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Schimmel J, van Wezel MD, van Schendel R, Tijsterman M. Chromosomal breaks at the origin of small tandem DNA duplications. Bioessays 2023; 45:e2200168. [PMID: 36385254 DOI: 10.1002/bies.202200168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 11/01/2022] [Accepted: 11/03/2022] [Indexed: 11/18/2022]
Abstract
Small tandem DNA duplications in the range of 15 to 300 base-pairs play an important role in the aetiology of human disease and contribute to genome diversity. Here, we discuss different proposed mechanisms for their occurrence and argue that this type of structural variation mainly results from mutagenic repair of chromosomal breaks. This hypothesis is supported by both bioinformatical analysis of insertions occurring in the genome of different species and disease alleles, as well as by CRISPR/Cas9-based experimental data from different model systems. Recent work points to fill-in synthesis at double-stranded DNA breaks with complementary sequences, regulated by end-joining mechanisms, to account for small tandem duplications. We will review the prevalence of small tandem duplications in the population, and we will speculate on the potential sources of DNA damage that could give rise to this mutational signature. With the development of novel algorithms to analyse sequencing data, small tandem duplications are now more frequently detected in the human genome and identified as oncogenic gain-of-function mutations. Understanding their origin could lead to optimized treatment regimens to prevent therapy-induced activation of oncogenes and might expose novel vulnerabilities in cancer.
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Affiliation(s)
- Joost Schimmel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marloes D van Wezel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin van Schendel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marcel Tijsterman
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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2
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Graph-based pangenomics maximizes genotyping density and reveals structural impacts on fungal resistance in melon. Nat Commun 2022; 13:7897. [PMID: 36550124 PMCID: PMC9780226 DOI: 10.1038/s41467-022-35621-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022] Open
Abstract
The genomic sequences segregating in experimental populations are often highly divergent from the community reference and from one another. Such divergence is problematic under various short-read-based genotyping strategies. In addition, large structural differences are often invisible despite being strong candidates for causal variation. These issues are exacerbated in specialty crop breeding programs with fewer, lower-quality sequence resources. Here, we examine the benefits of complete genomic information, based on long-read assemblies, in a biparental mapping experiment segregating at numerous disease resistance loci in the non-model crop, melon (Cucumis melo). We find that a graph-based approach, which uses both parental genomes, results in 19% more variants callable across the population and raw allele calls with a 2 to 3-fold error-rate reduction, even relative to single reference approaches using a parent genome. We show that structural variation has played a substantial role in shaping two Fusarium wilt resistance loci with known causal genes. We also report on the genetics of powdery mildew resistance, where copy number variation and local recombination suppression are directly interpretable via parental genome alignments. Benefits observed, even in this low-resolution biparental experiment, will inevitably be amplified in more complex populations.
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3
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Gehrke F, Schindele A, Puchta H. Nonhomologous end joining as key to CRISPR/Cas-mediated plant chromosome engineering. PLANT PHYSIOLOGY 2022; 188:1769-1779. [PMID: 34893907 PMCID: PMC8968298 DOI: 10.1093/plphys/kiab572] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 11/09/2021] [Indexed: 05/24/2023]
Abstract
Although clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-mediated gene editing has revolutionized biology and plant breeding, large-scale, heritable restructuring of plant chromosomes is still in its infancy. Duplications and inversions within a chromosome, and also translocations between chromosomes, can now be achieved. Subsequently, genetic linkages can be broken or can be newly created. Also, the order of genes on a chromosome can be changed. While natural chromosomal recombination occurs by homologous recombination during meiosis, CRISPR/Cas-mediated chromosomal rearrangements can be obtained best by harnessing nonhomologous end joining (NHEJ) pathways in somatic cells. NHEJ can be subdivided into the classical (cNHEJ) and alternative NHEJ (aNHEJ) pathways, which partially operate antagonistically. The cNHEJ pathway not only protects broken DNA ends from degradation but also suppresses the joining of previously unlinked broken ends. Hence, in the absence of cNHEJ, more inversions or translocations can be obtained which can be ascribed to the unrestricted use of the aNHEJ pathway for double-strand break (DSB) repair. In contrast to inversions or translocations, short tandem duplications can be produced by paired single-strand breaks via a Cas9 nickase. Interestingly, the cNHEJ pathway is essential for these kinds of duplications, whereas aNHEJ is required for patch insertions that can also be formed during DSB repair. As chromosome engineering has not only been accomplished in the model plant Arabidopsis (Arabidopsis thaliana) but also in the crop maize (Zea mays), we expect that this technology will soon transform the breeding process.
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Affiliation(s)
- Fabienne Gehrke
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
| | - Angelina Schindele
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
| | - Holger Puchta
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
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Wolter F, Schindele P, Beying N, Scheben A, Puchta H. Different DNA repair pathways are involved in single-strand break-induced genomic changes in plants. THE PLANT CELL 2021; 33:3454-3469. [PMID: 34375428 PMCID: PMC8566284 DOI: 10.1093/plcell/koab204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 08/04/2021] [Indexed: 05/03/2023]
Abstract
In nature, single-strand breaks (SSBs) in DNA occur more frequently (by orders of magnitude) than double-strand breaks (DSBs). SSBs induced by the CRISPR/Cas9 nickase at a distance of 50-100 bp on opposite strands are highly mutagenic, leading to insertions/deletions (InDels), with insertions mainly occurring as direct tandem duplications. As short tandem repeats are overrepresented in plant genomes, this mechanism seems to be important for genome evolution. We investigated the distance at which paired 5'-overhanging SSBs are mutagenic and which DNA repair pathways are essential for insertion formation in Arabidopsis thaliana. We were able to detect InDel formation up to a distance of 250 bp, although with much reduced efficiency. Surprisingly, the loss of the classical nonhomologous end joining (NHEJ) pathway factors KU70 or DNA ligase 4 completely abolished tandem repeat formation. The microhomology-mediated NHEJ factor POLQ was required only for patch-like insertions, which are well-known from DSB repair as templated insertions from ectopic sites. As SSBs can also be repaired using homology, we furthermore asked whether the classical homologous recombination (HR) pathway is involved in this process in plants. The fact that RAD54 is not required for homology-mediated SSB repair demonstrates that the mechanisms for DSB- and SSB-induced HR differ in plants.
