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Chakraborty C, Das A, Basak C, Roy S, Agarwal T, Ray S. Chloroplastic RecA protein from Physcomitrium patens is able to repair chloroplastic DNA damage by homologous recombination but unable to repair nuclear DNA damage. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2022; 28:2057-2067. [PMID: 36573145 PMCID: PMC9789214 DOI: 10.1007/s12298-022-01264-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/05/2022] [Accepted: 12/05/2022] [Indexed: 06/17/2023]
Abstract
Plants are unavoidably exposed to a range of environmental stress factors throughout their life. In addition to the external environmental factors, the production of reactive oxygen species as a product of the cellular metabolic process often causes DNA damage and thus affects genome stability. Homologous recombination (HR) is an essential mechanism used for DNA damage repair that helps to maintain genome integrity. Here we report that the recombinase, PpRecA2, a bacterial RecA homolog from moss Physcomitrium patens can partially complement the function of Escherichia coli RecA in the bacterial system. Transcript analysis showed induced expression of PpRecA2 upon experiencing DNA damaging stressors indicating its involvement in DNA damage sensing and repair mechanism. Over-expressing the chloroplast localizing PpRecA2 confers protection to the chloroplast genome against DNA damage by enhancing the chloroplastic HR frequency in transgenic tobacco plants. Although it fails to protect against nuclear DNA damage when engineered for nuclear localization due to the non-availability of interacting partners. Our results indicate that the chloroplastic HR repair mechanism differs from the nucleus, where chloroplastic HR involves RecA as a key player that resembles the bacterial system. Supplementary Information The online version contains supplementary material available at 10.1007/s12298-022-01264-7.
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Affiliation(s)
- Chandrima Chakraborty
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
| | - Arup Das
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
| | - Chandra Basak
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
| | - Shuddhanjali Roy
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
| | - Tanushree Agarwal
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
| | - Sudipta Ray
- Plant Functional Genomics Laboratory, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal 700019 India
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Ren K, Xu W, Ren B, Fu J, Jiang C, Zhang J. A simple technology for plastid transformation with fragmented DNA. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:6078-6088. [PMID: 35689813 DOI: 10.1093/jxb/erac256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Plastid engineering has several unique advantages such as high expression of transgenes due to high polyploidy of plastid genomes and environmental biosafety because of maternal inheritance of transgenes, and has become a promising tool for molecular farming, metabolic engineering, and genetic improvement. However, there are no standard vectors available for plastid transformation. Moreover, the construction of plastid transformation vectors containing long operons or genes encoding proteins that are toxic to Escherichia coli was tedious or difficult. Here, we developed a simple plastid transformation technology without the need for in vitro vector construction by using multiple linear DNA fragments which share homologous sequences (HSs) at their ends. The strategy is based on homologous recombination between HSs of DNA fragments via endogenous recombination machinery in plastids, which subsequently are integrated into the plastid genome. We found that HSs of 200 bp or longer were sufficient for mediating the integration into the plastid genome with at least similar efficiency to that of plasmid DNA-based plastid transformation. Furthermore, we successfully used this method to introduce a phage lysin-encoding gene and a long operon into a tobacco plastid genome. The establishment of this technology simplifies the plastid transformation procedure and provides a novel solution for expressing proteins, which are either toxic to the cloning host or large operons in plastids, without need of vector cloning.
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Affiliation(s)
- Kang Ren
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Wenbo Xu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Bailing Ren
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Jinqiu Fu
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Chunmei Jiang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Jiang Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
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Montenegro JD, Julca I, Chumbe-Nolasco LD, Rodríguez-Pérez LM, Sevilla Panizo R, Medina-Hoyos A, Gutiérrez-Reynoso DL, Guerrero-Abad JC, Amasifuen Guerra CA, García-Serquén AL. Phylogenomic Analysis of the Plastid Genome of the Peruvian Purple Maize Zea mays subsp. mays cv. 'INIA 601'. PLANTS (BASEL, SWITZERLAND) 2022; 11:2727. [PMID: 36297753 PMCID: PMC9612013 DOI: 10.3390/plants11202727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/03/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Peru is an important center of diversity for maize; its different cultivars have been adapted to distinct altitudes and water availability and possess an array of kernel colors (red, blue, and purple), which are highly appreciated by local populations. Specifically, Peruvian purple maize is a collection of native landraces selected and maintained by indigenous cultures due to its intense purple color in the seed, bract, and cob. This color is produced by anthocyanin pigments, which have gained interest due to their potential use in the food, agriculture, and pharmaceutical industry. It is generally accepted that the Peruvian purple maize originated from a single ancestral landrace 'Kculli', but it is not well understood. To study the origin of the Peruvian purple maize, we assembled the plastid genomes of the new cultivar 'INIA 601' with a high concentration of anthocyanins, comparing them with 27 cultivars/landraces of South America, 9 Z. mays subsp. parviglumis, and 5 partial genomes of Z. mays subsp. mexicana. Using these genomes, plus four other maize genomes and two outgroups from the NCBI database, we reconstructed the phylogenetic relationship of Z. mays. Our results suggest a polyphyletic origin of purple maize in South America and agree with a complex scenario of domestication with recurrent gene flow from wild relatives. Additionally, we identify 18 plastid positions that can be used as high-confidence genetic markers for further studies. Altogether, these plastid genomes constitute a valuable resource to study the evolution and domestication of Z. mays in South America.
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Affiliation(s)
- Juan D. Montenegro
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
- Department of Neurosciences and Developmental Biology, University of Vienna, Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Irene Julca
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Lenin D. Chumbe-Nolasco
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
| | - Lila M. Rodríguez-Pérez
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
| | - Ricardo Sevilla Panizo
- Departamento de Fitotecnia, Facultad de Agronomía, Universidad Nacional Agraria La Molina, Av. La Molina s/n, Lima 15024, Peru
| | - Alicia Medina-Hoyos
- Estación Experimental Agraria “Baños del Inca”, Instituto Nacional de Innovación Agraria (INIA), Km. 5.5 Carretera Cajamarca–Celendín, Cajamarca 06000, Peru
| | - Dina L. Gutiérrez-Reynoso
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
| | - Juan Carlos Guerrero-Abad
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
| | - Carlos A. Amasifuen Guerra
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
| | - Aura L. García-Serquén
- Laboratorio de Biología Molecular y Genómica, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria (INIA), Av. La Molina 1981, Lima 15024, Peru
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Stable Plastid Transformation of Petunia for Studies in Basic Research. Methods Mol Biol 2021. [PMID: 34028772 DOI: 10.1007/978-1-0716-1472-3_12] [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
Petunia hybrida is a commercial ornamental plant and is also an important model species for genetic analysis and transgenic research. Here we describe the steps required to isolate stable plastid transformants in P. hybrida using the commercial Pink Wave cultivar. Wave cultivars are popular spreading Petunias sold as ground cover and potted plants. Transgenes introduced into P. hybrida plastids exhibit stable expression over many generations. The development of plastid transformation in P. hybrida provides an enabling technology to bring the benefits of plastid engineering, including maternal inheritance and stable expression of performance-enhancing trait genes, to the important floriculture and horticulture industries.
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Abstract
The plastid genome (plastome ) has proved a valuable source of data for evaluating evolutionary relationships among angiosperms. Through basic and applied approaches, plastid transformation technology offers the potential to understand and improve plant productivity, providing food, fiber, energy, and medicines to meet the needs of a burgeoning global population. The growing genomic resources available to both phylogenetic and biotechnological investigations is allowing novel insights and expanding the scope of plastome research to encompass new species. In this chapter, we present an overview of some of the seminal and contemporary research that has contributed to our current understanding of plastome evolution and attempt to highlight the relationship between evolutionary mechanisms and the tools of plastid genetic engineering.
