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Marenkova TV, Kuznetsov VV, Deineko EV. Features of Expression of Foreign Genes in Complex Insertions in Transgenic Tobacco Plants with a Mosaic Pattern of nptII Gene Expression. RUSS J GENET+ 2021. [DOI: 10.1134/s1022795421030108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Vilperte V, Agapito-Tenfen SZ, Wikmark OG, Nodari RO. Levels of DNA methylation and transcript accumulation in leaves of transgenic maize varieties. ENVIRONMENTAL SCIENCES EUROPE 2016; 28:29. [PMID: 27942424 PMCID: PMC5120055 DOI: 10.1186/s12302-016-0097-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/15/2016] [Indexed: 05/26/2023]
Abstract
BACKGROUND Prior to their release in the environment, transgenic crops are examined for their health and environmental safety. In addition, transgene expression needs to be consistent in order to express the introduced trait (e.g. insecticidal and/or herbicide tolerance). Moreover, data on expression levels for GM events are usually required for approval, but these are rarely disclosed or they are considered insufficient. On the other hand, biosafety regulators do not consider epigenetic regulation (e.g. DNA methylation, ncRNAs and histone modifications), which are broadly known to affect gene expression, within their risk assessment analyses. Here we report the results of a DNA methylation (bisulfite sequencing) and transgene transcript accumulation (RT-qPCR) analysis of four Bt-expressing single transgenic maize hybrids, under different genetic backgrounds, and a stacked transgenic hybrid expressing both insecticidal and herbicide tolerance traits. RESULTS Our results showed differences in cytosine methylation levels in the FMV promoter and cry2Ab2 transgene of the four Bt-expressing hybrid varieties. The comparison between single and stacked hybrids under the same genetic background showed differences in the 35S promoter sequence. The results of transgene transcript accumulation levels showed differences in both cry1A.105 and cry2Ab2 transgenes among the four Bt-expressing hybrid varieties. The comparison between single and stacked hybrids showed difference for the cry2Ab2 transgene only. CONCLUSIONS Overall, our results show differences in DNA methylation patterns in all varieties, as well as in transgene transcript accumulation levels. Although the detection of changes in DNA methylation and transgenic accumulation levels does not present a safety issue per se, it demonstrates the need for additional studies that focus on detecting possible safety implications of such changes.
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Affiliation(s)
- Vinicius Vilperte
- Department of Crop Science, Federal University of Santa Catarina, Florianópolis, Santa Catarina Brazil
- GenØk - Centre for Biosafety, Tromsø, Norway
- Institute for Plant Genetics, Faculty of Natural Sciences, Leibniz University of Hannover, Hannover, Germany
| | | | - Odd-Gunnar Wikmark
- GenØk - Centre for Biosafety, Tromsø, Norway
- Unit for Environmental Science and Management, Potchefstroom Campus, North West University, Potchefstroom, South Africa
| | - Rubens Onofre Nodari
- Department of Crop Science, Federal University of Santa Catarina, Florianópolis, Santa Catarina Brazil
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Weinhold A, Kallenbach M, Baldwin IT. Progressive 35S promoter methylation increases rapidly during vegetative development in transgenic Nicotiana attenuata plants. BMC PLANT BIOLOGY 2013; 13:99. [PMID: 23837904 PMCID: PMC3716894 DOI: 10.1186/1471-2229-13-99] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/06/2013] [Indexed: 05/23/2023]
Abstract
BACKGROUND Genetically modified plants are widely used in agriculture and increasingly in ecological research to enable the selective manipulation of plant traits in the field. Despite their broad usage, many aspects of unwanted transgene silencing throughout plant development are still poorly understood. A transgene can be epigenetically silenced by a process called RNA directed DNA methylation (RdDM), which can be seen as a heritable loss of gene expression. The spontaneous nature of transgene silencing has been widely reported, but patterns of acquirement remain still unclear. RESULTS Transgenic wild tobacco plants (Nicotiana attenuata) expressing heterologous genes coding for antimicrobial peptides displayed an erratic and variable occurrence of transgene silencing. We focused on three independently transformed lines (PNA 1.2, PNA 10.1 and ICE 4.4) as they rapidly lost the expression of the resistance marker and down-regulated transgene expression by more than 200 fold after only one plant generation. Bisulfite sequencing indicated hypermethylation within the 35S and NOS promoters of these lines. To shed light on the progress of methylation establishment, we successively sampled leaf tissues from different stages during plant development and found a rapid increase in 35S promoter methylation during vegetative growth (up to 77% absolute increase within 45 days of growth). The levels of de novo methylation were inherited by the offspring without any visible discontinuation. A secondary callus regeneration step could interfere with the establishment of gene silencing and we found successfully restored transgene expression in the offspring of several regenerants. CONCLUSIONS The unpredictability of the gene silencing process requires a thorough selection and early detection of unstable plant lines. De novo methylation of the transgenes was acquired solely during vegetative development and did not require a generational change for its establishment or enhancement. A secondary callus regeneration step provides a convenient way to rescue transgene expression without causing undesirable morphological effects, which is essential for experiments that use transformed plants in the analysis of ecologically important traits.