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Affiliation(s)
- Felix Wolter
- Botanical Institute, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Patrick Schindele
- Botanical Institute, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Natalja Beying
- Botanical Institute, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Armin Scheben
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Holger Puchta
- Botanical Institute, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Author for correspondence:
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5
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A rapidly reversible mutation generates subclonal genetic diversity and unstable drug resistance. Proc Natl Acad Sci U S A 2021; 118:2019060118. [PMID: 34675074 PMCID: PMC8639346 DOI: 10.1073/pnas.2019060118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2021] [Indexed: 11/18/2022] Open
Abstract
Most genetic changes have negligible reversion rates. As most mutations that confer resistance to an adverse condition (e.g., drug treatment) also confer a growth defect in its absence, it is challenging for cells to genetically adapt to transient environmental changes. Here, we identify a set of rapidly reversible drug-resistance mutations in Schizosaccharomyces pombe that are caused by microhomology-mediated tandem duplication (MTD) and reversion back to the wild-type sequence. Using 10,000× coverage whole-genome sequencing, we identify nearly 6,000 subclonal MTDs in a single clonal population and determine, using machine learning, how MTD frequency is encoded in the genome. We find that sequences with the highest-predicted MTD rates tend to generate insertions that maintain the correct reading frame, suggesting that MTD formation has shaped the evolution of coding sequences. Our study reveals a common mechanism of reversible genetic variation that is beneficial for adaptation to environmental fluctuations and facilitates evolutionary divergence.
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Xia H, Zhao W, Shi Y, Wang XR, Wang B. Microhomologies Are Associated with Tandem Duplications and Structural Variation in Plant Mitochondrial Genomes. Genome Biol Evol 2021; 12:1965-1974. [PMID: 32790831 PMCID: PMC7643612 DOI: 10.1093/gbe/evaa172] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/09/2020] [Indexed: 12/15/2022] Open
Abstract
Short tandem repeats (STRs) contribute to structural variation in plant mitochondrial genomes, but the mechanisms underlying their formation and expansion are unclear. In this study, we detected high polymorphism in the nad7-1 region of the Pinus tabuliformis mitogenome caused by the rapid accumulation of STRs and rearrangements over a few million years ago. The STRs in nad7-1 have a 7-bp microhomology (TAG7) flanking the repeat array. We then scanned the mitogenomes of 136 seed plants to understand the role of microhomology in the formation of STR and mitogenome evolution. A total of 13,170 STRs were identified, and almost half of them were associated with microhomologies. A substantial amount (1,197) of microhomologies was long enough to mediate structural variation, and the length of microhomology is positively correlated with the length of tandem repeat unit. These results suggest that microhomology may be involved in the formation of tandem repeat via microhomology-mediated pathway, and the formation of longer duplicates required greater length of microhomology. We examined the abundance of these 1,197 microhomologies, and found 75% of them were enriched in the plant mitogenomes. Further analyses of the 400 prevalent microhomologies revealed that 175 of them showed differential enrichment between angiosperms and gymnosperms and 186 differed between angiosperms and conifers, indicating lineage-specific usage and expansion of microhomologies. Our study sheds light on the sources of structural variation in plant mitochondrial genomes and highlights the importance of microhomology in mitochondrial genome evolution.
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Affiliation(s)
- Hanhan Xia
- College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Wei Zhao
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- Department of Ecology and Environmental Science, UPSC, Umeå University, Umeå, Sweden
| | - Yong Shi
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Xiao-Ru Wang
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China
- Department of Ecology and Environmental Science, UPSC, Umeå University, Umeå, Sweden
| | - Baosheng Wang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Corresponding author: E-mail:
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Schimmel J, Muñoz-Subirana N, Kool H, van Schendel R, Tijsterman M. Small tandem DNA duplications result from CST-guided Pol α-primase action at DNA break termini. Nat Commun 2021; 12:4843. [PMID: 34376693 PMCID: PMC8355091 DOI: 10.1038/s41467-021-25154-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 07/20/2021] [Indexed: 12/11/2022] Open
Abstract
Small tandem duplications of DNA occur frequently in the human genome and are implicated in the aetiology of certain human cancers. Recent studies have suggested that DNA double-strand breaks are causal to this mutational class, but the underlying mechanism remains elusive. Here, we identify a crucial role for DNA polymerase α (Pol α)-primase in tandem duplication formation at breaks having complementary 3′ ssDNA protrusions. By including so-called primase deserts in CRISPR/Cas9-induced DNA break configurations, we reveal that fill-in synthesis preferentially starts at the 3′ tip, and find this activity to be dependent on 53BP1, and the CTC1-STN1-TEN1 (CST) and Shieldin complexes. This axis generates near-blunt ends specifically at DNA breaks with 3′ overhangs, which are subsequently repaired by non-homologous end-joining. Our study provides a mechanistic explanation for a mutational signature abundantly observed in the genomes of species and cancer cells. Error-prone repair of DNA double-strand breaks have been implied to cause cancer-associated genome alterations, but the mechanism of their formation remains unclear. Here the authors find that DNA polymerase α primase plays part in tandem duplication formation at CRISPR/Cas9-induced complementary 3′ ssDNA protrusions.
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Affiliation(s)
- Joost Schimmel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Núria Muñoz-Subirana
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Hanneke Kool
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin van Schendel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marcel Tijsterman
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands. .,Institute of Biology Leiden, Leiden University, Leiden, The Netherlands.