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Affiliation(s)
- Tracey A Ruhlman
- Integrative Biology, University of Texas at Austin, Austin, TX, USA.
| | - Robert K Jansen
- Integrative Biology, University of Texas at Austin, Austin, TX, USA
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6
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Transmission of Engineered Plastids in Sugarcane, a C 4 Monocotyledonous Plant, Reveals that Sorting of Preprogrammed Progenitor Cells Produce Heteroplasmy. PLANTS 2020; 10:plants10010026. [PMID: 33374390 PMCID: PMC7830296 DOI: 10.3390/plants10010026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 11/13/2020] [Accepted: 11/14/2020] [Indexed: 12/15/2022]
Abstract
We report here plastid transformation in sugarcane using biolistic transformation and embryogenesis-based regeneration approaches. Somatic embryos were developed from unfurled leaf sections, containing preprogrammed progenitor cells, to recover transformation events on antibiotic-containing regeneration medium. After developing a proficient regeneration system, the FLARE-S (fluorescent antibiotic resistance enzyme, spectinomycin and streptomycin) expression cassette that carries species-specific homologous sequence tails was used to transform plastids and track gene transmission and expression in sugarcane. Plants regenerated from streptomycin-resistant and genetically confirmed shoots were subjected to visual detection of the fluorescent enzyme using a fluorescent stereomicroscope, after genetic confirmation. The resultant heteroplasmic shoots remained to segregate on streptomycin-containing MS medium, referring to the unique pattern of division and sorting of cells in C4 monocotyledonous compared to C3 monocotyledonous and dicotyledonous plants since in sugarcane bundle sheath and mesophyll, cells are distinct and sort independently after division. Hence, the transformation of either mesophyll or bundle sheath cells will develop heteroplasmic transgenic plants, suggesting the transformation of both types of cells. Whilst developed transgenic sugarcane plants are heteroplasmic, and selection-based regeneration protocol envisaging the role of division and sorting of cells in the purification of transplastomic demands further improvement, the study has established many parameters that may open up exciting possibilities to express genes of agricultural or pharmaceutical importance in sugarcane.
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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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Narra M, Kota S, Velivela Y, Ellendula R, Allini VR, Abbagani S. Construction of chloroplast transformation vector and its functional evaluation in Momordica charantia L. 3 Biotech 2018; 8:140. [PMID: 29484279 PMCID: PMC5817051 DOI: 10.1007/s13205-018-1160-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Accepted: 02/06/2018] [Indexed: 12/20/2022] Open
Abstract
Chloroplast transformation vectors require an expression cassette flanked by homologous plastid sequences to drive plastome recombination. The rrn16-rrn23 plastome region was selected and using this region, a new species-specific plastid transformation vector CuIA was developed with pKS+II as a backbone by inserting the rrn16-trnI and trnA-rrn23 sequences from Cucumis sativus L. An independent expression cassette with aadA gene encoding aminoglycoside 3'-adenylyltransferase with psbA controlling elements is added into the trnI-trnA intergenic region that confers resistance to spectinomycin. An efficient plastid transformation in bitter melon (Momordica charantia L.) was achieved by bombardment of petiole segments. The frequency of transplastomic plants yielded using standardized biolistic parameters with CuIA vector was two per 15 bombarded plates, each containing 20 petiole explants. Integration of aadA gene was verified by PCR analysis in transplastomes. Transplastomic technology developed may be a novel approach for high level expression of pharmaceutical traits.
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Affiliation(s)
| | - Srinivas Kota
- Department of Biotechnology, Kakatiya University, Warangal, 506009 India
| | | | - Raghu Ellendula
- Department of Biotechnology, Kakatiya University, Warangal, 506009 India
| | - V. Rao Allini
- Department of Biotechnology, Kakatiya University, Warangal, 506009 India
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Ruhlman TA, Zhang J, Blazier JC, Sabir JSM, Jansen RK. Recombination-dependent replication and gene conversion homogenize repeat sequences and diversify plastid genome structure. AMERICAN JOURNAL OF BOTANY 2017; 104:559-572. [PMID: 28400415 DOI: 10.3732/ajb.1600453] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 02/23/2017] [Indexed: 05/21/2023]
Abstract
PREMISE OF THE STUDY There is a misinterpretation in the literature regarding the variable orientation of the small single copy region of plastid genomes (plastomes). The common phenomenon of small and large single copy inversion, hypothesized to occur through intramolecular recombination between inverted repeats (IR) in a circular, single unit-genome, in fact, more likely occurs through recombination-dependent replication (RDR) of linear plastome templates. If RDR can be primed through both intra- and intermolecular recombination, then this mechanism could not only create inversion isomers of so-called single copy regions, but also an array of alternative sequence arrangements. METHODS We used Illumina paired-end and PacBio single-molecule real-time (SMRT) sequences to characterize repeat structure in the plastome of Monsonia emarginata (Geraniaceae). We used OrgConv and inspected nucleotide alignments to infer ancestral nucleotides and identify gene conversion among repeats and mapped long (>1 kb) SMRT reads against the unit-genome assembly to identify alternative sequence arrangements. RESULTS Although M. emarginata lacks the canonical IR, we found that large repeats (>1 kilobase; kb) represent ∼22% of the plastome nucleotide content. Among the largest repeats (>2 kb), we identified GC-biased gene conversion and mapping filtered, long SMRT reads to the M. emarginata unit-genome assembly revealed alternative, substoichiometric sequence arrangements. CONCLUSION We offer a model based on RDR and gene conversion between long repeated sequences in the M. emarginata plastome and provide support that both intra-and intermolecular recombination between large repeats, particularly in repeat-rich plastomes, varies unit-genome structure while homogenizing the nucleotide sequence of repeats.
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Affiliation(s)
- Tracey A Ruhlman
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712 USA
| | - Jin Zhang
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712 USA
| | - John C Blazier
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712 USA
| | - Jamal S M Sabir
- Biotechnology Research Group, Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589 Saudi Arabia
| | - Robert K Jansen
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas 78712 USA
- Biotechnology Research Group, Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589 Saudi Arabia
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Muralikrishna N, Srinivas K, Kumar KB, Sadanandam A. Stable plastid transformation in Scoparia dulcis L. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2016; 22:575-581. [PMID: 27924130 PMCID: PMC5120043 DOI: 10.1007/s12298-016-0386-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 09/28/2016] [Accepted: 10/10/2016] [Indexed: 05/16/2023]
Abstract
In the present investigation we report stable plastid transformation in Scoparia dulcis L., a versatile medicinal herb via particle gun method. The vector KNTc, harbouring aadA as a selectable marker and egfp as a reporter gene which were under the control of synthetic promoter pNG1014a, targets inverted repeats, trnR/trnN of the plastid genome. By use of this heterologous vector, recovery of transplastomic lines with suitable selection protocol have been successfully established with overall efficiency of two transgenic lines for 25 bombarded leaf explants. PCR and Southern blot analysis demonstrated stable integration of foreign gene into the target sequences. The results represent a significant advancement of the plastid transformation technology in medicinal plants, which relevantly implements a change over in enhancing and regulating of certain metabolic pathways.
