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Zhu P, He T, Zheng Y, Chen L. The need for masked genomes in gymnosperms. FRONTIERS IN PLANT SCIENCE 2023; 14:1309744. [PMID: 38146270 PMCID: PMC10749308 DOI: 10.3389/fpls.2023.1309744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 11/27/2023] [Indexed: 12/27/2023]
Affiliation(s)
| | | | | | - Lingyan Chen
- Fujian Agriculture and Forestry University, Fuzhou, China
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Wan T, Gong Y, Liu Z, Zhou Y, Dai C, Wang Q. Evolution of complex genome architecture in gymnosperms. Gigascience 2022; 11:6659718. [PMID: 35946987 PMCID: PMC9364684 DOI: 10.1093/gigascience/giac078] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/09/2022] [Accepted: 07/15/2022] [Indexed: 11/25/2022] Open
Abstract
Gymnosperms represent an ancient lineage that diverged from early spermatophytes during the Devonian. The long fossil records and low diversity in living species prove their complex evolutionary history, which included ancient radiations and massive extinctions. Due to their ultra-large genome size, the whole-genome assembly of gymnosperms has only generated in the past 10 years and is now being further expanded into more taxonomic representations. Here, we provide an overview of the publicly available gymnosperm genome resources and discuss their assembly quality and recent findings in large genome architectures. In particular, we describe the genomic features most related to changes affecting the whole genome. We also highlight new realizations relative to repetitive sequence dynamics, paleopolyploidy, and long introns. Based on the results of relevant genomic studies of gymnosperms, we suggest additional efforts should be made toward exploring the genomes of medium-sized (5–15 gigabases) species. Lastly, more comparative analyses among high-quality assemblies are needed to understand the genomic shifts and the early species diversification of seed plants.
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Affiliation(s)
- Tao Wan
- Core Botanical Gardens/Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China.,Sino-Africa Joint Research Centre, Chinese Academy of Sciences, Wuhan 430074, China.,Key Laboratory of Southern Subtropical Plant Diversity, Fairy Lake Botanical Garden, Shenzhen & Chinese Academy of Science, Shenzhen 518004, China
| | - Yanbing Gong
- Department of Ecology, Tibetan Centre for Ecology and Conservation at WHU-TU, State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.,Research Center for Ecology, College of Science, Tibet University, Lhasa 850000, China
| | - Zhiming Liu
- Key Laboratory of Southern Subtropical Plant Diversity, Fairy Lake Botanical Garden, Shenzhen & Chinese Academy of Science, Shenzhen 518004, China
| | - YaDong Zhou
- School of Life Science, Nanchang University, Nanchang 330031, China
| | - Can Dai
- School of Resources and Environmental Science, Hubei University, Wuhan, China
| | - Qingfeng Wang
- Core Botanical Gardens/Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China.,Sino-Africa Joint Research Centre, Chinese Academy of Sciences, Wuhan 430074, China
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Luo X, He Z, Liu J, Wu H, Gong X. FISH Mapping of Telomeric and Non-Telomeric (AG3T3)3 Reveal the Chromosome Numbers and Chromosome Rearrangements of 41 Woody Plants. Genes (Basel) 2022; 13:genes13071239. [PMID: 35886022 PMCID: PMC9323580 DOI: 10.3390/genes13071239] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/12/2022] [Accepted: 07/12/2022] [Indexed: 02/05/2023] Open
Abstract
Data for the chromosomal FISH mapping localization of (AG3T3)3 are compiled for 37 species belonging 27 families; for 24 species and 14 families, this is the first such report. The chromosome number and length ranged from 14–136 and 0.56–14.48 μm, respectively. A total of 23 woody plants presented chromosome length less than 3 μm, thus belonging to the small chromosome group. Telomeric signals were observed at each chromosome terminus in 38 plants (90.5%) and were absent at several chromosome termini in only four woody plants (9.5%). Non-telomeric signals were observed in the chromosomes of 23 plants (54.8%); in particular, abundant non-telomeric (AG3T3)3 was obviously observed in Chimonanthus campanulatus. Telomeric signals outside of the chromosome were observed in 11 woody plants (26.2%). Overall, ten (AG3T3)3 signal pattern types were determined, indicating the complex genome architecture of the 37 considered species. The variation in signal pattern was likely due to chromosome deletion, duplication, inversion, and translocation. In addition, large primary constriction was observed in some species, probably due to or leading to chromosome breakage and the formation of new chromosomes. The presented results will guide further research focused on determining the chromosome number and disclosing chromosome rearrangements of woody plants.