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Vaughn JN, Korani W, Stein JC, Edwards JD, Peterson DG, Simpson SA, Youngblood RC, Grimwood J, Chougule K, Ware DH, McClung AM, Scheffler BE. Gene disruption by structural mutations drives selection in US rice breeding over the last century. PLoS Genet 2021; 17:e1009389. [PMID: 33735256 PMCID: PMC7971508 DOI: 10.1371/journal.pgen.1009389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 01/28/2021] [Indexed: 12/30/2022] Open
Abstract
The genetic basis of general plant vigor is of major interest to food producers, yet the trait is recalcitrant to genetic mapping because of the number of loci involved, their small effects, and linkage. Observations of heterosis in many crops suggests that recessive, malfunctioning versions of genes are a major cause of poor performance, yet we have little information on the mutational spectrum underlying these disruptions. To address this question, we generated a long-read assembly of a tropical japonica rice (Oryza sativa) variety, Carolina Gold, which allowed us to identify structural mutations (>50 bp) and orient them with respect to their ancestral state using the outgroup, Oryza glaberrima. Supporting prior work, we find substantial genome expansion in the sativa branch. While transposable elements (TEs) account for the largest share of size variation, the majority of events are not directly TE-mediated. Tandem duplications are the most common source of insertions and are highly enriched among 50-200bp mutations. To explore the relative impact of various mutational classes on crop fitness, we then track these structural events over the last century of US rice improvement using 101 resequenced varieties. Within this material, a pattern of temporary hybridization between medium and long-grain varieties was followed by recent divergence. During this long-term selection, structural mutations that impact gene exons have been removed at a greater rate than intronic indels and single-nucleotide mutations. These results support the use of ab initio estimates of mutational burden, based on structural data, as an orthogonal predictor in genomic selection. Some crop varieties have superior performance across years and environments. In hybrids, harmful mutations in one parent are masked by the ancestral alleles in the other parent, resulting in increased vigor. Unfortunately, these mutations are very difficult to identify precisely because, individually, they only have a small effect. In this study, we use long-read sequencing to characterize the entire mutational spectrum between two rice varieties. We then track these mutations through the last century of rice breeding. We show that large structural mutations in exons are selected against at a greater rate than any other mutational class. These findings illuminate the nature of deleterious alleles and will guide attempts to predict variety vigor based solely on genomic information.
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Affiliation(s)
- Justin N. Vaughn
- USDA-ARS, Genomics and Bioinformatics Research Unit, Stoneville, Mississippi, United States of America
- University of Georgia, Athens, Institute of Plant Breeding, Genetics, and Genomics, Athens, Georgia, United States of America
- * E-mail: (JNV); (BES)
| | - Walid Korani
- University of Georgia, Athens, Institute of Plant Breeding, Genetics, and Genomics, Athens, Georgia, United States of America
| | - Joshua C. Stein
- Cold Spring Harbor Laboratory, Cold Springs Harbor, New York, United States of America
| | - Jeremy D. Edwards
- USDA-ARS, Dale Bumpers National Rice Research Center, Stuttgart, Arkansas, United States of America
| | - Daniel G. Peterson
- Mississippi State University, Institute for Genomics, Biocomputing & Biotechnology, Starkville, Mississippi, United States of America
| | - Sheron A. Simpson
- USDA-ARS, Genomics and Bioinformatics Research Unit, Stoneville, Mississippi, United States of America
| | - Ramey C. Youngblood
- Mississippi State University, Institute for Genomics, Biocomputing & Biotechnology, Starkville, Mississippi, United States of America
| | - Jane Grimwood
- Hudson-Alpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - Kapeel Chougule
- Cold Spring Harbor Laboratory, Cold Springs Harbor, New York, United States of America
| | - Doreen H. Ware
- Cold Spring Harbor Laboratory, Cold Springs Harbor, New York, United States of America
- USDA-ARS, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States of America
| | - Anna M. McClung
- USDA-ARS, Dale Bumpers National Rice Research Center, Stuttgart, Arkansas, United States of America
| | - Brian E. Scheffler
- USDA-ARS, Genomics and Bioinformatics Research Unit, Stoneville, Mississippi, United States of America
- * E-mail: (JNV); (BES)
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9
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Color Intensity of the Red-Fleshed Berry Phenotype of Vitis vinifera Teinturier Grapes Varies Due to a 408 bp Duplication in the Promoter of VvmybA1. Genes (Basel) 2020; 11:genes11080891. [PMID: 32764272 PMCID: PMC7464560 DOI: 10.3390/genes11080891] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 07/28/2020] [Accepted: 07/31/2020] [Indexed: 11/18/2022] Open
Abstract
Grapevine (Vitis vinifera) teinturier cultivars are characterized by their typical reddish leaves and red-fleshed berries due to ectopic anthocyanin formation. Wines of these varieties have economic importance as they can be used for blending to enhance the color of red wines. The unique and heritable mutation has been known for a long time but the underlying genetic mechanism still is not yet understood. Here we describe the association of the red-fleshed berry phenotype with a 408 bp repetitive DNA element in the promoter of the VvmybA1 gene (grapevine color enhancer, GCE). Three different clones of ‘Teinturier’ were discovered with two, three and five allelic GCE repeats (MybA1t2, MybA1t3 and MybA1t5). All three clones are periclinal chimeras; these clones share the same L1 layer, but have distinct L2 layers with different quantities of GCE repeats. Quantitative real time PCR and HPLC analysis of leaf and berry samples showed that the GCE repeat number strongly correlates with an increase of the expression of VvmybA1 itself and the VvUFGT gene regulated by it and the anthocyanin content. A model is proposed based on autoregulation of VvmybA1t to explain the red phenotype which is similar to that of red-fleshed apples. This study presents results about the generation and modes of action of three MybA1t alleles responsible for the red-fleshed berry phenotype of teinturier grapevines.
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10
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Kamp JA, van Schendel R, Dilweg IW, Tijsterman M. BRCA1-associated structural variations are a consequence of polymerase theta-mediated end-joining. Nat Commun 2020; 11:3615. [PMID: 32680986 PMCID: PMC7368036 DOI: 10.1038/s41467-020-17455-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 07/01/2020] [Indexed: 12/03/2022] Open
Abstract
Failure to preserve the integrity of the genome is a hallmark of cancer. Recent studies have revealed that loss of the capacity to repair DNA breaks via homologous recombination (HR) results in a mutational profile termed BRCAness. The enzymatic activity that repairs HR substrates in BRCA-deficient conditions to produce this profile is currently unknown. We here show that the mutational landscape of BRCA1 deficiency in C. elegans closely resembles that of BRCA1-deficient tumours. We identify polymerase theta-mediated end-joining (TMEJ) to be responsible: knocking out polq-1 suppresses the accumulation of deletions and tandem duplications in brc-1 and brd-1 animals. We find no additional back-up repair in HR and TMEJ compromised animals; non-homologous end-joining does not affect BRCAness. The notion that TMEJ acts as an alternative to HR, promoting the genome alteration of HR-deficient cells, supports the idea that polymerase theta is a promising therapeutic target for HR-deficient tumours.
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Affiliation(s)
- J A Kamp
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - R van Schendel
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - I W Dilweg
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - M Tijsterman
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
- Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE, Leiden, The Netherlands.