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Affiliation(s)
| | - Kota Srinivas
- Department of Biotechnology, Kakatiya University, Warangal, 506009 India
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Daniell H, Lin CS, Yu M, Chang WJ. Chloroplast genomes: diversity, evolution, and applications in genetic engineering. Genome Biol 2016; 17:134. [PMID: 27339192 PMCID: PMC4918201 DOI: 10.1186/s13059-016-1004-2] [Citation(s) in RCA: 750] [Impact Index Per Article: 93.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chloroplasts play a crucial role in sustaining life on earth. The availability of over 800 sequenced chloroplast genomes from a variety of land plants has enhanced our understanding of chloroplast biology, intracellular gene transfer, conservation, diversity, and the genetic basis by which chloroplast transgenes can be engineered to enhance plant agronomic traits or to produce high-value agricultural or biomedical products. In this review, we discuss the impact of chloroplast genome sequences on understanding the origins of economically important cultivated species and changes that have taken place during domestication. We also discuss the potential biotechnological applications of chloroplast genomes.
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Affiliation(s)
- Henry Daniell
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, South 40th St, Philadelphia, PA, 19104-6030, USA.
| | - Choun-Sea Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan
| | - Ming Yu
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, South 40th St, Philadelphia, PA, 19104-6030, USA
| | - Wan-Jung Chang
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan
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Bock R. Engineering plastid genomes: methods, tools, and applications in basic research and biotechnology. ANNUAL REVIEW OF PLANT BIOLOGY 2015; 66:211-41. [PMID: 25494465 DOI: 10.1146/annurev-arplant-050213-040212] [Citation(s) in RCA: 218] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The small bacterial-type genome of the plastid (chloroplast) can be engineered by genetic transformation, generating cells and plants with transgenic plastid genomes, also referred to as transplastomic plants. The transformation process relies on homologous recombination, thereby facilitating the site-specific alteration of endogenous plastid genes as well as the precisely targeted insertion of foreign genes into the plastid DNA. The technology has been used extensively to analyze chloroplast gene functions and study plastid gene expression at all levels in vivo. Over the years, a large toolbox has been assembled that is now nearly comparable to the techniques available for plant nuclear transformation and that has enabled new applications of transplastomic technology in basic and applied research. This review describes the state of the art in engineering the plastid genomes of algae and land plants (Embryophyta). It provides an overview of the existing tools for plastid genome engineering, discusses current technological limitations, and highlights selected applications that demonstrate the immense potential of chloroplast transformation in several key areas of plant biotechnology.
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Affiliation(s)
- Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany;
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13
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Abstract
Petunia hybrida is a commercial ornamental plant and is also an important model species for genetic analysis and transgenic research. Here we describe the steps required to isolate stable plastid transformants in P. hybrida using the commercial Pink Wave cultivar. Wave cultivars are popular spreading Petunias sold as ground cover and potted plants. Transgenes introduced into P. hybrida plastids exhibit stable expression over many generations. The development of plastid transformation in P. hybrida provides an enabling technology to bring the benefits of plastid engineering, including maternal inheritance and stable expression of performance-enhancing trait genes, to the important floriculture and horticulture industries.
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14
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Abstract
The plastid genome (plastome) has proved a valuable source of data for evaluating evolutionary relationships among angiosperms. Through basic and applied approaches, plastid transformation technology offers the potential to understand and improve plant productivity, providing food, fiber, energy and medicines to meet the needs of a burgeoning global population. The growing genomic resources available to both phylogenetic and biotechnological investigations are allowing novel insights and expanding the scope of plastome research to encompass new species. In this chapter we present an overview of some of the seminal and contemporary research that has contributed to our current understanding of plastome evolution and attempt to highlight the relationship between evolutionary mechanisms and tools of plastid genetic engineering.
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Affiliation(s)
- Tracey A Ruhlman
- Integrative Biology, University of Texas at Austin, Austin, TX, USA
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15
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Segretin ME, Lentz EM, Wirth SA, Morgenfeld MM, Bravo-Almonacid FF. Transformation of Solanum tuberosum plastids allows high expression levels of β-glucuronidase both in leaves and microtubers developed in vitro. PLANTA 2012; 235:807-18. [PMID: 22071556 DOI: 10.1007/s00425-011-1541-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 10/21/2011] [Indexed: 05/03/2023]
Abstract
Plastid genome transformation offers an attractive methodology for transgene expression in plants, but for potato, only expression of gfp transgene (besides the selective gene aadA) has been published. We report here successful expression of β-glucuronidase in transplastomic Solanum tuberosum (var. Desiree) plants, with accumulation levels for the recombinant protein of up to 41% of total soluble protein in mature leaves. To our knowledge, this is the highest expression level reported for a heterologous protein in S. tuberosum. Accumulation of the recombinant protein in soil-grown minitubers was very low, as described in previous reports. Interestingly, microtubers developed in vitro showed higher accumulation of β-glucuronidase. As light exposure during their development could be the trigger for this high accumulation, we analyzed the effect of light on β-glucuronidase accumulation in transplastomic tubers. Exposure to light for 8 days increased β-glucuronidase accumulation in soil-grown tubers, acting as a light-inducible expression system for recombinant protein accumulation in tuber plastids. In this paper we show that plastid transformation in potato allows the highest recombinant protein accumulation in foliar tissue described so far for this food crop. We also demonstrate that in tubers high accumulation is possible and depends on light exposure. Because tubers have many advantages as protein storage organs, these results could lead to new recombinant protein production schemes based on potato.
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Affiliation(s)
- María Eugenia Segretin
- Laboratorio de Biotecnología Vegetal, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular-INGEBI-CONICET, Vuelta de Obligado 2490, 2do. Piso, C1428ADN, Ciudad Autónoma de Buenos Aires, Argentina.
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Valkov VT, Gargano D, Manna C, Formisano G, Dix PJ, Gray JC, Scotti N, Cardi T. High efficiency plastid transformation in potato and regulation of transgene expression in leaves and tubers by alternative 5' and 3' regulatory sequences. Transgenic Res 2011; 20:137-51. [PMID: 20464632 DOI: 10.1007/s11248-010-9402-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 04/22/2010] [Indexed: 11/28/2022]
Abstract
Transformation of potato plastids is limited by low transformation frequencies and low transgene expression in tubers. In order to improve the transformation efficiency, we modified the regeneration procedure and prepared novel vectors containing potato flanking sequences for transgene integration by homologous recombination in the Large Single Copy region of the plastome. Vector delivery was performed by the biolistic approach. By using the improved regeneration procedure and the potato flanking sequences, we regenerated about one shoot every bombardment. This efficiency corresponds to 15-18-fold improvement compared to previous results with potato and is comparable to that usually achieved with tobacco. Further, we tested five promoters and terminators, and four 5'-UTRs, to increase the expression of the gfp transgene in tubers. In leaves, accumulation of GFP to about 4% of total soluble protein (TSP) was obtained with the strong promoter of the rrn operon, a synthetic rbcL-derived 5'-UTR and the bacterial rrnB terminator. GFP protein was detected in tubers of plants transformed with only four constructs out of eleven. Best results (up to approximately 0.02% TSP) were achieved with the rrn promoter and rbcL 5'-UTR construct, described above, and another containing the same terminator, but with the promoter and 5'-UTR from the plastid clpP gene. The results obtained suggest the potential use of clpP as source of novel regulatory sequences in constructs aiming to express transgenes in amyloplasts and other non-green plastids. Furthermore, they represent a significant advancement of the plastid transformation technology in potato, of relevance to its implementation in potato breeding and biotechnology.