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Affiliation(s)
- Arne Weinhold
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, Jena 07745, Germany
| | - Mario Kallenbach
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, Jena 07745, Germany
| | - Ian Thomas Baldwin
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, Jena 07745, Germany
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K?í?ová K, Depicker A, Kova?ík A. Epigenetic switches of tobacco transgenes associate with transient redistribution of histone marks in callus culture. Epigenetics 2013; 8:666-76. [PMID: 23770973 PMCID: PMC3857346 DOI: 10.4161/epi.24613] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 03/28/2013] [Accepted: 04/08/2013] [Indexed: 11/19/2022] Open
Abstract
In plants, silencing is usually accompanied by DNA methylation and heterochromatic histone marks. We studied these epigenetic modifications in different epialleles of 35S promoter (P35S)-driven tobacco transgenes. In locus 1, the T-DNA was organized as an inverted repeat, and the residing neomycin phosphotransferase II reporter gene (P35S-nptII) was silenced at the posttranscriptional (PTGS) level. Transcriptionally silenced (TGS) epialleles were generated by trans-acting RNA signals in hybrids or in a callus culture. PTGS to TGS conversion in callus culture was accompanied by loss of the euchromatic H3K4me3 mark in the transcribed region of locus 1, but this change was not transmitted to the regenerated plants from these calli. In contrast, cytosine methylation that spread from the transcribed region into the promoter was maintained in regenerants. Also, the TGS epialleles generated by trans-acting siRNAs did not change their active histone modifications. Thus, both TGS and PTGS epialleles exhibit euchromatic (H3K4me3 and H3K9ac) histone modifications despite heavy DNA methylation in the promoter and transcribed region, respectively. However, in the TGS locus (271), abundant heterochromatic H3K9me2 marks and DNA methylation were present on P35S. Heterochromatic histone modifications are not automatically installed on transcriptionally silenced loci in tobacco, suggesting that repressive histone marks and cytosine methylation may be uncoupled. However, transient loss of euchromatic modifications may guide de novo DNA methylation leading to formation of stable repressed epialleles with recovered eukaryotic marks. Compilation of available data on epigenetic modification of inactivated P35S in different systems is provided.
