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Vatanparast M, Merkel L, Amari K. Exogenous Application of dsRNA in Plant Protection: Efficiency, Safety Concerns and Risk Assessment. Int J Mol Sci 2024; 25:6530. [PMID: 38928236 PMCID: PMC11204322 DOI: 10.3390/ijms25126530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 06/10/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
The use of double-stranded RNA (dsRNA) for plant protection shows great potential as a sustainable alternative to traditional pesticides. This review summarizes the current state of knowledge on using exogenous dsRNA in plant protection and includes the latest findings on the safety and efficiency of this strategy. The review also emphasizes the need for a cautious and comprehensive approach, considering safety considerations such as off-target effects and formulation challenges. The regulatory landscape in different regions is also discussed, underscoring the need for specific guidelines tailored to dsRNA-based pesticides. The review provides a crucial resource for researchers, regulators, and industry stakeholders, promoting a balanced approach incorporating innovation with thorough safety assessments. The continuous dialog emphasized in this review is essential for shaping the future of dsRNA-based plant protection. As the field advances, collaboration among scientists, regulators, and industry partners will play a vital role in establishing guidelines and ensuring the responsible, effective, and sustainable use of dsRNA in agriculture.
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Affiliation(s)
| | | | - Khalid Amari
- Julius Kühn Institute (JKI), Federal Research Centre for Cultivated Plant, Institute for Biosafety in Plant Biotechnology, D-06484 Quedlinburg, Germany
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Kumar M, Rani K. Epigenomics in stress tolerance of plants under the climate change. Mol Biol Rep 2023:10.1007/s11033-023-08539-6. [PMID: 37294468 DOI: 10.1007/s11033-023-08539-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 05/19/2023] [Indexed: 06/10/2023]
Abstract
BACKGROUND Climate change has had a tremendous impact on the environment in general as well as agricultural crops grown in these situations as time passed. Agricultural production of crops is less suited and of lower quality due to disturbances in plant metabolism brought on by sensitivity to environmental stresses, which are brought on by climate change. Abiotic stressors that are specific to climate change, including as drought, extremes in temperature, increasing CO2, waterlogging from heavy rain, metal toxicity, and pH changes, are known to negatively affect an array of species. Plants adapt to these challenges by undergoing genome-wide epigenetic changes, which are frequently accompanied by differences in transcriptional gene expression. The sum of a cell's biochemical modifications to its nuclear DNA, post-translational modifications to histones, and variations in the synthesis of non-coding RNAs is called an epigenome. These modifications frequently lead to variations in gene expression that occur without any alteration in the underlying base sequence. EPIGENETIC MECHANISMS AND MARKS The methylation of homologous loci by three different modifications-genomic (DNA methylation), chromatin (histone modifications), and RNA-directed DNA methylation (RdDM)-could be regarded as epigenetic mechanisms that control the regulation of differential gene expression. Stresses from the environment cause chromatin remodelling, which enables plant cells to adjust their expression patterns temporarily or permanently. EPIGENOMICS' CONSEQUENCES FOR GENOME STABILITY AND GENE EXPRESSION: DNA methylation affects gene expression in response to abiotic stressors by blocking or suppressing transcription. Environmental stimuli cause changes in DNA methylation levels, either upward in the case of hypermethylation or downward in the case of hypomethylation. The type of stress response that occurs as a result also affects the degree of DNA methylation alterations. Stress is also influenced by DRM2 and CMT3 methylating CNN, CNG, and CG. Both plant development and stress reactions depend on histone changes. Gene up-regulation is associated with histone tail phosphorylation, ubiquitination, and acetylation, while gene down-regulation is associated with de-acetylation and biotinylation. Plants undergo a variety of dynamic changes to histone tails in response to abiotic stressors. The relevance of these transcripts against stress is highlighted by the accumulation of numerous additional antisense transcripts, a source of siRNAs, caused by abiotic stresses. The study highlights the finding that plants can be protected from a range of abiotic stresses by epigenetic mechanisms such DNA methylation, histone modification, and RNA-directed DNA methylation. TRANSGENERATIONAL INHERITANCE AND SOURCES OF EPIGENETIC VARIATION: Stress results in the formation of epialleles, which are either transient or enduring epigenetic stress memory in plants. After the stress is gone, the stable memory is kept for the duration of the plant's remaining developmental cycles or passed on to the next generations, leading to plant evolution and adaptability. The bulk of epigenetic changes brought on by stress are temporary and return to normal after the stress has passed. Some of the modifications, however, might be long-lasting and transmitted across mitotic or even meiotic cell divisions. Epialleles often have genetic or non-genetic causes. Epialleles can arise spontaneously due to improper methylation state maintenance, short RNA off-target effects, or other non-genetic causes. Developmental or environmental variables that influence the stability of epigenetic states or direct chromatin modifications may also be non-genetic drivers of epigenetic variation. Transposon insertions that change local chromatin and structural rearrangements, such copy number changes that are genetically related or unrelated, are two genetic sources of epialleles. EPIGENOMICS IN CROP IMPROVEMENT To include epigenetics into crop breeding, it is necessary to create epigenetic variation as well as to identify and evaluate epialleles. Epigenome editing or epi-genomic selection may be required for epiallele creation and identification. In order to combat the challenges given by changing environments, these epigenetic mechanisms have generated novel epialleles that can be exploited to develop new crop types that are more climate-resilient. Numerous techniques can be used to alter the epigenome generally or at specific target loci in order to induce the epigenetic alterations necessary for crop development. Technologies like CRISPR/Cas9 and dCas, which have recently advanced, have opened up new avenues for the study of epigenetics. Epialleles could be employed in epigenomics-assisted breeding in addition to sequence-based markers for crop breeding. CONCLUSIONS AND FUTURE PROSPECTUS A few of the exciting questions that still need to be resolved in the area of heritable epigenetic variation include a better understanding of the epigenetic foundation of characteristics, the stability and heritability of epialleles, and the sources of epigenetic variation in crops. Investigating long intergenic non-coding RNAs (lincRNAs) as an epigenetic process might open up a new path to understanding crop plant's ability to withstand abiotic stress. For many of these technologies and approaches to be more applicable and deployable at a lower cost, technological breakthroughs will also be necessary. Breeders will probably need to pay closer attention to crop epialleles and how they can affect future responses to climate changes. The development of epialleles suitable for particular environmental circumstances may be made possible by creating targeted epigenetic changes in pertinent genes and by comprehending the molecular underpinnings of trans generational epigenetic inheritance. More research on a wider variety of plant species is required in order to fully comprehend the mechanisms that produce and stabilise epigenetic variation in crops. In addition to a collaborative and multidisciplinary effort by researchers in many fields of plant science, this will require a greater integration of the epigenomic data gathered in many crops. Before it may be applied generally, more study is required.
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Affiliation(s)
- Mithlesh Kumar
- AICRN On Potential Crops, ARS Mandor, Agriculture University, Jodhpur, 342 304, Rajasthan, India.
| | - Kirti Rani
- ICAR-National Bureau of Plant Genetic Resources (NBPGR), Regional Station, Jodhpur, 342 003, Rajasthan, India
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Gómez G, Marquez-Molins J, Martinez G, Pallas V. Plant epigenome alterations: an emergent player in viroid-host interactions. Virus Res 2022; 318:198844. [DOI: 10.1016/j.virusres.2022.198844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/31/2022] [Accepted: 06/05/2022] [Indexed: 10/18/2022]
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Uslu VV, Dalakouras A, Steffens VA, Krczal G, Wassenegger M. High-pressure sprayed siRNAs influence the efficiency but not the profile of transitive silencing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:1199-1212. [PMID: 34882879 DOI: 10.1111/tpj.15625] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 11/18/2021] [Accepted: 11/26/2021] [Indexed: 06/13/2023]
Abstract
In plants, small interfering RNAs (siRNAs) are a quintessential class of RNA interference (RNAi)-inducing molecules produced by the endonucleolytic cleavage of double-stranded RNAs (dsRNAs). In order to ensure robust RNAi, siRNAs are amplified through a positive feedback mechanism called transitivity. Transitivity relies on RNA-DIRECTED RNA POLYMERASE 6 (RDR6)-mediated dsRNA synthesis using siRNA-targeted RNA. The newly synthesized dsRNA is subsequently cleaved into secondary siRNAs by DICER-LIKE (DCL) endonucleases. Just like primary siRNAs, secondary siRNAs are also loaded into ARGONAUTE proteins (AGOs) to form an RNA-induced silencing complex reinforcing the cleavage of the target RNA. Although the molecular players underlying transitivity are well established, the mode of action of transitivity remains elusive. In this study, we investigated the influence of primary target sites on transgene silencing and transitivity using the green fluorescent protein (GFP)-expressing Nicotiana benthamiana 16C line, high-pressure spraying protocol, and synthetic 22-nucleotide (nt) long siRNAs. We found that the 22-nt siRNA targeting the 3' of the GFP transgene was less efficient in inducing silencing when compared with the siRNAs targeting the 5' and middle region of the GFP. Moreover, sRNA sequencing of locally silenced leaves showed that the amount but not the profile of secondary RNAs is shaped by the occupancy of the primary siRNA triggers on the target RNA. Our findings suggest that RDR6-mediated dsRNA synthesis is not primed by primary siRNAs and that dsRNA synthesis appears to be generally initiated at the 3'-end of the target RNA.