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Affiliation(s)
- Vladimir T Valkov
- CNR-IGV, Institute of Plant Genetics, Res. Div. Portici, via Università 133, 80055, Portici, Italy
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18
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Tungsuchat-Huang T, Sinagawa-García SR, Paredes-López O, Maliga P. Study of plastid genome stability in tobacco reveals that the loss of marker genes is more likely by gene conversion than by recombination between 34-bp loxP repeats. PLANT PHYSIOLOGY 2010; 153:252-9. [PMID: 20228154 PMCID: PMC2862435 DOI: 10.1104/pp.109.152892] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 03/01/2010] [Indexed: 05/28/2023]
Abstract
In transformed tobacco (Nicotiana tabacum) plastids, we flank the marker genes with recombinase target sites to facilitate their posttransformation excision. The P1 phage loxP sites are identical 34-bp direct repeats, whereas the phiC31 phage attB/attP sites are 54- and 215-bp sequences with partial homology within the 54-bp region. Deletions in the plastid genome are known to occur by recombination between directly repeated sequences. Our objective was to test whether or not the marker genes may be lost by homologous recombination via the directly repeated target sites in the absence of site-specific recombinases. The sequence between the target sites was the bar(au) gene that causes a golden-yellow (aurea) leaf color, so that the loss of the bar(au) gene can be readily detected by the appearance of green sectors. We report here that transplastomes carrying the bar(au) gene marker between recombinase target sites are relatively stable because no green sectors were detected in approximately 36,000 seedlings (Nt-pSS33 lines) carrying attB/attP-flanked bar(au) gene and in approximately 38,000 seedlings (Nt-pSS42 lines) carrying loxP-flanked bar(au) gene. Exceptions were six uniformly green plants in the Nt-pSS42-7A progeny. Sequencing the region of plastid DNA that may derive from the vector indicated that the bar(au) gene in the six green plants was lost by gene conversion using wild-type plastid DNA as template rather than by deletion via directly repeated loxP sites. Thus, the recombinase target sites incorporated in the plastid genome for marker gene excisions are too short to mediate the loss of marker genes by homologous recombination at a measurable frequency.
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Affiliation(s)
| | | | | | - Pal Maliga
- Waksman Institute, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854–8020 (T.T.-H., S.R.S.-G., P.M.); Departmento de Biotecnología y Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 36500 Irapuato, Mexico (S.R.S.-G., O.P.-L.)
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Ruhlman T, Verma D, Samson N, Daniell H. The role of heterologous chloroplast sequence elements in transgene integration and expression. PLANT PHYSIOLOGY 2010; 152:2088-104. [PMID: 20130101 PMCID: PMC2850035 DOI: 10.1104/pp.109.152017] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 01/30/2010] [Indexed: 05/15/2023]
Abstract
Heterologous regulatory elements and flanking sequences have been used in chloroplast transformation of several crop species, but their roles and mechanisms have not yet been investigated. Nucleotide sequence identity in the photosystem II protein D1 (psbA) upstream region is 59% across all taxa; similar variation was consistent across all genes and taxa examined. Secondary structure and predicted Gibbs free energy values of the psbA 5' untranslated region (UTR) among different families reflected this variation. Therefore, chloroplast transformation vectors were made for tobacco (Nicotiana tabacum) and lettuce (Lactuca sativa), with endogenous (Nt-Nt, Ls-Ls) or heterologous (Nt-Ls, Ls-Nt) psbA promoter, 5' UTR and 3' UTR, regulating expression of the anthrax protective antigen (PA) or human proinsulin (Pins) fused with the cholera toxin B-subunit (CTB). Unique lettuce flanking sequences were completely eliminated during homologous recombination in the transplastomic tobacco genomes but not unique tobacco sequences. Nt-Ls or Ls-Nt transplastomic lines showed reduction of 80% PA and 97% CTB-Pins expression when compared with endogenous psbA regulatory elements, which accumulated up to 29.6% total soluble protein PA and 72.0% total leaf protein CTB-Pins, 2-fold higher than Rubisco. Transgene transcripts were reduced by 84% in Ls-Nt-CTB-Pins and by 72% in Nt-Ls-PA lines. Transcripts containing endogenous 5' UTR were stabilized in nonpolysomal fractions. Stromal RNA-binding proteins were preferentially associated with endogenous psbA 5' UTR. A rapid and reproducible regeneration system was developed for lettuce commercial cultivars by optimizing plant growth regulators. These findings underscore the need for sequencing complete crop chloroplast genomes, utilization of endogenous regulatory elements and flanking sequences, as well as optimization of plant growth regulators for efficient chloroplast transformation.
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Affiliation(s)
| | | | | | - Henry Daniell
- Department of Molecular Biology and Microbiology, College of Medicine, University of Central Florida, Orlando, Florida 32816–2364
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Kumar S, Hahn FM, McMahan CM, Cornish K, Whalen MC. Comparative analysis of the complete sequence of the plastid genome of Parthenium argentatum and identification of DNA barcodes to differentiate Parthenium species and lines. BMC PLANT BIOLOGY 2009; 9:131. [PMID: 19917140 PMCID: PMC2784773 DOI: 10.1186/1471-2229-9-131] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 11/17/2009] [Indexed: 05/03/2023]
Abstract
BACKGROUND Parthenium argentatum (guayule) is an industrial crop that produces latex, which was recently commercialized as a source of latex rubber safe for people with Type I latex allergy. The complete plastid genome of P. argentatum was sequenced. The sequence provides important information useful for genetic engineering strategies. Comparison to the sequences of plastid genomes from three other members of the Asteraceae, Lactuca sativa, Guitozia abyssinica and Helianthus annuus revealed details of the evolution of the four genomes. Chloroplast-specific DNA barcodes were developed for identification of Parthenium species and lines. RESULTS The complete plastid genome of P. argentatum is 152,803 bp. Based on the overall comparison of individual protein coding genes with those in L. sativa, G. abyssinica and H. annuus, we demonstrate that the P. argentatum chloroplast genome sequence is most closely related to that of H. annuus. Similar to chloroplast genomes in G. abyssinica, L. sativa and H. annuus, the plastid genome of P. argentatum has a large 23 kb inversion with a smaller 3.4 kb inversion, within the large inversion. Using the matK and psbA-trnH spacer chloroplast DNA barcodes, three of the four Parthenium species tested, P. tomentosum, P. hysterophorus and P. schottii, can be differentiated from P. argentatum. In addition, we identified lines within P. argentatum. CONCLUSION The genome sequence of the P. argentatum chloroplast will enrich the sequence resources of plastid genomes in commercial crops. The availability of the complete plastid genome sequence may facilitate transformation efficiency by using the precise sequence of endogenous flanking sequences and regulatory elements in chloroplast transformation vectors. The DNA barcoding study forms the foundation for genetic identification of commercially significant lines of P. argentatum that are important for producing latex.
