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Sloan DB, Broz AK, Kuster SA, Muthye V, Peñafiel-Ayala A, Marron JR, Lavrov DV, Brieba LG. Expansion of the MutS Gene Family in Plants. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.17.603841. [PMID: 39071318 PMCID: PMC11275761 DOI: 10.1101/2024.07.17.603841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
The MutS gene family is distributed across the tree of life and is involved in recombination, DNA repair, and protein translation. Multiple evolutionary processes have expanded the set of MutS genes in plants relative to other eukaryotes. Here, we investigate the origins and functions of these plant-specific genes. Land plants, green algae, red algae, and glaucophytes share cyanobacterial-like MutS1 and MutS2 genes that presumably were gained via plastid endosymbiotic gene transfer. MutS1 was subsequently lost in some taxa, including seed plants, whereas MutS2 was duplicated in Viridiplantae (i.e., land plants and green algae) with widespread retention of both resulting paralogs. Viridiplantae also have two anciently duplicated copies of the eukaryotic MSH6 gene (i.e., MSH6 and MSH7) and acquired MSH1 via horizontal gene transfer - potentially from a nucleocytovirus. Despite sharing the same name, "plant MSH1" is not directly related to the gene known as MSH1 in some fungi and animals, which may be an ancestral eukaryotic gene acquired via mitochondrial endosymbiosis and subsequently lost in most eukaryotic lineages. There has been substantial progress in understanding the functions of MSH1 and MSH6/MSH7 in plants, but the roles of the cyanobacterial-like MutS1 and MutS2 genes remain uncharacterized. Known functions of bacterial homologs and predicted protein structures, including fusions to diverse nuclease domains, provide hypotheses about potential molecular mechanisms. Because most plant-specific MutS proteins are targeted to the mitochondria and/or plastids, the expansion of this family appears to have played a large role in shaping plant organelle genetics.
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Affiliation(s)
- Daniel B Sloan
- Department of Biology, Colorado State University, Fort Collins, CO, USA
| | - Amanda K Broz
- Department of Biology, Colorado State University, Fort Collins, CO, USA
| | - Shady A Kuster
- Department of Biology, Colorado State University, Fort Collins, CO, USA
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO, USA
| | - Viraj Muthye
- Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - Alejandro Peñafiel-Ayala
- Unidad de Genómica Avanzada, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Gto, México
| | - Jennifer R Marron
- Department of Biology, Colorado State University, Fort Collins, CO, USA
| | - Dennis V Lavrov
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA
| | - Luis G Brieba
- Unidad de Genómica Avanzada, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Gto, México
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2
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Peñafiel-Ayala A, Peralta-Castro A, Mora-Garduño J, García-Medel P, Zambrano-Pereira AG, Díaz-Quezada C, Abraham-Juárez MJ, Benítez-Cardoza CG, Sloan DB, Brieba LG. Plant Organellar MSH1 Is a Displacement Loop-Specific Endonuclease. PLANT & CELL PHYSIOLOGY 2024; 65:560-575. [PMID: 37756637 DOI: 10.1093/pcp/pcad112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/09/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023]
Abstract
MutS HOMOLOG 1 (MSH1) is an organellar-targeted protein that obstructs ectopic recombination and the accumulation of mutations in plant organellar genomes. MSH1 also modulates the epigenetic status of nuclear DNA, and its absence induces a variety of phenotypic responses. MSH1 is a member of the MutS family of DNA mismatch repair proteins but harbors an additional GIY-YIG nuclease domain that distinguishes it from the rest of this family. How MSH1 hampers recombination and promotes fidelity in organellar DNA inheritance is unknown. Here, we elucidate its enzymatic activities by recombinantly expressing and purifying full-length MSH1 from Arabidopsis thaliana (AtMSH1). AtMSH1 is a metalloenzyme that shows a strong binding affinity for displacement loops (D-loops). The DNA-binding abilities of AtMSH1 reside in its MutS domain and not in its GIY-YIG domain, which is the ancillary nickase of AtMSH1. In the presence of divalent metal ions, AtMSH1 selectively executes multiple incisions at D-loops, but not other DNA structures including Holliday junctions or dsDNA, regardless of the presence or absence of mismatches. The selectivity of AtMSH1 to dismantle D-loops supports the role of this enzyme in preventing recombination between short repeats. Our results suggest that plant organelles have evolved novel DNA repair routes centered around the anti-recombinogenic activity of MSH1.