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Affiliation(s)
- Veli Vural Uslu
- AlPlanta-Institute for Plant Research, RLP AgroScience GmbH, Neustadt an der Weinstraße, Germany
| | - Athanasios Dalakouras
- Institute of Industrial and Forage Crops, Hellenic Agricultural Organization ELGO-DEMETER, Larissa, Greece
| | - Victor A Steffens
- AlPlanta-Institute for Plant Research, RLP AgroScience GmbH, Neustadt an der Weinstraße, Germany
| | - Gabi Krczal
- AlPlanta-Institute for Plant Research, RLP AgroScience GmbH, Neustadt an der Weinstraße, Germany
| | - Michael Wassenegger
- AlPlanta-Institute for Plant Research, RLP AgroScience GmbH, Neustadt an der Weinstraße, Germany
- Centre for Organismal Studies Heidelberg, University of Heidelberg, Heidelberg, Germany
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5
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Hajieghrari B, Farrokhi N. Plant RNA-mediated gene regulatory network. Genomics 2021; 114:409-442. [PMID: 34954000 DOI: 10.1016/j.ygeno.2021.12.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 07/21/2021] [Accepted: 12/20/2021] [Indexed: 11/26/2022]
Abstract
Not all transcribed RNAs are protein-coding RNAs. Many of them are non-protein-coding RNAs in diverse eukaryotes. However, some of them seem to be non-functional and are resulted from spurious transcription. A lot of non-protein-coding transcripts have a significant function in the translation process. Gene expressions depend on complex networks of diverse gene regulatory pathways. Several non-protein-coding RNAs regulate gene expression in a sequence-specific system either at the transcriptional level or post-transcriptional level. They include a significant part of the gene expression regulatory network. RNA-mediated gene regulation machinery is evolutionarily ancient. They well-evolved during the evolutionary time and are becoming much more complex than had been expected. In this review, we are trying to summarizing the current knowledge in the field of RNA-mediated gene silencing.
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Affiliation(s)
- Behzad Hajieghrari
- Department of Agricultural Biotechnology, College of Agriculture, Jahrom University, Jahrom, Iran.
| | - Naser Farrokhi
- Department of Cell, Molecular Biology Faculty of Life Sciences, Biotechnology, Shahid Beheshti University, G. C Evin, Tehran, Iran.
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Dalakouras A, Vlachostergios D. Epigenetic approaches to crop breeding: current status and perspectives. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5356-5371. [PMID: 34017985 DOI: 10.1093/jxb/erab227] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 05/18/2021] [Indexed: 05/10/2023]
Abstract
In order to tackle the cumulative adverse effects of global climate change, reduced farmland, and heightened needs of an ever-increasing world population, modern agriculture is in urgent search of solutions that can ensure world food security and sustainable development. Classical crop breeding is still a powerful method to obtain crops with valued agronomical traits, but its potential is gradually being compromised by the menacing decline of genetic variation. Resorting to the epigenome as a source of variation could serve as a promising alternative. Here, we discuss current status of epigenetics-mediated crop breeding (epibreeding), highlight its advances and limitations, outline currently available methodologies, and propose novel RNA-based strategies to modify the epigenome in a gene-specific and transgene-free manner.
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Affiliation(s)
- Athanasios Dalakouras
- Institute of Industrial and Forage Crops, HAO-DEMETER, 41335 Larissa, Greece
- Institute of Plant Breeding and Genetic Resources, HAO-DEMETER, 57001 Thessaloniki, Greece
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7
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Viroids as a Tool to Study RNA-Directed DNA Methylation in Plants. Cells 2021; 10:cells10051187. [PMID: 34067940 PMCID: PMC8152041 DOI: 10.3390/cells10051187] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/10/2021] [Accepted: 05/10/2021] [Indexed: 12/11/2022] Open
Abstract
Viroids are plant pathogenic, circular, non-coding, single-stranded RNAs (ssRNAs). Members of the Pospiviroidae family replicate in the nucleus of plant cells through double-stranded RNA (dsRNA) intermediates, thus triggering the host’s RNA interference (RNAi) machinery. In plants, the two RNAi pillars are Post-Transcriptional Gene Silencing (PTGS) and RNA-directed DNA Methylation (RdDM), and the latter has the potential to trigger Transcriptional Gene Silencing (TGS). Over the last three decades, the employment of viroid-based systems has immensely contributed to our understanding of both of these RNAi facets. In this review, we highlight the role of Pospiviroidae in the discovery of RdDM, expound the gradual elucidation through the years of the diverse array of RdDM’s mechanistic details and propose a revised RdDM model based on the cumulative amount of evidence from viroid and non-viroid systems.
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Dalakouras A, Papadopoulou KK. Epigenetic Modifications: An Unexplored Facet of Exogenous RNA Application in Plants. PLANTS 2020; 9:plants9060673. [PMID: 32466487 PMCID: PMC7356522 DOI: 10.3390/plants9060673] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 05/22/2020] [Accepted: 05/23/2020] [Indexed: 01/09/2023]
Abstract
Exogenous RNA interference (exo-RNAi) is a powerful transgene-free tool in modern crop improvement and protection platforms. In exo-RNAi approaches, double-stranded RNAs (dsRNAs) or short-interfering RNAs (siRNAs) are externally applied in plants in order to selectively trigger degradation of target mRNAs. Yet, the applied dsRNAs may also trigger unintended epigenetic alterations and result in epigenetically modified plants, an issue that has not been sufficiently addressed and which merits more careful consideration.
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Affiliation(s)
- Athanasios Dalakouras
- Department of Biochemistry & Biotechnology, University of Thessaly, 41500 Larissa, Greece;
- Institute of Plant Breeding and Genetic Resources ELGO-DEMETER, 57001 Thessaloniki, Greece
- Correspondence:
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9
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Yu J, Park JY, Heo J, Kim K. The ORF2 protein of Fusarium graminearum virus 1 suppresses the transcription of FgDICER2 and FgAGO1 to limit host antiviral defences. MOLECULAR PLANT PATHOLOGY 2020; 21:230-243. [PMID: 31815356 PMCID: PMC6988435 DOI: 10.1111/mpp.12895] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The filamentous fungus Fusarium graminearum possesses an RNA-interference (RNAi) pathway that acts as a defence response against virus infections and exogenous double-stranded (ds) RNA. Fusarium graminearum virus 1 (FgV1), which infects F. graminearum, confers hypovirulence-associated traits such as reduced mycelial growth, increased pigmentation and reduced pathogenicity. In this study, we found that FgV1 can suppress RNA silencing by interfering with the induction of FgDICER2 and FgAGO1, which are involved in RNAi antiviral defence and the hairpin RNA/RNAi pathway in F. graminearum. In an FgAGO1- or FgDICER2-promoter/GFP-reporter expression assay the green fluorescent protein (GFP) transcript levels were reduced in FgV1-infected transformed mutant strains. By comparing transcription levels of FgDICER2 and FgAGO1 in fungal transformed mutants expressing each open reading frame (ORF) of FgV1 with or without a hairpin RNA construct, we determined that reduction of FgDICER2 and FgAGO1 transcript levels requires only the FgV1 ORF2-encoded protein (pORF2). Moreover, we confirmed that the pORF2 binds to the upstream region of FgDICERs and FgAGOs in vitro. These combined results indicate that the pORF2 of FgV1 counteracts the RNAi defence response of F. graminearum by interfering with the induction of FgDICER2 and FgAGO1 in a promoter-dependent manner.
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Affiliation(s)
- Jisuk Yu
- Plant Genomics and Breeding InstituteSeoul National UniversitySeoulKorea
| | - Ju Yeon Park
- Department of Agricultural BiotechnologySeoul National UniversitySeoulKorea
| | - Jeong‐In Heo
- Department of Agricultural BiotechnologySeoul National UniversitySeoulKorea
| | - Kook‐Hyung Kim
- Plant Genomics and Breeding InstituteSeoul National UniversitySeoulKorea
- Department of Agricultural BiotechnologySeoul National UniversitySeoulKorea
- Research Institute of Agriculture and Life SciencesSeoul National UniversitySeoulKorea
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10
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Small RNA Mobility: Spread of RNA Silencing Effectors and its Effect on Developmental Processes and Stress Adaptation in Plants. Int J Mol Sci 2019; 20:ijms20174306. [PMID: 31484348 PMCID: PMC6747330 DOI: 10.3390/ijms20174306] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/28/2019] [Accepted: 08/30/2019] [Indexed: 01/22/2023] Open
Abstract
Plants are exposed every day to multiple environmental cues, and tight transcriptome reprogramming is necessary to control the balance between responses to stress and processes of plant growth. In this context, the silencing phenomena mediated by small RNAs can drive transcriptional and epigenetic regulatory modifications, in turn shaping plant development and adaptation to the surrounding environment. Mounting experimental evidence has recently pointed to small noncoding RNAs as fundamental players in molecular signalling cascades activated upon exposure to abiotic and biotic stresses. Although, in the last decade, studies on stress responsive small RNAs increased significantly in many plant species, the physiological responses triggered by these molecules in the presence of environmental stresses need to be further explored. It is noteworthy that small RNAs can move either cell-to-cell or systemically, thus acting as mobile silencing effectors within the plant. This aspect has great importance when physiological changes, as well as epigenetic regulatory marks, are inspected in light of plant environmental adaptation. In this review, we provide an overview of the categories of mobile small RNAs in plants, particularly focusing on the biological implications of non-cell autonomous RNA silencing in the stress adaptive response and epigenetic modifications.