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Affiliation(s)
- Kate?ina K?í?ová
- Institute of Biophysics, Academy of Sciences; Královopolská, Brno, Czech Republic
| | - Ann Depicker
- Department of Plant Systems Biology; VIB; Gent, Belgium
- Department of Plant Biotechnology and Bioinformatics; Ghent University; Gent, Belgium
| | - Ale? Kova?ík
- Institute of Biophysics, Academy of Sciences; Královopolská, Brno, Czech Republic
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Krichevsky A, Zaltsman A, King L, Citovsky V. Expression of complete metabolic pathways in transgenic plants. Biotechnol Genet Eng Rev 2012; 28:1-13. [DOI: 10.5661/bger-28-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Kim JY, Kavas M, Fouad WM, Nong G, Preston JF, Altpeter F. Production of hyperthermostable GH10 xylanase Xyl10B from Thermotoga maritima in transplastomic plants enables complete hydrolysis of methylglucuronoxylan to fermentable sugars for biofuel production. PLANT MOLECULAR BIOLOGY 2011; 76:357-69. [PMID: 21080212 DOI: 10.1007/s11103-010-9712-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 10/27/2010] [Indexed: 05/10/2023]
Abstract
Overcoming the recalcitrance in lignocellulosic biomass for efficient hydrolysis of the polysaccharides cellulose and hemicellulose to fermentable sugars is a research priority for the transition from a fossilfuel-based economy to a renewable carbohydrate economy. Methylglucuronoxylans (MeGXn) are the major components of hemicellulose in woody biofuel crops. Here, we describe efficient production of the GH10 xylanase Xyl10B from Thermotoga maritima in transplastomic plants and demonstrate exceptional stability and catalytic activities of the in planta produced enzyme. Fully expanded leaves from homotransplastomic plants contained enzymatically active Xyl10B at a level of 11-15% of their total soluble protein. Transplastomic plants and their seed progeny were morphologically indistinguishable from non-transgenic plants. Catalytic activity of in planta produced Xyl10B was detected with poplar, sweetgum and birchwood xylan substrates following incubation between 40 and 90 °C and was also stable in dry and stored leaves. Optimal yields of Xyl10B were obtained from dry leaves if crude protein extraction was performed at 85 °C. The transplastomic plant derived Xyl10B showed exceptional catalytic activity and enabled the complete hydrolysis of MeGXn to fermentable sugars with the help of a single accessory enzyme (α-glucuronidase) as revealed by the sugar release assay. Even without this accessory enzyme, the majority of MeGXn was hydrolyzed by the transplastomic plant-derived Xyl10B to fermentable xylose and xylobiose.
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Affiliation(s)
- Jae Yoon Kim
- Agronomy Department, Plant Molecular and Cellular Biology Program, Genetics Institute, University of Florida-IFAS, Gainesville, FL, USA
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Meyers B, Zaltsman A, Lacroix B, Kozlovsky SV, Krichevsky A. Nuclear and plastid genetic engineering of plants: Comparison of opportunities and challenges. Biotechnol Adv 2010; 28:747-56. [DOI: 10.1016/j.biotechadv.2010.05.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 05/26/2010] [Accepted: 05/26/2010] [Indexed: 01/18/2023]
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Fischer U, Kuhlmann M, Pecinka A, Schmidt R, Mette MF. Local DNA features affect RNA-directed transcriptional gene silencing and DNA methylation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:1-10. [PMID: 17971044 DOI: 10.1111/j.1365-313x.2007.03311.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Transcription of a nopaline synthase promoter (pNOS) inverted repeat provides an RNA signal that can trigger transcriptional gene silencing and methylation of pNOS promoters in trans. The degree of silencing is influenced by the local DNA features close to the target promoter integration sites. Among 26 transgenic Arabidopsis thaliana lines harbouring single copies of a T-DNA including a pNOS-NPTII reporter gene at different chromosomal loci, NPTII RNA levels showed limited variation. When challenged by the silencer transgene providing the pNOS RNA signal, reduction of the NPTII RNA levels in the F(1) generation varied by more than 100-fold, ranging from no reduction to reduction to <1% of the non-silenced level. Silencing was generally correlated with proportional DNA methylation in the pNOS region, except for one target transgene showing substantial DNA methylation without adequate silencing. Silencing was progressive through generations. Differences in the degree of silencing among the target transgenes were transmitted at least to the F(3) generation, and seemed to be influenced by transgene-flanking sequences. Apparently, close-by repeats promoted, whereas close-by functional genes diminished, the response to the silencing signal.