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Affiliation(s)
- Alejandro Peñafiel-Ayala
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Antolin Peralta-Castro
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Josue Mora-Garduño
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Paola García-Medel
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Angie G Zambrano-Pereira
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Corina Díaz-Quezada
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - María Jazmín Abraham-Juárez
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
| | - Claudia G Benítez-Cardoza
- Laboratorio de Investigación Bioquímica, Programa Institucional en Biomedicina Molecular ENMyH-IPN, Guillermo Massieu Helguera No. 239, La Escalera Ticoman 07320 DF, México
| | - Daniel B Sloan
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Luis G Brieba
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, Irapuato, Guanajuato 36821, México
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3
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Lee Y, Cho CH, Noh C, Yang JH, Park SI, Lee YM, West JA, Bhattacharya D, Jo K, Yoon HS. Origin of minicircular mitochondrial genomes in red algae. Nat Commun 2023; 14:3363. [PMID: 37291154 PMCID: PMC10250338 DOI: 10.1038/s41467-023-39084-2] [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: 12/14/2021] [Accepted: 05/30/2023] [Indexed: 06/10/2023] Open
Abstract
Eukaryotic organelle genomes are generally of conserved size and gene content within phylogenetic groups. However, significant variation in genome structure may occur. Here, we report that the Stylonematophyceae red algae contain multipartite circular mitochondrial genomes (i.e., minicircles) which encode one or two genes bounded by a specific cassette and a conserved constant region. These minicircles are visualized using fluorescence microscope and scanning electron microscope, proving the circularity. Mitochondrial gene sets are reduced in these highly divergent mitogenomes. Newly generated chromosome-level nuclear genome assembly of Rhodosorus marinus reveals that most mitochondrial ribosomal subunit genes are transferred to the nuclear genome. Hetero-concatemers that resulted from recombination between minicircles and unique gene inventory that is responsible for mitochondrial genome stability may explain how the transition from typical mitochondrial genome to minicircles occurs. Our results offer inspiration on minicircular organelle genome formation and highlight an extreme case of mitochondrial gene inventory reduction.
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Affiliation(s)
- Yongsung Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Chung Hyun Cho
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Chanyoung Noh
- Department of Chemistry, Sogang University, Seoul, 04107, Korea
| | - Ji Hyun Yang
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Seung In Park
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Yu Min Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - John A West
- School of Biosciences 2, University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, 08901, USA
| | - Kyubong Jo
- Department of Chemistry, Sogang University, Seoul, 04107, Korea.
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea.
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4
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Mainkar P, Manape TK, Kad SK, Satheesh V, Anandhan S. Identification, cloning and characterization of AcMSH1 from Onion (Allium cepa L.). Mol Biol Rep 2023; 50:5147-5155. [PMID: 37119414 DOI: 10.1007/s11033-023-08414-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 03/28/2023] [Indexed: 05/01/2023]
Abstract
BACKGROUND MSH1 (MutS homolog1) is a nuclear-encoded protein that plays a crucial role in maintaining low mutation rates and stability of the organellar genome. While plastid MSH1 maintains nuclear epigenome plasticity and affects plant development patterns, mitochondrial MSH1 suppresses illegitimate recombination within the mitochondrial genome, affects mitochondrial genome substoichiometric shifting activity and induces cytoplasmic male sterility (CMS) in crops. However, a detailed functional investigation of onion MSH1 has yet to be achieved. MATERIALS AND RESULTS The homology analysis of onion genome database identified a single copy of the AcMSH1 gene in the onion cv. Bhima Super. In silico analysis of AcMSH1 protein sequence revealed the presence of 6 conserved functional domains including a unique MSH1-specific GIY-YIG endonuclease domain at the C-terminal end. At N-terminal end, it has signal peptide sequences targeting chloroplast and mitochondria. The concentration of AcMSH1 was found to be highest in isolated mitochondria, followed by chloroplasts, and negligible in the cytoplasmic fraction; which proved its localization to the mitochondria and chloroplasts. Quantitative expression analysis revealed that AcMSH1 protein levels were highest in leaves, followed by flower buds, root tips, flowers, and umbels, with the lowest amount found in callus tissue. CONCLUSION Onion genome has single copy of MSH1, with characteristic GIY-YIG endonuclease domain. AcMSH1 targeted towards both chloroplasts and mitochondria. The identification and characterisation of AcMSH1 may provide valuable insights into the development of CMS lines in onion.