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11
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Hanscom T, McVey M. Regulation of Error-Prone DNA Double-Strand Break Repair and Its Impact on Genome Evolution. Cells 2020; 9:E1657. [PMID: 32660124 PMCID: PMC7407515 DOI: 10.3390/cells9071657] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 12/17/2022] Open
Abstract
Double-strand breaks are one of the most deleterious DNA lesions. Their repair via error-prone mechanisms can promote mutagenesis, loss of genetic information, and deregulation of the genome. These detrimental outcomes are significant drivers of human diseases, including many cancers. Mutagenic double-strand break repair also facilitates heritable genetic changes that drive organismal adaptation and evolution. In this review, we discuss the mechanisms of various error-prone DNA double-strand break repair processes and the cellular conditions that regulate them, with a focus on alternative end joining. We provide examples that illustrate how mutagenic double-strand break repair drives genome diversity and evolution. Finally, we discuss how error-prone break repair can be crucial to the induction and progression of diseases such as cancer.
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Affiliation(s)
| | - Mitch McVey
- Department. of Biology, Tufts University, Medford, MA 02155, USA;
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12
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Viana VE, Pegoraro C, Busanello C, Costa de Oliveira A. Mutagenesis in Rice: The Basis for Breeding a New Super Plant. FRONTIERS IN PLANT SCIENCE 2019; 10:1326. [PMID: 31781133 PMCID: PMC6857675 DOI: 10.3389/fpls.2019.01326] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 09/24/2019] [Indexed: 05/28/2023]
Abstract
The high selection pressure applied in rice breeding since its domestication thousands of years ago has caused a narrowing in its genetic variability. Obtaining new rice cultivars therefore becomes a major challenge for breeders and developing strategies to increase the genetic variability has demanded the attention of several research groups. Understanding mutations and their applications have paved the way for advances in the elucidation of a genetic, physiological, and biochemical basis of rice traits. Creating variability through mutations has therefore grown to be among the most important tools to improve rice. The small genome size of rice has enabled a faster release of higher quality sequence drafts as compared to other crops. The move from structural to functional genomics is possible due to an array of mutant databases, highlighting mutagenesis as an important player in this progress. Furthermore, due to the synteny among the Poaceae, other grasses can also benefit from these findings. Successful gene modifications have been obtained by random and targeted mutations. Furthermore, following mutation induction pathways, techniques have been applied to identify mutations and the molecular control of DNA damage repair mechanisms in the rice genome. This review highlights findings in generating rice genome resources showing strategies applied for variability increasing, detection and genetic mechanisms of DNA damage repair.
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Affiliation(s)
| | | | | | - Antonio Costa de Oliveira
- Centro de Genômica e Fitomelhoramento, Faculdade de Agronomia Eliseu Maciel, Departamento de Fitotecnia, Universidade Federal de Pelotas, Campus Capão do Leão, Rio Grande do Sul, Brazil
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13
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Krasileva KV. The role of transposable elements and DNA damage repair mechanisms in gene duplications and gene fusions in plant genomes. CURRENT OPINION IN PLANT BIOLOGY 2019; 48:18-25. [PMID: 30849712 DOI: 10.1016/j.pbi.2019.01.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 01/16/2019] [Accepted: 01/29/2019] [Indexed: 05/02/2023]
Abstract
Plant genomes are shaped by structural variation. Gene-size insertions and among most prominent events and can have significant effects on amplification of gene families as well as facilitate new gene fusions. Transposable elements as well as plant DNA repair machinery have overlapping contributions to these events, and often work in synergy. Activity of transposable elements is often lineage specific and can preferentially affect specific gene families, such as disease resistance genes. Once duplicated, genes themselves can serve templates for additional variation that can arise from non-allelic homologous recombination. Non-homologous DNA repair mechanisms contribute to additional variation and diversify the mechanisms of gene movement, such as through ligation of extra-chromosomal DNA fragments. Genomic processes that generate structural variation can be induced by stress and, therefore, can provide adaptive potential. This review describes mechanisms that contribute to gene-size structural variation in plants, result in gene duplication and generation of new plant genes through gene fusion.
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Affiliation(s)
- Ksenia V Krasileva
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, United States.
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14
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Pereira JF, Ryan PR. The role of transposable elements in the evolution of aluminium resistance in plants. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:41-54. [PMID: 30325439 DOI: 10.1093/jxb/ery357] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 10/02/2018] [Indexed: 05/20/2023]
Abstract
Aluminium (Al) toxicity can severely reduce root growth and consequently affect plant development and yield. A mechanism by which many species resist the toxic effects of Al relies on the efflux of organic anions (OAs) from the root apices via OA transporters. Several of the genes encoding these OA transporters contain transposable elements (TEs) in the coding sequences or in flanking regions. Some of the TE-induced mutations impact Al resistance by modifying the level and/or location of gene expression so that OA efflux from the roots is increased. The importance of genomic modifications for improving the adaptation of plants to acid soils has been raised previously, but the growing number of examples linking TEs with these changes requires highlighting. Here, we review the role of TEs in creating genetic modifications that enhance the adaptation of plants to acid soils by increasing the release of OAs from the root apices. We argue that TEs have been an important source of beneficial mutations that have co-opted OA transporter proteins with other functions to perform this role. These changes have occurred relatively recently in the evolution of many species and likely facilitated their expansion into regions with acidic soils.
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Affiliation(s)
| | - Peter R Ryan
- CSIRO Agriculture and Food, Canberra, ACT, Australia
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15
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Schmidt C, Pacher M, Puchta H. DNA Break Repair in Plants and Its Application for Genome Engineering. Methods Mol Biol 2019; 1864:237-266. [PMID: 30415341 DOI: 10.1007/978-1-4939-8778-8_17] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Genome engineering is a biotechnological approach to precisely modify the genetic code of a given organism in order to change the context of an existing sequence or to create new genetic resources, e.g., for obtaining improved traits or performance. Efficient targeted genome alterations are mainly based on the induction of DNA double-strand breaks (DSBs) or adjacent single-strand breaks (SSBs). Naturally, all organisms continuously have to deal with DNA-damaging factors challenging the genetic integrity, and therefore a wide range of DNA repair mechanisms have evolved. A profound understanding of the different repair pathways is a prerequisite to control and enhance targeted gene modifications. DSB repair can take place by nonhomologous end joining (NHEJ) or homology-dependent repair (HDR). As the main outcome of NHEJ-mediated repair is accompanied by small insertions and deletions, it is applicable to specifically knock out genes or to rearrange linkage groups or whole chromosomes. The basic requirement for HDR is the presence of a homologous template; thus this process can be exploited for targeted integration of ectopic sequences into the plant genome. The development of different types of artificial site-specific nucleases allows for targeted DSB induction in the plant genome. Such synthetic nucleases have been used for both qualitatively studying DSB repair in vivo with respect to mechanistic differences and quantitatively in order to determine the role of key factors for NHEJ and HR, respectively. The conclusions drawn from these studies allow for a better understanding of genome evolution and help identifying synergistic or antagonistic genetic interactions while supporting biotechnological applications for transiently modifying the plant DNA repair machinery in favor of targeted genome engineering.
