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Yu X, Buck MJ. Pioneer factors and their in vitro identification methods. Mol Genet Genomics 2020; 295:825-835. [PMID: 32296927 DOI: 10.1007/s00438-020-01675-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 04/02/2020] [Indexed: 11/27/2022]
Abstract
Pioneer transcription factors are a special group of transcription factors that can interact with nucleosomal DNA and initiate regulatory events. Their binding to regulatory regions is the first event in gene activation and can occur in silent or heterochromatin regions. Several research groups have endeavored to define pioneer factors and study their binding characteristics using various techniques. In this review, we describe the in vitro methods used to define and characterize pioneer factors, paying particular attention to differences in methodologies and how these differences can affect results.
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Affiliation(s)
- Xinyang Yu
- Zhuhai Precision Medical Center, Zhuhai People's Hospital (Zhuhai Hospital Affiliated With Jinan University), Zhuhai, 519000, Guangdong, P.R. China.
| | - Michael J Buck
- Department of Biochemistry, New York State Center of Excellence in Bioinformatics and Life Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA.
- Department of Biomedical Informatics, State University of New York at Buffalo, Buffalo, NY, 14203, USA.
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Garcia S, Wendel JF, Borowska-Zuchowska N, Aïnouche M, Kuderova A, Kovarik A. The Utility of Graph Clustering of 5S Ribosomal DNA Homoeologs in Plant Allopolyploids, Homoploid Hybrids, and Cryptic Introgressants. FRONTIERS IN PLANT SCIENCE 2020; 11:41. [PMID: 32117380 PMCID: PMC7025596 DOI: 10.3389/fpls.2020.00041] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/13/2020] [Indexed: 05/18/2023]
Abstract
INTRODUCTION Ribosomal DNA (rDNA) loci have been widely used for identification of allopolyploids and hybrids, although few of these studies employed high-throughput sequencing data. Here we use graph clustering implemented in the RepeatExplorer (RE) pipeline to analyze homoeologous 5S rDNA arrays at the genomic level searching for hybridogenic origin of species. Data were obtained from more than 80 plant species, including several well-defined allopolyploids and homoploid hybrids of different evolutionary ages and from widely dispersed taxonomic groups. RESULTS (i) Diploids show simple circular-shaped graphs of their 5S rDNA clusters. In contrast, most allopolyploids and other interspecific hybrids exhibit more complex graphs composed of two or more interconnected loops representing intergenic spacers (IGS). (ii) There was a relationship between graph complexity and locus numbers. (iii) The sequences and lengths of the 5S rDNA units reconstituted in silico from k-mers were congruent with those experimentally determined. (iv) Three-genomic comparative cluster analysis of reads from allopolyploids and progenitor diploids allowed identification of homoeologous 5S rRNA gene families even in relatively ancient (c. 1 Myr) Gossypium and Brachypodium allopolyploids which already exhibit uniparental partial loss of rDNA repeats. (v) Finally, species harboring introgressed genomes exhibit exceptionally complex graph structures. CONCLUSION We found that the cluster graph shapes and graph parameters (k-mer coverage scores and connected component index) well-reflect the organization and intragenomic homogeneity of 5S rDNA repeats. We propose that the analysis of 5S rDNA cluster graphs computed by the RE pipeline together with the cytogenetic analysis might be a reliable approach for the determination of the hybrid or allopolyploid plant species parentage and may also be useful for detecting historical introgression events.