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Affiliation(s)
- Shashi Kumar
- Crop Improvement and Utilization Research Unit, Western Regional Research Center, ARS, USDA, 800 Buchanan Street, Albany CA 94710, USA
- Yulex Corporation, 37860 W Smith-Enke Road, Maricopa, AZ 85238-3010, USA
| | - Frederick M Hahn
- Crop Improvement and Utilization Research Unit, Western Regional Research Center, ARS, USDA, 800 Buchanan Street, Albany CA 94710, USA
| | - Colleen M McMahan
- Crop Improvement and Utilization Research Unit, Western Regional Research Center, ARS, USDA, 800 Buchanan Street, Albany CA 94710, USA
| | - Katrina Cornish
- Yulex Corporation, 37860 W Smith-Enke Road, Maricopa, AZ 85238-3010, USA
| | - Maureen C Whalen
- Crop Improvement and Utilization Research Unit, Western Regional Research Center, ARS, USDA, 800 Buchanan Street, Albany CA 94710, USA
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Sinagawa-García SR, Tungsuchat-Huang T, Paredes-López O, Maliga P. Next generation synthetic vectors for transformation of the plastid genome of higher plants. PLANT MOLECULAR BIOLOGY 2009; 70:487-98. [PMID: 19387846 DOI: 10.1007/s11103-009-9486-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Accepted: 03/29/2009] [Indexed: 05/27/2023]
Abstract
Plastid transformation vectors are E. coli plasmids carrying a plastid marker gene for selection, adjacent cloning sites and flanking plastid DNA to target insertions in the plastid genome by homologous recombination. We report here on a family of next generation plastid vectors carrying synthetic DNA vector arms targeting insertions in the rbcL-accD intergenic region of the tobacco (Nicotiana tabacum) plastid genome. The pSS22 plasmid carries only synthetic vector arms from which the undesirable restriction sites have been removed by point mutations. The pSS24 vector carries a c-Myc tagged spectinomycin resistance (aadA) marker gene whereas in vector pSS30 aadA is flanked with loxP sequences for post-transformation marker excision. The synthetic vectors will enable direct manipulation of passenger genes in the transformation vector targeting insertions in the rbcL-accD intergenic region that contains many commonly used restriction sites.
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Affiliation(s)
- Sugey Ramona Sinagawa-García
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA
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22
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Craig W, Lenzi P, Scotti N, De Palma M, Saggese P, Carbone V, McGrath Curran N, Magee AM, Medgyesy P, Kavanagh TA, Dix PJ, Grillo S, Cardi T. Transplastomic tobacco plants expressing a fatty acid desaturase gene exhibit altered fatty acid profiles and improved cold tolerance. Transgenic Res 2008; 17:769-82. [PMID: 18214708 DOI: 10.1007/s11248-008-9164-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 01/02/2008] [Indexed: 10/22/2022]
Abstract
The possibility of altering the unsaturation level of fatty acids in plant lipids by genetic transformation has implications for the stress tolerance of higher plants as well as for their nutritional value and industrial utilisation. While the integration and expression of transgenes in the plastome has several potential advantages over nuclear transformation, very few attempts have been made to manipulate fatty acid biosynthesis using plastid transformation. We produced transplastomic tobacco plants that express a Delta(9) desaturase gene from either the wild potato species Solanum commersonii or the cyanobacterium Anacystis nidulans, using PEG-mediated DNA uptake by protoplasts. Incorporation of chloroplast antibiotic-insensitive point mutations in the transforming DNA was used to select transformants. The presence of the transcript and the Delta(9) desaturase protein in transplastomic plants was confirmed by northern and western blot analyses. In comparison with control plants, transplastomic plants showed altered fatty acid profiles and an increase in their unsaturation level both in leaves and seeds. The two transgenes produced comparable results. The results obtained demonstrate the feasibility of using plastid transformation to engineer lipid metabolic pathways in both vegetative and reproductive tissues and suggest an increase of cold tolerance in transplastomic plants showing altered leaf fatty acid profiles. This is the first example of transplastomic plants expressing an agronomically relevant gene produced with the "binding-type" vectors, which do not contain a heterologous marker gene. In fact, the transplastomic plants expressing the S. commersonii gene contain only plant-derived sequences, a clear attraction from a public acceptability perspective.
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Affiliation(s)
- Wendy Craig
- CNR-IGV, Institute of Plant Genetics-Portici, Portici, NA, Italy
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Hanson MR, Sattarzadeh A. Dynamic morphology of plastids and stromules in angiosperm plants. PLANT, CELL & ENVIRONMENT 2008; 31:646-57. [PMID: 18088332 DOI: 10.1111/j.1365-3040.2007.01768.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Labelling of plastids with fluorescent proteins has revealed the diversity of their sizes and shapes in different tissues of vascular plants. Stromules, stroma-filled tubules comprising thin extensions of the stroma surrounded by the double envelope membrane, have been observed to emanate from all major types of plastid, though less common on chloroplasts. In some tissue types, stromules are highly dynamic, forming, shrinking, attaching, releasing and fragmenting. Stromule formation is negatively affected by treatment of tissue with cytoskeletal inhibitors. Plastids can be connected by stromules, through which green fluorescent protein (GFP) and fluorescently tagged chloroplast protein complexes have been observed to flow. Within the highly viscous stroma, proteins traffic by diffusion as well as by an active process of directional travel, whose mechanism is unknown. In addition to exchanging materials between plastids, stromules may also serve to increase the surface area of the envelope for import and export, reduce diffusion distance between plastids and other organelles for exchange of materials, and anchor the plastid onto attachment points for proper positioning with the plant cell. Future studies should reveal how these functions may affect plants in adapting to the challenges of a changing environment.
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Affiliation(s)
- Maureen R Hanson
- Department of Molecular Biology and Genetics, Cornell University, Biotechnology Building, Ithaca, NY 14853, USA.
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Adachi T, Takase H, Tomizawa KI. Introduction of a 50 kbp DNA fragment into the plastid genome. Biosci Biotechnol Biochem 2007; 71:2266-73. [PMID: 17827692 DOI: 10.1271/bbb.70241] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Plastid transformation technology has been used for the analysis and improvement of plastid metabolism. To create a transplastomic plant with a complicated and massive metabolic pathway, it is necessary to introduce a large amount of DNA into the plastid. However, to our knowledge, the largest DNA fragment introduced into a plastid genome was only 7 kbp long and consisted of just three genes. Here we report the introduction of foreign DNA of 23-50 kbp into the tobacco plastid genome with a bacterial artificial chromosome (BAC)-based plastid transformation vector. It was confirmed that the introduced DNA was passed on to the next generation. This is the first description of plastid transformation with a large amount of foreign DNA.
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Affiliation(s)
- Takashi Adachi
- Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizugawa-shi, Jyoto 619-0292, Japan.
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Abstract
Biolistic delivery of DNA initiated plastid transformation research and still is the most widelyused approach to generate transplastomic lines in both algae and higher plants. The principal designof transformation vectors is similar in both phylogenetic groups. Although important additions tothe list of species transformed in their plastomes have been made in algae and in higher plants, thekey organisms in the area are still the two species, in which stable plastid transformation was initiallysuccessful, i.e., Chlamydomonas reinhardtii and tobacco. Basicresearch into organelle biology has substantially benefited from the homologous recombination-basedcapability to precisely insert at predetermined loci, delete, disrupt, or exchange plastid genomesequences. Successful expression of recombinant proteins, including pharmaceutical proteins, hasbeen demonstrated in Chlamydomonas as well as in higher plants,where some interesting agronomic traits were also engineered through plastid transformation.
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Khan MS, Hameed W, Nozoe M, Shiina T. Disruption of the psbA gene by the copy correction mechanism reveals that the expression of plastid-encoded genes is regulated by photosynthesis activity. JOURNAL OF PLANT RESEARCH 2007; 120:421-30. [PMID: 17427034 DOI: 10.1007/s10265-007-0082-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 02/02/2007] [Indexed: 05/07/2023]
Abstract
The functional analysis of genes encoded by the chloroplast genome of tobacco by reverse genetics is routine. Nevertheless, for a small number of genes their deletion generates heteroplasmic genotypes, complicating their analysis. There is thus the need for additional strategies to develop deletion mutants for these genes. We have developed a homologous copy correction-based strategy for deleting/mutating genes encoded on the chloroplast genome. This system was used to produce psbA knockouts. The resulting plants are homoplasmic and lack photosystem II (PSII) activity. Further, the deletion mutants exhibit a distinct phenotype; young leaves are green, whereas older leaves are bleached, irrespective of light conditions. This suggests that senescence is promoted by the absence of psbA. Analysis of the transcript levels indicates that NEP (nuclear-encoded plastid RNA polymerase)-dependent plastid genes are up regulated in the psbA deletion mutants, whereas the bleached leaves retain plastid-encoded plastid RNA polymerase activity. Hence, the expression of NEP-dependent plastid genes may be regulated by photosynthesis, either directly or indirectly.