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11
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Mubin M, Briddon RW, Mansoor S. The V2 protein encoded by a monopartite begomovirus is a suppressor of both post-transcriptional and transcriptional gene silencing activity. Gene 2019; 686:43-48. [PMID: 30399424 DOI: 10.1016/j.gene.2018.11.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 10/08/2018] [Accepted: 11/01/2018] [Indexed: 11/23/2022]
Abstract
Papaya leaf curl virus (PaLCuV) is a begomovirus (genus Begomovirus; family Geminiviridae) with a monopartite genome that is usually associated with beta- and alphasatellites in plants. Geminiviruses are DNA viruses with small circular genomes that occur as minichromosomes in the nucleus and are susceptible to post-transcriptional gene silencing (PTGS) and transcriptional gene silencing (TGS). Transient expression of the PaLCuV V2 (PV2) protein together with the green fluorescent protein (GFP) in Nicotiana benthamiana resulted in enhanced levels of GFP fluorescence and GFP mRNA, indicative of suppression of PTGS. Expression of PV2 from a Potato virus X vector restored GFP expression in N. benthamiana plants harbouring a transcriptionally silenced GFP transgene, indicative of suppression of TGS. The results show that the PV2 protein encoded by PaLCuV has both suppressor of PTGS and TGS activity and is an important factor in overcoming host RNA-silencing based defenses.
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Affiliation(s)
- Muhammad Mubin
- Virology Lab, Centre of Agricultural Biochemistry and Biotechnology, University of Agriculture, Faisalabad 38000, Pakistan; Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan.
| | - Rob W Briddon
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan
| | - Shahid Mansoor
- Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan
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Kusch S, Frantzeskakis L, Thieron H, Panstruga R. Small RNAs from cereal powdery mildew pathogens may target host plant genes. Fungal Biol 2018; 122:1050-1063. [PMID: 30342621 DOI: 10.1016/j.funbio.2018.08.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/25/2018] [Accepted: 08/28/2018] [Indexed: 12/24/2022]
Abstract
Small RNAs (sRNAs) play a key role in eukaryotic gene regulation, for example by gene silencing via RNA interference (RNAi). The biogenesis of sRNAs depends on proteins that are generally conserved in all eukaryotic lineages, yet some species that lack part or all the components of the mechanism exist. Here we explored the presence of the RNAi machinery and its expression as well as the occurrence of sRNA candidates and their putative endogenous as well as host targets in phytopathogenic powdery mildew fungi. We focused on the species Blumeria graminis, which occurs in various specialized forms (formae speciales) that each have a strictly limited host range. B. graminis f. sp. hordei and B. graminis f. sp. tritici, colonizing barley and wheat, respectively, have genomes that are characterized by extensive gene loss. Nonetheless, we find that the RNAi machinery appears to be largely complete and expressed during infection. sRNA sequencing data enabled the identification of putative sRNAs in both pathogens. While a considerable part of the sRNA candidates have predicted target sites in endogenous genes and transposable elements, a small proportion appears to have targets in planta, suggesting potential cross-kingdom RNA transfer between powdery mildew fungi and their respective plant hosts.
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Affiliation(s)
- Stefan Kusch
- Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Worringerweg 1, D-52056 Aachen, Germany.
| | - Lamprinos Frantzeskakis
- Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Worringerweg 1, D-52056 Aachen, Germany.
| | - Hannah Thieron
- Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Worringerweg 1, D-52056 Aachen, Germany.
| | - Ralph Panstruga
- Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, Worringerweg 1, D-52056 Aachen, Germany.
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Sudan J, Raina M, Singh R. Plant epigenetic mechanisms: role in abiotic stress and their generational heritability. 3 Biotech 2018; 8:172. [PMID: 29556426 PMCID: PMC5845050 DOI: 10.1007/s13205-018-1202-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 03/07/2018] [Indexed: 10/17/2022] Open
Abstract
Plants have evolved various defense mechanisms including morphological adaptations, cellular pathways, specific signalling molecules and inherent immunity to endure various abiotic stresses during different growth stages. Most of the defense mechanisms are controlled by stress-responsive genes by transcribing and translating specific genes. However, certain modifications of DNA and chromatin along with small RNA-based mechanisms have also been reported to regulate the expression of stress-responsive genes and constitute another line of defense for plants in their struggle against stresses. More recently, studies have suggested that these modifications are heritable to the future generations as well, thereby indicating their possible role in the evolutionary mechanisms related to abiotic stresses.
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Affiliation(s)
- Jebi Sudan
- School of Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu and Kashmir India
| | - Meenakshi Raina
- School of Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu and Kashmir India
| | - Ravinder Singh
- School of Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu and Kashmir India
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Weinhold A. Transgenerational stress-adaption: an opportunity for ecological epigenetics. PLANT CELL REPORTS 2018; 37:3-9. [PMID: 29032426 DOI: 10.1007/s00299-017-2216-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/04/2017] [Indexed: 05/14/2023]
Abstract
In the recent years, there has been considerable interest to investigate the adaptive transgenerational plasticity of plants and how a "stress memory" can be transmitted to the following generation. Although, increasing evidence suggests that transgenerational adaptive responses have widespread ecological relevance, the underlying epigenetic processes have rarely been elucidated. On the other hand, model plant species have been deeply investigated in their genome-wide methylation landscape without connecting this to the ecological reality of the plant. What we need is the combination of an ecological understanding which plant species would benefit from transgenerational epigenetic stress-adaption in their natural habitat, combined with a deeper molecular analysis of non-model organisms. Only such interdisciplinary linkage in an ecological epigenetic study could unravel the full potential that epigenetics could play for the transgenerational stress-adaption of plants.
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Affiliation(s)
- Arne Weinhold
- Applied Zoology/Animal Ecology, Dahlem Centre of Plant Sciences (DCPS), Institute of Biology, FU Berlin, Haderslebener Str. 9, 12163, Berlin, Germany.
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Abbas Q, Amin I, Mansoor S, Shafiq M, Wassenegger M, Briddon RW. The Rep proteins encoded by alphasatellites restore expression of a transcriptionally silenced green fluorescent protein transgene in Nicotiana benthamiana. Virusdisease 2017; 30:101-105. [PMID: 31143837 DOI: 10.1007/s13337-017-0413-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 11/15/2017] [Indexed: 10/18/2022] Open
Abstract
Alphasatellites are non-essential satellite-like components associated with geminiviruses. The precise selective advantage to a geminivirus infection of an alphasatellite remains unclear. The ability of the cotton leaf curl Multan alphasatellite (CLCuMuA)-encoded replication-associated protein (Rep) to suppress TGS was investigated by using Nicotiana benthamiana line 16-TGS (16-TGS) harbouring a transcriptionally silenced green fluorescent protein (GFP) transgene. Inoculation of 16-TGS plants with a recombinant Potato virus X (PVX) vector carrying CLCuMuA Rep resulted in restoration of GFP expression. Northern blot analysis confirmed that the observed GFP fluorescence was associated with GFP mRNA accumulation. Inoculation with PVX vectors harbouring a further six Rep proteins, encoded by genetically distinct alphasatellites, were similarly shown to result in 16-TGS plants with restored GFP expression. These results indicate that the alphasatellite-encoded Rep can restore the expression of a transcriptionally silenced GFP transgene in N. benthamiana, indicating that alphasatellites are involved in overcoming host defence.
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Affiliation(s)
- Qamar Abbas
- 1National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan.,RLP-Agroscience, AlPlanta - Institute for Plant Research, Neustadt, Germany
| | - Imran Amin
- 1National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan
| | - Shahid Mansoor
- 1National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan
| | - Muhammad Shafiq
- 1National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan.,RLP-Agroscience, AlPlanta - Institute for Plant Research, Neustadt, Germany.,3Present Address: Department of Crop Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, Muscat, Oman
| | | | - Rob W Briddon
- 1National Institute for Biotechnology and Genetic Engineering, Jhang Road, Faisalabad, Pakistan
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16
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Shimada Y, Mohn F, Bühler M. The RNA-induced transcriptional silencing complex targets chromatin exclusively via interacting with nascent transcripts. Genes Dev 2016; 30:2571-2580. [PMID: 27941123 PMCID: PMC5204350 DOI: 10.1101/gad.292599.116] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 11/21/2016] [Indexed: 01/24/2023]
Abstract
Small RNAs regulate chromatin modification and transcriptional gene silencing across the eukaryotic kingdom. Although these processes have been well studied, fundamental mechanistic aspects remain obscure. Specifically, it is unclear exactly how small RNA-loaded Argonaute protein complexes target chromatin to mediate silencing. Here, using fission yeast, we demonstrate that transcription of the target locus is essential for RNA-directed formation of heterochromatin. However, high transcriptional activity is inhibitory; thus, a transcriptional window exists that is optimal for silencing. We further found that pre-mRNA splicing is compatible with RNA-directed heterochromatin formation. However, the kinetics of pre-mRNA processing is critical. Introns close to the 5' end of a transcript that are rapidly spliced result in a bistable response whereby the target either remains euchromatic or becomes fully silenced. Together, our results discount siRNA-DNA base pairing in RNA-mediated heterochromatin formation, and the mechanistic insights further reveal guiding paradigms for the design of small RNA-directed chromatin silencing studies in multicellular organisms.
