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Hövel I, Bader R, Louwers M, Haring M, Peek K, Gent JI, Stam M. RNA-directed DNA methylation mutants reduce histone methylation at the paramutated maize booster1 enhancer. PLANT PHYSIOLOGY 2024; 195:1161-1179. [PMID: 38366582 PMCID: PMC11142347 DOI: 10.1093/plphys/kiae072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/19/2023] [Accepted: 12/25/2023] [Indexed: 02/18/2024]
Abstract
Paramutation is the transfer of mitotically and meiotically heritable silencing information between two alleles. With paramutation at the maize (Zea mays) booster1 (b1) locus, the low-expressed B' epiallele heritably changes the high-expressed B-I epiallele into B' with 100% frequency. This requires specific tandem repeats and multiple components of the RNA-directed DNA methylation pathway, including the RNA-dependent RNA polymerase (encoded by mediator of paramutation1, mop1), the second-largest subunit of RNA polymerase IV and V (NRP(D/E)2a, encoded by mop2), and the largest subunit of RNA Polymerase IV (NRPD1, encoded by mop3). Mutations in mop genes prevent paramutation and release silencing at the B' epiallele. In this study, we investigated the effect of mutations in mop1, mop2, and mop3 on chromatin structure and DNA methylation at the B' epiallele, and especially the regulatory hepta-repeat 100 kb upstream of the b1 gene. Mutations in mop1 and mop3 resulted in decreased repressive histone modifications H3K9me2 and H3K27me2 at the hepta-repeat. Associated with this decrease were partial activation of the hepta-repeat enhancer function, formation of a multi-loop structure, and elevated b1 expression. In mop2 mutants, which do not show elevated b1 expression, H3K9me2, H3K27me2 and a single-loop structure like in wild-type B' were retained. Surprisingly, high CG and CHG methylation levels at the B' hepta-repeat remained in all three mutants, and CHH methylation was low in both wild type and mutants. Our results raise the possibility of MOP factors mediating RNA-directed histone methylation rather than RNA-directed DNA methylation at the b1 locus.
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Affiliation(s)
- Iris Hövel
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
| | - Rechien Bader
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
| | - Marieke Louwers
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
- argenx BV, Industriepark Zwijnaarde 7, 9052 Zwijnaarde (Ghent), Belgium
| | - Max Haring
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
- University Library, Universiteit van Amsterdam, P.O. Box 19185, 1000 GD Amsterdam, The Netherlands
| | - Kevin Peek
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
| | - Jonathan I Gent
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Maike Stam
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, P.O. Box 1210, 1090 GE Amsterdam, The Netherlands
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Deans NC, Talbot JERB, Li M, Sáez-González C, Hövel I, Heavens D, Stam M, Hollick JB. Paramutation at the maize pl1 locus is associated with RdDM activity at distal tandem repeats. PLoS Genet 2024; 20:e1011296. [PMID: 38814980 PMCID: PMC11166354 DOI: 10.1371/journal.pgen.1011296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 06/11/2024] [Accepted: 05/08/2024] [Indexed: 06/01/2024] Open
Abstract
Exceptions to Mendelian inheritance often highlight novel chromosomal behaviors. The maize Pl1-Rhoades allele conferring plant pigmentation can display inheritance patterns deviating from Mendelian expectations in a behavior known as paramutation. However, the chromosome features mediating such exceptions remain unknown. Here we show that small RNA production reflecting RNA polymerase IV function within a distal downstream set of five tandem repeats is coincident with meiotically-heritable repression of the Pl1-Rhoades transcription unit. A related pl1 haplotype with three, but not one with two, repeat units also displays the trans-homolog silencing typifying paramutations. 4C interactions, CHD3a-dependent small RNA profiles, nuclease sensitivity, and polyadenylated RNA levels highlight a repeat subregion having regulatory potential. Our comparative and mutant analyses show that transcriptional repression of Pl1-Rhoades correlates with 24-nucleotide RNA production and cytosine methylation at this subregion indicating the action of a specific DNA-dependent RNA polymerase complex. These findings support a working model in which pl1 paramutation depends on trans-chromosomal RNA-directed DNA methylation operating at a discrete cis-linked and copy-number-dependent transcriptional regulatory element.
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Affiliation(s)
- Natalie C. Deans
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, Ohio, United States of America
| | - Joy-El R. B. Talbot
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Mowei Li
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, Ohio, United States of America
| | - Cristian Sáez-González
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Iris Hövel
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, Amsterdam, The Netherlands
| | | | - Maike Stam
- Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, Amsterdam, The Netherlands
| | - Jay B. Hollick
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, Ohio, United States of America
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
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3
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Sidorenko LV, Chandler VL, Wang X, Peterson T. Transcribed enhancer sequences are required for maize p1 paramutation. Genetics 2024; 226:iyad178. [PMID: 38169343 PMCID: PMC10763531 DOI: 10.1093/genetics/iyad178] [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: 11/14/2021] [Accepted: 08/27/2023] [Indexed: 01/05/2024] Open
Abstract
Paramutation is a transfer of heritable silencing states between interacting endogenous alleles or between endogenous alleles and homologous transgenes. Prior results demonstrated that paramutation occurs at the P1-rr (red pericarp and red cob) allele of the maize p1 (pericarp color 1) gene when exposed to a transgene containing a 1.2-kb enhancer fragment (P1.2) of P1-rr. The paramutable P1-rr allele undergoes transcriptional silencing resulting in a paramutant light-pigmented P1-rr' state. To define more precisely the sequences required to elicit paramutation, the P1.2 fragment was further subdivided, and the fragments transformed into maize plants and crossed with P1-rr. Analysis of the progeny plants showed that the sequences required for paramutation are located within a ∼600-bp segment of P1.2 and that this segment overlaps with a previously identified enhancer that is present in 4 direct repeats in P1-rr. The paramutagenic segment is transcribed in both the expressed P1-rr and the silenced P1-rr'. Transcription is sensitive to α-amanitin, indicating that RNA polymerase II mediates most of the transcription of this sequence. Although transcription within the paramutagenic sequence was similar in all tested genotypes, small RNAs were more abundant in the silenced P1-rr' epiallele relative to the expressed P1-rr allele. In agreement with prior results indicating the association of RNA-mediated DNA methylation in p1 paramutation, DNA blot analyses detected increased cytosine methylation of the paramutant P1-rr' sequences homologous to the transgenic P1.2 subfragments. Together these results demonstrate that the P1-rr enhancer repeats mediate p1 paramutation.
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Affiliation(s)
- Lyudmila V Sidorenko
- Department of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA
- Corteva Agriscience, 7300 NW 62nd Ave, Johnston, IA 50131, USA
| | - Vicki L Chandler
- Department of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA
- Minerva University, 14 Mint Plaza, Suite 300, San Francisco, CA 94103, USA
| | - Xiujuan Wang
- Corteva Agriscience, 7300 NW 62nd Ave, Johnston, IA 50131, USA
- Department of Genetics, Development, and Cellular Biology, Department of Agronomy, Iowa State University, Ames, IA 50010, USA
| | - Thomas Peterson
- Department of Genetics, Development, and Cellular Biology, Department of Agronomy, Iowa State University, Ames, IA 50010, USA
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Dorador AP, Dalikova M, Cerbin S, Stillman CM, Zych MG, Hawley RS, Miller DE, Ray DA, Funikov SY, Evgen’ev MB, Blumenstiel JP. Paramutation-like Epigenetic Conversion by piRNA at the Telomere of Drosophila virilis. BIOLOGY 2022; 11:biology11101480. [PMID: 36290385 PMCID: PMC9598792 DOI: 10.3390/biology11101480] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/27/2022] [Accepted: 10/04/2022] [Indexed: 11/10/2022]
Abstract
First discovered in maize, paramutation is a phenomenon in which one allele can trigger an epigenetic conversion of an alternate allele. This conversion causes a genetically heterozygous individual to transmit alleles that are functionally the same, in apparent violation of Mendelian segregation. Studies over the past several decades have revealed a strong connection between mechanisms of genome defense against transposable elements by small RNA and the phenomenon of paramutation. For example, a system of paramutation in Drosophila melanogaster has been shown to be mediated by piRNAs, whose primary function is to silence transposable elements in the germline. In this paper, we characterize a second system of piRNA-mediated paramutation-like behavior at the telomere of Drosophila virilis. In Drosophila, telomeres are maintained by arrays of retrotransposons that are regulated by piRNAs. As a result, the telomere and sub-telomeric regions of the chromosome have unique regulatory and chromatin properties. Previous studies have shown that maternally deposited piRNAs derived from a sub-telomeric piRNA cluster can silence the sub-telomeric center divider gene of Drosophila virilis in trans. In this paper, we show that this silencing can also be maintained in the absence of the original silencing allele in a subsequent generation. The precise mechanism of this paramutation-like behavior may be explained by either the production of retrotransposon piRNAs that differ across strains or structural differences in the telomere. Altogether, these results show that the capacity for piRNAs to mediate paramutation in trans may depend on the local chromatin environment and proximity to the uniquely structured telomere regulated by piRNAs. This system promises to provide significant insights into the mechanisms of paramutation.
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Affiliation(s)
- Ana P. Dorador
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Martina Dalikova
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Stefan Cerbin
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Chris M. Stillman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Molly G. Zych
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Divisions of Basic Sciences and Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - R. Scott Hawley
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Danny E. Miller
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- Division of Genetic Medicine, Department of Pediatrics, University of Washington and Seattle Children’s Hospital, Seattle, WA 98195, USA
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | - David A. Ray
- Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA
| | - Sergei Y. Funikov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
| | - Michael B. Evgen’ev
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow 119991, Russia
| | - Justin P. Blumenstiel
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
- Correspondence:
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Tonosaki K, Fujimoto R, Dennis ES, Raboy V, Osabe K. Will epigenetics be a key player in crop breeding? FRONTIERS IN PLANT SCIENCE 2022; 13:958350. [PMID: 36247549 PMCID: PMC9562705 DOI: 10.3389/fpls.2022.958350] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
If food and feed production are to keep up with world demand in the face of climate change, continued progress in understanding and utilizing both genetic and epigenetic sources of crop variation is necessary. Progress in plant breeding has traditionally been thought to be due to selection for spontaneous DNA sequence mutations that impart desirable phenotypes. These spontaneous mutations can expand phenotypic diversity, from which breeders can select agronomically useful traits. However, it has become clear that phenotypic diversity can be generated even when the genome sequence is unaltered. Epigenetic gene regulation is a mechanism by which genome expression is regulated without altering the DNA sequence. With the development of high throughput DNA sequencers, it has become possible to analyze the epigenetic state of the whole genome, which is termed the epigenome. These techniques enable us to identify spontaneous epigenetic mutations (epimutations) with high throughput and identify the epimutations that lead to increased phenotypic diversity. These epimutations can create new phenotypes and the causative epimutations can be inherited over generations. There is evidence of selected agronomic traits being conditioned by heritable epimutations, and breeders may have historically selected for epiallele-conditioned agronomic traits. These results imply that not only DNA sequence diversity, but the diversity of epigenetic states can contribute to increased phenotypic diversity. However, since the modes of induction and transmission of epialleles and their stability differ from that of genetic alleles, the importance of inheritance as classically defined also differs. For example, there may be a difference between the types of epigenetic inheritance important to crop breeding and crop production. The former may depend more on longer-term inheritance whereas the latter may simply take advantage of shorter-term phenomena. With the advances in our understanding of epigenetics, epigenetics may bring new perspectives for crop improvement, such as the use of epigenetic variation or epigenome editing in breeding. In this review, we will introduce the role of epigenetic variation in plant breeding, largely focusing on DNA methylation, and conclude by asking to what extent new knowledge of epigenetics in crop breeding has led to documented cases of its successful use.