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Affiliation(s)
- Muhammad Sarwar Khan
- National Institute for Biotechnology and Genetic Engineering, Faisalabad, Pakistan.
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27
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DNA replication, recombination, and repair in plastids. CELL AND MOLECULAR BIOLOGY OF PLASTIDS 2007. [DOI: 10.1007/4735_2007_0231] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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McNutt PM, Dehart MJ, Matej LA. Characterization of the 16S-23S internal transcribed spacer among 34 higher plants: suitability for interspecific plastid transformation. PLANT CELL REPORTS 2007; 26:47-60. [PMID: 16912867 DOI: 10.1007/s00299-006-0203-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2006] [Revised: 06/03/2006] [Accepted: 06/18/2006] [Indexed: 05/11/2023]
Abstract
Biomanufacturing by chloroplast transgene expression has the potential to produce significant amounts of biopharmaceuticals, endow plants with novel commercial or humanitarian capabilities, enhance phytoremediation methods and harden plants against adverse environments. Plastid bioengineering exploits the phenomenon of homologous recombination to specifically integrate heterologous sequences into the plastid genome. Previous research suggests the plastid genome 16S-23S internal transcribed spacer provides an advantageous integration site for transgene expression. To characterize the suitability of the 16S-23S region for interspecific recombination, we developed primers against conserved plastid sequences and amplified approximately 2.6 kb from 25 plant species. We analyzed the amplicons with nine species from Genbank for homeology, phylogenetic relationships, potential to form chimeric rDNA elements disruptive to translational/replication systems, and the potential number of recombination events for various minimal essential processing segments (MEPS) lengths. Multiple sequence alignment of the 34 species revealed considerable conservation, with identities exceeding 95% among the angiosperms. Substitutions were statistically clustered, generally in noncoding sites, although proposed functional elements such as the OriA region and 3' terminus of the 16S rRNA exhibited unexpected variation. The nonrandom distribution of substitutions undermines the established, statistical method of estimating the number of recombination initiation sites. This finding is further substantiated by comparing statistical estimates of the number of MEPS sites to a direct count at three different MEPS lengths. We frame this in silico analysis in terms of the potential of the 16S-23S region as a target for interspecific transformation, and describe a 'primer-to-plastid' system to rapidly generate species-specific flanking regions for transformation vectors.
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MESH Headings
- Base Sequence
- DNA, Chloroplast/chemistry
- DNA, Chloroplast/genetics
- DNA, Ribosomal Spacer/chemistry
- DNA, Ribosomal Spacer/genetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Phylogeny
- Plants/classification
- Plants/genetics
- Plastids/genetics
- Polymerase Chain Reaction
- RNA, Ribosomal, 16S/chemistry
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 23S/chemistry
- RNA, Ribosomal, 23S/genetics
- Sequence Alignment
- Sequence Analysis, DNA
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Affiliation(s)
- Patrick M McNutt
- Department of Clinical Investigation, Madigan Army Medical Center, Fort Lewis, WA 98327, USA.
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Buhot L, Horvàth E, Medgyesy P, Lerbs-Mache S. Hybrid transcription system for controlled plastid transgene expression. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 46:700-7. [PMID: 16640605 DOI: 10.1111/j.1365-313x.2006.02718.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Plastid transformation technologies have developed rapidly over the last few years, reflecting their value in the study of the principal mechanisms of plastid gene expression and commercial interest in using plastids as bioreactors. Application of this technology is still limited by the difficulty of obtaining regulated, selective expression of plastid transgenes. The plastid genome is transcribed by two different types of RNA polymerase. One of them is of the eubacterial type of polymerase, and its subunits are encoded in the plastid genome [plastid-encoded RNA polymerase (PEP)]. The other one is of the phage type and nucleus-encoded [nucleus-encoded RNA polymerase (NEP)]. To obtain selective transgene expression, we have made use of the similarities and differences between the eubacterial and the plastid eubacterial type transcription systems. We created a hybrid transcription system in which the transgene is placed under the control of a eubacterial promoter which does not exist in the plastid genome and which is not recognized by the plastid endogenous transcriptional machinery. Selective transcription of the transgene is achieved by the supply of a chimeric transcription factor that interacts with PEP and directs it specifically to the foreign eubacterial-type transgene promoter. This hybrid transcription system could be used for biotechnological and fundamental research applications as well as in the characterization of the evolutionary differences between the eubacterial and the plastid eubacterial-type transcription systems.
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Affiliation(s)
- Laurence Buhot
- Laboratoire Plastes et Differenciation cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, BP 53, F-38041 Grenoble, France
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Kanamoto H, Yamashita A, Asao H, Okumura S, Takase H, Hattori M, Yokota A, Tomizawa KI. Efficient and stable transformation of Lactuca sativa L. cv. Cisco (lettuce) plastids. Transgenic Res 2006; 15:205-17. [PMID: 16604461 DOI: 10.1007/s11248-005-3997-2] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Accepted: 10/05/2005] [Indexed: 10/24/2022]
Abstract
Transgenic plastids offer unique advantages in plant biotechnology, including high-level foreign protein expression. However, broad application of plastid genome engineering in biotechnology has been largely hampered by the lack of plastid transformation systems for major crops. Here we describe the development of a plastid transformation system for lettuce, Lactuca sativa L. cv. Cisco. The transforming DNA carries a spectinomycin-resistance gene (aadA) under the control of lettuce chloroplast regulatory expression elements, flanked by two adjacent lettuce plastid genome sequences allowing its targeted insertion between the rbcL and accD genes. On average, we obtained 1 transplastomic lettuce plant per bombardment. We show that lettuce leaf chloroplasts can express transgene-encoded GFP to approximately 36% of the total soluble protein. All transplastomic T0 plants were fertile and the T1 progeny uniformly showed stability of the transgene in the chloroplast genome. This system will open up new possibilities for the efficient production of edible vaccines, pharmaceuticals, and antibodies in plants.
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Affiliation(s)
- Hirosuke Kanamoto
- Resarch Institute of Innovative Technology for the Earth, Kizu-cho Soraku-gun, Kyoto, Japan.
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Nugent GD, Ten Have M, van der Gulik A, Dix PJ, Uijtewaal BA, Mordhorst AP. Plastid transformants of tomato selected using mutations affecting ribosome structure. PLANT CELL REPORTS 2005; 24:341-9. [PMID: 15965679 DOI: 10.1007/s00299-005-0930-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Revised: 12/08/2004] [Accepted: 01/01/2005] [Indexed: 05/03/2023]
Abstract
Tomato plastid transformants were obtained using two vectors containing cloned plastid DNA of either Nicotiana tabacum or Solanum nigrum and including point mutations conferring resistance to spectinomycin and streptomycin. Transformants were recovered after PEG-mediated direct DNA uptake into protoplasts, followed by selection on spectinomycin-containing medium. Sixteen lines contained the point mutation, as confirmed by mapping restriction enzyme sites. One line obtained with each vector was analysed in more detail, in comparison with a spontaneous spectinomycin-resistant mutant. Integration of the cloned Solanum or Nicotiana plastid DNA, by multiple recombination events, into the tomato plastome was confirmed by sequence analysis of the targeted region of plastid DNA in the inverted repeat region. Maternal inheritance of spectinomycin and streptomycin resistances or sensitivity in seedlings also confirmed the transplastomic status of the two transformants. The results demonstrate the efficacy in tomato of a selection strategy which avoids the integration of a dominant bacterial antibiotic resistance gene.