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Affiliation(s)
- Yukiko Shimada
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland.,University of Basel, 4003 Basel, Switzerland
| | - Fabio Mohn
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland.,University of Basel, 4003 Basel, Switzerland
| | - Marc Bühler
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland.,University of Basel, 4003 Basel, Switzerland
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17
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Zhao JH, Fang YY, Duan CG, Fang RX, Ding SW, Guo HS. Genome-wide identification of endogenous RNA-directed DNA methylation loci associated with abundant 21-nucleotide siRNAs in Arabidopsis. Sci Rep 2016; 6:36247. [PMID: 27786269 PMCID: PMC5081565 DOI: 10.1038/srep36247] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 10/12/2016] [Indexed: 12/29/2022] Open
Abstract
In Arabidopsis, the 24-nucleotide (nt) small interfering RNAs (siRNAs) mediates RNA-directed DNA methylation (RdDM) and transcriptional gene silencing (TGS) of transposable elements (TEs). In the present study, we examined genome-wide changes in DNA methylation and siRNA accumulation in Arabidopsis induced by expression of the Cucumber mosaic virus silencing suppressor protein 2b known to directly bind to both the 21/24-nt siRNAs as well as their associated Argonaute proteins. We demonstrated a genome-wide reduction of CHH and CHG methylation in the 2b-transgenic plants. We found that 2b suppressed RdDM not only at the previously annotated loci directed by 24-nt siRNAs but also a new set of loci associated with 21/22-nt siRNAs. Further analysis showed that the reduced methylation of TEs and coding genes targeted by 21/22-nt siRNAs was associated with sequestration of the duplex siRNAs by the 2b protein but not with changes in either siRNA production or transcription. Notably, we detected both the deletion and/or the transposition of multicopy TEs associated with 2b-induced hypomethylation, suggesting potential TE reactivation. We propose that the silencing of many TEs in Arabidopsis is controlled by the 24- and 21-nt endogenous siRNAs analogous to Drosophila TE silencing by PIWI-interacting RNAs and siRNAs.
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Affiliation(s)
- Jian-Hua Zhao
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yuan-Yuan Fang
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Cheng-Guo Duan
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Rong-Xiang Fang
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Shou-Wei Ding
- Department of Plant Pathology and Microbiology, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Hui-Shan Guo
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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18
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Böhmdorfer G, Sethuraman S, Rowley MJ, Krzyszton M, Rothi MH, Bouzit L, Wierzbicki AT. Long non-coding RNA produced by RNA polymerase V determines boundaries of heterochromatin. eLife 2016; 5. [PMID: 27779094 PMCID: PMC5079748 DOI: 10.7554/elife.19092] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/06/2016] [Indexed: 01/10/2023] Open
Abstract
RNA-mediated transcriptional gene silencing is a conserved process where small RNAs target transposons and other sequences for repression by establishing chromatin modifications. A central element of this process are long non-coding RNAs (lncRNA), which in Arabidopsis thaliana are produced by a specialized RNA polymerase known as Pol V. Here we show that non-coding transcription by Pol V is controlled by preexisting chromatin modifications located within the transcribed regions. Most Pol V transcripts are associated with AGO4 but are not sliced by AGO4. Pol V-dependent DNA methylation is established on both strands of DNA and is tightly restricted to Pol V-transcribed regions. This indicates that chromatin modifications are established in close proximity to Pol V. Finally, Pol V transcription is preferentially enriched on edges of silenced transposable elements, where Pol V transcribes into TEs. We propose that Pol V may play an important role in the determination of heterochromatin boundaries. DOI:http://dx.doi.org/10.7554/eLife.19092.001
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Affiliation(s)
- Gudrun Böhmdorfer
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Shriya Sethuraman
- Bioinformatics Graduate Program, University of Michigan, Ann Arbor, United States
| | - M Jordan Rowley
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Michal Krzyszton
- Faculty of Biology, Institute of Genetics and Biotechnology, University of Warsaw, Warsaw, Poland
| | - M Hafiz Rothi
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Lilia Bouzit
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Andrzej T Wierzbicki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
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19
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Deuschle K, Kepp G, Jeske H. Differential methylation of the circular DNA in geminiviral minichromosomes. Virology 2016; 499:243-258. [PMID: 27716464 DOI: 10.1016/j.virol.2016.09.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 09/22/2016] [Accepted: 09/24/2016] [Indexed: 10/20/2022]
Abstract
Geminiviral minichromosomes were purified to explore epigenetic modifications. The levels of methylation in their covalently closed circular DNA were examined with the help of methylation-dependent restriction (MdR). DNA with 12 superhelical turns was preferentially modified, indicating minichromosomes with 12 nucleosomes leaving an open gap. MdR digestion yielded a specific product of genomic length, which was cloned and Sanger-sequenced, or amplified following ligation-mediated rolling circle amplification and deep-sequenced (circomics). The conventional approach revealed a single cleavage product indicating specific methylations at the borders of the common region. The circomics approach identified considerably more MdR sites in a preferential distance to each other of ~200 nts, which is the DNA length in a nucleosome. They accumulated in regions of nucleosome-free gaps, but scattered also along the genomic components. These results may hint at a function in specific gene regulation, as well as in virus resistance.
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Affiliation(s)
- Kathrin Deuschle
- Institut für Biomaterialien und biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Gabi Kepp
- Institut für Biomaterialien und biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Holger Jeske
- Institut für Biomaterialien und biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
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20
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Castellano M, Pallas V, Gomez G. A pathogenic long noncoding RNA redesigns the epigenetic landscape of the infected cells by subverting host Histone Deacetylase 6 activity. THE NEW PHYTOLOGIST 2016; 211:1311-22. [PMID: 27174164 DOI: 10.1111/nph.14001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 04/05/2016] [Indexed: 06/05/2023]
Abstract
Viroids - ancient plant-pathogenic long noncoding RNAs - have developed a singular evolutionary strategy based on reprogramming specific phases of host-metabolism to ensure that their infection cycle can be completed in infected cells. However, the molecular aspects governing this transregulatory phenomenon remain elusive. Here, we use immunoprecipitation assays and bisulfite sequencing of rDNA to shown that, in infected cucumber and Nicotiana benthamina plants, Hop stunt viroid (HSVd) recruits and functionally subverts Histone Deacetylase 6 (HDA6) to promote host-epigenetic alterations that trigger the transcriptional alterations observed during viroid pathogenesis. This notion is supported by the demonstration that, during infection, the HSVd-HDA6 complex occurs in vivo and that endogenous HDA6 expression is increased in HSVd-infected cells. Moreover, transient overexpression of recombinant HDA6 reverts the hypomethylation status of rDNA observed in HSVd-infected plants and reduces viroid accumulation. We hypothesize that the host-transcriptional alterations induced as a consequence of viroid-mediated HDA6 recruitment favor spurious recognition of HSVd-RNA as an RNA Pol II template, thereby improving viroid replication. Our results constitute the first description of a physical and functional interaction between a pathogenic RNA and a component of the host RNA silencing mechanism, providing novel evidence of the potential of these pathogenic lncRNAs to physically redesign the host-cell environment and reprogram their regulatory mechanisms.
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Affiliation(s)
- Mayte Castellano
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politecnica de Valencia (UPV), CPI, Edificio 8 E, Av. de los Naranjos s/n, Valencia, 46022, Spain
| | - Vicente Pallas
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politecnica de Valencia (UPV), CPI, Edificio 8 E, Av. de los Naranjos s/n, Valencia, 46022, Spain
| | - Gustavo Gomez
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politecnica de Valencia (UPV), CPI, Edificio 8 E, Av. de los Naranjos s/n, Valencia, 46022, Spain
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21
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Dalakouras A, Dadami E, Wassenegger M, Krczal G, Wassenegger M. RNA-directed DNA methylation efficiency depends on trigger and target sequence identity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 87:202-14. [PMID: 27121647 DOI: 10.1111/tpj.13193] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 04/06/2016] [Accepted: 04/06/2016] [Indexed: 06/05/2023]
Abstract
RNA-directed DNA methylation (RdDM) in plants has been extensively studied, but the RNA molecules guiding the RdDM machinery to their targets are still to be characterized. It is unclear whether these molecules require full complementarity with their target. In this study, we have generated Nicotiana tabacum (Nt) plants carrying an infectious tomato apical stunt viroid (TASVd) transgene (Nt-TASVd) and a non-infectious potato spindle tuber viroid (PSTVd) transgene (Nt-SB2). The two viroid sequences exhibit 81% sequence identity. Nt-TASVd and Nt-SB2 plants were genetically crossed. In the progeny plants (Nt-SB2/TASVd), deep sequencing of small RNAs (sRNAs) showed that TASVd infection was associated with the accumulation of abundant small interfering RNAs (siRNAs) that mapped along the entire TASVd but only partially matched the SB2 transgene. TASVd siRNAs efficiently targeted SB2 RNA for degradation, but no transitivity was detectable. Bisulfite sequencing in the Nt-SB2/TASVd plants revealed that the TASVd transgene was targeted for dense cis-RdDM along its entire sequence. In the same plants, the SB2 transgene was targeted for trans-RdDM. The SB2 methylation pattern, however, was weak and heterogeneous, pointing to a positive correlation between trigger-target sequence identity and RdDM efficiency. Importantly, trans-RdDM on SB2 was also detected at sites where no homologous siRNAs were detected. Our data indicate that RdDM efficiency depends on the trigger-target sequence identity, and is not restricted to siRNA occupancy. These findings support recent data suggesting that RNAs with sizes longer than 24 nt (>24-nt RNAs) trigger RdDM.