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Affiliation(s)
- Kaoru Tonosaki
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
| | - Ryo Fujimoto
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| | - Elizabeth S. Dennis
- Commonwealth Scientific and Industrial Research Organisation (CSIRO) Agriculture and Food, Canberra, ACT, Australia
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
| | - Victor Raboy
- Independent Researcher Portland, Portland, OR, United States
| | - Kenji Osabe
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, Osaka, Japan
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Aubert J, Bellegarde F, Oltehua-Lopez O, Leblanc O, Arteaga-Vazquez MA, Martienssen RA, Grimanelli D. AGO104 is a RdDM effector of paramutation at the maize b1 locus. PLoS One 2022; 17:e0273695. [PMID: 36040902 PMCID: PMC9426929 DOI: 10.1371/journal.pone.0273695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 08/12/2022] [Indexed: 11/19/2022] Open
Abstract
Although paramutation has been well-studied at a few hallmark loci involved in anthocyanin biosynthesis in maize, the cellular and molecular mechanisms underlying the phenomenon remain largely unknown. Previously described actors of paramutation encode components of the RNA-directed DNA-methylation (RdDM) pathway that participate in the biogenesis of 24-nucleotide small interfering RNAs (24-nt siRNAs) and long non-coding RNAs. In this study, we uncover an ARGONAUTE (AGO) protein as an effector of the RdDM pathway that is in charge of guiding 24-nt siRNAs to their DNA target to create de novo DNA methylation. We combined immunoprecipitation, small RNA sequencing and reverse genetics to, first, validate AGO104 as a member of the RdDM effector complex and, then, investigate its role in paramutation. We found that AGO104 binds 24-nt siRNAs involved in RdDM, including those required for paramutation at the b1 locus. We also show that the ago104-5 mutation causes a partial reversion of the paramutation phenotype at the b1 locus, revealed by intermediate pigmentation levels in stem tissues. Therefore, our results place AGO104 as a new member of the RdDM effector complex that plays a role in paramutation at the b1 locus in maize.
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Affiliation(s)
- Juliette Aubert
- DIADE, University of Montpellier, CIRAD, IRD, Montpellier, France
| | - Fanny Bellegarde
- DIADE, University of Montpellier, CIRAD, IRD, Montpellier, France
| | | | - Olivier Leblanc
- DIADE, University of Montpellier, CIRAD, IRD, Montpellier, France
| | | | - Robert A. Martienssen
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, New York, United States of America
| | - Daniel Grimanelli
- DIADE, University of Montpellier, CIRAD, IRD, Montpellier, France
- * E-mail:
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CHROMOMETHYLTRANSFERASE3/KRYPTONITE maintains the sulfurea paramutation in Solanum lycopersicum. Proc Natl Acad Sci U S A 2022; 119:e2112240119. [PMID: 35324329 PMCID: PMC9060480 DOI: 10.1073/pnas.2112240119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
SignificanceParamutation involves the transfer of a repressive epigenetic mark between silent and active alleles. It is best known from exceptional non-Mendelian inheritance of conspicuous phenotypes in maize but also in other plants and animals. Recent genomic studies, however, indicate that paramutation may be less exceptional. It may be a consequence of wide-cross hybridization and may contribute to quantitative trait variation or unstable phenotypes in crops. Using the sulfurea (sulf) locus in tomato, we demonstrate that a self-reinforcing feedback loop involving DNA- and histone-methyl transferases CHROMOMETHYLTRANSFERASE3 (CMT3) and KRYPTONITE (KYP) is required for paramutation of sulf and that there is a change in chromatin organization. These findings advance the understanding of non-Mendelian inheritance in plants.
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Cao S, Wang L, Han T, Ye W, Liu Y, Sun Y, Moose SP, Song Q, Chen ZJ. Small RNAs mediate transgenerational inheritance of genome-wide trans-acting epialleles in maize. Genome Biol 2022; 23:53. [PMID: 35139883 PMCID: PMC8827192 DOI: 10.1186/s13059-022-02614-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 01/17/2022] [Indexed: 12/13/2022] Open
Abstract
Background Hybridization and backcrossing are commonly used in animal and plant breeding to induce heritable variation including epigenetic changes such as paramutation. However, the molecular basis for hybrid-induced epigenetic memory remains elusive. Results Here, we report that hybridization between the inbred parents B73 and Mo17 induces trans-acting hypermethylation and hypomethylation at thousands of loci; several hundreds (~ 3%) are transmitted through six backcrossing and three selfing generations. Notably, many transgenerational methylation patterns resemble epialleles of the nonrecurrent parent, despite > 99% of overall genomic loci are converted to the recurrent parent. These epialleles depend on 24-nt siRNAs, which are eliminated in the isogenic hybrid Mo17xB73:mop1-1 that is defective in siRNA biogenesis. This phenomenon resembles paramutation-like events and occurs in both intraspecific (Mo17xB73) and interspecific (W22xTeosinte) hybrid maize populations. Moreover, siRNA abundance and methylation levels of these epialleles can affect expression of their associated epigenes, many of which are related to stress responses. Conclusion Divergent siRNAs between the hybridizing parents can induce trans-acting epialleles in the hybrids, while the induced epigenetic status is maintained for transgenerational inheritance during backcross and hybrid breeding, which alters epigene expression to enhance growth and adaptation. These genetic and epigenetic principles may apply broadly from plants to animals. Supplementary Information The online version contains supplementary material available at 10.1186/s13059-022-02614-0.
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Affiliation(s)
- Shuai Cao
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China
| | - Longfei Wang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China
| | - Tongwen Han
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China
| | - Wenxue Ye
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China
| | - Yang Liu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China
| | - Yi Sun
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Stephen P Moose
- Department of Crop Sciences, University of Illinois, Urbana, IL, 61801, USA
| | - Qingxin Song
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, 1 Weigang Road, Nanjing, 210095, China.
| | - Z Jeffrey Chen
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA.
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9
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Burton NO, Greer EL. Multigenerational epigenetic inheritance: Transmitting information across generations. Semin Cell Dev Biol 2021; 127:121-132. [PMID: 34426067 DOI: 10.1016/j.semcdb.2021.08.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 01/07/2023]
Abstract
Inherited epigenetic information has been observed to regulate a variety of complex organismal phenotypes across diverse taxa of life. This continually expanding body of literature suggests that epigenetic inheritance plays a significant, and potentially fundamental, role in inheritance. Despite the important role these types of effects play in biology, the molecular mediators of this non-genetic transmission of information are just now beginning to be deciphered. Here we provide an intellectual framework for interpreting these findings and how they can interact with each other. We also define the different types of mechanisms that have been found to mediate epigenetic inheritance and to regulate whether epigenetic information persists for one or many generations. The field of epigenetic inheritance is entering an exciting phase, in which we are beginning to understand the mechanisms by which non-genetic information is transmitted to, and deciphered by, subsequent generations to maintain essential environmental information without permanently altering the genetic code. A more complete understanding of how and when epigenetic inheritance occurs will advance our understanding of numerous different aspects of biology ranging from how organisms cope with changing environments to human pathologies influenced by a parent's environment.
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Affiliation(s)
- Nicholas O Burton
- Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK; Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK; Center for Epigenetics, Van Andel Institute, Grand Rapids, MI 49503, USA.
| | - Eric L Greer
- Division of Newborn Medicine, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Harvard Medical School Initiative for RNA Medicine, Boston, MA 02115, USA.
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Kang DR, Zhu Y, Li SL, Ai PH, Khan MA, Ding HX, Wang Y, Wang ZC. Transcriptome analysis of differentially expressed genes in chrysanthemum MET1 RNA interference lines. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2021; 27:1455-1468. [PMID: 34366589 PMCID: PMC8295425 DOI: 10.1007/s12298-021-01022-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 06/02/2021] [Accepted: 06/07/2021] [Indexed: 05/14/2023]
Abstract
UNLABELLED DNA methylation is the most important epigenetic modification involved in many essential biological processes. MET1 is one of DNA methyltransferases that affect the level of methylation in the entire genome. To explore the effect of MET1 gene silencing on gene expression profile of Chrysanthemum × morifolium 'Zijingling'. The stem section and leaves at the young stage were taken for transcriptome sequencing. MET1-RNAi leaves had 8 differentially expressed genes while 156 differentially expressed genes were observed in MET1-RNAi stem compared with control leaves and stem. These genes encode many key proteins in plant biological processes, such as transcription factors, signal transduction mechanisms, secondary metabolite synthesis, transport and catabolism and interaction. In general, 34.58% of the differentially expressed genes in leaves and stems were affected by the reduction of the MET1 gene. The differentially expressed genes in stem and leaves of transgenic plants went through significant changes. We found adequate amount of candidate genes associated with flowering, however, the number of genes with significant differences between transgenic and control lines was not too high. Several flowering related genes were screened out for gene expression verification and all of them were obseved as consistent with transcriptome data. These candidate genes may play important role in flowering variation of chrysanthemum. This study reveals the mechanism of CmMET1 interference on the growth and development of chrysanthemum at the transcriptional level, which provides the basis for further research on the epigenetic regulation mechanism in flower induction and development. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s12298-021-01022-1.