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Affiliation(s)
- Pawan Mainkar
- ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune, 410 505, Maharashtra, India
| | - Tushar Kashinath Manape
- ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune, 410 505, Maharashtra, India
| | - Snehal Krishna Kad
- ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune, 410 505, Maharashtra, India
| | - Viswanathan Satheesh
- Genome Informatics Facility, Office of Biotechnology, Iowa State University, Ames, Iowa, 50010, USA
| | - Sivalingam Anandhan
- ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune, 410 505, Maharashtra, India.
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5
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Zou Y, Zhu W, Sloan DB, Wu Z. Long-read sequencing characterizes mitochondrial and plastid genome variants in Arabidopsis msh1 mutants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 112:738-755. [PMID: 36097957 PMCID: PMC9617793 DOI: 10.1111/tpj.15976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 09/01/2022] [Accepted: 09/07/2022] [Indexed: 06/15/2023]
Abstract
The abundant repeats in plant mitochondrial genomes can cause rapid genome rearrangements and are also a major obstacle in short-read sequencing studies. Nuclear-encoded proteins such as MSH1 are known to suppress the generation of repeat-associated mitochondrial genome variants, but our understanding of these mechanisms has been constrained by the limitations of short-read technologies. Here, we used highly accurate long-read sequencing (PacBio HiFi) to characterize mitochondrial and plastid genome variants in Arabidopsis thaliana msh1 mutant individuals. The HiFi reads provided a global view of recombination dynamics with detailed quantification of parental and crossover recombination products for both large and small repeats. We found that recombination breakpoints were distributed relatively evenly across the length of repeated sequences and detected widespread internal exchanges of sequence variants between pairs of imperfect repeats in the mitochondrial genome of msh1 mutants. Long-read assemblies of mitochondrial genomes from seven other A. thaliana wild-type accessions differed by repeat-mediated structural rearrangements similar to those observed in msh1 mutants, but they were all in a simple low-heteroplasmy state. The Arabidopsis plastid genome generally lacks small repeats and exhibited a very different pattern of variant accumulation in msh1 mutants compared with the mitochondrial genome. Our data illustrate the power of HiFi technology in studying repeat-mediated recombination in plant organellar genomes and improved the sequence resolution for recombinational processes suppressed by MSH1. Plant organellar genomes can undergo rapid rearrangements. Long-read sequencing provides a detailed and quantitative view of mitochondrial and plastid genome variants normally suppressed by MSH1, advancing our understanding of plant organellar genome dynamics.
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Affiliation(s)
- Yi Zou
- Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, China
| | - Weidong Zhu
- Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, China
| | - Daniel B. Sloan
- Department of Biology, Colorado State University, Fort Collins, CO 80523
| | - Zhiqiang Wu
- Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, Guangdong 518120, China
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6
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Chustecki JM, Etherington RD, Gibbs DJ, Johnston IG. Altered collective mitochondrial dynamics in the Arabidopsis msh1 mutant compromising organelle DNA maintenance. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:5428-5439. [PMID: 35662332 PMCID: PMC9467644 DOI: 10.1093/jxb/erac250] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/01/2022] [Indexed: 05/19/2023]
Abstract
Mitochondria form highly dynamic populations in the cells of plants (and almost all eukaryotes). The characteristics and benefits of this collective behaviour, and how it is influenced by nuclear features, remain to be fully elucidated. Here, we use a recently developed quantitative approach to reveal and analyse the physical and collective 'social' dynamics of mitochondria in an Arabidopsis msh1 mutant where the organelle DNA maintenance machinery is compromised. We use a newly created line combining the msh1 mutant with mitochondrially targeted green fluorescent protein (GFP), and characterize mitochondrial dynamics with a combination of single-cell time-lapse microscopy, computational tracking, and network analysis. The collective physical behaviour of msh1 mitochondria is altered from that of the wild type in several ways: mitochondria become less evenly spread, and networks of inter-mitochondrial encounters become more connected, with greater potential efficiency for inter-organelle exchange-reflecting a potential compensatory mechanism for the genetic challenge to the mitochondrial DNA population, supporting more inter-organelle exchange. We find that these changes are similar to those observed in friendly, where mitochondrial dynamics are altered by a physical perturbation, suggesting that this shift to higher connectivity may reflect a general response to mitochondrial challenges, where physical dynamics of mitochondria may be altered to control the genetic structure of the mtDNA population.