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Affiliation(s)
- Sònia Garcia
- Institut Botànic de Barcelona (IBB, CSIC - Ajuntament de Barcelona), Barcelona, Spain
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia
| | - Jonathan F. Wendel
- Department of Ecology, Evolution & Organismal Biology, Iowa State University, Ames, IA, United States
| | - Natalia Borowska-Zuchowska
- Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Malika Aïnouche
- UMR CNRS 6553 ECOBIO, Université de Rennes 1, Rennes, France
| | - Alena Kuderova
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia
| | - Ales Kovarik
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia
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Fulneček J, Matyášek R. The origin of exon 3 skipping of paternal GLOBOSA pre-mRNA in some Nicotiana tabacum lines correlates with a point mutation of the very last nucleotide of the exon. Mol Genet Genomics 2016; 291:801-18. [PMID: 26603606 DOI: 10.1007/s00438-015-1149-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 11/13/2015] [Indexed: 10/22/2022]
Abstract
In plants, genome duplication followed by genome diversification and selection is recognized as a major evolutionary process. Rapid epigenetic and genetic changes that affect the transcription of parental genes are frequently observed after polyploidization. The pattern of alternative splicing is also frequently altered, yet the related molecular processes remain largely unresolved. Here, we study the inheritance and expression of parental variants of three floral organ identity genes in allotetraploid tobacco. DEFICIENS and GLOBOSA are B-class genes, and AGAMOUS is a C-class gene. Parental variants of these genes were found to be maintained in the tobacco genome, and the respective mRNAs were present in flower buds in comparable amounts. However, among five tobacco cultivars, we identified two in which the majority of paternal GLOBOSA pre-mRNA transcripts undergo exon 3 skipping, producing an mRNA with a premature termination codon. At the DNA level, we identified a G-A transition at the very last position of exon 3 in both cultivars. Although alternative splicing resulted in a dramatic decrease in full-length paternal GLOBOSA mRNA, no phenotypic effect was observed. Our finding likely serves as an example of the initiation of homoeolog diversification in a relatively young polyploid genome.
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Affiliation(s)
- Jaroslav Fulneček
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, CZ-61265, Brno, Czech Republic.
| | - Roman Matyášek
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, CZ-61265, Brno, Czech Republic
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Dancing together and separate again: gymnosperms exhibit frequent changes of fundamental 5S and 35S rRNA gene (rDNA) organisation. Heredity (Edinb) 2013; 111:23-33. [PMID: 23512008 PMCID: PMC3692318 DOI: 10.1038/hdy.2013.11] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In higher eukaryotes, the 5S rRNA genes occur in tandem units and are arranged either
separately (S-type arrangement) or linked to other repeated genes, in most cases to rDNA
locus encoding 18S–5.8S–26S genes (L-type arrangement). Here we used Southern
blot hybridisation, PCR and sequencing approaches to analyse genomic organisation of rRNA
genes in all large gymnosperm groups, including Coniferales, Ginkgoales, Gnetales and
Cycadales. The data are provided for 27 species (21 genera). The 5S units linked to the
35S rDNA units occur in some but not all Gnetales, Coniferales and in Ginkgo
(∼30% of the species analysed), while the remaining exhibit separate
organisation. The linked 5S rRNA genes may occur as single-copy insertions or as short
tandems embedded in the 26S–18S rDNA intergenic spacer (IGS). The 5S transcript may
be encoded by the same (Ginkgo, Ephedra) or opposite
(Podocarpus) DNA strand as the 18S–5.8S–26S genes. In addition,
pseudogenised 5S copies were also found in some IGS types. Both L- and S-type units have
been largely homogenised across the genomes. Phylogenetic relationships based on the
comparison of 5S coding sequences suggest that the 5S genes independently inserted IGS at
least three times in the course of gymnosperm evolution. Frequent transpositions and
rearrangements of basic units indicate relatively relaxed selection pressures imposed on
genomic organisation of 5S genes in plants.
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Garcia S, Crhák Khaitová L, Kovařík A. Expression of 5 S rRNA genes linked to 35 S rDNA in plants, their epigenetic modification and regulatory element divergence. BMC PLANT BIOLOGY 2012; 12:95. [PMID: 22716941 PMCID: PMC3409069 DOI: 10.1186/1471-2229-12-95] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/20/2012] [Indexed: 05/09/2023]
Abstract
BACKGROUND In plants, the 5 S rRNA genes usually occur as separate tandems (S-type arrangement) or, less commonly, linked to 35 S rDNA units (L-type). The activity of linked genes remains unknown so far. We studied the homogeneity and expression of 5 S genes in several species from family Asteraceae known to contain linked 35 S-5 S units. Additionally, their methylation status was determined using bisulfite sequencing. Fluorescence in situ hybridization was applied to reveal the sub-nuclear positions of rDNA arrays. RESULTS We found that homogenization of L-type units went to completion in most (4/6) but not all species. Two species contained major L-type and minor S-type units (termed L(s)-type). The linked genes dominate 5 S rDNA expression while the separate tandems do not seem to be expressed. Members of tribe Anthemideae evolved functional variants of the polymerase III promoter in which a residing C-box element differs from the canonical angiosperm motif by as much as 30%. On this basis, a more relaxed consensus sequence of a plant C-box: (5'-RGSWTGGGTG-3') is proposed. The 5 S paralogs display heavy DNA methylation similarly as to their unlinked counterparts. FISH revealed the close association of 35 S-5 S arrays with nucleolar periphery indicating that transcription of 5 S genes may occur in this territory. CONCLUSIONS We show that the unusual linked arrangement of 5 S genes, occurring in several plant species, is fully compatible with their expression and functionality. This extraordinary 5 S gene dynamics is manifested at different levels, such as variation in intrachromosomal positions, unit structure, epigenetic modification and considerable divergence of regulatory motifs.