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Affiliation(s)
- Dong-ru Kang
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Yi Zhu
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Shuai-lei Li
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Peng-hui Ai
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Muhammad Ayoub Khan
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Hong-xu Ding
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Ying Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
| | - Zi-cheng Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, Plant Germplasm Resources and Genetic Laboratory, Kaifeng Key Laboratory of Chrysanthemum Biology, School of Life Sciences, Henan University. Jinming Road, Kaifeng, 475004 Henan China
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Bente H, Foerster AM, Lettner N, Mittelsten Scheid O. Polyploidy-associated paramutation in Arabidopsis is determined by small RNAs, temperature, and allele structure. PLoS Genet 2021; 17:e1009444. [PMID: 33690630 PMCID: PMC7978347 DOI: 10.1371/journal.pgen.1009444] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 03/19/2021] [Accepted: 02/24/2021] [Indexed: 11/18/2022] Open
Abstract
Paramutation is a form of non-Mendelian inheritance in which the expression of a paramutable allele changes when it encounters a paramutagenic allele. This change in expression of the paramutable alleles is stably inherited even after segregation of both alleles. While the discovery of paramutation and studies of its underlying mechanism were made with alleles that change plant pigmentation, paramutation-like phenomena are known to modulate the expression of other traits and in other eukaryotes, and many cases have probably gone undetected. It is likely that epigenetic mechanisms are responsible for the phenomenon, as paramutation forms epialleles, genes with identical sequences but different expression states. This could account for the intergenerational inheritance of the paramutated allele, providing profound evidence that triggered epigenetic changes can be maintained over generations. Here, we use a case of paramutation that affects a transgenic selection reporter gene in tetraploid Arabidopsis thaliana. Our data suggest that different types of small RNA are derived from paramutable and paramutagenic epialleles. In addition, deletion of a repeat within the epiallele changes its paramutability. Further, the temperature during the growth of the epiallelic hybrids determines the degree and timing of the allelic interaction. The data further make it plausible why paramutation in this system becomes evident only in the segregating F2 population of tetraploid plants containing both epialleles. In summary, the results support a model for polyploidy-associated paramutation, with similarities as well as distinctions from other cases of paramutation.
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Affiliation(s)
- Heinrich Bente
- Gregor Mendel Institute of Molecular Plant Biology (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria
| | - Andrea M. Foerster
- Gregor Mendel Institute of Molecular Plant Biology (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria
| | - Nicole Lettner
- Gregor Mendel Institute of Molecular Plant Biology (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria
| | - Ortrun Mittelsten Scheid
- Gregor Mendel Institute of Molecular Plant Biology (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Vienna, Austria
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12
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Locus-specific paramutation in Zea mays is maintained by a PICKLE-like chromodomain helicase DNA-binding 3 protein controlling development and male gametophyte function. PLoS Genet 2020; 16:e1009243. [PMID: 33320854 PMCID: PMC7837471 DOI: 10.1371/journal.pgen.1009243] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 01/26/2021] [Accepted: 11/02/2020] [Indexed: 12/22/2022] Open
Abstract
Paramutations represent directed and meiotically-heritable changes in gene regulation leading to apparent violations of Mendelian inheritance. Although the mechanism and evolutionary importance of paramutation behaviors remain largely unknown, genetic screens in maize (Zea mays) identify five components affecting 24 nucleotide RNA biogenesis as required to maintain repression of a paramutant purple plant1 (pl1) allele. Currently, the RNA polymerase IV largest subunit represents the only component also specifying proper development. Here we identify a chromodomain helicase DNA-binding 3 (CHD3) protein orthologous to Arabidopsis (Arabidopsis thaliana) PICKLE as another component maintaining both pl1 paramutation and normal somatic development but without affecting overall small RNA biogenesis. In addition, genetic tests show this protein contributes to proper male gametophyte function. The similar mutant phenotypes documented in Arabidopsis and maize implicate some evolutionarily-conserved gene regulation while developmental defects associated with the two paramutation mutants are largely distinct. Our results show that a CHD3 protein responsible for normal plant ontogeny and sperm transmission also helps maintain meiotically-heritable epigenetic regulatory variation for specific alleles. This finding implicates an intersection of RNA polymerase IV function and nucleosome positioning in the paramutation process. Genes are switched “on” and “off” during normal development by regulating DNA accessibility within the chromosomes. How certain gene variants permanently maintain “off” states from one generation to the next remains unclear, but studies in multiple eukaryotes implicate roles for specific types of small RNAs, some of which define cytosine methylation patterns. In corn, these RNAs come from at least two RNA polymerase II-derived complexes sharing a common catalytic subunit (RPD1). Although RPD1 both controls the normal developmental switching of many genes and permanently maintains some of these “off” states across generations, how RPD1 function defines heritable DNA accessibility is unknown. We discovered that a protein (CHD3a) belonging to a group known to alter nucleosome positioning is also required to help maintain a heritable “off” state for one particular corn gene variant controlling both plant and flower color. We also found CHD3a necessary for normal plant development and sperm transmission consistent with the idea that proper nucleosome positioning defines evolutionarily-important gene expression patterns. Because both CHD3a and RPD1 maintain the heritable “off” state of a specific gene variant, their functions appear to be mechanistically linked.
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13
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Pontvianne F, Grob S. Three-dimensional nuclear organization in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2020; 133:479-488. [PMID: 32240449 DOI: 10.1007/s10265-020-01185-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 03/19/2020] [Indexed: 05/22/2023]
Abstract
In recent years, the study of plant three-dimensional nuclear architecture received increasing attention. Enabled by technological advances, our knowledge on nuclear architecture has greatly increased and we can now access large data sets describing its manifold aspects. The principles of nuclear organization in plants do not significantly differ from those in animals. Plant nuclear organization comprises various scales, ranging from gene loops to topologically associating domains to nuclear compartmentalization. However, whether plant three-dimensional chromosomal features also exert similar functions as in animals is less clear. This review discusses recent advances in the fields of three-dimensional chromosome folding and nuclear compartmentalization and describes a novel silencing mechanism, which is closely linked to nuclear architecture.
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Affiliation(s)
- Frédéric Pontvianne
- UPVD, LGDP, UMR5096, Université de Perpignan, Perpignan, France.
- CNRS, LGDP, UMR5096, Université de Perpignan, Perpignan, France.
| | - Stefan Grob
- Institute of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
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14
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Sarkies P. Molecular mechanisms of epigenetic inheritance: Possible evolutionary implications. Semin Cell Dev Biol 2020; 97:106-115. [PMID: 31228598 PMCID: PMC6945114 DOI: 10.1016/j.semcdb.2019.06.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/04/2019] [Accepted: 06/18/2019] [Indexed: 12/30/2022]
Abstract
Recently interest in multi-generational epigenetic phenomena have been fuelled by highly reproducible intergenerational and transgenerational inheritance paradigms in several model organisms. Such paradigms are essential in order to begin to use genetics to unpick the mechanistic bases of how epigenetic information may be transmitted between generations; indeed great strides have been made towards understanding these mechanisms. Far less well understood is the relationship between epigenetic inheritance, ecology and evolution. In this review I focus on potential connections between laboratory studies of transgenerational epigenetic inheritance phenomena and evolutionary processes that occur in natural populations. In the first section, I consider whether transgenerational epigenetic inheritance might provide an advantage to organisms over the short term in adapting to their environment. Second, I consider whether epigenetic changes can contribute to the evolution of species by contributing to stable phenotypic variation within a population. Finally I discuss whether epigenetic changes could influence evolution by either directly or indirectly promoting DNA sequence changes that could impact phenotypic divergence. Additionally, I will discuss how epigenetic changes could influence the evolution of human cancer and thus be directly relevant for the development of this disease.
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Affiliation(s)
- Peter Sarkies
- MRC London Institute of Medical Sciences, Du Cane Road, London, W120NN, United Kingdom; Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W120NN, United Kingdom.
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15
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Wang PH, Wittmeyer KT, Lee TF, Meyers BC, Chopra S. Overlapping RdDM and non-RdDM mechanisms work together to maintain somatic repression of a paramutagenic epiallele of maize pericarp color1. PLoS One 2017; 12:e0187157. [PMID: 29112965 PMCID: PMC5675401 DOI: 10.1371/journal.pone.0187157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/14/2017] [Indexed: 11/18/2022] Open
Abstract
Allelic variation at the Zea mays (maize) pericarp color1 (p1) gene has been attributed to epigenetic gene regulation. A p1 distal enhancer, 5.2 kb upstream of the transcriptional start site, has demonstrated variation in DNA methylation in different p1 alleles/epialleles. In addition, DNA methylation of sequences within the 3’ end of intron 2 also plays a role in tissue-specific expression of p1 alleles. We show here a direct evidence for small RNAs’ involvement in regulating p1 that has not been demonstrated previously. The role of mediator of paramutation1 (mop1) was tested in the maintenance of somatic silencing at distinct p1 alleles: the non-paramutagenic P1-wr allele and paramutagenic P1-rr’ epiallele. The mop1-1 mutation gradually relieves the silenced phenotype after multiple generations of exposure; P1-wr;mop1-1 plants display a loss of 24-nt small RNAs and DNA methylation in the 3’ end of the intron 2, a region close to a Stowaway transposon. In addition, a MULE sequence within the proximal promoter of P1-wr shows depletion of 24nt siRNAs in mop1-1 plants. Release of silencing was not correlated with small RNAs at the distal enhancer region of the P1-wr allele. We found that the somatic silencing of the paramutagenic P1-rr’ is correlated with significantly reduced H3K9me2 in the distal enhancer of P1-rr’; mop1-1 plants, while symmetric DNA methylation is not significantly different. This study highlights that the epigenetic regulation of p1 alleles is controlled both via RdDM as well as non-RdDM mechanisms.
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Affiliation(s)
- Po-Hao Wang
- Department of Plant Science, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Kameron T. Wittmeyer
- Department of Plant Science, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Plant Biology Program, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Tzuu-fen Lee
- Department of Plant & Soil Sciences and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware, United States of America
| | - Blake C. Meyers
- Department of Plant & Soil Sciences and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware, United States of America
| | - Surinder Chopra
- Department of Plant Science, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Plant Biology Program, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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16
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Li Y, Ding X, Wang X, He T, Zhang H, Yang L, Wang T, Chen L, Gai J, Yang S. Genome-wide comparative analysis of DNA methylation between soybean cytoplasmic male-sterile line NJCMS5A and its maintainer NJCMS5B. BMC Genomics 2017; 18:596. [PMID: 28806912 PMCID: PMC5557475 DOI: 10.1186/s12864-017-3962-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 07/25/2017] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND DNA methylation is an important epigenetic modification. It can regulate the expression of many key genes without changing the primary structure of the genomic DNA, and plays a vital role in the growth and development of the organism. The genome-wide DNA methylation profile of the cytoplasmic male sterile (CMS) line in soybean has not been reported so far. RESULTS In this study, genome-wide comparative analysis of DNA methylation between soybean CMS line NJCMS5A and its maintainer NJCMS5B was conducted by whole-genome bisulfite sequencing. The results showed 3527 differentially methylated regions (DMRs) and 485 differentially methylated genes (DMGs), including 353 high-credible methylated genes, 56 methylated genes coding unknown protein and 76 novel methylated genes with no known function were identified. Among them, 25 DMRs were further validated that the genome-wide DNA methylation data were reliable through bisulfite treatment, and 9 DMRs were confirmed the relationship between DNA methylation and gene expression by qRT-PCR. Finally, 8 key DMGs possibly associated with soybean CMS were identified. CONCLUSIONS Genome-wide DNA methylation profile of the soybean CMS line NJCMS5A and its maintainer NJCMS5B was obtained for the first time. Several specific DMGs which participated in pollen and flower development were further identified to be probably associated with soybean CMS. This study will contribute to further understanding of the molecular mechanism behind soybean CMS.