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Affiliation(s)
- G D Nugent
- Biology Department, National University of Ireland, Maynooth, County Kildare, Ireland
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Schmitz-Linneweber C, Kushnir S, Babiychuk E, Poltnigg P, Herrmann RG, Maier RM. Pigment deficiency in nightshade/tobacco cybrids is caused by the failure to edit the plastid ATPase alpha-subunit mRNA. THE PLANT CELL 2005; 17:1815-28. [PMID: 15894714 PMCID: PMC1143079 DOI: 10.1105/tpc.105.032474] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Revised: 04/17/2005] [Accepted: 04/17/2005] [Indexed: 05/02/2023]
Abstract
The subgenomes of the plant cell, the nuclear genome, the plastome, and the chondriome are known to interact through various types of coevolving macromolecules. The combination of the organellar genome from one species with the nuclear genome of another species often leads to plants with deleterious phenotypes, demonstrating that plant subgenomes coevolve. The molecular mechanisms behind this nuclear-organellar incompatibility have been elusive, even though the phenomenon is widespread and has been known for >70 years. Here, we show by direct and reverse genetic approaches that the albino phenotype of a flowering plant with the nuclear genome of Atropa belladonna (deadly nightshade) and the plastome of Nicotiana tabacum (tobacco) develops as a result of a defect in RNA editing of a tobacco-specific editing site in the plastid ATPase alpha-subunit transcript. A plastome-wide analysis of RNA editing in these cytoplasmic hybrids and in plants with a tobacco nucleus and nightshade chloroplasts revealed additional defects in the editing of species-specific editing sites, suggesting that differences in RNA editing patterns in general contribute to the pigment deficiencies observed in interspecific nuclear-plastidial incompatibilities.
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Abstract
Plastid transformation results in stably expressed foreign genes, which for most Angiosperms are largely excluded from sperm cells, thereby greatly reducing the risk of foreign gene spread through pollen. Prior to this work, fertile plastid transformants were restricted to tobacco, tomato and Lesquerella. Application of plastid engineering in the important floriculture industry requires the development of stable plastid transformation in a major ornamental plant species such as Petunia hybrida. Here we describe the successful isolation of fertile and stable plastid transformants in a commercial cultivar of P. hybrida (var. Pink Wave). Plastid targeting regions from tobacco were used to integrate aadA and gusA between the accD and rbcL genes of P. hybrida plastid DNA following particle bombardment of leaves. For three spectinomycin and streptomycin resistant lines, DNA blot analysis confirmed transgene integration into plastid DNA and homoplasmy. Maternal inheritance and homoplasmy resulted in 100% transmission of spectinomycin resistance to progeny after selfing. Plastid transformants expressed the gusA gene uniformly within leaves and to comparable levels in all three lines. Insertion of trait genes in place of gusA coding sequences enables immediate applications of our plastid transformation vector. Establishment of plastid transformation in P. hybrida facilitates a safe and reliable use of this important ornamental plant for research and plant biotechnology.
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Affiliation(s)
- Mikhajlo K Zubkot
- School of Biological Sciences, The University of Manchester, Manchester M13 9PT, UK
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Rumeau D, Bécuwe-Linka N, Beyly A, Carrier P, Cuiné S, Genty B, Medgyesy P, Horvath E, Peltier G. Increased zinc content in transplastomic tobacco plants expressing a polyhistidine-tagged Rubisco large subunit. PLANT BIOTECHNOLOGY JOURNAL 2004; 2:389-99. [PMID: 17168886 DOI: 10.1111/j.1467-7652.2004.00083.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Rubisco is a hexadecameric enzyme composed of two subunits: a small subunit (SSU) encoded by a nuclear gene (rbcS), and a large subunit (LSU) encoded by a plastid gene (rbcL). Due to its high abundance, Rubisco represents an interesting target to express peptides or small proteins as fusion products at high levels. In an attempt to modify the plant metal content, a polyhistidine sequence was fused to Rubisco, the most abundant protein of plants. Plastid transformation was used to express a polyhistidine (6x) fused to the C-terminal extremity of the tobacco LSU. Transplastomic tobacco plants were generated by cotransformation of polyethylene glycol-treated protoplasts using two vectors: one containing the 16SrDNA marker gene, conferring spectinomycin resistance, and the other the polyhistidine-tagged rbcL gene. Homoplasmic plants containing L8-(His)6S8 as a single enzyme species were obtained. These plants contained normal Rubisco amounts and activity and displayed normal photosynthetic properties and growth. Interestingly, transplastomic plants accumulated higher zinc amounts than the wild-type when grown on zinc-enriched media. The highest zinc increase observed exceeded the estimated chelating ability of the polyhistidine sequence, indicating a perturbation in intracellular zinc homeostasis. We discuss the possibility of using Rubisco to express foreign peptides as fusion products and to confer new properties to higher plants.
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Affiliation(s)
- Dominique Rumeau
- CEA Cadarache, Direction des Sciences du Vivant, Département d'Ecophysiologie Végétale et de Microbiologie, Unité Mixte de Recherche 6191 CNRS-CEA-Université de la Méditerranée, France.
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35
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Abstract
Plastids of higher plants are semi-autonomous organelles with a small, highly polyploid genome and their own transcription-translation machinery. This review provides an overview of the technology for the genetic modification of the plastid genome including: vectors, marker genes and gene design, the use of gene knockouts and over-expression to probe plastid function and the application of site-specific recombinases for excision of target DNA. Examples for applications in basic science include the study of plastid gene transcription, mRNA editing, photosynthesis and evolution. Examples for biotechnological applications are incorporation of transgenes in the plastid genome for containment and high-level expression of recombinant proteins for pharmaceutical and industrial applications. Plastid transformation is routine only in tobacco. Progress in implementing the technology in other crops is discussed.
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Affiliation(s)
- Pal Maliga
- Waksman Institute, Rutgers University, Piscataway, New Jersey 08854-8020, USA.
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Skarjinskaia M, Svab Z, Maliga P. Plastid transformation in Lesquerella fendleri, an oilseed Brassicacea. Transgenic Res 2003; 12:115-22. [PMID: 12650530 DOI: 10.1023/a:1022110402302] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A plastid transformation protocol was developed for Lesquerella fendleri, a species with a high capacity for plant regeneration in tissue culture. Transformation vector pZS391B carried an aadA16gfp marker gene conferring streptomycin-spectinomycin resistance and green fluorescence under UV light. Biolistic transformation of 51 Lesquerella leaf samples, followed by spectinomycin selection, yielded two transplastomic clones. The AAD-GFP fusion protein, the marker gene product, was localized to chloroplasts by confocal laser microscopy. Fertile plants and seed progeny were obtained in line Lf-pZS391B-1. In the 51 samples a large number (108) of spontaneous mutants were identified. In five of the lines spectinomycin resistance was localized to a conserved stem structure by sequencing 16S rRNA genes. Success in L. fendleri, a wild oilseed species, extends plastid transformation beyond Arabidopsis thaliana in the Brassicaceae family.