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Affiliation(s)
| | | | - Daniel J Gibbs
- School of Biosciences, University of Birmingham, Birmingham, UK
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7
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Verma P, Kumari P, Negi S, Yadav G, Gaur V. Holliday junction resolution by At-HIGLE: an SLX1 lineage endonuclease from Arabidopsis thaliana with a novel in-built regulatory mechanism. Nucleic Acids Res 2022; 50:4630-4646. [PMID: 35412622 PMCID: PMC9071465 DOI: 10.1093/nar/gkac239] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/24/2022] [Accepted: 04/01/2022] [Indexed: 12/14/2022] Open
Abstract
Holliday junction is the key homologous recombination intermediate, resolved by structure-selective endonucleases (SSEs). SLX1 is the most promiscuous SSE of the GIY-YIG nuclease superfamily. In fungi and animals, SLX1 nuclease activity relies on a non-enzymatic partner, SLX4, but no SLX1-SLX4 like complex has ever been characterized in plants. Plants exhibit specialized DNA repair and recombination machinery. Based on sequence similarity with the GIY-YIG nuclease domain of SLX1 proteins from fungi and animals, At-HIGLE was identified to be a possible SLX1 like nuclease from plants. Here, we elucidated the crystal structure of the At-HIGLE nuclease domain from Arabidopsis thaliana, establishing it as a member of the SLX1-lineage of the GIY-YIG superfamily with structural changes in DNA interacting regions. We show that At-HIGLE can process branched-DNA molecules without an SLX4 like protein. Unlike fungal SLX1, At-HIGLE exists as a catalytically active homodimer capable of generating two coordinated nicks during HJ resolution. Truncating the extended C-terminal region of At-HIGLE increases its catalytic activity, changes the nicking pattern, and monomerizes At-HIGLE. Overall, we elucidated the first structure of a plant SLX1-lineage protein, showed its HJ resolving activity independent of any regulatory protein, and identified an in-built novel regulatory mechanism engaging its C-terminal region.
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Affiliation(s)
- Prabha Verma
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Poonam Kumari
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Shreya Negi
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Gitanjali Yadav
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Vineet Gaur
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India
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8
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Lencina F, Landau A, Prina AR. The Barley Chloroplast Mutator (cpm) Mutant: All Roads Lead to the Msh1 Gene. Int J Mol Sci 2022; 23:ijms23031814. [PMID: 35163736 PMCID: PMC8836938 DOI: 10.3390/ijms23031814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/11/2021] [Accepted: 11/19/2021] [Indexed: 12/10/2022] Open
Abstract
The barley chloroplast mutator (cpm) is a nuclear gene mutant that induces a wide spectrum of cytoplasmically inherited chlorophyll deficiencies. Plastome instability of cpm seedlings was determined by identification of a particular landscape of polymorphisms that suggests failures in a plastome mismatch repair (MMR) protein. In Arabidopsis, MSH genes encode proteins that are in charge of mismatch repair and have anti-recombination activity. In this work, barley homologs of these genes were identified, and their sequences were analyzed in control and cpm mutant seedlings. A substitution, leading to a premature stop codon and a truncated MSH1 protein, was identified in the Msh1 gene of cpm plants. The relationship between this mutation and the presence of chlorophyll deficiencies was established in progenies from crosses and backcrosses. These results strongly suggest that the mutation identified in the Msh1 gene of the cpm mutant is responsible for the observed plastome instabilities. Interestingly, comparison of mutant phenotypes and molecular changes induced by the barley cpm mutant with those of Arabidopsis MSH1 mutants revealed marked differences.