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Affiliation(s)
- Yanwei Li
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Xianlong Ding
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Xuan Wang
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Tingting He
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Hao Zhang
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Longshu Yang
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Tanliu Wang
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Linfeng Chen
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Junyi Gai
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
| | - Shouping Yang
- Soybean Research Institute, National Center for Soybean Improvement, Key Laboratory of Biology and Genetic Improvement of Soybean (General, Ministry of Agriculture), State Key Laboratory of Crop Genetics and Germplasm Enhancement, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing, 210095 China
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17
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Aldrich JC, Leibholz A, Cheema MS, Ausiό J, Ferree PM. A 'selfish' B chromosome induces genome elimination by disrupting the histone code in the jewel wasp Nasonia vitripennis. Sci Rep 2017; 7:42551. [PMID: 28211924 PMCID: PMC5304203 DOI: 10.1038/srep42551] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 01/10/2017] [Indexed: 01/04/2023] Open
Abstract
Intragenomic conflict describes a phenomenon in which genetic elements act ‘selfishly’ to gain a transmission advantage at the expense of the whole genome. A non-essential, selfish B chromosome known as Paternal Sex Ratio (PSR) induces complete elimination of the sperm-derived hereditary material in the jewel wasp Nasonia vitripennis. PSR prevents the paternal chromatin from forming chromosomes during the first embryonic mitosis, leading to its loss. Although paternally transmitted, PSR evades self-elimination in order to be inherited. We examined important post-translational modifications to the DNA packaging histones on the normal genome and the PSR chromosome in the fertilized embryo. Three histone marks – H3K9me2,3, H3K27me1, and H4K20me1 – became abnormally enriched and spread to ectopic positions on the sperm’s chromatin before entry into mitosis. In contrast, other histone marks and DNA methylation were not affected by PSR, suggesting that its effect on the paternal genome is specific to a subset of histone marks. Contrary to the paternally derived genome, the PSR chromosome was visibly devoid of the H3K27me1 and H4K20me1 marks. These findings strongly suggest that PSR causes paternal genome elimination by disrupting at least three histone marks following fertilization, while PSR avoids self-elimination by evading two of these marks.
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Affiliation(s)
- John C Aldrich
- W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA 91711, USA
| | - Alexandra Leibholz
- W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA 91711, USA
| | - Manjinder S Cheema
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W-3P6, Canada
| | - Juan Ausiό
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W-3P6, Canada
| | - Patrick M Ferree
- W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA 91711, USA
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18
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19
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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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20
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Taylor DH, Chu ETJ, Spektor R, Soloway PD. Long non-coding RNA regulation of reproduction and development. Mol Reprod Dev 2015; 82:932-56. [PMID: 26517592 PMCID: PMC4762656 DOI: 10.1002/mrd.22581] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 09/03/2015] [Indexed: 12/13/2022]
Abstract
Noncoding RNAs (ncRNAs) have long been known to play vital roles in eukaryotic gene regulation. Studies conducted over a decade ago revealed that maturation of spliced, polyadenylated coding mRNA occurs by reactions involving small nuclear RNAs and small nucleolar RNAs; mRNA translation depends on activities mediated by transfer RNAs and ribosomal RNAs, subject to negative regulation by micro RNAs; transcriptional competence of sex chromosomes and some imprinted genes is regulated in cis by ncRNAs that vary by species; and both small-interfering RNAs and piwi-interacting RNAs bound to Argonaute-family proteins regulate post-translational modifications on chromatin and local gene expression states. More recently, gene-regulating noncoding RNAs have been identified, such as long intergenic and long noncoding RNAs (collectively referred to as lncRNAs)--a class totaling more than 100,000 transcripts in humans, which include some of the previously mentioned RNAs that regulate dosage compensation and imprinted gene expression. Here, we provide an overview of lncRNA activities, and then review the role of lncRNAs in processes vital to reproduction, such as germ cell specification, sex determination and gonadogenesis, sex hormone responses, meiosis, gametogenesis, placentation, non-genetic inheritance, and pathologies affecting reproductive tissues. Results from many species are presented to illustrate the evolutionarily conserved processes lncRNAs are involved in.
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Affiliation(s)
- David H. Taylor
- Field of Genetics, Genomics and Development, Cornell University, Ithaca, New York
| | - Erin Tsi-Jia Chu
- Field of Comparative Biomedical Sciences, Cornell University, Ithaca, New York
| | - Roman Spektor
- Field of Genetics, Genomics and Development, Cornell University, Ithaca, New York
| | - Paul D. Soloway
- Field of Genetics, Genomics and Development, Cornell University, Ithaca, New York
- Field of Comparative Biomedical Sciences, Cornell University, Ithaca, New York
- Division of Nutritional Sciences, Cornell University, Ithaca, New York
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21
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Liu L, Du Y, Shen X, Li M, Sun W, Huang J, Liu Z, Tao Y, Zheng Y, Yan J, Zhang Z. KRN4 Controls Quantitative Variation in Maize Kernel Row Number. PLoS Genet 2015; 11:e1005670. [PMID: 26575831 PMCID: PMC4648495 DOI: 10.1371/journal.pgen.1005670] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/23/2015] [Indexed: 12/27/2022] Open
Abstract
Kernel row number (KRN) is an important component of yield during the domestication and improvement of maize and controlled by quantitative trait loci (QTL). Here, we fine-mapped a major KRN QTL, KRN4, which can enhance grain productivity by increasing KRN per ear. We found that a ~3-Kb intergenic region about 60 Kb downstream from the SBP-box gene Unbranched3 (UB3) was responsible for quantitative variation in KRN by regulating the level of UB3 expression. Within the 3-Kb region, the 1.2-Kb Presence-Absence variant was found to be strongly associated with quantitative variation in KRN in diverse maize inbred lines, and our results suggest that this 1.2-Kb transposon-containing insertion is likely responsible for increased KRN. A previously identified A/G SNP (S35, also known as Ser220Asn) in UB3 was also found to be significantly associated with KRN in our association-mapping panel. Although no visible genetic effect of S35 alone could be detected in our linkage mapping population, it was found to genetically interact with the 1.2-Kb PAV to modulate KRN. The KRN4 was under strong selection during maize domestication and the favorable allele for the 1.2-Kb PAV and S35 has been significantly enriched in modern maize improvement process. The favorable haplotype (Hap1) of 1.2-Kb-PAV-S35 was selected during temperate maize improvement, but is still rare in tropical and subtropical maize germplasm. The dissection of the KRN4 locus improves our understanding of the genetic basis of quantitative variation in complex traits in maize. Maize (Zea mays L.) is one of the world's most important sources of calories for humans. With an expanding global population, the demands for maize-derived food, feed, and fuel are rapidly increasing. To meet these needs, geneticists and breeders are facing the challenge of enhancing grain yield through genetic improvement of maize germplasm. Understanding the genetic basis of grain yield is necessary to guide breeding efforts towards the development of high-yielding hybrids. Kernel row number (KRN) in maize is one of the most important yield components and a significant breeding target. Over the last few decades, many genes that determine inflorescence development and architecture have been identified and characterized. The formation of kernel rows is an integral part of the development of the female inflorescence in maize. Nevertheless, the genetic basis and molecular regulation of quantitative variation in KRN is poorly understood. This study provides experimental evidence for the hypothesis that variation in intergenic regions can regulate quantitative variation of important grain yield-related traits, and also provides tools for improving KRN in maize.
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Affiliation(s)
- Lei Liu
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Yanfang Du
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Xiaomeng Shen
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Manfei Li
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Wei Sun
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Juan Huang
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Zhijie Liu
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Yongsheng Tao
- College of Agronomy, Hebei Agricultural University, Baoding Hebei, People's Republic of China
| | - Yonglian Zheng
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Jianbing Yan
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
| | - Zuxin Zhang
- National Key Lab of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan Hubei, People's Republic of China
- Hubei Collaborative Innovation Center for Grain Crops, Jingzhou Hubei, People's Republic of China
- * E-mail:
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22
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Ong-Abdullah M, Ordway JM, Jiang N, Ooi SE, Kok SY, Sarpan N, Azimi N, Hashim AT, Ishak Z, Rosli SK, Malike FA, Bakar NAA, Marjuni M, Abdullah N, Yaakub Z, Amiruddin MD, Nookiah R, Singh R, Low ETL, Chan KL, Azizi N, Smith SW, Bacher B, Budiman MA, Van Brunt A, Wischmeyer C, Beil M, Hogan M, Lakey N, Lim CC, Arulandoo X, Wong CK, Choo CN, Wong WC, Kwan YY, Alwee SSRS, Sambanthamurthi R, Martienssen RA. Loss of Karma transposon methylation underlies the mantled somaclonal variant of oil palm. Nature 2015; 525:533-7. [PMID: 26352475 PMCID: PMC4857894 DOI: 10.1038/nature15365] [Citation(s) in RCA: 268] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 08/10/2015] [Indexed: 12/25/2022]
Abstract
Somaclonal variation arises in plants and animals when differentiated somatic cells are induced into a pluripotent state, but the resulting clones differ from each other and from their parents. In agriculture, somaclonal variation has hindered the micropropagation of elite hybrids and genetically modified crops, but the mechanism responsible remains unknown. The oil palm fruit 'mantled' abnormality is a somaclonal variant arising from tissue culture that drastically reduces yield, and has largely halted efforts to clone elite hybrids for oil production. Widely regarded as an epigenetic phenomenon, 'mantling' has defied explanation, but here we identify the MANTLED locus using epigenome-wide association studies of the African oil palm Elaeis guineensis. DNA hypomethylation of a LINE retrotransposon related to rice Karma, in the intron of the homeotic gene DEFICIENS, is common to all mantled clones and is associated with alternative splicing and premature termination. Dense methylation near the Karma splice site (termed the Good Karma epiallele) predicts normal fruit set, whereas hypomethylation (the Bad Karma epiallele) predicts homeotic transformation, parthenocarpy and marked loss of yield. Loss of Karma methylation and of small RNA in tissue culture contributes to the origin of mantled, while restoration in spontaneous revertants accounts for non-Mendelian inheritance. The ability to predict and cull mantling at the plantlet stage will facilitate the introduction of higher performing clones and optimize environmentally sensitive land resources.