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Affiliation(s)
- Marina Skarjinskaia
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA
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Reiss B. Homologous recombination and gene targeting in plant cells. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 228:85-139. [PMID: 14667043 DOI: 10.1016/s0074-7696(03)28003-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Gene targeting has become an indispensable tool for functional genomics in yeast and mouse; however, this tool is still missing in plants. This review discusses the gene targeting problem in plants in the context of general knowledge on recombination and gene targeting. An overview on the history of gene targeting is followed by a general introduction to genetic recombination of bacteria, yeast, and vertebrates. This abridged discussion serves as a guide to the following sections, which cover plant-specific aspects of recombination assay systems, the mechanism of recombination, plant recombination genes, the relationship of recombination to the environment, approaches to stimulate homologous recombination and gene targeting, and a description of two plant systems, the moss Physcomitrella patens and the chloroplast, that naturally have high efficiencies of gene targeting. The review concludes with a discussion of alternatives to gene targeting.
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Affiliation(s)
- Bernd Reiss
- Max-Planck-Institut für Zuechtungsforschung, Carl-von-Linne-Weg 10, D-50829 Köln, Germany
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38
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Abstract
The plastid genome of higher plants is an attractive target for engineering because it provides readily obtainable high protein levels, the feasibility of expressing multiple proteins from polycistronic mRNAs and gene containment through the lack of pollen transmission. A chloroplast-based expression system that is suitable for the commercial production of recombinant proteins in tobacco leaves has been developed recently. This expression system includes vectors, expression cassettes and site-specific recombinases for the selective elimination of marker genes. Progress in expressing proteins that are biomedically relevant, in engineering metabolic pathways, and in manipulating photosynthesis and agronomic traits is discussed, as are the problems of implementing the technology in crops.
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Affiliation(s)
- Pal Maliga
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, New Jersey 08854-8020, USA.
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Aragão FJL, Brasileiro ACM. Positive, negative and marker-free strategies for transgenic plant selection. ACTA ACUST UNITED AC 2002. [DOI: 10.1590/s1677-04202002000100001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this review, the use of the most common selection marker genes on plant transformation and the effects of their respective selective agents are discussed. These genes could be divided in two categories according their mode of action: genes for positive and negative selection. The retention of the marker gene flow through chloroplast transformation is also discussed. Further, strategies to recover marker-free transgenic plants, involving multi-auto-transformation (MAT), co-transformation, site-specific recombination and intragenomic relocation of transgenes through transposable elements are reviewed.
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40
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Abstract
Facile methods of genetic transformation are of outstanding importance for both basic and applied research. For many years, transgenic technologies for plants were restricted to manipulations of the nuclear genome. More recently, a second genome of the plant cell has become amenable to genetic engineering: the prokaryotically organized circular genome of the chloroplast. The possibility to directly manipulate chloroplast genome-encoded information has paved the way to detailed in vivo studies of virtually all aspects of plastid gene expression. Moreover, plastid transformation technologies have been intensely used in functional genomics by performing gene knockouts and site-directed mutageneses of plastid genes. These studies have contributed greatly to our understanding of the physiology and biochemistry of biogenergetic processes inside the plastid compartment. Plastid transformation technologies have also stirred considerable excitement among plant biotechnologists, since transgene expression from the plastid genome offers a number of most attractive advantages, including high-level foreign protein expression and transgene containment due to lack of pollen transmission. This review describes the generation of plants with transgenic plastids, summarizes our current understanding of the transformation process and highlights selected applications of transplastomic technologies in basic and applied research.
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Affiliation(s)
- R Bock
- Westfälische Wilhelms-Universität Münster, Institut für Biochemie und Biotechnologie der Pflanzen, Hindenburgplatz 55, Münster, D-48143, Germany.
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41
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Abstract
The genome of the plastid has generated much interest as a target for plant transformation. The characteristics of plastid transgenes both reflect the prokaryotic origin of plastid organelles and provide a unique set of features that are currently lacking in genes introduced into the plant nucleus. Recent progress has been made in understanding plastid expression of recombinant proteins.
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Affiliation(s)
- P B Heifetz
- Torrey Mesa Research Institute, 3115 Merryfield Row, California 92121, San Diego, USA.
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42
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Abstract
Engineering the nuclear genome of plants is perceived to be associated with problems regarding biosafety and the stability of expression of the transgene. Alternative transformation strategies using the genomic outfit of the plastid promise to be more successful in this respect. Over the past few years progress has been made in screening procedures, and plastid transformation technology has allowed function to be assigned to open reading frames, massive expression of insecticidal agents and proteins involved in herbicide resistance, and the accumulation of biopolymers. Recently, the design of a novel femtoinjection technique that allows injection into chloroplasts has provided the opportunity to further manipulate and understand chloroplastic gene expression.
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Affiliation(s)
- A J van Bel
- Institute for General Botany and Plant Physiology, Justus Liebig University, Senckenbergstrasse 17, D-35390 Giessen, Germany.
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Horváth EM, Peter SO, Joët T, Rumeau D, Cournac L, Horváth GV, Kavanagh TA, Schäfer C, Peltier G, Medgyesy P. Targeted inactivation of the plastid ndhB gene in tobacco results in an enhanced sensitivity of photosynthesis to moderate stomatal closure. PLANT PHYSIOLOGY 2000; 123:1337-50. [PMID: 10938352 PMCID: PMC59092 DOI: 10.1104/pp.123.4.1337] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/1999] [Accepted: 04/17/2000] [Indexed: 05/18/2023]
Abstract
The ndh genes encoding for the subunits of NAD(P)H dehydrogenase complex represent the largest family of plastid genes without a clearly defined function. Tobacco (Nicotiana tabacum) plastid transformants were produced in which the ndhB gene was inactivated by replacing it with a mutant version possessing translational stops in the coding region. Western-blot analysis indicated that no functional NAD(P)H dehydrogenase complex can be assembled in the plastid transformants. Chlorophyll fluorescence measurements showed that dark reduction of the plastoquinone pool by stromal reductants was impaired in ndhB-inactivated plants. Both the phenotype and photosynthetic performance of the plastid transformants was completely normal under favorable conditions. However, an enhanced growth retardation of ndhB-inactivated plants was revealed under humidity stress conditions causing a moderate decline in photosynthesis via stomatal closure. This distinctive phenotype was mimicked under normal humidity by spraying plants with abscisic acid. Measurements of CO(2) fixation demonstrated an enhanced decline in photosynthesis in the mutant plants under humidity stress, which could be restored to wild-type levels by elevating the external CO(2) concentration. These results suggest that the plastid NAD(P)H:plastoquinone oxidoreductase in tobacco performs a significant physiological role by facilitating photosynthesis at moderate CO(2) limitation.
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Affiliation(s)
- E M Horváth
- Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary
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44
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Abstract
Transformation of the plastid genome has a number of inherent advantages for the engineering of gene expression in plants. These advantages include: 10-50 times higher transgene expression levels; the absence of gene silencing and position effect variation; the ability to express polycistronic messages from a single promoter; uniparental plastid gene inheritance in most crop plants that prevents pollen transmission of foreign DNA; integration via a homologous recombination process that facilitates targeted gene replacement and precise transgene control; and sequestration of foreign proteins in the organelle which prevents adverse interactions with the cytoplasmic environment. It is now 12 years since the first conclusive demonstration of stable introduction of cloned DNA into the Chlamydomonas chloroplast by the Boynton and Gillham laboratory, and 10 years since the laboratory of Pal Maliga successfully extended these approaches to tobacco. Since then, technical developments in plastid transformation and advances in our understanding of the rules of plastid gene expression have facilitated tremendous progress towards the goal of establishing the chloroplast as a feasible platform for genetic modification of plants.
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Affiliation(s)
- P B Heifetz
- Novartis Agribusiness Biotechnology Research, Inc., 3054 Cornwallis Road, Research Triangle Park, NC 27709-2257, USA.
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