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Occhialini A, Pfotenhauer AC, Li L, Harbison SA, Lail AJ, Burris JN, Piasecki C, Piatek AA, Daniell H, Stewart CN, Lenaghan SC. Mini-synplastomes for plastid genetic engineering. PLANT BIOTECHNOLOGY JOURNAL 2022; 20:360-373. [PMID: 34585834 PMCID: PMC8753362 DOI: 10.1111/pbi.13717] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 09/08/2021] [Accepted: 09/25/2021] [Indexed: 05/19/2023]
Abstract
In the age of synthetic biology, plastid engineering requires a nimble platform to introduce novel synthetic circuits in plants. While effective for integrating relatively small constructs into the plastome, plastid engineering via homologous recombination of transgenes is over 30 years old. Here we show the design-build-test of a novel synthetic genome structure that does not disturb the native plastome: the 'mini-synplastome'. The mini-synplastome was inspired by dinoflagellate plastome organization, which is comprised of numerous minicircles residing in the plastid instead of a single organellar genome molecule. The first mini-synplastome in plants was developed in vitro to meet the following criteria: (i) episomal replication in plastids; (ii) facile cloning; (iii) predictable transgene expression in plastids; (iv) non-integration of vector sequences into the endogenous plastome; and (v) autonomous persistence in the plant over generations in the absence of exogenous selection pressure. Mini-synplastomes are anticipated to revolutionize chloroplast biotechnology, enable facile marker-free plastid engineering, and provide an unparalleled platform for one-step metabolic engineering in plants.
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Affiliation(s)
- Alessandro Occhialini
- Department of Food ScienceUniversity of TennesseeKnoxvilleTNUSA
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
| | - Alexander C. Pfotenhauer
- Department of Food ScienceUniversity of TennesseeKnoxvilleTNUSA
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
| | - Li Li
- Department of Food ScienceUniversity of TennesseeKnoxvilleTNUSA
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
| | - Stacee A. Harbison
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - Andrew J. Lail
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - Jason N. Burris
- Department of Food ScienceUniversity of TennesseeKnoxvilleTNUSA
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
| | | | | | - Henry Daniell
- Department of Basic and Translational SciencesSchool of Dental MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - C. Neal Stewart
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - Scott C. Lenaghan
- Department of Food ScienceUniversity of TennesseeKnoxvilleTNUSA
- Center for Agricultural Synthetic BiologyUniversity of Tennessee Institute of AgricultureKnoxvilleTNUSA
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Abstract
The plastid genome (plastome ) has proved a valuable source of data for evaluating evolutionary relationships among angiosperms. Through basic and applied approaches, plastid transformation technology offers the potential to understand and improve plant productivity, providing food, fiber, energy, and medicines to meet the needs of a burgeoning global population. The growing genomic resources available to both phylogenetic and biotechnological investigations is allowing novel insights and expanding the scope of plastome research to encompass new species. In this chapter, we present an overview of some of the seminal and contemporary research that has contributed to our current understanding of plastome evolution and attempt to highlight the relationship between evolutionary mechanisms and the tools of plastid genetic engineering.
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Affiliation(s)
- Tracey A Ruhlman
- Integrative Biology, University of Texas at Austin, Austin, TX, USA.
| | - Robert K Jansen
- Integrative Biology, University of Texas at Austin, Austin, TX, USA
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Sugimoto H, Hirano M, Tanaka H, Tanaka T, Kitagawa-Yogo R, Muramoto N, Mitsukawa N. Plastid-targeted forms of restriction endonucleases enhance the plastid genome rearrangement rate and trigger the reorganization of its genomic architecture. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 102:1042-1057. [PMID: 31925982 DOI: 10.1111/tpj.14687] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/25/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
Plant cells have acquired chloroplasts (plastids) with a unique genome (ptDNA), which developed during the evolution of endosymbiosis. The gene content and genome structure of ptDNAs in land plants are considerably stable, although those of algal ptDNAs are highly varied. Plant cells seem, therefore, to be intolerant of any structural or organizational changes in the ptDNA. Genome rearrangement functions as a driver of genomic evolutionary divergence. Here, we aimed to create various types of rearrangements in the ptDNA of Arabidopsis genomes using plastid-targeted forms of restriction endonucleases (pREs). Arabidopsis plants expressing each of the three specific pREs, i.e., pTaqI, pHinP1I, and pMseI, were generated; they showed the leaf variegation phenotypes associated with impaired chloroplast development. We confirmed that these pREs caused double-stranded breaks (DSB) at their recognition sites in ptDNAs. Genome-wide analysis of ptDNAs revealed that the transgenic lines exhibited a large number of rearrangements such as inversions and deletions/duplications, which were dominantly repaired by microhomology-mediated recombination and microhomology-mediated end-joining, and less by non-homologous end-joining. Notably, pHinP1I, which recognized a small number of sites in ptDNA, induced drastic structural changes, including regional copy number variations throughout ptDNAs. In contrast, the transient expression of either pTaqI or pMseI, whose recognition site numbers were relatively larger, resulted in small-scale changes at the whole genome level. These results indicated that DSB frequencies and their distribution are major determinants in shaping ptDNAs.