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MESH Headings
- Animals
- Asteraceae/chemistry
- Asteraceae/genetics
- Asteraceae/metabolism
- Base Sequence
- Consensus Sequence
- DNA Methylation
- DNA, Plant/chemistry
- DNA, Plant/genetics
- DNA, Plant/metabolism
- Epigenesis, Genetic
- Evolution, Molecular
- Gene Expression Regulation, Plant
- Molecular Sequence Data
- Promoter Regions, Genetic
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- Regulatory Sequences, Nucleic Acid
- Response Elements
- Sequence Alignment
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Affiliation(s)
- Sònia Garcia
- Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s. n., Barcelona, Catalonia, 08028, Spain
| | - Lucie Crhák Khaitová
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, CZ-6125, Czech Republic
| | - Aleš Kovařík
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, CZ-6125, Czech Republic
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Garcia S, Lim KY, Chester M, Garnatje T, Pellicer J, Vallès J, Leitch AR, Kovarík A. Linkage of 35S and 5S rRNA genes in Artemisia (family Asteraceae): first evidence from angiosperms. Chromosoma 2008; 118:85-97. [PMID: 18779974 DOI: 10.1007/s00412-008-0179-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 07/22/2008] [Accepted: 08/20/2008] [Indexed: 10/24/2022]
Abstract
Typically in plants, the 5S and 35S ribosomal DNA (rDNA) encoding two major ribosomal RNA species occur at separate loci. However, in some algae, bryophytes and ferns, they are at the same locus (linked arranged). Southern blot hybridisation, polymerase chain reactions (PCR), fluorescent in situ hybridisation, cloning and sequencing were used to reveal 5S and 35S rDNA genomic organisation in Artemisia. We observed thousands of rDNA units at two-three loci containing 5S rDNA in an inverted orientation within the inter-genic spacer (IGS) of 35S rDNA. The sequenced clones of 26-18S IGS from Artemisia absinthium appeared to contain a conserved 5S gene insertion proximal to the 26S gene terminus (5S rDNA-1) and a second less conserved 5S insertion (5S rDNA-2) further downstream. Whilst the 5S rDNA-1 showed all the structural features of a functional gene, the 5S-rDNA-2 had a deletion in the internal promoter and probably represents a pseudogene. The linked arrangement probably evolved before the divergence of Artemisia from the rest of Asteraceae (>10 Myrs). This arrangement may have involved retrotransposons and once formed spread via mechanisms of concerted evolution. Heterogeneity in unit structure may reflect ongoing homogenisation of variant unit types without fixation for any particular variant.
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Affiliation(s)
- Sònia Garcia
- Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Catalonia, Spain
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Zhu XY, Cai DT, Ding Y. Molecular and cytological characterization of 5S rDNA inOryzaspecies: genomic organization and phylogenetic implications. Genome 2008; 51:332-40. [DOI: 10.1139/g08-016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the molecular characteristics and chromosomal organization of 5S rDNA in the genus Oryza , including diploid and tetraploid species. A phylogenetic tree of Oryza species was constructed based on the non-transcribed spacer sequences of 5S rDNA, and some novel relationships were discovered. Specifically, comparative sequence analysis of 5S rDNA in several wild rice species showed unique characteristics inconsistent with the model of concerted evolution: (1) multiple distinct 5S rDNA types were detected within a species, leading to intraspecific divergence of 5S rDNA; (2) multiple identical 5S rDNA types were shared among species, resulting in interspecies clustering of 5S rDNA types; and (3) intraspecific nucleotide diversity was detected within a 5S rDNA class. Our results obtained by fluorescence in situ hybridization revealed that each rice species studied contained only one 5S rDNA locus with two hybridization sites, which were located on either chromosome 7 or chromosome 11. These results suggest that different 5S rDNA classes within the rice genome were arranged together and that one pair of 5S rDNA loci from a diploid progenitor of the tetraploid species might have been lost during evolution. Taken together, our data show that 5S rDNA in rice species is more informative at the gene level than at the chromosome level.