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Maravilla AJ, Rosato M, Rosselló JA. Interstitial Telomeric-like Repeats (ITR) in Seed Plants as Assessed by Molecular Cytogenetic Techniques: A Review. PLANTS (BASEL, SWITZERLAND) 2021; 10:2541. [PMID: 34834904 PMCID: PMC8621592 DOI: 10.3390/plants10112541] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 05/12/2023]
Abstract
The discovery of telomeric repeats in interstitial regions of plant chromosomes (ITRs) through molecular cytogenetic techniques was achieved several decades ago. However, the information is scattered and has not been critically evaluated from an evolutionary perspective. Based on the analysis of currently available data, it is shown that ITRs are widespread in major evolutionary lineages sampled. However, their presence has been detected in only 45.6% of the analysed families, 26.7% of the sampled genera, and in 23.8% of the studied species. The number of ITR sites greatly varies among congeneric species and higher taxonomic units, and range from one to 72 signals. ITR signals mostly occurs as homozygous loci in most species, however, odd numbers of ITR sites reflecting a hemizygous state have been reported in both gymnosperm and angiosperm groups. Overall, the presence of ITRs appears to be poor predictors of phylogenetic and taxonomic relatedness at most hierarchical levels. The presence of ITRs and the number of sites are not significantly associated to the number of chromosomes. The longitudinal distribution of ITR sites along the chromosome arms indicates that more than half of the ITR presences are between proximal and terminal locations (49.5%), followed by proximal (29.0%) and centromeric (21.5%) arm regions. Intraspecific variation concerning ITR site number, chromosomal locations, and the differential presence on homologous chromosome pairs has been reported in unrelated groups, even at the population level. This hypervariability and dynamism may have likely been overlooked in many lineages due to the very low sample sizes often used in cytogenetic studies.
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Affiliation(s)
| | | | - Josep A. Rosselló
- Jardín Botánico, ICBiBE, Universitat de València, c/Quart 80, E-46008 València, Spain; (A.J.M.); (M.R.)
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Zhang M, Tang YW, Xu Y, Yonezawa T, Shao Y, Wang YG, Song ZP, Yang J, Zhang WJ. Concerted and birth-and-death evolution of 26S ribosomal DNA in Camellia L. ANNALS OF BOTANY 2021; 127:63-73. [PMID: 32939535 PMCID: PMC7750723 DOI: 10.1093/aob/mcaa169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/15/2020] [Indexed: 05/05/2023]
Abstract
BACKGROUND AND AIMS The ribosomal DNA (rDNA) gene family, encoding ribosomal RNA (rRNA), has long been regarded as an archetypal example illustrating the model of concerted evolution. However, controversy is arising, as rDNA in many eukaryotic species has been proved to be polymorphic. Here, a metagenomic strategy was applied to detect the intragenomic polymorphism as well as the evolutionary patterns of 26S rDNA across the genus Camellia. METHODS Degenerate primer pairs were designed to amplify the 26S rDNA fragments from different Camellia species. The amplicons were then paired-end sequenced on the Illumina MiSeq platform. KEY RESULTS An extremely high level of rDNA polymorphism existed universally in Camellia. However, functional rDNA was still the major component of the family, and was relatively conserved among different Camellia species. Sequence variations mainly came from rRNA pseudogenes and favoured regions that are rich in GC. Specifically, some rRNA pseudogenes have existed in the genome for a long time, and have even experienced several expansion events, which has greatly enriched the abundance of rDNA polymorphism. CONCLUSIONS Camellia represents a group in which rDNA is subjected to a mixture of concerted and birth-and-death evolution. Some rRNA pseudogenes may still have potential functions. Conversely, when released from selection constraint, they can evolve in the direction of decreasing GC content and structural stability through a methylation-induced process, and finally be eliminated from the genome.
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Affiliation(s)
- Min Zhang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, China
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Yi-Wei Tang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Ying Xu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
- Shanghai Railway Entry-Exit Inspection and Quarantine Bureau, Shanghai, China
| | - Takahiro Yonezawa
- Faculty of Agriculture, Tokyo University of Agriculture, Funako, Atsugi, Kanagawa, Japan
| | - Yang Shao
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Yu-Guo Wang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Zhi-Ping Song
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Ji Yang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
| | - Wen-Ju Zhang
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China
- For correspondence. E-mail
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New chromosome number and cyto-molecular characterization of the African Baobab (Adansonia digitata L.) - "The Tree of Life". Sci Rep 2020; 10:13174. [PMID: 32764541 PMCID: PMC7413363 DOI: 10.1038/s41598-020-68697-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 06/22/2020] [Indexed: 11/08/2022] Open
Abstract
The African baobab (Adansonia digitata L.), also referred to as the "Tree of Life", is a majestic, long-lived and multipurpose tree of sub-Saharan Africa. Internationally, a growing demand for baobab products in the food, pharmaceutical and cosmetics industries has been observed. Considering this, there is a need for scientific information on the genetics and breeding of A. digitata, including cytogenetics, genetic diversity and reproductive biology. The objectives of our cytogenetic research were to determine the genome size, chromosome number, and organization of ribosomal DNA (45S and 5SrDNA) of A. digitata. Flow cytometry analysis revealed a 2C-DNA value of 3.8 ± 0.6 pg (1Cx monoploid genome size 919.1 ± 62.9 Mbp). Using our improved chromosome preparation technique, we were able to unequivocally count the chromosomes resulting in 2n = 4x = 168, a revised chromosome number for A. digitata. Fluorescent in situ hybridization (FISH) analysis revealed two massively large variants of 45S rDNA and their corresponding nucleolus organizer regions (NOR). The NOR variants were about two to four times larger than the main body of their respective chromosomes. To our knowledge, this is the first report of this phenomenon in a plant species. Furthermore, we found that FISH analysis using the Arabidopsis-type telomere repeat sequence probe clarified and confirmed the new chromosome number and characterized the 45S rDNA structural organization.