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Affiliation(s)
- Hiroki Sugimoto
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Minoru Hirano
- Bio System Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Hidenori Tanaka
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Tomoko Tanaka
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Ritsuko Kitagawa-Yogo
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Nobuhiko Muramoto
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
| | - Norihiro Mitsukawa
- Genome Engineering Program, Strategic Research Division, Toyota Central R&D Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
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Demongeot J, Seligmann H. Deamination gradients within codons after 1<->2 position swap predict amino acid hydrophobicity and parallel β-sheet conformational preference. Biosystems 2020; 191-192:104116. [PMID: 32081715 DOI: 10.1016/j.biosystems.2020.104116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 12/04/2019] [Accepted: 02/10/2020] [Indexed: 12/16/2022]
Abstract
Deaminations C->T and A->G are frequent mutations producing nucleotide content gradients across genomes proportional to singlestrandedness during replication/transcription. Hence, within single codons, deamination risks increase from first to third codon positions, while second codon positions are functionally most crucial. Here genetic codes are analyzed assuming that after anticodons protected codons from deaminations, first and second codon positions swapped (N2N1N3->N1N2N3), with lowest deamination risks for N2 in presumed primitive N2N1N3 codons. N2N1N3, not standard N1N2N3, codon structure minimizes deaminations inversely proportionally to cognate amino acid hydrophobicity and parallel betasheet conformational preference. For N1N2N3, deamination minimization increases with genetic code integration order of cognate amino acids: during the presumed N2N1N3->N1N2N3 codon structure transition, protein synthesis combined direct codon-amino acid interactions for late amino acids and tRNA-based translation for early amino acids. Hence N2N1N3 codons would correspond to tRNA-free translation by spontaneous codon-amino acid affinities, and tRNA-mediated translation presumably caused N2N1N3->N1N2N3 swaps. Results show that rational, not arbitrary rules link codon and amino acid structures. Some analyses detect mitochondrial RNAs and peptides in public data corresponding to systematic position swaps, suggesting occasional swapping polymerase activity.
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Affiliation(s)
- Jacques Demongeot
- Université Grenoble Alpes, Faculty of Medicine, Laboratory AGEIS EA 7407, Team Tools for e-Gnosis Medical, F-38700, La Tronche, France.
| | - Hervé Seligmann
- Université Grenoble Alpes, Faculty of Medicine, Laboratory AGEIS EA 7407, Team Tools for e-Gnosis Medical, F-38700, La Tronche, France; The National Natural History Collections, The Hebrew University of Jerusalem, 91404, Jerusalem, Israel.