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Affiliation(s)
- Meilina Ong-Abdullah
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Jared M Ordway
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Nan Jiang
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Siew-Eng Ooi
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Sau-Yee Kok
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Norashikin Sarpan
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Nuraziyan Azimi
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Ahmad Tarmizi Hashim
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Zamzuri Ishak
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Samsul Kamal Rosli
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Fadila Ahmad Malike
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Nor Azwani Abu Bakar
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Marhalil Marjuni
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Norziha Abdullah
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Zulkifli Yaakub
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Mohd Din Amiruddin
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Rajanaidu Nookiah
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Rajinder Singh
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Eng-Ti Leslie Low
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Kuang-Lim Chan
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Norazah Azizi
- Malaysian Palm Oil Board, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Steven W Smith
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Blaire Bacher
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | | | - Andrew Van Brunt
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Corey Wischmeyer
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Melissa Beil
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Michael Hogan
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Nathan Lakey
- Orion Genomics, 4041 Forest Park Avenue, St Louis, Missouri 63108, USA
| | - Chin-Ching Lim
- United Plantations Berhad, Jendarata Estate, 36009 Teluk Intan, Perak, Malaysia
| | - Xaviar Arulandoo
- United Plantations Berhad, Jendarata Estate, 36009 Teluk Intan, Perak, Malaysia
| | - Choo-Kien Wong
- Applied Agricultural Resources Sdn Bhd, No. 11, Jalan Teknologi 3/6, Taman Sains Selangor 1, 47810 Kota Damansara, Petaling Jaya, Selangor, Malaysia
| | - Chin-Nee Choo
- Applied Agricultural Resources Sdn Bhd, No. 11, Jalan Teknologi 3/6, Taman Sains Selangor 1, 47810 Kota Damansara, Petaling Jaya, Selangor, Malaysia
| | - Wei-Chee Wong
- Applied Agricultural Resources Sdn Bhd, No. 11, Jalan Teknologi 3/6, Taman Sains Selangor 1, 47810 Kota Damansara, Petaling Jaya, Selangor, Malaysia
| | - Yen-Yen Kwan
- FELDA Global Ventures R&D Sdn Bhd, c/o FELDA Biotechnology Centre, PT 23417, Lengkuk Teknologi, 71760 Bandar Enstek, Negeri Sembilan, Malaysia
| | - Sharifah Shahrul Rabiah Syed Alwee
- FELDA Global Ventures R&D Sdn Bhd, c/o FELDA Biotechnology Centre, PT 23417, Lengkuk Teknologi, 71760 Bandar Enstek, Negeri Sembilan, Malaysia
| | | | - Robert A Martienssen
- Howard Hughes Medical Institute-Gordon and Betty Moore Foundation, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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23
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Springer NM, McGinnis KM. Paramutation in evolution, population genetics and breeding. Semin Cell Dev Biol 2015; 44:33-8. [PMID: 26325077 DOI: 10.1016/j.semcdb.2015.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 08/18/2015] [Indexed: 11/19/2022]
Abstract
Paramutation is a fascinating phenomenon in which directed allelic interactions result in heritable changes in the state of an allele. Paramutation has been carefully characterized at a handful of loci but the prevalence of paramutable/paramutagenic alleles is not well characterized within genomes or populations. In order to consider the role of paramutation in evolutionary processes and plant breeding, we focused on several questions. First, what causes certain alleles to become subject to paramutation? While paramutation clearly involves epigenetic regulation it is also true that only certain alleles defined by genetic sequences are able to participate in paramutation. Second, what is the prevalence of paramutation? There are only a handful of well-documented examples of paramutation. However, there is growing evidence that many loci may undergo changes in chromatin state or expression that are similar to changes observed as a result of paramutation. Third, how will paramutation events be inherited in natural or artificial populations? Many factors, including stability of epigenetic state, mating style and ploidy, may influence the prevalence of paramutation states within populations. Developing a clear understanding of the mechanisms and frequency of paramutation in crop plant genomes will facilitate new opportunities in genetic manipulation, and will also enhance plant breeding programs and our understanding of genome evolution.
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Affiliation(s)
- Nathan M Springer
- Microbial and Plant Genomics Institute, Department of Plant Biology, University of Minnesota, Saint Paul, MN 55108, USA.
| | - Karen M McGinnis
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
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24
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Gabriel JM, Hollick JB. Paramutation in maize and related behaviors in metazoans. Semin Cell Dev Biol 2015; 44:11-21. [PMID: 26318741 DOI: 10.1016/j.semcdb.2015.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Accepted: 08/18/2015] [Indexed: 12/31/2022]
Abstract
Paramutation refers to both the process and results of trans-homolog interactions causing heritable changes in both gene regulation and silencing abilities. Originally described in plants, paramutation-like behaviors have now been reported in model metazoans. Here we detail our current understanding of the paramutation mechanism as defined in Zea mays and compare this paradigm to these metazoan examples. Experimental results implicate functional roles of small RNAs in all these model organisms that highlight a diversity of mechanisms by which these molecules specify meiotically heritable regulatory information in the eukarya.
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Affiliation(s)
- Janelle M Gabriel
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Jay B Hollick
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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25
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Erwin AA, Galdos MA, Wickersheim ML, Harrison CC, Marr KD, Colicchio JM, Blumenstiel JP. piRNAs Are Associated with Diverse Transgenerational Effects on Gene and Transposon Expression in a Hybrid Dysgenic Syndrome of D. virilis. PLoS Genet 2015; 11:e1005332. [PMID: 26241928 PMCID: PMC4524669 DOI: 10.1371/journal.pgen.1005332] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 06/03/2015] [Indexed: 11/29/2022] Open
Abstract
Sexual reproduction allows transposable elements (TEs) to proliferate, leading to rapid divergence between populations and species. A significant outcome of divergence in the TE landscape is evident in hybrid dysgenic syndromes, a strong form of genomic incompatibility that can arise when (TE) family abundance differs between two parents. When TEs inherited from the father are absent in the mother's genome, TEs can become activated in the progeny, causing germline damage and sterility. Studies in Drosophila indicate that dysgenesis can occur when TEs inherited paternally are not matched with a pool of corresponding TE silencing PIWI-interacting RNAs (piRNAs) provisioned by the female germline. Using the D. virilis syndrome of hybrid dysgenesis as a model, we characterize the effects that divergence in TE profile between parents has on offspring. Overall, we show that divergence in the TE landscape is associated with persisting differences in germline TE expression when comparing genetically identical females of reciprocal crosses and these differences are transmitted to the next generation. Moreover, chronic and persisting TE expression coincides with increased levels of genic piRNAs associated with reduced gene expression. Combined with these effects, we further demonstrate that gene expression is idiosyncratically influenced by differences in the genic piRNA profile of the parents that arise though polymorphic TE insertions. Overall, these results support a model in which early germline events in dysgenesis establish a chronic, stable state of both TE and gene expression in the germline that is maintained through adulthood and transmitted to the next generation. This work demonstrates that divergence in the TE profile is associated with diverse piRNA-mediated transgenerational effects on gene expression within populations. Transposable elements (TEs) are selfish elements that copy themselves. More than half of the human genome is comprised of such elements. Studies in the fruit flies Drosophila melanogaster and D. virilis have been important in demonstrating a role for RNA silencing by PIWI-interacting RNAs (piRNAs) in protecting the genome against these harmful elements. These small RNAs are capable of recognizing TE mRNAs and mediating their destruction. They are also transmitted by the female germline to offspring in order to maintain a stable genome across generations. When males carrying a particular TE family are crossed with females lacking the element, the mother is unable to provide genome defense via complementary piRNAs that target the element. This leads to excess TE activation in the germline and sterility, a phenomenon known as hybrid dysgenesis. In this article we characterize the genomic landscape of TE destabilization that occurs in dysgenic crosses of D. virilis. We demonstrate that this mobilization is associated with an increased level of germline TE expression that persists through adulthood. In addition, we find that TE activation is associated with diverse effects on normal gene expression that are also mediated by piRNAs.
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Affiliation(s)
- Alexandra A. Erwin
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Mauricio A. Galdos
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Michelle L. Wickersheim
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Chris C. Harrison
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Kendra D. Marr
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Jack M. Colicchio
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Justin P. Blumenstiel
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
- * E-mail:
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26
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Giacopelli BJ, Hollick JB. Trans-Homolog Interactions Facilitating Paramutation in Maize. PLANT PHYSIOLOGY 2015; 168:1226-36. [PMID: 26149572 PMCID: PMC4528761 DOI: 10.1104/pp.15.00591] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 07/03/2015] [Indexed: 05/13/2023]
Abstract
Paramutations represent locus-specific trans-homolog interactions affecting the heritable silencing properties of endogenous alleles. Although examples of paramutation are well studied in maize (Zea mays), the responsible mechanisms remain unclear. Genetic analyses indicate roles for plant-specific DNA-dependent RNA polymerases that generate small RNAs, and current working models hypothesize that these small RNAs direct heritable changes at sequences often acting as transcriptional enhancers. Several studies have defined specific sequences that mediate paramutation behaviors, and recent results identify a diversity of DNA-dependent RNA polymerase complexes operating in maize. Other reports ascribe broader roles for some of these complexes in normal genome function. This review highlights recent research to understand the molecular mechanisms of paramutation and examines evidence relevant to small RNA-based modes of transgenerational epigenetic inheritance.
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Affiliation(s)
- Brian John Giacopelli
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Jay Brian Hollick
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
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27
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Cis-acting determinants of paramutation. Semin Cell Dev Biol 2015; 44:22-32. [DOI: 10.1016/j.semcdb.2015.08.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/20/2015] [Indexed: 11/23/2022]
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28
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Greaves IK, Gonzalez-Bayon R, Wang L, Zhu A, Liu PC, Groszmann M, Peacock WJ, Dennis ES. Epigenetic Changes in Hybrids. PLANT PHYSIOLOGY 2015; 168:1197-205. [PMID: 26002907 PMCID: PMC4528738 DOI: 10.1104/pp.15.00231] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 05/18/2015] [Indexed: 05/19/2023]
Abstract
Genome-wide approaches to the study of hybrid vigor have identified epigenetic changes in the hybrid nucleus in Arabidopsis (Arabidopsis thaliana), maize (Zea mays), and rice (Oryza sativa). DNA methylation associated with 24-nucleotide small interfering RNAs exhibits transallelic effects in hybrids of Arabidopsis and other species. Some of the transmethylation changes are inherited and some affect gene expression. Hybrids have larger leaves than those of the parents and have increases in cell size and number. The increased leaf size results in a greater photosynthetic capacity, which may support the increased vegetative and reproductive yields of the F1 hybrids. Genes and metabolic pathways that have altered expression relative to the parents include loci involved in responses to hormones and to biotic and abiotic stress. Whereas epigenetically induced changes in gene expression may contribute to hybrid vigor, the link between the transcriptional changes and the hybrid phenotype is not confirmed. Recurrent selection of high yielding F1 lines from the F2/F3 of a number of crops has fixed heterosis yields in pure breeding lines. These hybrid-like lines may have valuable applications in crop systems.