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Maughan PJ, Lee R, Walstead R, Vickerstaff RJ, Fogarty MC, Brouwer CR, Reid RR, Jay JJ, Bekele WA, Jackson EW, Tinker NA, Langdon T, Schlueter JA, Jellen EN. Genomic insights from the first chromosome-scale assemblies of oat (Avena spp.) diploid species. BMC Biol 2019; 17:92. [PMID: 31757219 PMCID: PMC6874827 DOI: 10.1186/s12915-019-0712-y] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/21/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cultivated hexaploid oat (Common oat; Avena sativa) has held a significant place within the global crop community for centuries; although its cultivation has decreased over the past century, its nutritional benefits have garnered increased interest for human consumption. We report the development of fully annotated, chromosome-scale assemblies for the extant progenitor species of the As- and Cp-subgenomes, Avena atlantica and Avena eriantha respectively. The diploid Avena species serve as important genetic resources for improving common oat's adaptive and food quality characteristics. RESULTS The A. atlantica and A. eriantha genome assemblies span 3.69 and 3.78 Gb with an N50 of 513 and 535 Mb, respectively. Annotation of the genomes, using sequenced transcriptomes, identified ~ 50,000 gene models in each species-including 2965 resistance gene analogs across both species. Analysis of these assemblies classified much of each genome as repetitive sequence (~ 83%), including species-specific, centromeric-specific, and telomeric-specific repeats. LTR retrotransposons make up most of the classified elements. Genome-wide syntenic comparisons with other members of the Pooideae revealed orthologous relationships, while comparisons with genetic maps from common oat clarified subgenome origins for each of the 21 hexaploid linkage groups. The utility of the diploid genomes was demonstrated by identifying putative candidate genes for flowering time (HD3A) and crown rust resistance (Pc91). We also investigate the phylogenetic relationships among other A- and C-genome Avena species. CONCLUSIONS The genomes we report here are the first chromosome-scale assemblies for the tribe Poeae, subtribe Aveninae. Our analyses provide important insight into the evolution and complexity of common hexaploid oat, including subgenome origin, homoeologous relationships, and major intra- and intergenomic rearrangements. They also provide the annotation framework needed to accelerate gene discovery and plant breeding.
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Affiliation(s)
- Peter J Maughan
- Department of Plant & Wildlife Sciences, Brigham Young University, 4105 LSB, Provo, UT, 84602, USA.
| | - Rebekah Lee
- Department of Plant & Wildlife Sciences, Brigham Young University, 4105 LSB, Provo, UT, 84602, USA
| | - Rachel Walstead
- University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
| | | | - Melissa C Fogarty
- Department of Plant & Wildlife Sciences, Brigham Young University, 4105 LSB, Provo, UT, 84602, USA
| | - Cory R Brouwer
- University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
| | - Robert R Reid
- University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
| | - Jeremy J Jay
- University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
| | | | | | | | - Tim Langdon
- IBERS, Aberystwyth University, Aberystwyth, Wales, UK
| | | | - Eric N Jellen
- Department of Plant & Wildlife Sciences, Brigham Young University, 4105 LSB, Provo, UT, 84602, USA
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Wang W, Wan T, Becher H, Kuderova A, Leitch IJ, Garcia S, Leitch AR, Kovařík A. Remarkable variation of ribosomal DNA organization and copy number in gnetophytes, a distinct lineage of gymnosperms. ANNALS OF BOTANY 2019; 123:767-781. [PMID: 30265284 PMCID: PMC6526317 DOI: 10.1093/aob/mcy172] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 09/04/2018] [Indexed: 05/10/2023]
Abstract
INTRODUCTION Gnetophytes, comprising the genera Ephedra, Gnetum and Welwitschia, are an understudied, enigmatic lineage of gymnosperms with a controversial phylogenetic relationship to other seed plants. Here we examined the organization of ribosomal DNA (rDNA) across representative species. METHODS We applied high-throughput sequencing approaches to isolate and reconstruct rDNA units and to determine their intragenomic homogeneity. In addition, fluorescent in situ hybridization and Southern blot hybridization techniques were used to reveal the chromosome and genomic organization of rDNA. KEY RESULTS The 5S and 35S rRNA genes were separate (S-type) in Gnetum montanum, Gnetum gnemon and Welwitschia mirabilis and linked (L-type) in Ephedra altissima. There was considerable variability in 5S rDNA abundance, ranging from as few as ~4000 (W. mirabilis) to >100 000 (G. montanum) copies. A similar large variation was also observed in 5S rDNA locus numbers (two to 16 sites per diploid cell). 5S rRNA pseudogenes were interspersed between functional genes forming a single unit in E. altissima and G. montanum. Their copy number was comparable or even higher than that of functional 5S rRNA genes. In E. altissima internal transcribed spacers of 35S rDNA were long and intrinsically repetitive while in G. montanum and W. mirabilis they were short without the subrepeats. CONCLUSIONS Gnetophytes are distinct from other gymnosperms and angiosperms as they display surprisingly large variability in rDNA organization and rDNA copy and locus numbers between genera, with no relationship between copy numbers and genome sizes apparent. Concerted evolution of 5S rDNA units seems to have led to the amplification of 5S pseudogenes in both G. montanum and E. altissima. Evolutionary patterns of rDNA show both gymnosperm and angiosperm features underlining the diversity of the group.