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Affiliation(s)
- Xiao-Yan Zhu
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, P.R. China
- College of Life Sciences, Hubei University, Wuhan 430072, P.R. China
| | - De-Tian Cai
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, P.R. China
- College of Life Sciences, Hubei University, Wuhan 430072, P.R. China
| | - Yi Ding
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, P.R. China
- College of Life Sciences, Hubei University, Wuhan 430072, P.R. China
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Fulnecek J, Kovarik A. Low abundant spacer 5S rRNA transcripts are frequently polyadenylated in Nicotiana. Mol Genet Genomics 2007; 278:565-73. [PMID: 17671796 DOI: 10.1007/s00438-007-0273-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 06/22/2007] [Accepted: 06/27/2007] [Indexed: 10/23/2022]
Abstract
In plants, 5S rRNA genes (5S rDNA) encoding 120-nt structural RNA molecules of ribosomes are organized in tandem arrays comprising thousands of units. Failure to correctly terminate transcription would generate longer inaccurately processed transcripts interfering with ribosome biogenesis. Hence multiple termination signals occur immediately after the 5S rRNA coding sequence. To obtain information about the efficiency of termination of 5S rDNA transcription in plants we analyzed 5S rRNA pools in three Nicotiana species, N. sylvestris, N. tomentosiformis and N. tabacum. In addition to highly abundant 120-nt 5S rRNA transcripts, we also detected RNA species composed of a genic region and variable lengths of intergenic sequences. These genic-intergenic RNA molecules occur at a frequency severalfold lower than the mature 120-nt transcripts, and are posttranscriptionally modified by polyadenylation at their 3' end in contrast to 120-nt transcripts. An absence of 5S small RNAs (smRNA) argue against a dominant role for the smRNA biosynthesis pathway in the degradation of aberrant 5S rRNA in Nicotiana. This work is the first description of polyadenylated 5S rRNA species in higher eukaryotes originating from a read-through transcription into the intergenic spacer. We propose that polyadenylation may function in a "quality control" pathway ensuring that only correctly processed molecules enter the ribosome biogenesis.
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Affiliation(s)
- Jaroslav Fulnecek
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i, Kralovopolska 135, 612 65, Brno, Czech Republic.
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Douet J, Tourmente S. Transcription of the 5S rRNA heterochromatic genes is epigenetically controlled in Arabidopsis thaliana and Xenopus laevis. Heredity (Edinb) 2007; 99:5-13. [PMID: 17487217 DOI: 10.1038/sj.hdy.6800964] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
5S ribosomal DNA is a highly conserved tandemly repeated multigenic family. As suggested for a long time, we have shown that only a fraction of the 5S rRNA genes are expressed in Arabidopsis thaliana. In Xenopus laevis, there is a developmental control of the expression of the 5S rRNA genes with only one of the two 5S rDNA families expressed during oogenesis. For both Arabidopsis and Xenopus, the strongest transcription of 5S rRNA, respectively in the seed and during oogenesis is correlated with heterogeneity in the transcribed 5S rRNAs. Epigenetic mechanisms such as modification of the chromatin structure are involved in the transcriptional regulation of the 5S rRNA genes in both organisms. In Arabidopsis, two silencing pathways, methylation-dependent (RNAi) and methylation-independent (MOM pathway), are involved in the silencing of a 5S rDNA fraction.
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Affiliation(s)
- J Douet
- Unité Mixte de Recherche CNRS 6547 BIOMOVE, Université Blaise Pascal, Aubière Cedex, France
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