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Affiliation(s)
- Carla Schmidt
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Michael Pacher
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Holger Puchta
- Botanical Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany.
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16
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Kumlehn J, Pietralla J, Hensel G, Pacher M, Puchta H. The CRISPR/Cas revolution continues: From efficient gene editing for crop breeding to plant synthetic biology. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2018; 60:1127-1153. [PMID: 30387552 DOI: 10.1111/jipb.12734] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 10/30/2018] [Indexed: 05/18/2023]
Abstract
Since the discovery that nucleases of the bacterial CRISPR (clustered regularly interspaced palindromic repeat)-associated (Cas) system can be used as easily programmable tools for genome engineering, their application massively transformed different areas of plant biology. In this review, we assess the current state of their use for crop breeding to incorporate attractive new agronomical traits into specific cultivars of various crop plants. This can be achieved by the use of Cas9/12 nucleases for double-strand break induction, resulting in mutations by non-homologous recombination. Strategies for performing such experiments - from the design of guide RNA to the use of different transformation technologies - are evaluated. Furthermore, we sum up recent developments regarding the use of nuclease-deficient Cas9/12 proteins, as DNA-binding moieties for targeting different kinds of enzyme activities to specific sites within the genome. Progress in base deamination, transcriptional induction and transcriptional repression, as well as in imaging in plants, is also discussed. As different Cas9/12 enzymes are at hand, the simultaneous application of various enzyme activities, to multiple genomic sites, is now in reach to redirect plant metabolism in a multifunctional manner and pave the way for a new level of plant synthetic biology.
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Affiliation(s)
- Jochen Kumlehn
- Plant Reproductive Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466 Seeland OT Gatersleben, Germany
| | - Janine Pietralla
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Goetz Hensel
- Plant Reproductive Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), 06466 Seeland OT Gatersleben, Germany
| | - Michael Pacher
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Holger Puchta
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
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17
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Birth and Death of LTR-Retrotransposons in Aegilops tauschii. Genetics 2018; 210:1039-1051. [PMID: 30158124 DOI: 10.1534/genetics.118.301198] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 08/20/2018] [Indexed: 11/18/2022] Open
Abstract
Long terminal repeat-retrotransposons (LTR-RTs) are a major component of all flowering plant genomes. To analyze the time dynamics of LTR-RTs, we modeled the insertion rates of the 35 most abundant LTR-RT families in the genome of Aegilops tauschii, one of the progenitors of wheat. Our model of insertion rate (birth) takes into account random variation in LTR divergence and the deletion rate (death) of LTR-RTs. Modeling the death rate is crucial because ignoring it would underestimate insertion rates in the distant past. We rejected the hypothesis of constancy of insertion rates for all 35 families and showed by simulations that our hypothesis test controlled the false-positive rate. LTR-RT insertions peaked from 0.064 to 2.39 MYA across the 35 families. Among other effects, the average age of elements within a family was negatively associated with recombination rate along a chromosome, with proximity to the closest gene, and weakly associated with the proximity to its 5' end. Elements within a family that were near genes colinear with genes in the genome of tetraploid emmer wheat tended to be younger than those near noncolinear genes. We discuss these associations in the context of genome evolution and stability of genome sizes in the tribe Triticeae. We demonstrate the general utility of our models by analyzing the two most abundant LTR-RT families in Arabidopsis lyrata, and show that these families differed in their insertion dynamics. Our estimation methods are available in the R package TE on CRAN.
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Thind AK, Wicker T, Müller T, Ackermann PM, Steuernagel B, Wulff BBH, Spannagl M, Twardziok SO, Felder M, Lux T, Mayer KFX, Keller B, Krattinger SG. Chromosome-scale comparative sequence analysis unravels molecular mechanisms of genome dynamics between two wheat cultivars. Genome Biol 2018; 19:104. [PMID: 30115097 PMCID: PMC6097286 DOI: 10.1186/s13059-018-1477-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 07/10/2018] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Recent improvements in DNA sequencing and genome scaffolding have paved the way to generate high-quality de novo assemblies of pseudomolecules representing complete chromosomes of wheat and its wild relatives. These assemblies form the basis to compare the dynamics of wheat genomes on a megabase scale. RESULTS Here, we provide a comparative sequence analysis of the 700-megabase chromosome 2D between two bread wheat genotypes-the old landrace Chinese Spring and the elite Swiss spring wheat line 'CH Campala Lr22a'. Both chromosomes were assembled into megabase-sized scaffolds. There is a high degree of sequence conservation between the two chromosomes. Analysis of large structural variations reveals four large indels of more than 100 kb. Based on the molecular signatures at the breakpoints, unequal crossing over and double-strand break repair were identified as the molecular mechanisms that caused these indels. Three of the large indels affect copy number of NLRs, a gene family involved in plant immunity. Analysis of SNP density reveals four haploblocks of 4, 8, 9 and 48 Mb with a 35-fold increased SNP density compared to the rest of the chromosome. Gene content across the two chromosomes was highly conserved. Ninety-nine percent of the genic sequences were present in both genotypes and the fraction of unique genes ranged from 0.4 to 0.7%. CONCLUSIONS This comparative analysis of two high-quality chromosome assemblies enabled a comprehensive assessment of large structural variations and gene content. The insight obtained from this analysis will form the basis of future wheat pan-genome studies.
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Affiliation(s)
- Anupriya Kaur Thind
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland
| | - Thomas Wicker
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland
| | - Thomas Müller
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland
| | - Patrick M Ackermann
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland
| | | | | | | | | | | | - Thomas Lux
- Helmholtz Zentrum Munich, Munich, Germany
| | - Klaus F X Mayer
- Helmholtz Zentrum Munich, Munich, Germany
- School of Life Sciences, Technical University Munich, Munich, Germany
- College of Science, King Saud University, Riad, Kingdom of Saudi Arabia
| | - Beat Keller
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland
| | - Simon G Krattinger
- Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, Zurich, Switzerland.