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Affiliation(s)
- Wencai Wang
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Tao Wan
- Key Laboratory of Southern Subtropical Plant Diversity, Fairy Lake Botanical Garden, Shenzhen and Chinese Academy of Sciences, Shenzen, PR China
- Sino-Africa Joint Research Center, Chinese Academy of Science, Wuhan, PR China
| | - Hannes Becher
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Alena Kuderova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic
| | - Ilia J Leitch
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, UK
| | - Sònia Garcia
- Institut Botànic de Barcelona (IBB-CSIC-ICUB), Passeig del Migdia s/n, Parc de Montjuïc, Barcelona, Catalonia, Spain
| | - Andrew R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Aleš Kovařík
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic
- For correspondence. E-mail
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Lin X, Faridi N, Casola C. An Ancient Transkingdom Horizontal Transfer of Penelope-Like Retroelements from Arthropods to Conifers. Genome Biol Evol 2016; 8:1252-66. [PMID: 27190138 PMCID: PMC4860704 DOI: 10.1093/gbe/evw076] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Comparative genomics analyses empowered by the wealth of sequenced genomes have revealed numerous instances of horizontal DNA transfers between distantly related species. In eukaryotes, repetitive DNA sequences known as transposable elements (TEs) are especially prone to move across species boundaries. Such horizontal transposon transfers, or HTTs, are relatively common within major eukaryotic kingdoms, including animals, plants, and fungi, while rarely occurring across these kingdoms. Here, we describe the first case of HTT from animals to plants, involving TEs known as Penelope-like elements, or PLEs, a group of retrotransposons closely related to eukaryotic telomerases. Using a combination of in situ hybridization on chromosomes, polymerase chain reaction experiments, and computational analyses we show that the predominant PLE lineage, EN(+)PLEs, is highly diversified in loblolly pine and other conifers, but appears to be absent in other gymnosperms. Phylogenetic analyses of both protein and DNA sequences reveal that conifers EN(+)PLEs, or Dryads, form a monophyletic group clustering within a clade of primarily arthropod elements. Additionally, no EN(+)PLEs were detected in 1,928 genome assemblies from 1,029 nonmetazoan and nonconifer genomes from 14 major eukaryotic lineages. These findings indicate that Dryads emerged following an ancient horizontal transfer of EN(+)PLEs from arthropods to a common ancestor of conifers approximately 340 Ma. This represents one of the oldest known interspecific transmissions of TEs, and the most conspicuous case of DNA transfer between animals and plants.