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Lloyd Evans D, Hlongwane TT, Joshi SV, Riaño Pachón DM. The sugarcane mitochondrial genome: assembly, phylogenetics and transcriptomics. PeerJ 2019; 7:e7558. [PMID: 31579570 PMCID: PMC6764373 DOI: 10.7717/peerj.7558] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 07/26/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Chloroplast genomes provide insufficient phylogenetic information to distinguish between closely related sugarcane cultivars, due to the recent origin of many cultivars and the conserved sequence of the chloroplast. In comparison, the mitochondrial genome of plants is much larger and more plastic and could contain increased phylogenetic signals. We assembled a consensus reference mitochondrion with Illumina TruSeq synthetic long reads and Oxford Nanopore Technologies MinION long reads. Based on this assembly we also analyzed the mitochondrial transcriptomes of sugarcane and sorghum and improved the annotation of the sugarcane mitochondrion as compared with other species. METHODS Mitochondrial genomes were assembled from genomic read pools using a bait and assemble methodology. The mitogenome was exhaustively annotated using BLAST and transcript datasets were mapped with HISAT2 prior to analysis with the Integrated Genome Viewer. RESULTS The sugarcane mitochondrion is comprised of two independent chromosomes, for which there is no evidence of recombination. Based on the reference assembly from the sugarcane cultivar SP80-3280 the mitogenomes of four additional cultivars (R570, LCP85-384, RB72343 and SP70-1143) were assembled (with the SP70-1143 assembly utilizing both genomic and transcriptomic data). We demonstrate that the sugarcane plastome is completely transcribed and we assembled the chloroplast genome of SP80-3280 using transcriptomic data only. Phylogenomic analysis using mitogenomes allow closely related sugarcane cultivars to be distinguished and supports the discrimination between Saccharum officinarum and Saccharum cultum as modern sugarcane's female parent. From whole chloroplast comparisons, we demonstrate that modern sugarcane arose from a limited number of Saccharum cultum female founders. Transcriptomic and spliceosomal analyses reveal that the two chromosomes of the sugarcane mitochondrion are combined at the transcript level and that splice sites occur more frequently within gene coding regions than without. We reveal one confirmed and one potential cytoplasmic male sterility (CMS) factor in the sugarcane mitochondrion, both of which are transcribed. CONCLUSION Transcript processing in the sugarcane mitochondrion is highly complex with diverse splice events, the majority of which span the two chromosomes. PolyA baited transcripts are consistent with the use of polyadenylation for transcript degradation. For the first time we annotate two CMS factors within the sugarcane mitochondrion and demonstrate that sugarcane possesses all the molecular machinery required for CMS and rescue. A mechanism of cross-chromosomal splicing based on guide RNAs is proposed. We also demonstrate that mitogenomes can be used to perform phylogenomic studies on sugarcane cultivars.
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Affiliation(s)
- Dyfed Lloyd Evans
- Plant Breeding, South African Sugarcane Research Institute, Durban, KwaZulu-Natal, South Africa
- Cambridge Sequence Services (CSS), Waterbeach, Cambridgeshire, UK
- Department of Computer Sciences, Université Cheikh Anta Diop de Dakar, Dakar, Sénégal
| | | | - Shailesh V. Joshi
- Plant Breeding, South African Sugarcane Research Institute, Durban, KwaZulu-Natal, South Africa
- School of Life Sciences, College of Agriculture Engineering and Science, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa
| | - Diego M. Riaño Pachón
- Computational, Evolutionary and Systems Biology Laboratory, Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, São Paulo, Brazil
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Demongeot J, Seligmann H. Theoretical minimal RNA rings designed according to coding constraints mimic deamination gradients. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2019; 106:44. [DOI: 10.1007/s00114-019-1638-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 06/18/2019] [Accepted: 06/19/2019] [Indexed: 11/27/2022]
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Tonti-Filippini J, Nevill PG, Dixon K, Small I. What can we do with 1000 plastid genomes? THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:808-818. [PMID: 28112435 DOI: 10.1111/tpj.13491] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/17/2017] [Accepted: 01/17/2017] [Indexed: 05/21/2023]
Abstract
The plastid genome of plants is the smallest and most gene-rich of the three genomes in each cell and the one generally present in the highest copy number. As a result, obtaining plastid DNA sequence is a particularly cost-effective way of discovering genetic information about a plant. Until recently, the sequence information gathered in this way was generally limited to small portions of the genome amplified by polymerase chain reaction, but recent advances in sequencing technology have stimulated a substantial rate of increase in the sequencing of complete plastid genomes. Within the last year, the number of complete plastid genomes accessible in public sequence repositories has exceeded 1000. This sudden flood of data raises numerous challenges in data analysis and interpretation, but also offers the keys to potential insights across large swathes of plant biology. We examine what has been learnt so far, what more could be learnt if we look at the data in the right way, and what we might gain from the tens of thousands more genome sequences that will surely arrive in the next few years. The most exciting new discoveries are likely to be made at the interdisciplinary interfaces between molecular biology and ecology.