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Affiliation(s)
- Ian K Greaves
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Rebeca Gonzalez-Bayon
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Li Wang
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Anyu Zhu
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Pei-Chuan Liu
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Michael Groszmann
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - W James Peacock
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
| | - Elizabeth S Dennis
- Commonwealth Scientific and Industrial Research Organization Agricultural Flagship, Canberra, Australian Capital Territory 2600, Australia (I.K.G., R.G.-B., L.W., A.Z., P.-C.L., W.J.P., E.S.D.);Division of Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia (M.G.); andUniversity of Technology, Sydney, New South Wales 2007, Australia (W.J.P., E.S.D.)
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29
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Zheng Z, Yu H, Miki D, Jin D, Zhang Q, Ren Z, Gong Z, Zhang H, Zhu JK. Involvement of Multiple Gene-Silencing Pathways in a Paramutation-like Phenomenon in Arabidopsis. Cell Rep 2015; 11:1160-7. [PMID: 25981044 PMCID: PMC4484736 DOI: 10.1016/j.celrep.2015.04.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 02/12/2015] [Accepted: 04/16/2015] [Indexed: 12/24/2022] Open
Abstract
Paramutation is an epigenetic phenomenon that has been observed in a number of multicellular organisms. The epigenetically silenced state of paramutated alleles is not only meiotically stable but also "infectious" to active homologous alleles. The molecular mechanism of paramutation remains unclear, but components involved in RNA-directed DNA methylation (RdDM) are required. Here, we report a multi-copy pRD29A-LUC transgene in Arabidopsis thaliana that behaves like a paramutation locus. The silent state of LUC is induced by mutations in the DNA glycosylase gene ROS1. The silent alleles of LUC are not only meiotically stable but also able to transform active LUC alleles into silent ones, in the absence of ros1 mutations. Maintaining silencing at the LUC gene requires action of multiple pathways besides RdDM. Our study identified specific factors that are involved in the paramutation-like phenomenon and established a model system for the study of paramutation in Arabidopsis.
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Affiliation(s)
- Zhimin Zheng
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China.
| | - Hasi Yu
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China
| | - Daisuke Miki
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China
| | - Dan Jin
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Qingzhu Zhang
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China
| | - Zhonghai Ren
- State Key Laboratory of Crop Biology, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Huanghuai Region), Ministry of Agriculture, College of Horticulture Science and Engineering, Shandong Agricultural University, Daizong Road No. 61, Tai'an 271018, China
| | - Zhizhong Gong
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Heng Zhang
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China.
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 210602, China; Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
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30
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Sapetschnig A, Sarkies P, Lehrbach NJ, Miska EA. Tertiary siRNAs mediate paramutation in C. elegans. PLoS Genet 2015; 11:e1005078. [PMID: 25811365 PMCID: PMC4374809 DOI: 10.1371/journal.pgen.1005078] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 02/17/2015] [Indexed: 12/17/2022] Open
Abstract
In the nematode Caenorhabditis elegans, different small RNA-dependent gene silencing mechanisms act in the germline to initiate transgenerational gene silencing. Piwi-interacting RNAs (piRNAs) can initiate transposon and gene silencing by acting upstream of endogenous short interfering RNAs (siRNAs), which engage a nuclear RNA interference (RNAi) pathway to trigger transcriptional gene silencing. Once gene silencing has been established, it can be stably maintained over multiple generations without the requirement of the initial trigger and is also referred to as RNAe or paramutation. This heritable silencing depends on the integrity of the nuclear RNAi pathway. However, the exact mechanism by which silencing is maintained across generations is not understood. Here we demonstrate that silencing of piRNA targets involves the production of two distinct classes of small RNAs with different genetic requirements. The first class, secondary siRNAs, are localized close to the direct target site for piRNAs. Nuclear import of the secondary siRNAs by the Argonaute HRDE-1 leads to the production of a distinct class of small RNAs that map throughout the transcript, which we term tertiary siRNAs. Both classes of small RNAs are necessary for full repression of the target gene and can be maintained independently of the initial piRNA trigger. Consistently, we observed a form of paramutation associated with tertiary siRNAs. Once paramutated, a tertiary siRNA generating allele confers dominant silencing in the progeny regardless of its own transmission, suggesting germline-transmitted siRNAs are sufficient for multigenerational silencing. This work uncovers a multi-step siRNA amplification pathway that promotes germline integrity via epigenetic silencing of endogenous and invading genetic elements. In addition, the same pathway can be engaged in environmentally induced heritable gene silencing and could therefore promote the inheritance of acquired traits. Transgenerational epigenetic gene silencing has been shown to be important for organisms to react directly to their environment without the need to acquire genetic mutations. The inheritance of acquired traits via the gametes can prove advantageous in fast reproducing organisms. In Caenorhabditis elegans, a free-living nematode, multigenerational epigenetic inheritance can be induced by exogenous (experimentally provided) and endogenous cues that trigger small RNA-dependent gene silencing in the germline of these animals. PIWI interacting small RNAs (piRNAs) are required for the initiation of stable silencing of invading genomic elements in the germline such as transposons. Gene silencing established by piRNAs can subsequently be maintained over multiple generations without the original trigger. In C. elegans, this stable maintenance of silencing requires an additional class of small interfering RNAs (siRNAs) that must be amplified in each generation in order to maintain multigenerational silencing. Here we show that these siRNAs fall into two distinct classes, which we call secondary and tertiary siRNAs. We find that the production of tertiary siRNAs is part of a nuclear amplification pathway associated with the stable heritable silencing of an allele, a form of paramutation. This amplification pathway therefore promotes germline integrity and possibly the inheritance of acquired physiological traits.
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Affiliation(s)
- Alexandra Sapetschnig
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry and Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Peter Sarkies
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry and Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Nicolas J. Lehrbach
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry and Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Eric A. Miska
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry and Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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31
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Diverse gene-silencing mechanisms with distinct requirements for RNA polymerase subunits in Zea mays. Genetics 2014; 198:1031-42. [PMID: 25164883 DOI: 10.1534/genetics.114.168518] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In Zea mays, transcriptional regulation of the b1 (booster1) gene requires a distal enhancer and MEDIATOR OF PARAMUTATION1 (MOP1), MOP2, and MOP3 proteins orthologous to Arabidopsis components of the RNA-dependent DNA methylation pathway. We compared the genetic requirements for MOP1, MOP2, and MOP3 for endogenous gene silencing by two hairpin transgenes with inverted repeats of the a1 (anthocyaninless1) gene promoter (a1pIR) and the b1 gene enhancer (b1IR), respectively. The a1pIR transgene induced silencing of endogenous A1 in mop1-1 and mop3-1, but not in Mop2-1 homozygous plants. This finding suggests that transgene-derived small interfering RNAs (siRNAs) circumvented the requirement for MOP1, a predicted RNA-dependent RNA polymerase, and MOP3, the predicted largest subunit of RNA polymerase IV (Pol IV). Because the Arabidopsis protein orthologous to MOP2 is the second largest subunit of Pol IV and V, our results may indicate that hairpin-induced siRNAs cannot bypass the requirement for the predicted scaffolding activity of Pol V. In contrast to a1pIR, the b1IR transgene silenced endogenous B1 in all three homozygous mutant genotypes--mop1-1, Mop2-1, and mop3-1--suggesting that transgene mediated b1 silencing did not involve MOP2-containing Pol V complexes. Based on the combined results for a1, b1, and three previously described loci, we propose a speculative hypothesis of locus-specific deployment of Pol II, MOP2-containing Pol V, or alternative versions of Pol V with second largest subunits other than MOP2 to explain the mechanistic differences in silencing at specific loci, including one example associated with paramutation.
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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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Natural occurring epialleles determine vitamin E accumulation in tomato fruits. Nat Commun 2014; 5:3027. [PMID: 24967512 DOI: 10.1038/ncomms5027] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 05/02/2014] [Indexed: 01/29/2023] Open
Abstract
Vitamin E (VTE) content is a low heritability nutritional trait for which the genetic determinants are poorly understood. Here, we focus on a previously detected major tomato VTE quantitative trait loci (QTL; mQTL(9-2-6)) and identify the causal gene as one encoding a 2-methyl-6-phytylquinol methyltransferase (namely VTE3(1)) that catalyses one of the final steps in the biosynthesis of γ- and α-tocopherols, which are the main forms of VTE. By reverse genetic approaches, expression analyses, siRNA profiling and DNA methylation assays, we demonstrate that mQTL(9-2-6) is an expression QTL associated with differential methylation of a SINE retrotransposon located in the promoter region of VTE3(1). Promoter DNA methylation can be spontaneously reverted leading to different epialleles affecting VTE3(1) expression and VTE content in fruits. These findings indicate therefore that naturally occurring epialleles are responsible for regulation of a nutritionally important metabolic QTL and provide direct evidence of a role for epigenetics in the determination of agronomic traits.
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Abstract
Since the human genome was sequenced, the term "epigenetics" is increasingly being associated with the hope that we are more than just the sum of our genes. Might what we eat, the air we breathe, or even the emotions we feel influence not only our genes but those of descendants? The environment can certainly influence gene expression and can lead to disease, but transgenerational consequences are another matter. Although the inheritance of epigenetic characters can certainly occur-particularly in plants-how much is due to the environment and the extent to which it happens in humans remain unclear.
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Abstract
RNA-directed DNA methylation (RdDM) is the major small RNA-mediated epigenetic pathway in plants. RdDM requires a specialized transcriptional machinery that comprises two plant-specific RNA polymerases - Pol IV and Pol V - and a growing number of accessory proteins, the functions of which in the RdDM mechanism are only partially understood. Recent work has revealed variations in the canonical RdDM pathway and identified factors that recruit Pol IV and Pol V to specific target sequences. RdDM, which transcriptionally represses a subset of transposons and genes, is implicated in pathogen defence, stress responses and reproduction, as well as in interallelic and intercellular communication.
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A MITE transposon insertion is associated with differential methylation at the maize flowering time QTL Vgt1. G3-GENES GENOMES GENETICS 2014; 4:805-12. [PMID: 24607887 PMCID: PMC4025479 DOI: 10.1534/g3.114.010686] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
One of the major quantitative trait loci for flowering time in maize, the Vegetative to generative transition 1 (Vgt1) locus, corresponds to an upstream (70 kb) noncoding regulatory element of ZmRap2.7, a repressor of flowering. At Vgt1, a miniature transposon (MITE) insertion into a conserved noncoding sequence was previously found to be highly associated with early flowering in independent studies. Because cytosine methylation is known to be associated with transposons and to influence gene expression, we aimed to investigate how DNA methylation patterns in wild-type and mutant Vgt1 correlate with ZmRap2.7 expression. The methylation state at Vgt1 was assayed in leaf samples of maize inbred and F1 hybrid samples, and at the syntenic region in sorghum. The Vgt1-linked conserved noncoding sequence was very scarcely methylated both in maize and sorghum. However, in the early maize Vgt1 allele, the region immediately flanking the highly methylated MITE insertion was significantly more methylated and showed features of methylation spreading. Allele-specific expression assays revealed that the presence of the MITE and its heavy methylation appear to be linked to altered ZmRap2.7 transcription. Although not providing proof of causative connection, our results associate transposon-linked differential methylation with allelic state and gene expression at a major flowering time quantitative trait locus in maize.