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Affiliation(s)
- Xuan Lin
- Department of Ecosystem Science and Management, Texas A&M University
| | - Nurul Faridi
- Department of Ecosystem Science and Management, Texas A&M University Southern Institute of Forest Genetics, USDA Forest Service Southern Research Station, Saucier, Mississippi
| | - Claudio Casola
- Department of Ecosystem Science and Management, Texas A&M University
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Hizume M, N. Ohtaka K, Takeda KM, Fujii S, Yamasaki Y, Kondo K. Chromosome banding in the genus Pinus IV. Fluorescent banding patterns of chromosomes in eight taxa of haploxylone pines. ACTA ACUST UNITED AC 2016. [DOI: 10.3199/iscb.11.61] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Masahiro Hizume
- Faculty of Education, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
| | - Kozue N. Ohtaka
- Faculty of Education, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
| | - Kaoru M. Takeda
- Faculty of Education, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
| | - Satomi Fujii
- Faculty of Education, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
| | - Yoko Yamasaki
- Faculty of Education, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
| | - Katsuhiko Kondo
- Institute of Evolutionary Biology, 2-4-28 Kamiyouga, Setagaya-Ku, Tokyo 158-0098, Japan
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Shibata F, Matsusaki Y, Hizume M. A Comparative Analysis of Multi-Probe Fluorescence In Situ Hybridisation (FISH) Karyotypes in 26 Pinus Species (Pinaceae). CYTOLOGIA 2016. [DOI: 10.1508/cytologia.81.409] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Wang W, Ma L, Becher H, Garcia S, Kovarikova A, Leitch IJ, Leitch AR, Kovarik A. Astonishing 35S rDNA diversity in the gymnosperm species Cycas revoluta Thunb. Chromosoma 2015; 125:683-99. [PMID: 26637996 PMCID: PMC5023732 DOI: 10.1007/s00412-015-0556-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 11/05/2015] [Indexed: 11/28/2022]
Abstract
In all eukaryotes, the highly repeated 35S ribosomal DNA (rDNA) sequences encoding 18S-5.8S-26S ribosomal RNA (rRNA) typically show high levels of intragenomic uniformity due to homogenisation processes, leading to concerted evolution of 35S rDNA repeats. Here, we compared 35S rDNA divergence in several seed plants using next generation sequencing and a range of molecular and cytogenetic approaches. Most species showed similar 35S rDNA homogeneity indicating concerted evolution. However, Cycas revoluta exhibits an extraordinary diversity of rDNA repeats (nucleotide sequence divergence of different copies averaging 12 %), influencing both the coding and non-coding rDNA regions nearly equally. In contrast, its rRNA transcriptome was highly homogeneous suggesting that only a minority of genes (<20 %) encode functional rRNA. The most common SNPs were C > T substitutions located in symmetrical CG and CHG contexts which were also highly methylated. Both functional genes and pseudogenes appear to cluster on chromosomes. The extraordinary high levels of 35S rDNA diversity in C. revoluta, and probably other species of cycads, indicate that the frequency of repeat homogenisation has been much lower in this lineage, compared with all other land plant lineages studied. This has led to the accumulation of methylation-driven mutations and pseudogenisation. Potentially, the reduced homology between paralogs prevented their elimination by homologous recombination, resulting in long-term retention of rDNA pseudogenes in the genome.
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Affiliation(s)
- Wencai Wang
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Lu Ma
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Hannes Becher
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Sònia Garcia
- Laboratori de Botànica-Unitat associada CSIC, Facultat de Farmàcia, Universitat de Barcelona, 08028, Barcelona, Catalonia, Spain
| | - Alena Kovarikova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, CZ-61265, Czech Republic
| | - Ilia J Leitch
- Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
| | - Andrew R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK
| | - Ales Kovarik
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, CZ-61265, Czech Republic.
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Galián JA, Rosato M, Rosselló JA. Incomplete sequence homogenization in 45S rDNA multigene families: intermixed IGS heterogeneity within the single NOR locus of the polyploid species Medicago arborea (Fabaceae). ANNALS OF BOTANY 2014; 114:243-51. [PMID: 24925322 PMCID: PMC4111382 DOI: 10.1093/aob/mcu115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/02/2014] [Indexed: 05/04/2023]
Abstract
BACKGROUND AND AIMS Ribosomal sequences have become the classical example of the genomic homogenization of nuclear multigene families. Despite theoretical advantages and modelling predictions that support concerted evolution of the 45S rDNA, several reports have found intragenomic polymorphisms. However, the origins and causes of these rDNA polymorphisms are difficult to assess because seed plants show a wide range of 45S rDNA loci number variation, especially in polyploids. Medicago arborea is a tetraploid species that has a single 45S rDNA locus. This feature makes this species a suitable case study to assess the fate of ribosomal IGS homogenization in polyploid species showing nucleolus organizer region (NOR) reduction. METHODS The intergenic spacer (IGS) region was amplified by long PCR and the fragments were cloned and sequenced by a primer-walking strategy. The physical mapping of the whole and partial IGS variants was assessed by fluorescent in situ hybridization (FISH) and fibre-FISH methods on mitotic chromosomes and extended DNA fibres, respectively. KEY RESULTS Two IGS fragments of 4·8 and 3·5 kb were obtained showing structural features of functional sequences. The shorter variant appears to be a truncated copy of the 4·8 kb fragment that lacks the duplication of the transcription initiation site region and the entire D region. The physical localization of the two IGS variants on metaphase chromosomes and extended DNA fibres using FISH corroborated their joint presence within the same locus. In addition, no spatial structure of the two variants was detected within the NOR. CONCLUSIONS The results suggest that full sequence homogenization is not operating within the NOR locus of M. arborea. The structure of the NOR locus reported here departs from the models of IGS heterogeneity present in plants and caution against assuming the widespread belief that intragenomic ribosomal heterogeneity is mainly due to sequence variation between paralogous loci.