- King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia.
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Bennetzen JL, Wang X. Relationships between Gene Structure and Genome Instability in Flowering Plants. MOLECULAR PLANT 2018; 11:407-413. [PMID: 29462722 DOI: 10.1016/j.molp.2018.02.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/11/2018] [Accepted: 02/13/2018] [Indexed: 06/08/2023]
Abstract
Flowering plant (angiosperm) genomes are exceptional in their variability with respect to genome size, ploidy, chromosome number, gene content, and gene arrangement. Gene movement, although observed in some of the earliest plant genome comparisons, has been relatively underinvestigated. We present herein a description of several interesting properties of plant gene and genome structure that are pertinent to the successful movement of a gene to a new location. These considerations lead us to propose a model that can explain the frequent success of plant gene mobility, namely that Small Insulated Genes Move Around (SIGMAR). The SIGMAR model is then compared with known processes for gene mobilization, and predictions of the SIGMAR model are formulated to encourage future experimentation. The overall results indicate that the frequent gene movement in angiosperm genomes is partly an outcome of the unusual properties of angiosperm genes, especially their small size and insulation from epigenetic silencing.
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Affiliation(s)
- Jeffrey L Bennetzen
- State Key Laboratory of Tea Plant Biology and Utilization/Key Laboratory of Tea Biology and Processing, Ministry of Agriculture, Anhui Agricultural University, Hefei, Anhui 230036, People's Republic of China; Department of Genetics, University of Georgia, Athens, GA 30602, USA.
| | - Xuewen Wang
- State Key Laboratory of Tea Plant Biology and Utilization/Key Laboratory of Tea Biology and Processing, Ministry of Agriculture, Anhui Agricultural University, Hefei, Anhui 230036, People's Republic of China; Department of Genetics, University of Georgia, Athens, GA 30602, USA
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20
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Sinn BT, Sedmak DD, Kelly LM, Freudenstein JV. Total duplication of the small single copy region in the angiosperm plastome: Rearrangement and inverted repeat instability in Asarum. AMERICAN JOURNAL OF BOTANY 2018; 105:71-84. [PMID: 29532923 DOI: 10.1002/ajb2.1001] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 11/27/2017] [Indexed: 05/21/2023]
Abstract
PREMISE OF THE STUDY As more plastomes are assembled, it is evident that rearrangements, losses, intergenic spacer expansion and contraction, and syntenic breaks within otherwise functioning plastids are more common than was thought previously, and such changes have developed independently in disparate lineages. However, to date, the magnoliids remain characterized by their highly conserved plastid genomes (plastomes). METHODS Illumina HiSeq and MiSeq platforms were used to sequence the plastomes of Saruma henryi and those of representative species from each of the six taxonomic sections of Asarum. Sequenced plastomes were compared in a phylogenetic context provided by maximum likelihood and parsimony inferences made using an additional 18 publicly available plastomes from early-diverging angiosperm lineages. KEY RESULTS In contrast to previously published magnoliid plastomes and the newly sequenced Saruma henryi plastome published here, Asarum plastomes have undergone extensive disruption and contain extremely lengthy AT-repeat regions. The entirety of the small single copy region (SSC) of A. canadense and A. sieboldii var. sieboldii has been incorporated into the inverted repeat regions (IR), and the SSC of A. delavayi is only 14 bp long. All sampled Asarum plastomes share an inversion of a large portion of the large single copy region (LSC) such that trnE-UUC is adjacent to the LSC-IR boundary. CONCLUSIONS Plastome divergence in Asarum appears to be consistent with trends seen in highly rearranged plastomes of the monocots and eudicots. We propose that plastome instability in Asarum is due to repetitive motifs that serve as recombinatory substrates and reduce genome stability.
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Affiliation(s)
- Brandon T Sinn
- The Ohio State University Museum of Biological Diversity, Department of Evolution, Ecology, and Organismal Biology, Columbus, Ohio 43212, USA
- West Virginia University, Department of Biology, Morgantown, West Virginia 26505, USA
| | - Dylan D Sedmak
- The Ohio State University Museum of Biological Diversity, Department of Evolution, Ecology, and Organismal Biology, Columbus, Ohio 43212, USA
| | | | - John V Freudenstein
- The Ohio State University Museum of Biological Diversity, Department of Evolution, Ecology, and Organismal Biology, Columbus, Ohio 43212, USA
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21
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Schimmel J, Kool H, van Schendel R, Tijsterman M. Mutational signatures of non-homologous and polymerase theta-mediated end-joining in embryonic stem cells. EMBO J 2017; 36:3634-3649. [PMID: 29079701 PMCID: PMC5730883 DOI: 10.15252/embj.201796948] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 09/05/2017] [Accepted: 09/29/2017] [Indexed: 12/11/2022] Open
Abstract
Cells employ potentially mutagenic DNA repair mechanisms to avoid the detrimental effects of chromosome breaks on cell survival. While classical non-homologous end-joining (cNHEJ) is largely error-free, alternative end-joining pathways have been described that are intrinsically mutagenic. Which end-joining mechanisms operate in germ and embryonic cells and thus contribute to heritable mutations found in congenital diseases is, however, still largely elusive. Here, we determined the genetic requirements for the repair of CRISPR/Cas9-induced chromosomal breaks of different configurations, and establish the mutational consequences. We find that cNHEJ and polymerase theta-mediated end-joining (TMEJ) act both parallel and redundant in mouse embryonic stem cells and account for virtually all end-joining activity. Surprisingly, mutagenic repair by polymerase theta (Pol θ, encoded by the Polq gene) is most prevalent for blunt double-strand breaks (DSBs), while cNHEJ dictates mutagenic repair of DSBs with protruding ends, in which the cNHEJ polymerases lambda and mu play minor roles. We conclude that cNHEJ-dependent repair of DSBs with protruding ends can explain de novo formation of tandem duplications in mammalian genomes.