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78495111110.1016/j.cell.2014.02.045" />
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Li L, Eichten SR, Shimizu R, Petsch K, Yeh CT, Wu W, Chettoor AM, Givan SA, Cole RA, Fowler JE, Evans MMS, Scanlon MJ, Yu J, Schnable PS, Timmermans MCP, Springer NM, Muehlbauer GJ. Genome-wide discovery and characterization of maize long non-coding RNAs. Genome Biol 2014; 15:R40. [PMID: 24576388 PMCID: PMC4053991 DOI: 10.1186/gb-2014-15-2-r40] [Citation(s) in RCA: 319] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 02/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long non-coding RNAs (lncRNAs) are transcripts that are 200 bp or longer, do not encode proteins, and potentially play important roles in eukaryotic gene regulation. However, the number, characteristics and expression inheritance pattern of lncRNAs in maize are still largely unknown. RESULTS By exploiting available public EST databases, maize whole genome sequence annotation and RNA-seq datasets from 30 different experiments, we identified 20,163 putative lncRNAs. Of these lncRNAs, more than 90% are predicted to be the precursors of small RNAs, while 1,704 are considered to be high-confidence lncRNAs. High confidence lncRNAs have an average transcript length of 463 bp and genes encoding them contain fewer exons than annotated genes. By analyzing the expression pattern of these lncRNAs in 13 distinct tissues and 105 maize recombinant inbred lines, we show that more than 50% of the high confidence lncRNAs are expressed in a tissue-specific manner, a result that is supported by epigenetic marks. Intriguingly, the inheritance of lncRNA expression patterns in 105 recombinant inbred lines reveals apparent transgressive segregation, and maize lncRNAs are less affected by cis- than by trans-genetic factors. CONCLUSIONS We integrate all available transcriptomic datasets to identify a comprehensive set of maize lncRNAs, provide a unique annotation resource of the maize genome and a genome-wide characterization of maize lncRNAs, and explore the genetic control of their expression using expression quantitative trait locus mapping.
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Cruz-Ramírez A, Díaz-Triviño S, Wachsman G, Du Y, Arteága-Vázquez M, Zhang H, Benjamins R, Blilou I, Neef AB, Chandler V, Scheres B. A SCARECROW-RETINOBLASTOMA protein network controls protective quiescence in the Arabidopsis root stem cell organizer. PLoS Biol 2013; 11:e1001724. [PMID: 24302889 PMCID: PMC3841101 DOI: 10.1371/journal.pbio.1001724] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 10/22/2013] [Indexed: 01/17/2023] Open
Abstract
Ben Scheres and colleagues report that in the growing tip of plant roots, a gene regulatory network that includes the plant homologue of Retinoblastoma regulates the divisions of long-term stem cells to replenish tissue and to protect the root stem cell niche. Quiescent long-term somatic stem cells reside in plant and animal stem cell niches. Within the Arabidopsis root stem cell population, the Quiescent Centre (QC), which contains slowly dividing cells, maintains surrounding short-term stem cells and may act as a long-term reservoir for stem cells. The RETINOBLASTOMA-RELATED (RBR) protein cell-autonomously reinforces mitotic quiescence in the QC. RBR interacts with the stem cell transcription factor SCARECROW (SCR) through an LxCxE motif. Disruption of this interaction by point mutation in SCR or RBR promotes asymmetric divisions in the QC that renew short-term stem cells. Analysis of the in vivo role of quiescence in the root stem cell niche reveals that slow cycling within the QC is not needed for structural integrity of the niche but allows the growing root to cope with DNA damage. In the plant Arabidposis thaliana, root meristems (in the growing tip of the root) contain slowly dividing cells that act as an organizing center for the root stem cells that surround them. This centre is called the quiescent centre (QC). In this study, we show that the slow rate of division in the QC is regulated by the interaction between two proteins: Retinoblastoma homolog (RBR) and SCARECROW (SCR), a transcription factor that controls stem cell maintenance. RBR and SCR regulate quiescence in the QC by repressing an asymmetric cell division that generates short-term stem cells. Here we genetically manipulate the cells in the QC to alter their quiescence by regulating the RBR/SCR interaction to demonstrate that quiescence is not needed for the organizing capacity of the QC but instead provides cells with a higher resistance to genotoxic stress, allowing stem cells in the QC to survive even if more rapidly cycling stem cells are damaged. A role for mitotic quiescence has been reported in animal stem cells, in which Rb has been implicated. These findings indicate that it might serve a similar role in plant stem cells.
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Affiliation(s)
- Alfredo Cruz-Ramírez
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
- Laboratorio Nacional de Genmica para la Biodiversidad, Cinvestav Sede Irapuato, Irapuato, Mexico
| | - Sara Díaz-Triviño
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Guy Wachsman
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Yujuan Du
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Mario Arteága-Vázquez
- Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana, Xalapa, Veracruz, Mexico
| | - Hongtao Zhang
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Rene Benjamins
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Ikram Blilou
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
| | - Anne B. Neef
- Institute of Organic Chemistry, University of Zurich, Zurich, Switzerland
| | - Vicki Chandler
- BIO5 Institute and Department of Plant Sciences, University of Arizona, Tucson, Arizona, United States of America
| | - Ben Scheres
- Department of Molecular Genetics, Utrecht University, Utrecht, The Netherlands
- * E-mail:
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Turck F, Coupland G. Natural variation in epigenetic gene regulation and its effects on plant developmental traits. Evolution 2013; 68:620-31. [PMID: 24117443 DOI: 10.1111/evo.12286] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 09/30/2013] [Indexed: 01/02/2023]
Abstract
In plants, epigenetic variation contributes to phenotypic differences in developmental traits. At the mechanistic level, this variation is conferred by DNA methylation and histone modifications. We describe several examples in which changes in gene expression caused by variation in DNA methylation lead to alterations in plant development. In these examples, the presence of repeated sequences or transposons within the promoters of the affected genes are associated with DNA methylation and gene inactivation. Small interfering RNAs expressed from these sequences recruit DNA methylation to the gene. Some of these methylated alleles are unstable giving rise to revertant sectors during mitosis and to progeny in which the methylated state is lost. However, others are stable for many generations and persist through speciation. These examples indicate that although DNA methylation influences gene expression, this is frequently dependent on classical changes to DNA sequence such as transposon insertions. By contrast, forms of histone methylation cause repression of gene expression that is stably inherited through mitosis but that can also be erased over time or during meiosis. A striking example involves the induction of flowering by exposure to low winter temperatures in Arabidopsis thaliana and its relatives. Histone methylation participates in repression of expression of an inhibitor of flowering during cold. In annual, semelparous species such as A. thaliana, this histone methylation is stably inherited through mitosis after return from cold to warm temperatures allowing the plant to flower continuously during spring and summer until it senesces. However, in perennial, iteroparous relatives the histone modification rapidly disappears when temperatures rise, allowing expression of the floral inhibitor to increase and limiting flowering to a short interval. In this case, epigenetic histone modifications control a key adaptive trait, and their pattern changes rapidly during evolution associated with life-history strategy. We discuss these examples of epigenetic developmental traits with emphasis on the underlying mechanisms, their stability, and adaptive value.
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Affiliation(s)
- Franziska Turck
- Max Planck Institute for Plant Breeding Research, Carl von Linne Weg 10, D-50829, Cologne, Germany.
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Belele CL, Sidorenko L, Stam M, Bader R, Arteaga-Vazquez MA, Chandler VL. Specific tandem repeats are sufficient for paramutation-induced trans-generational silencing. PLoS Genet 2013; 9:e1003773. [PMID: 24146624 PMCID: PMC3798267 DOI: 10.1371/journal.pgen.1003773] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 07/24/2013] [Indexed: 11/19/2022] Open
Abstract
Paramutation is a well-studied epigenetic phenomenon in which trans communication between two different alleles leads to meiotically heritable transcriptional silencing of one of the alleles. Paramutation at the b1 locus involves RNA-mediated transcriptional silencing and requires specific tandem repeats that generate siRNAs. This study addressed three important questions: 1) are the tandem repeats sufficient for paramutation, 2) do they need to be in an allelic position to mediate paramutation, and 3) is there an association between the ability to mediate paramutation and repeat DNA methylation levels? Paramutation was achieved using multiple transgenes containing the b1 tandem repeats, including events with tandem repeats of only one half of the repeat unit (413 bp), demonstrating that these sequences are sufficient for paramutation and an allelic position is not required for the repeats to communicate. Furthermore, the transgenic tandem repeats increased the expression of a reporter gene in maize, demonstrating the repeats contain transcriptional regulatory sequences. Transgene-mediated paramutation required the mediator of paramutation1 gene, which is necessary for endogenous paramutation, suggesting endogenous and transgene-mediated paramutation both require an RNA-mediated transcriptional silencing pathway. While all tested repeat transgenes produced small interfering RNAs (siRNAs), not all transgenes induced paramutation suggesting that, as with endogenous alleles, siRNA production is not sufficient for paramutation. The repeat transgene-induced silencing was less efficiently transmitted than silencing induced by the repeats of endogenous b1 alleles, which is always 100% efficient. The variability in the strength of the repeat transgene-induced silencing enabled testing whether the extent of DNA methylation within the repeats correlated with differences in efficiency of paramutation. Transgene-induced paramutation does not require extensive DNA methylation within the transgene. However, increased DNA methylation within the endogenous b1 repeats after transgene-induced paramutation was associated with stronger silencing of the endogenous allele. Paramutation is a fascinating process in which genes communicate to efficiently establish changes in their expression that are stably transmitted to future generations without any changes in DNA sequences. While paramutation was first described in the 1950s and extensively studied through the 1960s, its underlying mechanism remained mysterious for many years. Over the past ten years paramutation at the b1 locus in maize was shown to require transcribed, non-coding tandem repeats located 100 kb upstream of b1. These repeats generate small RNAs, and mutations in multiple genes mediating small RNA silencing at the transcriptional level prevent paramutation. While underlying mechanisms are shared, current models for RNA-mediated transcriptional silencing that are based on experiments with S. pombe and Arabidopsis do not explain many aspects of paramutation. In this manuscript we used a transgenic approach to demonstrate that the b1 non-coding tandem repeats are sufficient to send and respond to the paramutation signals and that this occurs even when the repeats are not at their normal chromosomal location.