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Affiliation(s)
- José A Galián
- Jardín Botánico, ICBiBE, Universidad de Valencia, c/Quart 80, E-46008, Valencia, Spain
| | - Marcela Rosato
- Jardín Botánico, ICBiBE, Universidad de Valencia, c/Quart 80, E-46008, Valencia, Spain
| | - Josep A Rosselló
- Jardín Botánico, ICBiBE, Universidad de Valencia, c/Quart 80, E-46008, Valencia, Spain Marimurtra Bot. Garden, Carl Faust Fdn, PO Box 112, E-17300 Blanes, Catalonia, Spain
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Dancing together and separate again: gymnosperms exhibit frequent changes of fundamental 5S and 35S rRNA gene (rDNA) organisation. Heredity (Edinb) 2013; 111:23-33. [PMID: 23512008 PMCID: PMC3692318 DOI: 10.1038/hdy.2013.11] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In higher eukaryotes, the 5S rRNA genes occur in tandem units and are arranged either
separately (S-type arrangement) or linked to other repeated genes, in most cases to rDNA
locus encoding 18S–5.8S–26S genes (L-type arrangement). Here we used Southern
blot hybridisation, PCR and sequencing approaches to analyse genomic organisation of rRNA
genes in all large gymnosperm groups, including Coniferales, Ginkgoales, Gnetales and
Cycadales. The data are provided for 27 species (21 genera). The 5S units linked to the
35S rDNA units occur in some but not all Gnetales, Coniferales and in Ginkgo
(∼30% of the species analysed), while the remaining exhibit separate
organisation. The linked 5S rRNA genes may occur as single-copy insertions or as short
tandems embedded in the 26S–18S rDNA intergenic spacer (IGS). The 5S transcript may
be encoded by the same (Ginkgo, Ephedra) or opposite
(Podocarpus) DNA strand as the 18S–5.8S–26S genes. In addition,
pseudogenised 5S copies were also found in some IGS types. Both L- and S-type units have
been largely homogenised across the genomes. Phylogenetic relationships based on the
comparison of 5S coding sequences suggest that the 5S genes independently inserted IGS at
least three times in the course of gymnosperm evolution. Frequent transpositions and
rearrangements of basic units indicate relatively relaxed selection pressures imposed on
genomic organisation of 5S genes in plants.
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Mackay J, Dean JFD, Plomion C, Peterson DG, Cánovas FM, Pavy N, Ingvarsson PK, Savolainen O, Guevara MÁ, Fluch S, Vinceti B, Abarca D, Díaz-Sala C, Cervera MT. Towards decoding the conifer giga-genome. PLANT MOLECULAR BIOLOGY 2012; 80:555-69. [PMID: 22960864 DOI: 10.1007/s11103-012-9961-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 08/24/2012] [Indexed: 05/21/2023]
Abstract
Several new initiatives have been launched recently to sequence conifer genomes including pines, spruces and Douglas-fir. Owing to the very large genome sizes ranging from 18 to 35 gigabases, sequencing even a single conifer genome had been considered unattainable until the recent throughput increases and cost reductions afforded by next generation sequencers. The purpose of this review is to describe the context for these new initiatives. A knowledge foundation has been acquired in several conifers of commercial and ecological interest through large-scale cDNA analyses, construction of genetic maps and gene mapping studies aiming to link phenotype and genotype. Exploratory sequencing in pines and spruces have pointed out some of the unique properties of these giga-genomes and suggested strategies that may be needed to extract value from their sequencing. The hope is that recent and pending developments in sequencing technology will contribute to rapidly filling the knowledge vacuum surrounding their structure, contents and evolution. Researchers are also making plans to use comparative analyses that will help to turn the data into a valuable resource for enhancing and protecting the world's conifer forests.
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Affiliation(s)
- John Mackay
- Center for Forest Research, Institute for Integrative and Systems Biology, Université Laval, Québec, Québec G1V 0A6, Canada
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16
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Roa F, Guerra M. Distribution of 45S rDNA sites in chromosomes of plants: structural and evolutionary implications. BMC Evol Biol 2012. [PMID: 23181612 PMCID: PMC3583730 DOI: 10.1186/1471-2148-12-225] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Background 45S rDNA sites are the most widely documented chromosomal regions in eukaryotes. The analysis of the distribution of these sites along the chromosome in several genera has suggested some bias in their distribution. In order to evaluate if these loci are in fact non-randomly distributed and what is the influence of some chromosomal and karyotypic features on the distribution of these sites, a database was built with the position and number of 45S rDNA sites obtained by FISH together with other karyotypic data from 846 plant species. Results In angiosperms the most frequent numbers of sites per diploid karyotype were two and four, suggesting that in spite of the wide dispersion capacity of these sequences the number of rDNA sites tends to be restricted. The sites showed a preferential distribution on the short arms, mainly in the terminal regions. Curiously, these sites were frequently found on the short arms of acrocentric chromosomes where they usually occupy the whole arm. The trend to occupy the terminal region is especially evident in holokinetic chromosomes, where all of them were terminally located. In polyploids there is a trend towards reduction in the number of sites per monoploid complement. In gymnosperms, however, the distribution of rDNA sites varied strongly among the sampled families. Conclusions The location of 45S rDNA sites do not vary randomly, occurring preferentially on the short arm and in the terminal region of chromosomes in angiosperms. The meaning of this preferential location is not known, but some hypotheses are considered and the observed trends are discussed.