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Affiliation(s)
- Athanasios Dalakouras
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Neustadt, 67435, Germany
| | - Elena Dadami
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Neustadt, 67435, Germany
| | - Michèle Wassenegger
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Neustadt, 67435, Germany
| | - Gabi Krczal
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Neustadt, 67435, Germany
| | - Michael Wassenegger
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Neustadt, 67435, Germany
- Centre for Organismal Studies (COS) Heidelberg, University of Heidelberg, Heidelberg, 69120, Germany
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22
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De Marchis F, Valeri MC, Pompa A, Bouveret E, Alagna F, Grisan S, Stanzione V, Mariotti R, Cultrera N, Baldoni L, Bellucci M. Overexpression of the olive acyl carrier protein gene (OeACP1) produces alterations in fatty acid composition of tobacco leaves. Transgenic Res 2016; 25:45-61. [PMID: 26560313 DOI: 10.1007/s11248-015-9919-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 11/05/2015] [Indexed: 01/24/2023]
Abstract
Taking into account that fatty acid (FA) biosynthesis plays a crucial role in lipid accumulation in olive (Olea europaea L.) mesocarp, we investigated the effect of olive acyl carrier protein (ACP) on FA composition by overexpressing an olive ACP cDNA in tobacco plants. The OeACP1.1A cDNA was inserted in the nucleus or in the chloroplast DNA of different tobacco plants, resulting in extensive transcription of the transgenes. The transplastomic plants accumulated lower olive ACP levels in comparison to nuclear-transformed plants. Moreover, the phenotype of the former plants was characterized by pale green/white cotyledons with abnormal chloroplasts, delayed germination and reduced growth. We suggest that the transplastomic phenotype was likely caused by inefficient olive ACP mRNA translation in chloroplast stroma. Conversely, total lipids from leaves of nuclear transformants expressing high olive ACP levels showed a significant increase in oleic acid (18:1) and linolenic acid (18:3), and a concomitant significant reduction of hexadecadienoic acid (16:2) and hexadecatrienoic acid (16:3). This implies that in leaves of tobacco transformants, as likely in the mesocarp of olive fruit, olive ACP not only plays a general role in FA synthesis, but seems to be specifically involved in chain length regulation forwarding the elongation to C18 FAs and the subsequent desaturation to 18:1 and 18:3.
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Affiliation(s)
- Francesca De Marchis
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | - Maria Cristina Valeri
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
- PlantLab, Institute of Life Sciences, Scuola Superiore Sant'Anna, 56127, Pisa, Italy
| | - Andrea Pompa
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | | | - Fiammetta Alagna
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
- Research Unit for Table Grapes and Wine Growing in Mediterranean Environment, CREA, Via Casamassima 148, Turi, 70010, Bari, Italy
| | - Simone Grisan
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | - Vitale Stanzione
- Institute for Agricultural and Forest Systems in the Mediterranean (ISAFOM), Research Division of Perugia, CNR, Via Madonna Alta 128, 06128, Perugia, Italy
| | - Roberto Mariotti
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | - Nicolò Cultrera
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | - Luciana Baldoni
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy
| | - Michele Bellucci
- Institute of Biosciences and Bioresources (IBBR), Research Division of Perugia, CNR, Via Madonna Alta 130, 06128, Perugia, Italy.
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23
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Dicer-independent RNA-directed DNA methylation in Arabidopsis. Cell Res 2015; 26:66-82. [PMID: 26642813 DOI: 10.1038/cr.2015.145] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 12/30/2022] Open
Abstract
RNA-directed DNA methylation (RdDM) is an important de novo DNA methylation pathway in plants. Small interfering RNAs (siRNAs) generated by Dicers from RNA polymerase IV (Pol IV) transcripts are thought to guide sequence-specific DNA methylation. To gain insight into the mechanism of RdDM, we performed whole-genome bisulfite sequencing of a collection of Arabidopsis mutants, including plants deficient in Pol IV (nrpd1) or Dicer (dcl1/2/3/4) activity. Unexpectedly, of the RdDM target loci that required Pol IV and/or Pol V, only 16% were fully dependent on Dicer activity. DNA methylation was partly or completely independent of Dicer activity at the remaining Pol IV- and/or Pol V-dependent loci, despite the loss of 24-nt siRNAs. Instead, DNA methylation levels correlated with the accumulation of Pol IV-dependent 25-50 nt RNAs at most loci in Dicer mutant plants. Our results suggest that RdDM in plants is largely guided by a previously unappreciated class of Dicer-independent non-coding RNAs, and that siRNAs are required to maintain DNA methylation at only a subset of loci.
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24
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Kotakis C. Non-coding RNAs' partitioning in the evolution of photosynthetic organisms via energy transduction and redox signaling. RNA Biol 2015; 12:101-4. [PMID: 25826417 DOI: 10.1080/15476286.2015.1017201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Ars longa, vita brevis -Hippocrates Chloroplasts and mitochondria are genetically semi-autonomous organelles inside the plant cell. These constructions formed after endosymbiosis and keep evolving throughout the history of life. Experimental evidence is provided for active non-coding RNAs (ncRNAs) in these prokaryote-like structures, and a possible functional imprinting on cellular electrophysiology by those RNA entities is described. Furthermore, updated knowledge on RNA metabolism of organellar genomes uncovers novel inter-communication bridges with the nucleus. This class of RNA molecules is considered as a unique ontogeny which transforms their biological role as a genetic rheostat into a synchronous biochemical one that can affect the energetic charge and redox homeostasis inside cells. A hypothesis is proposed where such modulation by non-coding RNAs is integrated with genetic signals regulating gene transfer. The implications of this working hypothesis are discussed, with particular reference to ncRNAs involvement in the organellar and nuclear genomes evolution since their integrity is functionally coupled with redox signals in photosynthetic organisms.
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Affiliation(s)
- Christos Kotakis
- a Agro-environmental cooperative BioNet West Hellas ; Gastouni Ileias, Hellas , Greece
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25
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Lin YT, Wei HM, Lu HY, Lee YI, Fu SF. Developmental- and Tissue-Specific Expression of NbCMT3-2 Encoding a Chromomethylase in Nicotiana benthamiana. PLANT & CELL PHYSIOLOGY 2015; 56:1124-43. [PMID: 25745030 DOI: 10.1093/pcp/pcv036] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 02/23/2015] [Indexed: 05/11/2023]
Abstract
The chromomethylase (CMT) protein family is unique to plants and controls non-CpG methylation. Here, we investigated the developmental expression of CMT3-2 in Nicotiana benthamiana (NbCMT3-2) and its significance by analyzing plants with silenced NbCMT3-2 and leaf tissues transiently expressing the N-terminal polypeptide. Alignment of the NbCMT3-2 amino acid sequence with that of other plant CMT3s showed a specific N-terminal extension required for nuclear localization. Transient expression of the N-terminal polypeptide in N. benthamiana resulted in chlorotic lesions. NbCMT3-2 was expressed mainly in proliferating tissues such as the shoot apex and developing leaves. We generated transgenic N. benthamiana harboring a fusion reporter construct linking the NbCMT3-2 promoter region and the β-glucuronidase (GUS) reporter (pNbCMT3-2::GUS) to analyze the tissue-specific expression of NbCMT3-2. NbCMT3-2 was expressed in the shoot and root apical meristem and leaf primordia in young seedlings and highly expressed in developing leaves and ovary as well as lateral buds in mature plants. Virus-induced gene silencing used to knock down the expression of NbCMT3 or NbCMT3-2 or both led to partial loss of genomic DNA methylation. Plants with suppressed NbCMT3 expression grew and developed normally, whereas leaves with NbCMT3-2 knockdown showed mild curling as compared with controls. Silencing NbCMT3/3-2 severely interfered with leaf development and directly or indirectly affected the expression of genes involved in jasmonate homeostasis. The differential roles of NbCMT3 and NbCMT3-2 were investigated and compared. We reveal the expression patterns of NbCMT3-2 in proliferating tissues. NbCMT3-2 may play an essential role in leaf development by modulating jasmonate pathways.