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9
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MSH1 is required for maintenance of the low mutation rates in plant mitochondrial and plastid genomes. Proc Natl Acad Sci U S A 2020; 117:16448-16455. [PMID: 32601224 DOI: 10.1073/pnas.2001998117] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial and plastid genomes in land plants exhibit some of the slowest rates of sequence evolution observed in any eukaryotic genome, suggesting an exceptional ability to prevent or correct mutations. However, the mechanisms responsible for this extreme fidelity remain unclear. We tested seven candidate genes involved in cytoplasmic DNA replication, recombination, and repair (POLIA, POLIB, MSH1, RECA3, UNG, FPG, and OGG1) for effects on mutation rates in the model angiosperm Arabidopsis thaliana by applying a highly accurate DNA sequencing technique (duplex sequencing) that can detect newly arisen mitochondrial and plastid mutations even at low heteroplasmic frequencies. We find that disrupting MSH1 (but not the other candidate genes) leads to massive increases in the frequency of point mutations and small indels and changes to the mutation spectrum in mitochondrial and plastid DNA. We also used droplet digital PCR to show transmission of de novo heteroplasmies across generations in msh1 mutants, confirming a contribution to heritable mutation rates. This dual-targeted gene is part of an enigmatic lineage within the mutS mismatch repair family that we find is also present outside of green plants in multiple eukaryotic groups (stramenopiles, alveolates, haptophytes, and cryptomonads), as well as certain bacteria and viruses. MSH1 has previously been shown to limit ectopic recombination in plant cytoplasmic genomes. Our results point to a broader role in recognition and correction of errors in plant mitochondrial and plastid DNA sequence, leading to greatly suppressed mutation rates perhaps via initiation of double-stranded breaks and repair pathways based on faithful homologous recombination.
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10
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Wynn E, Purfeerst E, Christensen A. Mitochondrial DNA Repair in an Arabidopsis thaliana Uracil N-Glycosylase Mutant. PLANTS (BASEL, SWITZERLAND) 2020; 9:E261. [PMID: 32085412 PMCID: PMC7076443 DOI: 10.3390/plants9020261] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 02/14/2020] [Accepted: 02/16/2020] [Indexed: 02/07/2023]
Abstract
Substitution rates in plant mitochondrial genes are extremely low, indicating strong selective pressure as well as efficient repair. Plant mitochondria possess base excision repair pathways; however, many repair pathways such as nucleotide excision repair and mismatch repair appear to be absent. In the absence of these pathways, many DNA lesions must be repaired by a different mechanism. To test the hypothesis that double-strand break repair (DSBR) is that mechanism, we maintained independent self-crossing lineages of plants deficient in uracil-N-glycosylase (UNG) for 11 generations to determine the repair outcomes when that pathway is missing. Surprisingly, no single nucleotide polymorphisms (SNPs) were fixed in any line in generation 11. The pattern of heteroplasmic SNPs was also unaltered through 11 generations. When the rate of cytosine deamination was increased by mitochondrial expression of the cytosine deaminase APOBEC3G, there was an increase in heteroplasmic SNPs but only in mature leaves. Clearly, DNA maintenance in reproductive meristem mitochondria is very effective in the absence of UNG while mitochondrial genomes in differentiated tissue are maintained through a different mechanism or not at all. Several genes involved in DSBR are upregulated in the absence of UNG, indicating that double-strand break repair is a general system of repair in plant mitochondria. It is important to note that the developmental stage of tissues is critically important for these types of experiments.
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Affiliation(s)
- Emily Wynn
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (E.W.); (E.P.)
- United States Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA
| | - Emma Purfeerst
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (E.W.); (E.P.)
- Athletics Department, Bethany Lutheran College, Mankato, MN 56001, USA
| | - Alan Christensen
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA; (E.W.); (E.P.)
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11
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Factors Affecting Organelle Genome Stability in Physcomitrella patens. PLANTS 2020; 9:plants9020145. [PMID: 31979236 PMCID: PMC7076466 DOI: 10.3390/plants9020145] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/21/2020] [Accepted: 01/21/2020] [Indexed: 01/25/2023]
Abstract
Organelle genomes are essential for plants; however, the mechanisms underlying the maintenance of organelle genomes are incompletely understood. Using the basal land plant Physcomitrella patens as a model, nuclear-encoded homologs of bacterial-type homologous recombination repair (HRR) factors have been shown to play an important role in the maintenance of organelle genome stability by suppressing recombination between short dispersed repeats. In this review, I summarize the factors and pathways involved in the maintenance of genome stability, as well as the repeats that cause genomic instability in organelles in P. patens, and compare them with findings in other plant species. I also discuss the relationship between HRR factors and organelle genome structure from the evolutionary standpoint.