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Affiliation(s)
- Fernando Roa
- Department of Botany Laboratory of Plant Cytogenetics and Evolution, Federal University of Pernambuco Center of Biological Sciences, Rua Nelson Chaves, s/n Cidade Universitária, Recife, PE, 50,670-420, Brazil
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17
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Nkongolo K, Mehes-Smith M. Karyotype evolution in the Pinaceae: implication with molecular phylogeny. Genome 2012. [DOI: 10.1139/g2012-061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The family Pinaceae is made up mostly of diploid species (2n = 24). Systematization of karyotype analysis was developed to make comparison of intra- and interspecific karyotypes among the Pinaceae more accurate and reliable. Considering all parameters, the genera Pseudotsuga and Pseudolarix have the “most derived” (or advanced) and asymmetric karyotypes in the Pinaceae, followed by Larix, Picea, Abies, and Cedrus. The genus Pinus was the “least derived” (or ancestral) of all the genera of the Pinaceae analyzed. Differences in karyotype formulae and asymmetry indices were found among species within the same genera, suggesting that structural changes may have contributed to the diversification of the genus. This review is a detailed analysis of comparative karyotyping based on similar parameters, including numeric data and cytogenetic information. Telomeric sequence repeats and rDNA distribution in the Pinaceae were surveyed. The role of transposition in rDNA chromosome distribution is analyzed. Cytogenetic implications of hybridization between related species are reported. Likewise, the relationships between molecular phylogenetic and karyotype evolution is discussed in light of several reports. Within many genera, chromosomal organization was conserved despite independent molecular divergence and adaptation through the evolutionary history of the species of the Pinaceae.
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Affiliation(s)
- K.K. Nkongolo
- Department of Biology and Biomolecular Science Program, Laurentian University, Sudbury, ON P3E 2C6, Canada
| | - M. Mehes-Smith
- Department of Biology and Biomolecular Science Program, Laurentian University, Sudbury, ON P3E 2C6, Canada
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18
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Young HA, Sarath G, Tobias CM. Karyotype variation is indicative of subgenomic and ecotypic differentiation in switchgrass. BMC PLANT BIOLOGY 2012; 12:117. [PMID: 22834676 PMCID: PMC3492167 DOI: 10.1186/1471-2229-12-117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 07/11/2012] [Indexed: 05/07/2023]
Abstract
BACKGROUND Karyotypes can provide information about taxonomic relationships, genetic aberrations, and the evolutionary origins of species. However, differentiation of the tiny chromosomes of switchgrass (Panicum virgatum L.) and creation of a standard karyotype for this bioenergy crop has not been accomplished due to lack of distinguishing features and polyploidy. RESULTS A cytogenetic study was conducted on a dihaploid individual (2n = 2X = 18) of switchgrass to establish a chromosome karyotype. Size differences, condensation patterns, and arm-length ratios were used as identifying features and fluorescence in-situ hybridization (FISH) assigned 5S and 45S rDNA loci to chromosomes 7 and 2 respectively. Both a maize CentC and a native switchgrass centromeric repeat (PviCentC) that shared 73% sequence identity demonstrated a strong signal on chromosome 3. However, only the PviCentC probe labeled the centromeres of all chromosomes. Unexpected PviCentC and 5S rDNA hybidization patterns were consistent with severe reduction or total deletion of these repeats in one subgenome. These patterns were maintained in tetraploid and octoploid individuals. The 45S rDNA repeat produced the expected number of loci in dihaploid, tetraploid and octoploid individuals. Differences observed at the 5S rDNA loci between the upland and lowland ecotypes of switchgrass provided a basis for distinguishing these subpopulations. CONCLUSION Collectively, these results provide a quantitative karyotype of switchgrass chromosomes. FISH analyses indicate genetic divergence between subgenomes and allow for the classification of switchgrass plants belonging to divergent genetic pools. Furthermore, the karyotype structure and cytogenetic analysis of switchgrass provides a framework for future genetic and genomic studies.