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Affiliation(s)
- Joost Schimmel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Hanneke Kool
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin van Schendel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marcel Tijsterman
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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22
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Ruiz-Hernández V, Hermans B, Weiss J, Egea-Cortines M. Genetic Analysis of Natural Variation in Antirrhinum Scent Profiles Identifies BENZOIC ACID CARBOXYMETHYL TRANSFERASE As the Major Locus Controlling Methyl Benzoate Synthesis. FRONTIERS IN PLANT SCIENCE 2017; 8:27. [PMID: 28154577 PMCID: PMC5244254 DOI: 10.3389/fpls.2017.00027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 01/05/2017] [Indexed: 05/31/2023]
Abstract
The Antirrhinum genus has a considerable complexity in the scent profiles produced by different species. We have analyzed the genetic differences between A. majus and A. linkianum, two species divergent in the emission of methyl benzoate, methyl cinnamate, acetophenone, and ocimene. The genetic analysis showed that all compounds segregated in a Mendelian fashion attributable to one or two loci with simple or epistatic interactions. Several lines lacked methyl benzoate, a major Volatile Organic Compound emitted by A. majus but missing in A. linkianum. Using a candidate gene approach, we found that the BENZOIC ACID CARBOXYMETHYL TRANSFERASE from A. linkianum appeared to be a null allele as we could not detect mRNA expression. The coding region did not show significant differences that could explain the loss of expression. The intron-exon boundaries was also conserved indicating that there is no alternative splicing in A. linkianum as compared to A. majus. However, it showed multiple polymorphisms in the 5' promoter region including two insertions, one harboring an IDLE MITE transposon with additional sequences with high homology to the PLENA locus and a second one with somewhat lower homology to the regulatory region of the VENOSA locus. It also had a 778 bp deletion as compared to the A. majus BAMT promoter region. Our results show that the differences in scent emission between A. majus and A. linkianum may be traced back to single genes involved in discrete biosynthetic reactions such as benzoic acid methylation. Thus, natural variation of this complex trait maybe the result of combinations of wild type, and loss of function alleles in different genes involved in discrete VOCs biosynthesis. Furthermore, the presence of active transposable elements in the genus may account for rapid evolution and instability, raising the possibility of adaptation to local pollinators.
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Repair of adjacent single-strand breaks is often accompanied by the formation of tandem sequence duplications in plant genomes. Proc Natl Acad Sci U S A 2016; 113:7266-71. [PMID: 27307441 DOI: 10.1073/pnas.1603823113] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Duplication of existing sequences is a major mechanism of genome evolution. It has been previously shown that duplications can occur by replication slippage, unequal sister chromatid exchange, homologous recombination, and aberrant double-strand break-induced synthesis-dependent strand annealing reactions. In a recent study, the abundant presence of short direct repeats was documented by comparative bioinformatics analysis of different rice genomes, and the hypothesis was put forward that such duplications might arise due to the concerted repair of adjacent single-strand breaks (SSBs). Applying the CRISPR/Cas9 technology, we were able to test this hypothesis experimentally in the model plant Arabidopsis thaliana Using a Cas9 nickase to induce adjacent genomic SSBs in different regions of the genome (genic, intergenic, and heterochromatic) and at different distances (∼20, 50, and 100 bps), we analyzed the repair outcomes by deep sequencing. In addition to deletions, we regularly detected the formation of direct repeats close to the break sites, independent of the genomic context. The formation of these duplications as well as deletions may be associated with the presence of microhomologies. Most interestingly, we found that even the induction of two SSBs on the same DNA strand can cause genome alterations, albeit at a much lower level. Because such a scenario reflects a natural step during nucleotide excision repair, and given that the germline is set aside only late during development in plants, the repair of adjacent SSBs indeed seems to have an important influence on the shaping of plant genomes during evolution.
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Bai Z, Chen J, Liao Y, Wang M, Liu R, Ge S, Wing RA, Chen M. The impact and origin of copy number variations in the Oryza species. BMC Genomics 2016; 17:261. [PMID: 27025496 PMCID: PMC4812662 DOI: 10.1186/s12864-016-2589-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 03/15/2016] [Indexed: 02/16/2023] Open
Abstract
Background Copy number variation (CNV), a complex genomic rearrangement, has been extensively studied in humans and other organisms. In plants, CNVs of several genes were found to be responsible for various important traits; however, the cause and consequence of CNVs remains largely unknown. Recently released next-generation sequencing (NGS) data provide an opportunity for a genome-wide study of CNVs in rice. Results Here, by an NGS-based approach, we generated a CNV map comprising 9,196 deletions compared to the reference genome ‘Nipponbare’. Using Oryza glaberrima as the outgroup, 80 % of the CNV events turned out to be insertions in Nipponbare. There were 2,806 annotated genes affected by these CNV events. We experimentally validated 28 functional CNV genes including OsMADS56, BPH14, OsDCL2b and OsMADS30, implying that CNVs might have contributed to phenotypic variations in rice. Most CNV genes were found to be located in non-co-linear positions by comparison to O. glaberrima. One of the origins of these non-co-linear genes was genomic duplications caused by transposon activity or double-strand break repair. Comprehensive analysis of mutation mechanisms suggested an abundance of CNVs formed by non-homologous end-joining and mobile element insertion. Conclusions This study showed the impact and origin of copy number variations in rice on a genomic scale. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2589-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zetao Bai
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jinfeng Chen
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yi Liao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Meijiao Wang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Rong Liu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Song Ge
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Rod A Wing
- Arizona Genomics Institute, School of Plant Science, University of Arizona, Tucson, AZ, 85721, USA
| | - Mingsheng Chen
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
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Acquired Flucytosine Resistance during Combination Therapy with Caspofungin and Flucytosine for Candida glabrata Cystitis. Antimicrob Agents Chemother 2015; 60:662-5. [PMID: 26525799 DOI: 10.1128/aac.02265-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 10/27/2015] [Indexed: 12/17/2022] Open
Abstract
Treatment of Candida glabrata cystitis remains a therapeutic challenge, and an antifungal combination using flucytosine is one option. We describe two patients with refractory C. glabrata cystitis who failed flucytosine combined with caspofungin with early-acquired high-level resistance to flucytosine due to nonsense mutations in the FUR1 gene. Rapidly acquired flucytosine resistance with microbiological failure should discourage combination of caspofungin and flucytosine during urinary candidiasis.
