgene at minimal cost. Thus, the MoChlo kit represents a valuable tool for fast and flexible design of heterologous metabolic pathways for plastid metabolic engineering.
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Affiliation(s)
- Alessandro Occhialini
- Department of Food Science, University of Tennessee, Knoxville, Tennessee 37996
- Center for Agricultural Synthetic Biology, Institute of Agriculture, University of Tennessee, Knoxville, Tennessee 37996
| | - Agnieszka A Piatek
- Department of Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996
| | - Alexander C Pfotenhauer
- Department of Food Science, University of Tennessee, Knoxville, Tennessee 37996
- Center for Agricultural Synthetic Biology, Institute of Agriculture, University of Tennessee, Knoxville, Tennessee 37996
| | - Taylor P Frazier
- Center for Agricultural Synthetic Biology, Institute of Agriculture, University of Tennessee, Knoxville, Tennessee 37996
- Department of Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996
- Elo Life Systems, Durham, North Carolina 27709
| | - C Neal Stewart
- Center for Agricultural Synthetic Biology, Institute of Agriculture, University of Tennessee, Knoxville, Tennessee 37996
- Department of Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996
| | - Scott C Lenaghan
- Department of Food Science, University of Tennessee, Knoxville, Tennessee 37996
- Center for Agricultural Synthetic Biology, Institute of Agriculture, University of Tennessee, Knoxville, Tennessee 37996
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Esland L, Larrea-Alvarez M, Purton S. Selectable Markers and Reporter Genes for Engineering the Chloroplast of Chlamydomonas reinhardtii. BIOLOGY 2018; 7:E46. [PMID: 30309004 PMCID: PMC6315944 DOI: 10.3390/biology7040046] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 10/02/2018] [Accepted: 10/03/2018] [Indexed: 02/07/2023]
Abstract
Chlamydomonas reinhardtii is a model alga of increasing interest as a cell factory for the production of valuable compounds, including therapeutic proteins and bioactive metabolites. Expression of foreign genes in the chloroplast is particularly advantageous as: (i) accumulation of product in this sub-cellular compartment minimises potential toxicity to the rest of the cell; (ii) genes can integrate at specific loci of the chloroplast genome (plastome) by homologous recombination; (iii) the high ploidy of the plastome and the high-level expression of chloroplast genes can be exploited to achieve levels of recombinant protein as high as 5% total cell protein; (iv) the lack of any gene silencing mechanisms in the chloroplast ensures stable expression of transgenes. However, the generation of C. reinhardtii chloroplast transformants requires efficient methods of selection, and ideally methods for subsequent marker removal. Additionally, the use of reporter genes is critical to achieving a comprehensive understanding of gene expression, thereby informing experimental design for recombinant applications. This review discusses currently available selection and reporter systems for chloroplast engineering in C. reinhardtii, as well as those used for chloroplast engineering in higher plants and other microalgae, and looks to the future in terms of possible new markers and reporters that will further advance the C. reinhardtii chloroplast as an expression platform.
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Affiliation(s)
- Lola Esland
- Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
| | - Marco Larrea-Alvarez
- School of Biological Sciences and Engineering, Yachay-Tech University, Hacienda San José, Urcuquí-Imbabura 100650, Ecuador.
| | - Saul Purton
- Institute of Structural & Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
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Fuentes P, Armarego-Marriott T, Bock R. Plastid transformation and its application in metabolic engineering. Curr Opin Biotechnol 2018; 49:10-15. [DOI: 10.1016/j.copbio.2017.07.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 06/14/2017] [Accepted: 07/03/2017] [Indexed: 12/31/2022]
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12
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El Hajj M, Hamdan MFB, Avila EM, Day A. Rescue of Deletion Mutants to Isolate Plastid Transformants in Higher Plants. Methods Mol Biol 2018; 1829:325-339. [PMID: 29987732 DOI: 10.1007/978-1-4939-8654-5_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Plastid transformation is an attractive alternative to nuclear transformation enabling manipulation of native plastid genes and the insertion of foreign genes into plastids for applications in agriculture and industrial biotechnology. Transformation is achieved using dominant positive selection markers that confer resistance to antibiotics. The very high copy number of plastid DNA means that a prolonged selection step is required to obtain a uniform population of transgenic plastid genomes. Repair of mutant plastid genes with the corresponding functional allele allows selection based on restoration of the wild type phenotype. The use of deletion rather than point mutants avoids spontaneous reversion back to wild type. Combining antibiotic resistance markers with native plastid genes speeds up the attainment of homoplasmy and allows early transfer of transplastomic lines to soil where antibiotic selection is replaced by selection for photoautotrophic growth. Here we describe our method using the wild type rbcL gene as a plastid transformation marker to restore pigmentation and photosynthesis to a pale green heterotrophic rbcL mutant.
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Affiliation(s)
- Mohammad El Hajj
- School of Biological Sciences, The University of Manchester, Manchester, UK
| | | | - Elena Martin Avila
- School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Anil Day
- School of Biological Sciences, The University of Manchester, Manchester, UK.