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Affiliation(s)
- Yu-Ting Lin
- Department of Biology, National Changhua University of Education, No. 1, Jin-De Road, Changhua, 500, Taiwan
| | - Huei-Mei Wei
- Department of Biology, National Changhua University of Education, No. 1, Jin-De Road, Changhua, 500, Taiwan
| | - Hsueh-Yu Lu
- Department of Biology, National Changhua University of Education, No. 1, Jin-De Road, Changhua, 500, Taiwan
| | - Yung-I Lee
- Botany Department, National Museum of Natural Science, No. 1, Guancian Road, Taichung 404, Taiwan
| | - Shih-Feng Fu
- Department of Biology, National Changhua University of Education, No. 1, Jin-De Road, Changhua, 500, Taiwan
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26
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Saeed M, Krczal G, Wassenegger M. Three gene products of a begomovirus-betasatellite complex restore expression of a transcriptionally silenced green fluorescent protein transgene in Nicotiana benthamiana. Virus Genes 2015; 50:340-4. [PMID: 25537949 DOI: 10.1007/s11262-014-1155-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/04/2014] [Indexed: 11/30/2022]
Abstract
Single-stranded DNA geminiviruses replicate via double-stranded DNA intermediates forming mini-chromosomes that are targets for transcriptional gene silencing (TGS) in plants. The ability of the cotton leaf curl Kokhran virus (CLCuKoV)-cotton leaf curl Multan betasatellite (CLCuMuB) proteins, replication-associated protein (Rep), transcriptional activator protein (TrAP), C4, V2 and βC1, to suppress TGS was investigated by using the Nicotiana benthamiana line 16-TGS (16-TGS) harbouring a transcriptionally silenced green fluorescent protein (GFP) transgene. Inoculation of 16-TGS plants with a recombinant potato virus X vector carrying Rep, TrAP or βC1 resulted in re-expression of GFP. Northern blot analysis confirmed that the observed GFP fluorescence was associated with GFP mRNA accumulation. These results indicated that Rep, TrAP and βC1 proteins of CLCuKoV-CLCuMuB can re-activate the expression of a transcriptionally silenced GFP transgene in N. benthamiana. Although Rep, TrAP, or βC1 proteins have, for other begomoviruses or begomoviruses-betasatellites, been previously shown to have TGS suppressor activity, this is the first report demonstrating that a single begomovirus-betasatellite complex encodes three suppressors of TGS.
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Affiliation(s)
- Muhammad Saeed
- RLP AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, 67435, Neustadt, Germany,
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27
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Abstract
DNA methylation is a type of epigenetic modification where a methyl group is added to the cytosine or adenine residue of a given DNA sequence. It has been observed that DNA methylation is achieved by some collaborative agglomeration of certain proteins and non-coding RNAs. The assembly of IDN2 and its homologous proteins with siRNAs recruits the enzyme DRM2, which adds a methyl group at certain cytosine residues within the DNA sequence. In this study, it was found that de novo DNA methylation might be regulated by miRNAs through systematic targeting of the genes involved in DNA methylation. A comprehensive genome-wide and system-level study of miRNA targeting, transcription factors, DNA-methylation-causing genes and their target genes has provided a clear picture of an interconnected relationship of all these factors which regulate DNA methylation in Arabidopsis. The study has identified a DNA methylation system that is controlled by four different genes: IDN2, IDNl1, IDNl2 and DRM2. These four genes along with various critical transcription factors appear to be controlled by five different miRNAs. Altogether, DNA methylation appears to be a finely tuned process of opposite control systems of DNAmethylation- causing genes and certain miRNAs pitted against each other.
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Affiliation(s)
- Ashwani Jha
- Studio of Computational Biology and Bioinformatics, Biotechnology Division, CSIR-Institute of Himalayan Bioresource Technology (CSIR-IHBT), Palampur 176 061, India
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28
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Dalakouras A, Dadami E, Bassler A, Zwiebel M, Krczal G, Wassenegger M. Replicating Potato spindle tuber viroid mediates de novo methylation of an intronic viroid sequence but no cleavage of the corresponding pre-mRNA. RNA Biol 2015; 12:268-75. [PMID: 25826660 PMCID: PMC4615544 DOI: 10.1080/15476286.2015.1017216] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/05/2015] [Accepted: 01/05/2015] [Indexed: 10/23/2022] Open
Abstract
In plants, Potato spindle tuber viroid (PSTVd) replication triggers post-transcriptional gene silencing (PTGS) and RNA-directed DNA methylation (RdDM) of homologous RNA and DNA sequences, respectively. PTGS predominantly occurs in the cytoplasm, but nuclear PTGS has been also reported. In this study, we investigated whether the nuclear replicating PSTVd is able to trigger nuclear PTGS. Transgenic tobacco plants carrying cytoplasmic and nuclear PTGS sensor constructs were PSTVd-infected resulting in the generation of abundant PSTVd-derived small interfering RNAs (vd-siRNAs). Northern blot analysis revealed that, in contrast to the cytoplasmic sensor, the nuclear sensor transcript was not targeted for RNA degradation. Bisulfite sequencing analysis showed that the nuclear PTGS sensor transgene was efficiently targeted for RdDM. Our data suggest that PSTVd fails to trigger nuclear PTGS, and that RdDM and nuclear PTGS are not necessarily coupled.
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Affiliation(s)
| | - Elena Dadami
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Alexandra Bassler
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Michele Zwiebel
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Gabi Krczal
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Michael Wassenegger
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
- Centre for Organismal Studies (COS) Heidelberg; University of Heidelberg; Heidelberg, Germany
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Yaish MW, Sunkar R, Zheng Y, Ji B, Al-Yahyai R, Farooq SA. A genome-wide identification of the miRNAome in response to salinity stress in date palm (Phoenix dactylifera L.). FRONTIERS IN PLANT SCIENCE 2015; 6:946. [PMID: 26594218 PMCID: PMC4633500 DOI: 10.3389/fpls.2015.00946] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 10/17/2015] [Indexed: 05/22/2023]
Abstract
Although date palm is relatively salt-tolerant, little is known about the underlying molecular mechanisms that contribute to its salt tolerance. Only recently, investigators have uncovered microRNA-mediated post-transcriptional gene regulation, which is critical for typical plant development and adaptation to stress conditions such as salinity. To identify conserved and novel miRNAs in date palm and to characterize miRNAs that could play a role in salt tolerance, we have generated sRNA libraries from the leaves and roots of NaCl-treated and untreated seedlings of date palm. Deep sequencing of these four sRNA libraries yielded approximately 251 million reads. The bioinformatics analysis has identified 153 homologs of conserved miRNAs, 89 miRNA variants, and 180 putative novel miRNAs in date palm. Expression profiles under salinity revealed differential regulation of some miRNAs in date palm. In leaves, 54 of the identified miRNAs were significantly affected and the majority (70%) of them were upregulated, whereas in roots, 25 of the identified miRNAs were significantly affected and 76% of them were upregulated by the salinity stress. The salt-responsiveness of some of these miRNAs was further validated using semi-quantitative PCR (qPCR). Some of the predicted targets for the identified miRNA include genes with known functions in plant salt tolerance, such as potassium channel AKT2-like proteins, vacuolar protein sorting-associated protein, calcium-dependent and mitogen-activated proteins. As one of the first cultivated trees in the world that can tolerate a wide range of abiotic stresses, date palm contains a large population of conserved and non-conserved miRNAs that function at the post-transcriptional level. This study provided insights into miRNA-mediated gene expression that are important for adaptation to salinity in date palms.
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Affiliation(s)
- Mahmoud W. Yaish
- Department of Biology, College of Science, Sultan Qaboos UniversityMuscat, Oman
- *Correspondence: Mahmoud W. Yaish
| | - Ramanjulu Sunkar
- Department of Biochemistry and Molecular Biology, Oklahoma State UniversityStillwater, OK, USA
| | - Yun Zheng
- Faculty of Life Science and Technology, Kunming University of Science and TechnologyKunming, China
| | - Bo Ji
- Faculty of Life Science and Technology, Kunming University of Science and TechnologyKunming, China
| | - Rashid Al-Yahyai
- Department of Crop Science, College of Agriculture, Sultan Qaboos UniversityMuscat, Oman
| | - Sardar A. Farooq
- Department of Biology, College of Science, Sultan Qaboos UniversityMuscat, Oman
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Matzke MA, Kanno T, Matzke AJM. RNA-Directed DNA Methylation: The Evolution of a Complex Epigenetic Pathway in Flowering Plants. ANNUAL REVIEW OF PLANT BIOLOGY 2015; 66:243-67. [PMID: 25494460 DOI: 10.1146/annurev-arplant-043014-114633] [Citation(s) in RCA: 284] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
RNA-directed DNA methylation (RdDM) is an epigenetic process in plants that involves both short and long noncoding RNAs. The generation of these RNAs and the induction of RdDM rely on complex transcriptional machineries comprising two plant-specific, RNA polymerase II (Pol II)-related RNA polymerases known as Pol IV and Pol V, as well as a host of auxiliary factors that include both novel and refashioned proteins. We present current views on the mechanism of RdDM with a focus on evolutionary innovations that occurred during the transition from a Pol II transcriptional pathway, which produces mRNA precursors and numerous noncoding RNAs, to the Pol IV and Pol V pathways, which are specialized for RdDM and gene silencing. We describe recently recognized deviations from the canonical RdDM pathway, discuss unresolved issues, and speculate on the biological significance of RdDM for flowering plants, which have a highly developed Pol V pathway.