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MESH Headings
- Amino Acid Oxidoreductases/metabolism
- Arabidopsis/genetics
- DNA Methylation
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Plant/metabolism
- Gene Expression Regulation, Plant
- Gene Silencing
- Genes, Plant/genetics
- Genes, Reporter
- Nucleic Acid Conformation
- Plants, Genetically Modified
- Promoter Regions, Genetic/genetics
- RNA, Double-Stranded/genetics
- Repetitive Sequences, Nucleic Acid
- Transcription, Genetic/genetics
- Transformation, Genetic
- Transgenes
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Affiliation(s)
- Ute Fischer
- Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany
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Skårn M, Eike MC, Meza TJ, Mercy IS, Jakobsen KS, Aalen RB. An inverted repeat transgene with a structure that cannot generate double-stranded RNA, suffers silencing independent of DNA methylation. Transgenic Res 2006; 15:489-500. [PMID: 16906449 DOI: 10.1007/s11248-006-0019-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 03/23/2006] [Indexed: 10/24/2022]
Abstract
Transgene silencing in plants is most often dependent on homologous sequences, e.g. tandemly repeated T-DNAs. We have identified an Arabidopsis line (ex2-4 line 4) displaying silencing of the T-DNA-born nptII gene. This line contains a truncated copy of the T-DNA encompassing the nptII gene with its nos promoter adjacent to an intact T-DNA copy. The orientation of the intact and the truncated copies preclude the generation of a double-stranded nptII transcript. Therefore, we have investigated the genomic landscape surrounding T-DNA insertion in the silenced ex2-4 line 4 and five single-copy ex2-4 lines without silencing in search of features that might explain the silencing phenomenon. GC content, putative matrix-attachment regions and transcriptional interference from neighbouring genes could all be ruled out as major causes of silencing. Bisulphite sequencing revealed de novo methylation of the nos promoter both in non-silenced and silenced plants of this line, thus silencing was not correlated to DNA methylation level. Also, the methylation pattern deviated from that characteristic for RNA-mediated DNA methylation and silencing. Our data therefore suggest that ex2-4 line 4 represents a case where silencing is due to DNA-DNA pairing, i.e. pairing between the intact T-DNA and the adjacent truncated, inverted T-DNA copy.
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Affiliation(s)
- Magne Skårn
- Department of Molecular Biosciences, University of Oslo, P.O. Box 1041, Blindern, Oslo 0316, Norway
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Fojtová M, Bleys A, Bedřichová J, Van Houdt H, Křížová K, Depicker A, Kovařík A. The trans-silencing capacity of invertedly repeated transgenes depends on their epigenetic state in tobacco. Nucleic Acids Res 2006; 34:2280-93. [PMID: 16670434 PMCID: PMC1456325 DOI: 10.1093/nar/gkl180] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 03/13/2006] [Accepted: 03/22/2006] [Indexed: 11/13/2022] Open
Abstract
We studied the in trans-silencing capacities of a transgene locus that carried the neomycin phosphotransferase II reporter gene linked to the 35S promoter in an inverted repeat (IR). This transgene locus was originally posttranscriptionally silenced but switched to a transcriptionally silenced epiallele after in vitro tissue culture. Here, we show that both epialleles were strongly methylated in the coding region and IR center. However, by genomic sequencing, we found that the 1.0 kb region around the transcription start site was heavily methylated in symmetrical and non-symmetrical contexts in transcriptionally but not in posttranscriptionally silenced epilallele. Also, the posttranscriptionally silenced epiallele could trans-silence and trans-methylate homologous transgene loci irrespective of their genomic organization. We demonstrate that this in trans-silencing was accompanied by the production of small RNA molecules. On the other hand, the transcriptionally silenced variant could neither trans-silence nor trans-methylate homologous sequences, even after being in the same genetic background for generations and meiotic cycles. Interestingly, 5-aza-2-deoxy-cytidine-induced hypomethylation could partially restore signaling from the transcriptionally silenced epiallele. These results are consistent with the hypothesis that non-transcribed highly methylated IRs are poor silencers of homologous loci at non-allelic positions even across two generations and that transcription of the inverted sequences is essential for their trans-silencing potential.
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Affiliation(s)
- Miloslava Fojtová
- Institute of Biophysics, Academy of Sciences of the Czech RepublicCZ-612 65 Brno, Czech Republic
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Annick Bleys
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Jana Bedřichová
- Institute of Biophysics, Academy of Sciences of the Czech RepublicCZ-612 65 Brno, Czech Republic
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Helena Van Houdt
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Kateřina Křížová
- Institute of Biophysics, Academy of Sciences of the Czech RepublicCZ-612 65 Brno, Czech Republic
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Anna Depicker
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent UniversityB-9052 Ghent, Belgium
| | - Aleš Kovařík
- To whom correspondence should be addressed at Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ 612 65 Brno, Czech Republic. Tel: +420 541 517 178; Fax: +420 541 211 293;
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