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Affiliation(s)
- Christiane L. Belele
- Department of Plant Sciences, BIO5, University of Arizona, Tucson, Arizona, United States of America
| | - Lyudmila Sidorenko
- Department of Plant Sciences, BIO5, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
| | - Maike Stam
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Rechien Bader
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Mario A. Arteaga-Vazquez
- Department of Plant Sciences, BIO5, University of Arizona, Tucson, Arizona, United States of America
| | - Vicki L. Chandler
- Department of Plant Sciences, BIO5, University of Arizona, Tucson, Arizona, United States of America
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Zhang H, Chen X, Wang C, Xu Z, Wang Y, Liu X, Kang Z, Ji W. Long non-coding genes implicated in response to stripe rust pathogen stress in wheat (Triticum aestivum L.). Mol Biol Rep 2013; 40:6245-53. [PMID: 24065539 DOI: 10.1007/s11033-013-2736-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 09/14/2013] [Indexed: 02/01/2023]
Abstract
The non-protein-coding genes have been reported as a critical control role in the regulation of gene expression in abiotic stress. We previously identified four expressed sequence tags numbered S18 (EL773024), S73 (EL773035), S106 (EL773041) and S108 (EL773042) from a SSH-cDNA library of bread wheat Shaanmai 139 infected with Puccinia striiformis f. sp. tritici (Pst). Here, we isolated four cDNA clones and referred them as TalncRNA18, TalncRNA73, TalncRNA106 and TalncRNA108 (GenBank: KC549675-KC549678). These cDNA separately consisted of 1,393, 667, 449 and 647 nucleotides but without any open reading frame. The alignment result showed that TalncRNA18 is a partial cDNA of E3 ubiquitin-protein ligase UPL1-like gene, TalncRNA73 is an antisense transcript of hypothetical protein, TalncRNA108 is a homolog to RRNA intron-encoded homing endonuclease, and lncRNA106 had no similarly sequence. Quantitative RT-PCR studies confirmed that these four lncRNAs were differentially expressed in three near isogenic lines. TalncRNA108 was significantly stepwise decreased at early stage of inoculation with Pst, while the others were upregulated, especially at 1 and 3 dpi (days post-inoculation). Using Chinese Spring nulli-tetrasomic lines and its ditelosomic lines, TalncRNA73 and TalncRNA108 were located to wheat chromosome 7A and the short arm of chromosome 4B, respectively, while TalncRNA18 and TalncRNA106 were located to chromosome 5B. Comparing the sequence of DNA and cDNA of four lncRNAs with polymerase chain reaction primers, the results showed that all of them have no introns. The kinetics analyses of lncRNAs expression as a result of pathogen challenge in immune resistant genotype indicated that they may play the roles of modulating or silencing the protein-coding gene into pathogen-defence response.
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Affiliation(s)
- Hong Zhang
- State Key Laboratory of Crop Stress Biology for Arid Area, College of Agronomy, Northwest A&F University, Yangling, 712100, Shaanxi, China,
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Labonne JDJ, Dorweiler JE, McGinnis KM. Changes in nucleosome position at transcriptional start sites of specific genes in Zea mays mediator of paramutation1 mutants. Epigenetics 2013; 8:398-408. [PMID: 23538550 PMCID: PMC3674049 DOI: 10.4161/epi.24199] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Nucleosomes facilitate compaction of DNA within the confines of the eukaryotic nucleus. This packaging of DNA and histone proteins must accommodate cellular processes, such as transcription and DNA replication. The repositioning of nucleosomes to facilitate cellular processes is likely regulated by several factors. In Zea mays, Mediator of paramutation1 (MOP1) has been demonstrated to be an epigenetic regulator of gene expression. Based on sequence orthology and mutant phenotypes, MOP1 is likely to function in an RNA-dependent pathway to mediate changes to chromatin. High-resolution microarrays were used to assay the distribution of nucleosomes across the transcription start sites (TSSs) of ~400 maize genes in wild type and mutant mop1-1 tissues. Analysis of nucleosome distribution in leaf, immature tassel and ear shoot tissues resulted in the identification of three genes showing consistent differences in nucleosome positioning and occupancy between wild type and mutant mop1-1. These specific changes in nucleosome distribution were located upstream as well as downstream of the TSS. No direct relationship between the specific changes in nucleosome distribution and transcription were observed through quantitative expression analysis in these tissues. In silico prediction suggests that nucleosome positioning is not dictated by intrinsic DNA sequence signals in the TSSs of two of the identified genes, suggesting a role for chromatin remodeling proteins in MOP1-mediated pathways. These results also indicate that MOP1 contributions to nucleosome position may be either separate from changes in gene expression, or cooperative with development and other levels of regulation in coordinating gene expression.
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Affiliation(s)
| | - Jane E Dorweiler
- Department of Biological Sciences; Marquette University; Milwaukee, WI USA
| | - Karen M McGinnis
- Department of Biological Science; Florida State University; Tallahassee, FL USA
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Grimanelli D, Roudier F. Epigenetics and development in plants: green light to convergent innovations. Curr Top Dev Biol 2013; 104:189-222. [PMID: 23587242 DOI: 10.1016/b978-0-12-416027-9.00006-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Plants are sessile organisms that must constantly adjust to their environment. In contrast to animals, plant development mainly occurs postembryonically and is characterized by continuous growth and extensive phenotypic plasticity. Chromatin-level regulation of transcriptional patterns plays a central role in the ability of plants to adapt to internal and external cues. Here, we review selected examples of chromatin-based mechanisms involved in the regulation of key aspects of plant development. These illustrate that, in addition to mechanisms conserved between plants and animals, plant-specific innovations lead to particular chromatin dynamics related to their developmental and life strategies.
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Affiliation(s)
- Daniel Grimanelli
- Institut de Recherche pour le Développement, UMR 232, Université de Montpellier II, Montpellier, France.
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Goettel W, Messing J. Paramutagenicity of a p1 epiallele in maize. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2013; 126:159-77. [PMID: 22986680 DOI: 10.1007/s00122-012-1970-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 08/16/2012] [Indexed: 05/09/2023]
Abstract
Complex silencing mechanisms in plants and other kingdoms target transposons, repeat sequences, invasive viral nucleic acids and transgenes, but also endogenous genes and genes involved in paramutation. Paramutation occurs in a heterozygote when a transcriptionally active allele heritably adopts the epigenetic state of a transcriptionally and/or post-transcriptionally repressed allele. P1-rr and its silenced epiallele P1-pr, which encode a Myb-like transcription factor mediating pigmentation in floral organs of Zea mays, differ in their cytosine methylation pattern and chromatin structure at a complex enhancer site. Here, we tested whether P1-pr is able to heritably silence its transcriptionally active P1-rr allele in a heterozygote and whether DNA methylation is associated with the establishment and maintenance of P1-rr silencing. We found that P1-pr participates in paramutation as the repressing allele and P1-rr as the sensitive allele. Silencing of P1-rr is highly variable compared to the inducing P1-pr resulting in a wide range of gene expression. Whereas cytosine methylation at P1-rr is negatively correlated with transcription and pigment levels after segregation of P1-pr, methylation lags behind the establishment of the repressed p1 gene expression. We propose a model in which P1-pr paramutation is triggered by changing epigenetic states of transposons immediately adjacent to a P1-rr enhancer sequence. Considering the vast amount of transposable elements in the maize genome close to regulatory elements of genes, numerous loci could undergo paramutation-induced allele silencing, which could also have a significant impact on breeding agronomically important traits.
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Affiliation(s)
- Wolfgang Goettel
- Waksman Institute of Microbiology, Rutgers University, 190 Frelinghuysen Road, Piscataway, NJ 08854, USA
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Mirouze M. The Small RNA-Based Odyssey of Epigenetic Information in Plants: From Cells to Species. DNA Cell Biol 2012; 31:1650-6. [DOI: 10.1089/dna.2012.1681] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Marie Mirouze
- Institut de Recherche pour le Développement, UMR232, ERL5300 IRD UM2 CNRS, Montpellier, France
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Hollick JB. Paramutation: a trans-homolog interaction affecting heritable gene regulation. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:536-543. [PMID: 23017240 DOI: 10.1016/j.pbi.2012.09.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 07/17/2012] [Accepted: 09/05/2012] [Indexed: 06/01/2023]
Abstract
Paramutation describes both the process and results of trans-sensing between chromosomes that causes specific heritable changes in gene regulation. RNA molecules are implicated in mediating similar events in maize, mouse, and Drosophila. Changes in both small RNA profiles and cytosine methylation patterns in Arabidopsis hybrids represent a potential molecular equivalent to the interactions responsible for paramutations. Despite a seemingly unifying feature of RNA-directed changes, both recent and historical works show that paramutations in maize require plant-specific proteins and lack expected hallmarks of a trans-effect mediated solely by RNAs. Recent examples of nearby transposons affecting RNA polymerase II functions lead to an opinion that paramutations represent an emergent property of the transcriptional dynamics ongoing in plant genomes between repetitious features and nearby genes.
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Affiliation(s)
- Jay B Hollick
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA.
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Abstract
Paramutation, a phenomenon of epigenetic switching that violates Mendel's Law of Segregation, was first discovered in maize and later observed in other plants. In a recent report in Nature, de Vanssay and colleagues (2012) describe in Drosophila an operationally analogous phenomenon to paramutation that is mediated by piwi-interacting RNAs.
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Affiliation(s)
- James A Birchler
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA.
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de Vanssay A, Bougé AL, Boivin A, Hermant C, Teysset L, Delmarre V, Antoniewski C, Ronsseray S. Paramutation in Drosophila linked to emergence of a piRNA-producing locus. Nature 2012; 490:112-5. [PMID: 22922650 DOI: 10.1038/nature11416] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/16/2012] [Indexed: 11/10/2022]
Abstract
A paramutation is an epigenetic interaction between two alleles of a locus, through which one allele induces a heritable modification in the other allele without modifying the DNA sequence. The paramutated allele itself becomes paramutagenic, that is, capable of epigenetically converting a new paramutable allele. Here we describe a case of paramutation in animals showing long-term transmission over generations. We previously characterized a homology-dependent silencing mechanism referred to as the trans-silencing effect (TSE), involved in P-transposable-element repression in the germ line. We now show that clusters of P-element-derived transgenes that induce strong TSE can convert other homologous transgene clusters incapable of TSE into strong silencers, which transmit the acquired silencing capacity through 50 generations. The paramutation occurs without any need for chromosome pairing between the paramutagenic and the paramutated loci, and is mediated by maternal inheritance of cytoplasm carrying Piwi-interacting RNAs (piRNAs) homologous to the transgenes. The repression capacity of the paramutated locus is abolished by a loss-of-function mutation of the aubergine gene involved in piRNA biogenesis, but not by a loss-of-function mutation of the Dicer-2 gene involved in siRNA production. The paramutated cluster, previously producing barely detectable levels of piRNAs, is converted into a stable, strong piRNA-producing locus by the paramutation and becomes fully paramutagenic itself. Our work provides a genetic model for the emergence of piRNA loci, as well as for RNA-mediated trans-generational repression of transposable elements.
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Affiliation(s)
- Augustin de Vanssay
- Laboratoire Biologie du Développement, UMR7622, CNRS-Université Pierre et Marie Curie, 9 quai Saint Bernard, 75005 Paris, France
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