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Affiliation(s)
- Julian Tonti-Filippini
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia
| | - Paul G Nevill
- Department of Environment and Agriculture, ARC Centre for Mine Site Restoration, Curtin University, Kent Street, Bentley, WA, 6102, Australia
| | - Kingsley Dixon
- Department of Environment and Agriculture, ARC Centre for Mine Site Restoration, Curtin University, Kent Street, Bentley, WA, 6102, Australia
| | - Ian Small
- ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia
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Blazier JC, Jansen RK, Mower JP, Govindu M, Zhang J, Weng ML, Ruhlman TA. Variable presence of the inverted repeat and plastome stability in Erodium. ANNALS OF BOTANY 2016; 117:1209-20. [PMID: 27192713 PMCID: PMC4904181 DOI: 10.1093/aob/mcw065] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 01/05/2016] [Accepted: 02/22/2016] [Indexed: 05/18/2023]
Abstract
BACKGROUND AND AIMS Several unrelated lineages such as plastids, viruses and plasmids, have converged on quadripartite genomes of similar size with large and small single copy regions and a large inverted repeat (IR). Except for Erodium (Geraniaceae), saguaro cactus and some legumes, the plastomes of all photosynthetic angiosperms display this structure. The functional significance of the IR is not understood and Erodium provides a system to examine the role of the IR in the long-term stability of these genomes. We compared the degree of genomic rearrangement in plastomes of Erodium that differ in the presence and absence of the IR. METHODS We sequenced 17 new Erodium plastomes. Using 454, Illumina, PacBio and Sanger sequences, 16 genomes were assembled and categorized along with one incomplete and two previously published Erodium plastomes. We conducted phylogenetic analyses among these species using a dataset of 19 protein-coding genes and determined if significantly higher evolutionary rates had caused the long branch seen previously in phylogenetic reconstructions within the genus. Bioinformatic comparisons were also performed to evaluate plastome evolution across the genus. KEY RESULTS Erodium plastomes fell into four types (Type 1-4) that differ in their substitution rates, short dispersed repeat content and degree of genomic rearrangement, gene and intron content and GC content. Type 4 plastomes had significantly higher rates of synonymous substitutions (dS) for all genes and for 14 of the 19 genes non-synonymous substitutions (dN) were significantly accelerated. We evaluated the evidence for a single IR loss in Erodium and in doing so discovered that Type 4 plastomes contain a novel IR. CONCLUSIONS The presence or absence of the IR does not affect plastome stability in Erodium. Rather, the overall repeat content shows a negative correlation with genome stability, a pattern in agreement with other angiosperm groups and recent findings on genome stability in bacterial endosymbionts.
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Affiliation(s)
- John C Blazier
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Robert K Jansen
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA Department of Biological Science, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Jeffrey P Mower
- Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Madhu Govindu
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Jin Zhang
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Mao-Lun Weng
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | - Tracey A Ruhlman
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
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9
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Oldenburg DJ, Bendich AJ. DNA maintenance in plastids and mitochondria of plants. FRONTIERS IN PLANT SCIENCE 2015; 6:883. [PMID: 26579143 PMCID: PMC4624840 DOI: 10.3389/fpls.2015.00883] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 10/05/2015] [Indexed: 05/02/2023]
Abstract
The DNA molecules in plastids and mitochondria of plants have been studied for over 40 years. Here, we review the data on the circular or linear form, replication, repair, and persistence of the organellar DNA (orgDNA) in plants. The bacterial origin of orgDNA appears to have profoundly influenced ideas about the properties of chromosomal DNA molecules in these organelles to the point of dismissing data inconsistent with ideas from the 1970s. When found at all, circular genome-sized molecules comprise a few percent of orgDNA. In cells active in orgDNA replication, most orgDNA is found as linear and branched-linear forms larger than the size of the genome, likely a consequence of a virus-like DNA replication mechanism. In contrast to the stable chromosomal DNA molecules in bacteria and the plant nucleus, the molecular integrity of orgDNA declines during leaf development at a rate that varies among plant species. This decline is attributed to degradation of damaged-but-not-repaired molecules, with a proposed repair cost-saving benefit most evident in grasses. All orgDNA maintenance activities are proposed to occur on the nucleoid tethered to organellar membranes by developmentally-regulated proteins.
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Abstract
The plastid genome (plastome) has proved a valuable source of data for evaluating evolutionary relationships among angiosperms. Through basic and applied approaches, plastid transformation technology offers the potential to understand and improve plant productivity, providing food, fiber, energy and medicines to meet the needs of a burgeoning global population. The growing genomic resources available to both phylogenetic and biotechnological investigations are allowing novel insights and expanding the scope of plastome research to encompass new species. In this chapter we present an overview of some of the seminal and contemporary research that has contributed to our current understanding of plastome evolution and attempt to highlight the relationship between evolutionary mechanisms and tools of plastid genetic engineering.