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Pauwels K, De Keersmaecker SC, De Schrijver A, du Jardin P, Roosens NH, Herman P. Next-generation sequencing as a tool for the molecular characterisation and risk assessment of genetically modified plants: Added value or not? Trends Food Sci Technol 2015. [DOI: 10.1016/j.tifs.2015.07.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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27
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Ladics GS, Bartholomaeus A, Bregitzer P, Doerrer NG, Gray A, Holzhauser T, Jordan M, Keese P, Kok E, Macdonald P, Parrott W, Privalle L, Raybould A, Rhee SY, Rice E, Romeis J, Vaughn J, Wal JM, Glenn K. Genetic basis and detection of unintended effects in genetically modified crop plants. Transgenic Res 2015; 24:587-603. [PMID: 25716164 PMCID: PMC4504983 DOI: 10.1007/s11248-015-9867-7] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 02/14/2015] [Indexed: 11/26/2022]
Abstract
In January 2014, an international meeting sponsored by the International Life Sciences Institute/Health and Environmental Sciences Institute and the Canadian Food Inspection Agency titled “Genetic Basis of Unintended Effects in Modified Plants” was held in Ottawa, Canada, bringing together over 75 scientists from academia, government, and the agro-biotech industry. The objectives of the meeting were to explore current knowledge and identify areas requiring further study on unintended effects in plants and to discuss how this information can inform and improve genetically modified (GM) crop risk assessments. The meeting featured presentations on the molecular basis of plant genome variability in general, unintended changes at the molecular and phenotypic levels, and the development and use of hypothesis-driven evaluations of unintended effects in assessing conventional and GM crops. The development and role of emerging “omics” technologies in the assessment of unintended effects was also discussed. Several themes recurred in a number of talks; for example, a common observation was that no system for genetic modification, including conventional methods of plant breeding, is without unintended effects. Another common observation was that “unintended” does not necessarily mean “harmful”. This paper summarizes key points from the information presented at the meeting to provide readers with current viewpoints on these topics.
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Affiliation(s)
- Gregory S. Ladics
- DuPont Pioneer Agricultural Biotechnology, DuPont Experimental Station, 200 Powder Mill Road, Wilmington, DE 19803 USA
| | - Andrew Bartholomaeus
- Therapeutics Research Centre, School of Medicine, Queensland University, Brisbane, QLD 4072 Australia
- Faculty of Health, School of Pharmacy, University of Canberra, Locked Bag 1, Canberra, ACT 2601 Australia
| | - Phil Bregitzer
- National Small Grains Germplasm Research Facility, US Department of Agriculture – Agricultural Research Service, 1691 S. 2700 W., Aberdeen, ID 83210 USA
| | - Nancy G. Doerrer
- ILSI Health and Environmental Sciences Institute, 1156 15th St., NW, Suite 200, Washington, DC 20005 USA
| | - Alan Gray
- Centre for Ecology and Hydrology, CEH Wallingford, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB UK
| | - Thomas Holzhauser
- Division of Allergology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany
| | - Mark Jordan
- Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB R6M 1Y5 Canada
| | - Paul Keese
- Office of the Gene Technology Regulator, Australian Government, MDP54, GPO Box 9848, Canberra, ACT 2601 Australia
| | - Esther Kok
- RIKILT Wageningen UR, P.O. Box 230, 6700 AE Wageningen, The Netherlands
| | - Phil Macdonald
- Canadian Food Inspection Agency, 1400 Merivale Rd, Ottawa, ON K1A 0Y9 Canada
| | - Wayne Parrott
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA 30602 USA
| | - Laura Privalle
- Bayer CropScience, 407 Davis Drive, Morrisville, NC 27560 USA
| | - Alan Raybould
- Syngenta Ltd, Jealott’s Hill International Research Centre, Bracknell, RG42 6EY UK
- Present Address: Syngenta Crop Protection AG, Schwarzwaldallee 215, 4058 Basel, Switzerland
| | - Seung Yon Rhee
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama St., Stanford, CA 94305 USA
| | - Elena Rice
- Monsanto Company, 700 Chesterfield Pkwy W., CC5A, Chesterfield, MO 63017 USA
| | - Jörg Romeis
- Agroscope, Institute for Sustainability Sciences ISS, Reckenholzstr. 191, 8046 Zurich, Switzerland
| | - Justin Vaughn
- University of Georgia, 111 Riverbend Road, Athens, GA 30602 USA
| | - Jean-Michel Wal
- Dept. SVS, AgroParisTech, 16 rue Claude Bernard, 75231 Paris, France
| | - Kevin Glenn
- Monsanto Company, 800 N. Lindbergh Blvd, U4NA, St. Louis, MO 63167 USA
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Schiml S, Fauser F, Puchta H. The CRISPR/Cas system can be used as nuclease for in planta gene targeting and as paired nickases for directed mutagenesis in Arabidopsis resulting in heritable progeny. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 80:1139-50. [PMID: 25327456 DOI: 10.1111/tpj.12704] [Citation(s) in RCA: 214] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/07/2014] [Accepted: 10/13/2014] [Indexed: 05/03/2023]
Abstract
The CRISPR/Cas nuclease is becoming a major tool for targeted mutagenesis in eukaryotes by inducing double-strand breaks (DSBs) at pre-selected genomic sites that are repaired by non-homologous end joining (NHEJ) in an error-prone way. In plants, it could be demonstrated that the Cas9 nuclease is able to induce heritable mutations in Arabidopsis thaliana and rice. Gene targeting (GT) by homologous recombination (HR) can also be induced by DSBs. Using a natural nuclease and marker genes, we previously developed an in planta GT strategy in which both a targeting vector and targeting locus are activated simultaneously via DSB induction during plant development. Here, we demonstrate that this strategy can be used for natural genes by CRISPR/Cas-mediated DSB induction. We were able to integrate a resistance cassette into the ADH1 locus of A. thaliana via HR. Heritable events were identified using a PCR-based genotyping approach, characterised by Southern blotting and confirmed on the sequence level. A major concern is the specificity of the CRISPR/Cas nucleases. Off-target effects might be avoided using two adjacent sgRNA target sequences to guide the Cas9 nickase to each of the two DNA strands, resulting in the formation of a DSB. By amplicon deep sequencing, we demonstrate that this Cas9 paired nickase strategy has a mutagenic potential comparable with that of the nuclease, while the resulting mutations are mostly deletions. We also demonstrate the stable inheritance of such mutations in A. thaliana.
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Affiliation(s)
- Simon Schiml
- Botanical Institute II, Karlsruhe Institute of Technology, POB 6980, 76049, Karlsruhe, Germany
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