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Affiliation(s)
- Marjori A Matzke
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 115, Taiwan; , ,
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31
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Nongenetic inheritance and transgenerational epigenetics. Trends Mol Med 2014; 21:134-44. [PMID: 25601643 DOI: 10.1016/j.molmed.2014.12.004] [Citation(s) in RCA: 171] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 11/21/2022]
Abstract
The idea that inherited genotypes define phenotypes has been paramount in modern biology. The question remains, however, whether stable phenotypes could be also inherited from parents independently of the genetic sequence per se. Recent data suggest that parental experiences can be transmitted behaviorally, through in utero exposure of the developing fetus to the maternal environment, or through either the male or female germline. The challenge is to delineate a plausible mechanism. In the past decade it has been proposed that epigenetic mechanisms are involved in multigenerational transmission of phenotypes and transgenerational inheritance. The prospect that ancestral experiences are written in our epigenome has immense implications for our understanding of human behavior, health, and disease.
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32
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Zhao M, San León D, Delgadillo MO, García JA, Simón-Mateo C. Virus-induced gene silencing in transgenic plants: transgene silencing and reactivation associate with two patterns of transgene body methylation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 79:440-452. [PMID: 24916614 DOI: 10.1111/tpj.12579] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/09/2014] [Accepted: 05/21/2014] [Indexed: 06/03/2023]
Abstract
We used bisulfite sequencing to study the methylation of a viral transgene whose expression was silenced upon plum pox virus infection of the transgenic plant and its subsequent recovery as a consequence of so-called virus-induced gene silencing (VIGS). VIGS was associated with a general increase in the accumulation of small RNAs corresponding to the coding region of the viral transgene. After VIGS, the transgene promoter was not methylated and the coding region showed uneven methylation, with the 5' end being mostly unmethylated in the recovered tissue or mainly methylated at CG sites in regenerated silenced plants. The methylation increased towards the 3' end, which showed dense methylation in all three contexts (CG, CHG and CHH). This methylation pattern and the corresponding silenced status were maintained after plant regeneration from recovered silenced tissue and did not spread into the promoter region, but were not inherited in the sexual offspring. Instead, a new pattern of methylation was observed in the progeny plants consisting of disappearance of the CHH methylation, similar CHG methylation at the 3' end, and an overall increase in CG methylation in the 5' end. The latter epigenetic state was inherited over several generations and did not correlate with transgene silencing and hence virus resistance. These results suggest that the widespread CG methylation pattern found in body gene bodies located in euchromatic regions of plant genomes may reflect an older silencing event, and most likely these genes are no longer silenced.
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Affiliation(s)
- Mingmin Zhao
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas or (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049, Madrid, Spain
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Dadami E, Dalakouras A, Zwiebel M, Krczal G, Wassenegger M. An endogene-resembling transgene is resistant to DNA methylation and systemic silencing. RNA Biol 2014; 11:934-41. [PMID: 25180820 PMCID: PMC4179966 DOI: 10.4161/rna.29623] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 06/11/2014] [Accepted: 06/17/2014] [Indexed: 11/19/2022] Open
Abstract
In plants, endogenes are less prone to RNA silencing than transgenes. While both can be efficiently targeted by small RNAs for post-transcriptional gene silencing (PTGS), generally only transgene PTGS is accompanied by transitivity, RNA-directed DNA methylation (RdDM) and systemic silencing. In order to investigate whether a transgene could mimick an endogene and thus be less susceptible to RNA silencing, we generated an intron-containing, endogene-resembling GREEN FLUORESCENT PROTEIN (GFP) transgene (GFP(endo)). Upon agroinfiltration of a hairpin GFP (hpF) construct, transgenic Nicotiana benthamiana plants harboring GFP(endo) (Nb-GFP(endo)) were susceptible to local PTGS. Yet, in the local area, PTGS was not accompanied by RdDM of the GFP(endo) coding region. Importantly, hpF-agroinfiltrated Nb-GFP(endo) plants were resistant to systemic silencing. For reasons of comparison, transgenic N. benthamiana plants (Nb-GFP(cDNA)) carrying a GFP cDNA transgene (GFP(cDNA)) were included in the analysis. HpF-agroinfiltrated Nb-GFP(cDNA) plants exhibited local PTGS and RdDM. In addition, systemic silencing was established in Nb-GFP(cDNA) plants. In agreement with previous reports using grafted scions, in systemically silenced tissue, siRNAs mapping to the 3' of GFP were predominantly detectable by Northern blot analysis. Yet, in contrast to other reports, in systemically silenced leaves, PTGS was also accompanied by dense RdDM comprising the entire GFP(cDNA) coding region. Overall, our analysis indicated that cDNA transgenes are prone to systemic PTGS and RdDM, while endogene-resembling ones are resistant to RNA silencing.
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Affiliation(s)
- Elena Dadami
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | | | - Michele Zwiebel
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Gabi Krczal
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
| | - Michael Wassenegger
- RLP AgroScience GmbH; AlPlanta-Institute for Plant Research; Neustadt, Germany
- Centre for Organismal Studies (COS) Heidelberg; University of Heidelberg; Heidelberg, Germany
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34
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Sasaki T, Lee TF, Liao WW, Naumann U, Liao JL, Eun C, Huang YY, Fu JL, Chen PY, Meyers BC, Matzke AJM, Matzke M. Distinct and concurrent pathways of Pol II- and Pol IV-dependent siRNA biogenesis at a repetitive trans-silencer locus in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 79:127-138. [PMID: 24798377 DOI: 10.1111/tpj.12545] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/21/2014] [Accepted: 04/25/2014] [Indexed: 06/03/2023]
Abstract
Short interfering RNAs (siRNAs) homologous to transcriptional regulatory regions can induce RNA-directed DNA methylation (RdDM) and transcriptional gene silencing (TGS) of target genes. In our system, siRNAs are produced by transcribing an inverted DNA repeat (IR) of enhancer sequences, yielding a hairpin RNA that is processed by several Dicer activities into siRNAs of 21-24 nt. Primarily 24-nt siRNAs trigger RdDM of the target enhancer in trans and TGS of a downstream GFP reporter gene. We analyzed siRNA accumulation from two different structural forms of a trans-silencer locus in which tandem repeats are embedded in the enhancer IR and distinguished distinct RNA polymerase II (Pol II)- and Pol IV-dependent pathways of siRNA biogenesis. At the original silencer locus, Pol-II transcription of the IR from a 35S promoter produces a hairpin RNA that is diced into abundant siRNAs of 21-24 nt. A silencer variant lacking the 35S promoter revealed a normally masked Pol IV-dependent pathway that produces low levels of 24-nt siRNAs from the tandem repeats. Both pathways operate concurrently at the original silencer locus. siRNAs accrue only from specific regions of the enhancer and embedded tandem repeat. Analysis of these sequences and endogenous tandem repeats producing siRNAs revealed the preferential accumulation of siRNAs at GC-rich regions containing methylated CG dinucleotides. In addition to supporting a correlation between base composition, DNA methylation and siRNA accumulation, our results highlight the complexity of siRNA biogenesis at repetitive loci and show that Pol II and Pol IV use different promoters to transcribe the same template.
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Affiliation(s)
- Taku Sasaki
- Institute of Plant and Microbial Biology, Academia Sinica, 128, Sec. 2, Academia Road, Nankang, 115, Taipei, Taiwan; Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Dr. Bohr-Gasse 3, Vienna, Austria
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Madzima TF, Huang J, McGinnis KM. Chromatin structure and gene expression changes associated with loss of MOP1 activity in Zea mays. Epigenetics 2014; 9:1047-59. [PMID: 24786611 PMCID: PMC4143406 DOI: 10.4161/epi.29022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Though the mechanisms governing nuclear organization are not well understood, it is apparent that epigenetic modifications coordinately modulate chromatin organization as well as transcription. In maize, MEDIATOR OF PARAMUTATION1 (MOP1) is required for 24 nt siRNA-mediated epigenetic regulation and transcriptional gene silencing via a putative Pol IV- RdDM pathway. To elucidate the mechanisms of nuclear chromatin organization, we investigated the relationship between chromatin structure and transcription in response to loss of MOP1 function. We used a microarray based micrococcal nuclease sensitivity assay to identify genome-wide changes in chromatin structure in mop1-1 immature ears and observed an increase in chromatin accessibility at chromosome arms associated with loss of MOP1 function. Within the many genes misregulated in mop1 mutants, we identified one subset likely to be direct targets of epigenetic transcriptional silencing via Pol-IV RdDM. We found that target specificity for MOP1-mediated RdDM activity is governed by multiple signals that include accumulation of 24 nt siRNAs and the presence of specific classes of gene-proximal transposons, but neither of these attributes alone is sufficient to predict transcriptional misregulation in mop1-1 homozygous mutants. Our results suggest a role for MOP1 in regulation of higher-order chromatin organization where loss of MOP1 activity at a subset of loci triggers a broader cascade of transcriptional consequences and genome-wide changes in chromatin structure.