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Shao M, Blechl A, Thomson JG. Small serine recombination systems ParA-MRS and CinH-RS2 perform precise excision of plastid DNA. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:1577-1589. [PMID: 28421718 PMCID: PMC5698047 DOI: 10.1111/pbi.12740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 06/07/2023]
Abstract
Selectable marker genes (SMGs) are necessary for selection of transgenic plants. However, once stable transformants have been identified, the marker gene is no longer needed. In this study, we demonstrate the use of the small serine recombination systems, ParA-MRS and CinH-RS2, to precisely excise a marker gene from the plastid genome of tobacco. Transplastomic plants transformed with the pTCH-MRS and pTCH-RS2 vectors, containing the visual reporter gene DsRed flanked by directly oriented MRS and RS2 recognition sites, respectively, were crossed with nuclear-genome transformed tobacco plants expressing plastid-targeted ParA and CinH recombinases, respectively. One hundred per cent of both types of F1 hybrids exhibited excision of the DsRed marker gene. PCR and Southern blot analyses of DNA from F2 plants showed that approximately 30% (CinH-RS2) or 40% (ParA-MRS) had lost the recombinase genes by segregation. The postexcision transformed plastid genomes were stable and the excision events heritable. The ParA-MRS and CinH-RS2 recombination systems will be useful tools for site-specific manipulation of the plastid genome and for generating marker-free plants, an essential step for reuse of SMG and for addressing concerns about the presence of antibiotic resistance genes in transgenic plants.
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Affiliation(s)
- Min Shao
- UC Davis Department of Plant SciencesDavisCAUSA
| | - Ann Blechl
- USDA‐WRRC‐ARS Crop Improvement and Genetics Research UnitAlbanyCAUSA
| | - James G. Thomson
- USDA‐WRRC‐ARS Crop Improvement and Genetics Research UnitAlbanyCAUSA
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14
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Zhang W, Zhao Z, Yang Y, Liu X, Bai Z. Construction of an expression vector that uses the aph promoter for protein expression in Corynebacterium glutamicum. Plasmid 2017; 94:1-6. [PMID: 28986243 DOI: 10.1016/j.plasmid.2017.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 09/10/2017] [Accepted: 09/30/2017] [Indexed: 01/21/2023]
Abstract
Corynebacterium glutamicum is an attractive host for the production of heterologous proteins despite its traditional use in fermentative production of amino acids. To enhance the expression levels of target genes, the development of useful promoters is required in the construction of expression systems. Here, we developed a new promoter, the aph promoter from aminoglycoside-3'-phosphotransferase gene, and used it to construct monocistronic and bicistronic expression systems that host different ribosome binding site (RBS) sequences. First, the expression level of the reporter protein, enhanced green fluorescent protein (EGFP), varied with changes in the RBS sequences in the constructed vectors. The results showed that the fluorescence intensities of the bicistronic group were higher than those of the monocistronic group and that RM3E showed the highest fluorescence intensity, which was 42-fold higher than the lowest (RA2E') among these groups. Next, taking advantage of the optimized aph promoter, we successfully employed this aph promoter for α-amylase and VHH (camelid antibody fragment) expression. The secretion of α-amylase improved 1.5-fold after promoter mutation. This promoter will be useful for heterologous protein production in C. glutamicum cells.
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Affiliation(s)
- Wei Zhang
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Zihao Zhao
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Yankun Yang
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xiuxia Liu
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
| | - Zhonghu Bai
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
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Zhang L, Rylott EL, Bruce NC, Strand SE. Phytodetoxification of TNT by transplastomic tobacco (Nicotiana tabacum) expressing a bacterial nitroreductase. PLANT MOLECULAR BIOLOGY 2017; 95:99-109. [PMID: 28762129 DOI: 10.1007/s11103-017-0639-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 07/19/2017] [Indexed: 06/07/2023]
Abstract
KEY MESSAGE Expression of the bacterial nitroreductase gene, nfsI, in tobacco plastids conferred the ability to detoxify TNT. The toxic pollutant 2,4,6-trinitrotoluene (TNT) is recalcitrant to degradation in the environment. Phytoremediation is a potentially low cost remediation technique that could be applied to soil contaminated with TNT; however, progress is hindered by the phytotoxicity of this compound. Previous studies have demonstrated that plants transformed with the bacterial nitroreductase gene, nfsI have increased ability to tolerate and detoxify TNT. It has been proposed that plants engineered to express nfsI could be used to remediate TNT on military ranges, but this could require steps to mitigate transgene flow to wild populations. To address this, we have developed nfsI transplastomic tobacco (Nicotiana tabacum L.) to reduce pollen-borne transgene flow. Here we have shown that when grown on solid or liquid media, the transplastomic tobacco expressing nfsI were significantly more tolerant to TNT, produced increased biomass and removed more TNT from the media than untransformed plants. Additionally, transplastomic plants expressing nfsI regenerated with high efficiency when grown on medium containing TNT, suggesting that nfsI and TNT could together be used to provide a selectable screen for plastid transformation.
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Affiliation(s)
- Long Zhang
- Department of Civil and Environmental Engineering, University of Washington, Box 355014, Seattle, WA, 98195-5014, USA
| | | | - Neil C Bruce
- CNAP, Department of Biology, University of York, York, YO10 5DD, UK
| | - Stuart E Strand
- Department of Civil and Environmental Engineering, University of Washington, Box 355014, Seattle, WA, 98195-5014, USA.
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