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12
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Chevigny N, Schatz-Daas D, Lotfi F, Gualberto JM. DNA Repair and the Stability of the Plant Mitochondrial Genome. Int J Mol Sci 2020; 21:E328. [PMID: 31947741 PMCID: PMC6981420 DOI: 10.3390/ijms21010328] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/27/2019] [Accepted: 01/01/2020] [Indexed: 12/13/2022] Open
Abstract
The mitochondrion stands at the center of cell energy metabolism. It contains its own genome, the mtDNA, that is a relic of its prokaryotic symbiotic ancestor. In plants, the mitochondrial genetic information influences important agronomic traits including fertility, plant vigor, chloroplast function, and cross-compatibility. Plant mtDNA has remarkable characteristics: It is much larger than the mtDNA of other eukaryotes and evolves very rapidly in structure. This is because of recombination activities that generate alternative mtDNA configurations, an important reservoir of genetic diversity that promotes rapid mtDNA evolution. On the other hand, the high incidence of ectopic recombination leads to mtDNA instability and the expression of gene chimeras, with potential deleterious effects. In contrast to the structural plasticity of the genome, in most plant species the mtDNA coding sequences evolve very slowly, even if the organization of the genome is highly variable. Repair mechanisms are probably responsible for such low mutation rates, in particular repair by homologous recombination. Herein we review some of the characteristics of plant organellar genomes and of the repair pathways found in plant mitochondria. We further discuss how homologous recombination is involved in the evolution of the plant mtDNA.
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Affiliation(s)
| | | | | | - José Manuel Gualberto
- Institut de biologie moléculaire des plantes, CNRS, Université de Strasbourg, 67081 Strasbourg, France; (N.C.); (D.S.-D.); (F.L.)
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13
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Repetti SI, Jackson CJ, Judd LM, Wick RR, Holt KE, Verbruggen H. The inflated mitochondrial genomes of siphonous green algae reflect processes driving expansion of noncoding DNA and proliferation of introns. PeerJ 2020; 8:e8273. [PMID: 31915577 PMCID: PMC6944098 DOI: 10.7717/peerj.8273] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 11/22/2019] [Indexed: 02/06/2023] Open
Abstract
Within the siphonous green algal order Bryopsidales, the size and gene arrangement of chloroplast genomes has been examined extensively, while mitochondrial genomes have been mostly overlooked. The recently published mitochondrial genome of Caulerpa lentillifera is large with expanded noncoding DNA, but it remains unclear if this is characteristic of the entire order. Our study aims to evaluate the evolutionary forces shaping organelle genome dynamics in the Bryopsidales based on the C. lentillifera and Ostreobium quekettii mitochondrial genomes. In this study, the mitochondrial genome of O. quekettii was characterised using a combination of long and short read sequencing, and bioinformatic tools for annotation and sequence analyses. We compared the mitochondrial and chloroplast genomes of O. quekettii and C. lentillifera to examine hypotheses related to genome evolution. The O. quekettii mitochondrial genome is the largest green algal mitochondrial genome sequenced (241,739 bp), considerably larger than its chloroplast genome. As with the mtDNA of C. lentillifera, most of this excess size is from the expansion of intergenic DNA and proliferation of introns. Inflated mitochondrial genomes in the Bryopsidales suggest effective population size, recombination and/or mutation rate, influenced by nuclear-encoded proteins, differ between the genomes of mitochondria and chloroplasts, reducing the strength of selection to influence evolution of their mitochondrial genomes.