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Affiliation(s)
- Thelma F Madzima
- Department of Biological Science; Florida State University; Tallahassee, FL USA
| | - Ji Huang
- Department of Biological Science; Florida State University; Tallahassee, FL USA
| | - Karen M McGinnis
- Department of Biological Science; Florida State University; Tallahassee, FL USA
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Houben A, Banaei-Moghaddam AM, Klemme S, Timmis JN. Evolution and biology of supernumerary B chromosomes. Cell Mol Life Sci 2014; 71:467-78. [PMID: 23912901 PMCID: PMC11113615 DOI: 10.1007/s00018-013-1437-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 07/02/2013] [Accepted: 07/24/2013] [Indexed: 12/23/2022]
Abstract
B chromosomes (Bs) are dispensable components of the genome exhibiting non-Mendelian inheritance and have been widely reported on over several thousand eukaryotes, but still remain an evolutionary mystery ever since their first discovery over a century ago [1]. Recent advances in genome analysis have significantly improved our knowledge on the origin and composition of Bs in the last few years. In contrast to the prevalent view that Bs do not harbor genes, recent analysis revealed that Bs of sequenced species are rich in gene-derived sequences. We summarize the latest findings on supernumerary chromosomes with a special focus on the origin, DNA composition, and the non-Mendelian accumulation mechanism of Bs.
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Affiliation(s)
- Andreas Houben
- Chromosome Structure and Function Laboratory, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466, Gatersleben, Germany,
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37
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Rechavi O. Guest list or black list: heritable small RNAs as immunogenic memories. Trends Cell Biol 2013; 24:212-20. [PMID: 24231398 DOI: 10.1016/j.tcb.2013.10.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 10/10/2013] [Accepted: 10/11/2013] [Indexed: 11/24/2022]
Abstract
Small RNA-mediated gene silencing plays a pivotal role in genome immunity by recognizing and eliminating viruses and transposons that may otherwise colonize the genome. However, individual genomic parasites are highly diverse and employ multiple immune-evasion techniques, making this silencing challenging. Here I review a new theory proposing that the integrity of the germline is maintained by transgenerationally transmitted RNA 'memories' that record ancestral gene expression patterns and delineate 'self' from 'foreign' sequences. To maintain such recollection, two tactics are employed in parallel: 'black listing' of invading nucleic acids and 'guest listing' of endogenous genes. Studies in several organisms have shown that this memorization is used by the next generation of small RNAs to act as 'inherited vaccines' that attack invading elements or as 'inherited licenses' that permit the transcription of autogenous sequences.
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Affiliation(s)
- Oded Rechavi
- Department of Neurobiology, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel 69978; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel 69978.
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Weinheimer I, Boonrod K, Moser M, Wassenegger M, Krczal G, Butcher SJ, Valkonen JPT. Binding and processing of small dsRNA molecules by the class 1 RNase III protein encoded by sweet potato chlorotic stunt virus. J Gen Virol 2013; 95:486-495. [PMID: 24187016 DOI: 10.1099/vir.0.058693-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Sweet potato chlorotic stunt virus (SPCSV; genus Crinivirus, family Closteroviridae) causes heavy yield losses in sweet potato plants co-infected with other viruses. The dsRNA-specific class 1 RNase III-like endoribonuclease (RNase3) encoded by SPCSV suppresses post-transcriptional gene silencing and eliminates antiviral defence in sweet potato plants in an endoribonuclease activity-dependent manner. RNase3 can cleave long dsRNA molecules, synthetic small interfering RNAs (siRNAs), and plant- and virus-derived siRNAs extracted from sweet potato plants. In this study, conditions for efficient expression and purification of enzymically active recombinant RNase3 were established. Similar to bacterial class 1 RNase III enzymes, RNase3-Ala (a dsRNA cleavage-deficient mutant) bound to and processed double-stranded siRNA (ds-siRNA) as a dimer. The results support the classification of SPCSV RNase3 as a class 1 RNase III enzyme. There is little information about the specificity of RNase III enzymes on small dsRNAs. In vitro assays indicated that ds-siRNAs and microRNAs (miRNAs) with a regular A-form conformation were cleaved by RNase3, but asymmetrical bulges, extensive mismatches and 2'-O-methylation of ds-siRNA and miRNA interfered with processing. Whereas Mg(2+) was the cation that best supported the catalytic activity of RNase3, binding of 21 nt small dsRNA molecules was most efficient in the presence of Mn(2+). Processing of long dsRNA by RNase3 was efficient at pH 7.5 and 8.5, whereas ds-siRNA was processed more efficiently at pH 8.5. The results revealed factors that influence binding and processing of small dsRNA substrates by class 1 RNase III in vitro or make them unsuitable for processing by the enzyme.
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Affiliation(s)
- Isabel Weinheimer
- AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, Neustadt a.d.W., Germany.,Department of Agricultural Sciences, PO Box 27, 00014 University of Helsinki, Helsinki, Finland
| | - Kajohn Boonrod
- AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, Neustadt a.d.W., Germany
| | - Mirko Moser
- AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, Neustadt a.d.W., Germany
| | - Michael Wassenegger
- Centre for Organismal Studies (COS) Heidelberg, Im Neuenheimer Feld 230, Heidelberg, Germany.,AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, Neustadt a.d.W., Germany
| | - Gabi Krczal
- AgroScience GmbH, AlPlanta-Institute for Plant Research, Breitenweg 71, Neustadt a.d.W., Germany
| | - Sarah J Butcher
- Institute of Biotechnology, PO Box 65, 00014 University of Helsinki, Helsinki, Finland
| | - Jari P T Valkonen
- Department of Agricultural Sciences, PO Box 27, 00014 University of Helsinki, Helsinki, Finland
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Krokida A, Delis C, Geisler K, Garagounis C, Tsikou D, Peña-Rodríguez LM, Katsarou D, Field B, Osbourn AE, Papadopoulou KK. A metabolic gene cluster in Lotus japonicus discloses novel enzyme functions and products in triterpene biosynthesis. THE NEW PHYTOLOGIST 2013; 200:675-690. [PMID: 23909862 DOI: 10.1111/nph.12414] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 06/20/2013] [Indexed: 05/03/2023]
Abstract
Genes for triterpene biosynthetic pathways exist as metabolic gene clusters in oat and Arabidopsis thaliana plants. We characterized the presence of an analogous gene cluster in the model legume Lotus japonicus. In the genomic regions flanking the oxidosqualene cyclase AMY2 gene, genes for two different classes of cytochrome P450 and a gene predicted to encode a reductase were identified. Functional characterization of the cluster genes was pursued by heterologous expression in Nicotiana benthamiana. The gene expression pattern was studied under different developmental and environmental conditions. The physiological role of the gene cluster in nodulation and plant development was studied in knockdown experiments. A novel triterpene structure, dihydrolupeol, was produced by AMY2. A new plant cytochrome P450, CYP71D353, which catalyses the formation of 20-hydroxybetulinic acid in a sequential three-step oxidation of 20-hydroxylupeol was characterized. The genes within the cluster are highly co-expressed during root and nodule development, in hormone-treated plants and under various environmental stresses. A transcriptional gene silencing mechanism that appears to be involved in the regulation of the cluster genes was also revealed. A tightly co-regulated cluster of functionally related genes is involved in legume triterpene biosynthesis, with a possible role in plant development.
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Affiliation(s)
- Afrodite Krokida
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
| | - Costas Delis
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
| | - Katrin Geisler
- Department of Metabolic Biology, John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK
| | - Constantine Garagounis
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
| | - Daniela Tsikou
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
| | - Luis M Peña-Rodríguez
- Unidad de Biotecnología, Centro de Investigación Científica de Yucatán, Mérida, Yucatán, México
| | - Dimitra Katsarou
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
| | - Ben Field
- Department of Metabolic Biology, John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK
| | - Anne E Osbourn
- Department of Metabolic Biology, John Innes Centre, Colney Lane, Norwich, NR4 7UH, UK
| | - Kalliope K Papadopoulou
- Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 & Aeolou Str., Larisa, 41221, Greece
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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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Mohan KN, Chaillet JR. Cell and molecular biology of DNA methyltransferase 1. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 306:1-42. [PMID: 24016522 DOI: 10.1016/b978-0-12-407694-5.00001-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The DNA cytosine methyltransferase 1 (DNMT1) is a ubiquitous nuclear enzyme that catalyzes the well-established reaction of placing methyl groups on the unmethylated cytosines in methyl-CpG:CpG base pairs in the hemimethylated DNA formed by methylated parent and unmethylated daughter strands. This activity regenerates fully methylated methyl-CpG:methyl-CpG pairs. Despite the straightforward nature of its catalytic activity, detailed biochemical, genetic, and developmental studies revealed intricate details of the central regulatory role of DNMT1 in governing the epigenetic makeup of the nuclear genome. DNMT1 mediates demethylation and also participates in seemingly wide cellular functions unrelated to maintenance DNA methylation. This review brings together mechanistic details of maintenance methylation by DNMT1, its regulation at transcriptional and posttranscriptional levels, and the seemingly unexpected functions of DNMT1 in the context of DNA methylation which is central to epigenetic changes that occur during development and the process of cell differentiation.
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Affiliation(s)
- K Naga Mohan
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, Hyderabad Campus, Hyderabad, Andhra Pradesh, India
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