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Affiliation(s)
- Tracey A Ruhlman
- Integrative Biology, University of Texas at Austin, Austin, TX, USA
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Janouskovec J, Sobotka R, Lai DH, Flegontov P, Koník P, Komenda J, Ali S, Prásil O, Pain A, Oborník M, Lukes J, Keeling PJ. Split photosystem protein, linear-mapping topology, and growth of structural complexity in the plastid genome of Chromera velia. Mol Biol Evol 2013; 30:2447-62. [PMID: 23974208 DOI: 10.1093/molbev/mst144] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The canonical photosynthetic plastid genomes consist of a single circular-mapping chromosome that encodes a highly conserved protein core, involved in photosynthesis and ATP generation. Here, we demonstrate that the plastid genome of the photosynthetic relative of apicomplexans, Chromera velia, departs from this view in several unique ways. Core photosynthesis proteins PsaA and AtpB have been broken into two fragments, which we show are independently transcribed, oligoU-tailed, translated, and assembled into functional photosystem I and ATP synthase complexes. Genome-wide transcription profiles support expression of many other highly modified proteins, including several that contain extensions amounting to hundreds of amino acids in length. Canonical gene clusters and operons have been fragmented and reshuffled into novel putative transcriptional units. Massive genomic coverage by paired-end reads, coupled with pulsed-field gel electrophoresis and polymerase chain reaction, consistently indicate that the C. velia plastid genome is linear-mapping, a unique state among all plastids. Abundant intragenomic duplication probably mediated by recombination can explain protein splits, extensions, and genome linearization and is perhaps the key driving force behind the many features that defy the conventional ways of plastid genome architecture and function.
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Affiliation(s)
- Jan Janouskovec
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
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Shah K, Krishnamachari A. Nucleotide correlation based measure for identifying origin of replication in genomic sequences. Biosystems 2012; 107:52-5. [PMID: 21945744 DOI: 10.1016/j.biosystems.2011.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 08/30/2011] [Accepted: 09/10/2011] [Indexed: 12/18/2022]
Abstract
Computational prediction of the origin of replication is a challenging problem and of immense interest to biologists. Several methods have been proposed for identifying the replicon site for various classes of organisms. However, these methods have limited applicability since the replication mechanism is different in different organisms. We propose a correlation measure and show that it is correctly able to predict the origin of replication in most of the bacterial genomes. When applied to Methanocaldococcus jannaschii, Plasmodium falciparum apicoplast and Nicotiana tabacum plastid, this correlation based method is able to correctly predict the origin of replication whereas the generally used GC skew measure fails. Thus, this correlation based measure is a novel and promising tool for predicting the origin of replication in a wide class of organisms. This could have important implications in not only gaining a deeper understanding of the replication machinery in higher organisms, but also for drug discovery.
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Affiliation(s)
- Kushal Shah
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
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Brouard JS, Otis C, Lemieux C, Turmel M. The chloroplast genome of the green alga Schizomeris leibleinii (Chlorophyceae) provides evidence for bidirectional DNA replication from a single origin in the chaetophorales. Genome Biol Evol 2011; 3:505-15. [PMID: 21546564 PMCID: PMC3138424 DOI: 10.1093/gbe/evr037] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In the Chlorophyceae, the chloroplast genome is extraordinarily fluid in architecture and displays unique features relative to other groups of green algae. For the Chaetophorales, 1 of the 5 major lineages of the Chlorophyceae, it has been shown that the distinctive architecture of the 223,902-bp genome of Stigeoclonium helveticum is consistent with bidirectional DNA replication from a single origin. Here, we report the 182,759-bp chloroplast genome sequence of Schizomeris leibleinii, a member of the earliest diverging lineage of the Chaetophorales. Like its Stigeoclonium homolog, the Schizomeris genome lacks a large inverted repeat encoding the rRNA operon and displays a striking bias in coding regions that is associated with a bias in base composition along each strand. Our results support the notion that these two chaetophoralean genomes replicate bidirectionally from a putative origin located in the vicinity of the small subunit ribosomal RNA gene. Their shared structural characteristics were most probably inherited from the common ancestor of all chaetophoralean algae. Short dispersed repeats account for most of the 41-kb size variation between the Schizomeris and Stigeoclonium genomes, and there is no indication that homologous recombination between these repeated elements led to the observed gene rearrangements. A comparison of the extent of variation sustained by the Stigeoclonium and Schizomeris chloroplast DNAs (cpDNAs) with that observed for the cpDNAs of the chlamydomonadalean Chlamydomonas and Volvox suggests that gene rearrangements as well as changes in the abundance of intergenic and intron sequences occurred at a slower pace in the Chaetophorales than in the Chlamydomonadales.
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Affiliation(s)
- Jean-Simon Brouard
- Département de Biochimie, de Microbiologie et de Bio-Informatique, Université Laval, Ville de Québec, Québec, Canada
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