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Affiliation(s)
- Sonja I Repetti
- School of BioSciences, University of Melbourne, Melbourne, VIC, Australia
| | | | - Louise M Judd
- Department of Infectious Diseases, Monash University, Melbourne, VIC, Australia
| | - Ryan R Wick
- Department of Infectious Diseases, Monash University, Melbourne, VIC, Australia
| | - Kathryn E Holt
- Department of Infectious Diseases, Monash University, Melbourne, VIC, Australia
| | - Heroen Verbruggen
- School of BioSciences, University of Melbourne, Melbourne, VIC, Australia
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14
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Gaur V, Ziajko W, Nirwal S, Szlachcic A, Gapińska M, Nowotny M. Recognition and processing of branched DNA substrates by Slx1-Slx4 nuclease. Nucleic Acids Res 2019; 47:11681-11690. [PMID: 31584081 PMCID: PMC6902002 DOI: 10.1093/nar/gkz842] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 09/16/2019] [Accepted: 10/01/2019] [Indexed: 12/11/2022] Open
Abstract
Structure-selective endonucleases cleave branched DNA substrates. Slx1 is unique among structure-selective nucleases because it can cleave all branched DNA structures at multiple sites near the branch point. The mechanism behind this broad range of activity is unknown. The present study structurally and biochemically investigated fungal Slx1 to define a new protein interface that binds the non-cleaved arm of branched DNAs. The DNA arm bound at this new site was positioned at a sharp angle relative to the arm that was modeled to interact with the active site, implying that Slx1 uses DNA bending to localize the branch point as a flexible discontinuity in DNA. DNA binding at the new interface promoted a disorder-order transition in a region of the protein that was located in the vicinity of the active site, potentially participating in its formation. This appears to be a safety mechanism that ensures that DNA cleavage occurs only when the new interface is occupied by the non-cleaved DNA arm. Models of Slx1 that interacted with various branched DNA substrates were prepared. These models explain the way in which Slx1 cuts DNA toward the 3' end away from the branch point and elucidate the unique ability of Slx1 to cleave various DNA structures.
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Affiliation(s)
- Vineet Gaur
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
| | - Weronika Ziajko
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
| | - Shivlee Nirwal
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
| | - Aleksandra Szlachcic
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
| | - Marta Gapińska
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
| | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, 4 Trojdena St., 02-109 Warsaw, Poland
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15
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Brieba LG. Structure-Function Analysis Reveals the Singularity of Plant Mitochondrial DNA Replication Components: A Mosaic and Redundant System. PLANTS 2019; 8:plants8120533. [PMID: 31766564 PMCID: PMC6963530 DOI: 10.3390/plants8120533] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 02/06/2023]
Abstract
Plants are sessile organisms, and their DNA is particularly exposed to damaging agents. The integrity of plant mitochondrial and plastid genomes is necessary for cell survival. During evolution, plants have evolved mechanisms to replicate their mitochondrial genomes while minimizing the effects of DNA damaging agents. The recombinogenic character of plant mitochondrial DNA, absence of defined origins of replication, and its linear structure suggest that mitochondrial DNA replication is achieved by a recombination-dependent replication mechanism. Here, I review the mitochondrial proteins possibly involved in mitochondrial DNA replication from a structural point of view. A revision of these proteins supports the idea that mitochondrial DNA replication could be replicated by several processes. The analysis indicates that DNA replication in plant mitochondria could be achieved by a recombination-dependent replication mechanism, but also by a replisome in which primers are synthesized by three different enzymes: Mitochondrial RNA polymerase, Primase-Helicase, and Primase-Polymerase. The recombination-dependent replication model and primers synthesized by the Primase-Polymerase may be responsible for the presence of genomic rearrangements in plant mitochondria.
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Affiliation(s)
- Luis Gabriel Brieba
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 629, Irapuato, Guanajuato C.P. 36821, Mexico
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16
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Plant Organelle Genome Replication. PLANTS 2019; 8:plants8100358. [PMID: 31546578 PMCID: PMC6843274 DOI: 10.3390/plants8100358] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 09/14/2019] [Accepted: 09/18/2019] [Indexed: 12/21/2022]
Abstract
Mitochondria and chloroplasts perform essential functions in respiration, ATP production, and photosynthesis, and both organelles contain genomes that encode only some of the proteins that are required for these functions. The proteins and mechanisms for organelle DNA replication are very similar to bacterial or phage systems. The minimal replisome may consist of DNA polymerase, a primase/helicase, and a single-stranded DNA binding protein (SSB), similar to that found in bacteriophage T7. In Arabidopsis, there are two genes for organellar DNA polymerases and multiple potential genes for SSB, but there is only one known primase/helicase protein to date. Genome copy number varies widely between type and age of plant tissues. Replication mechanisms are only poorly understood at present, and may involve multiple processes, including recombination-dependent replication (RDR) in plant mitochondria and perhaps also in chloroplasts. There are still important questions remaining as to how the genomes are maintained in new organelles, and how genome copy number is determined. This review summarizes our current understanding of these processes.
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