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Affiliation(s)
- Hugh A Young
- Genomics and Gene Discovery Research Unit, USDA-Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
| | - Gautam Sarath
- USDA Central-East Regional Biomass Center, 137 Keim Hall, East Campus, UNL, Lincoln, NE, 68583, USA
| | - Christian M Tobias
- Genomics and Gene Discovery Research Unit, USDA-Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
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Leitch AR, Leitch IJ. Ecological and genetic factors linked to contrasting genome dynamics in seed plants. THE NEW PHYTOLOGIST 2012; 194:629-646. [PMID: 22432525 DOI: 10.1111/j.1469-8137.2012.04105.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The large-scale replacement of gymnosperms by angiosperms in many ecological niches over time and the huge disparity in species numbers have led scientists to explore factors (e.g. polyploidy, developmental systems, floral evolution) that may have contributed to the astonishing rise of angiosperm diversity. Here, we explore genomic and ecological factors influencing seed plant genomes. This is timely given the recent surge in genomic data. We compare and contrast the genomic structure and evolution of angiosperms and gymnosperms and find that angiosperm genomes are more dynamic and diverse, particularly amongst the herbaceous species. Gymnosperms typically have reduced frequencies of a number of processes (e.g. polyploidy) that have shaped the genomes of other vascular plants and have alternative mechanisms to suppress genome dynamism (e.g. epigenetics and activity of transposable elements). Furthermore, the presence of several characters in angiosperms (e.g. herbaceous habit, short minimum generation time) has enabled them to exploit new niches and to be viable with small population sizes, where the power of genetic drift can outweigh that of selection. Together these processes have led to increased rates of genetic divergence and faster fixation times of variation in many angiosperms compared with gymnosperms.
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Affiliation(s)
- A R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, E1 4NS, UK
| | - I J Leitch
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK
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20
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Echt CS, Saha S, Krutovsky KV, Wimalanathan K, Erpelding JE, Liang C, Nelson CD. An annotated genetic map of loblolly pine based on microsatellite and cDNA markers. BMC Genet 2011; 12:17. [PMID: 21269494 PMCID: PMC3038140 DOI: 10.1186/1471-2156-12-17] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 01/26/2011] [Indexed: 12/21/2022] Open
Abstract
Background Previous loblolly pine (Pinus taeda L.) genetic linkage maps have been based on a variety of DNA polymorphisms, such as AFLPs, RAPDs, RFLPs, and ESTPs, but only a few SSRs (simple sequence repeats), also known as simple tandem repeats or microsatellites, have been mapped in P. taeda. The objective of this study was to integrate a large set of SSR markers from a variety of sources and published cDNA markers into a composite P. taeda genetic map constructed from two reference mapping pedigrees. A dense genetic map that incorporates SSR loci will benefit complete pine genome sequencing, pine population genetics studies, and pine breeding programs. Careful marker annotation using a variety of references further enhances the utility of the integrated SSR map. Results The updated P. taeda genetic map, with an estimated genome coverage of 1,515 cM(Kosambi) across 12 linkage groups, incorporated 170 new SSR markers and 290 previously reported SSR, RFLP, and ESTP markers. The average marker interval was 3.1 cM. Of 233 mapped SSR loci, 84 were from cDNA-derived sequences (EST-SSRs) and 149 were from non-transcribed genomic sequences (genomic-SSRs). Of all 311 mapped cDNA-derived markers, 77% were associated with NCBI Pta UniGene clusters, 67% with RefSeq proteins, and 62% with functional Gene Ontology (GO) terms. Duplicate (i.e., redundant accessory) and paralogous markers were tentatively identified by evaluating marker sequences by their UniGene cluster IDs, clone IDs, and relative map positions. The average gene diversity, He, among polymorphic SSR loci, including those that were not mapped, was 0.43 for 94 EST-SSRs and 0.72 for 83 genomic-SSRs. The genetic map can be viewed and queried at http://www.conifergdb.org/pinemap. Conclusions Many polymorphic and genetically mapped SSR markers are now available for use in P. taeda population genetics, studies of adaptive traits, and various germplasm management applications. Annotating mapped genes with UniGene clusters and GO terms allowed assessment of redundant and paralogous EST markers and further improved the quality and utility of the genetic map for P. taeda.
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Affiliation(s)
- Craig S Echt
- Southern Institute of Forest Genetics, Southern Research Station, USDA Forest Service, Saucier, MS 39574, USA.
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21
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Adventures in the enormous: a 1.8 million clone BAC library for the 21.7 Gb genome of loblolly pine. PLoS One 2011; 6:e16214. [PMID: 21283709 PMCID: PMC3025025 DOI: 10.1371/journal.pone.0016214] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 12/10/2010] [Indexed: 11/19/2022] Open
Abstract
Loblolly pine (LP; Pinus taeda L.) is the most economically important tree in the U.S. and a cornerstone species in southeastern forests. However, genomics research on LP and other conifers has lagged behind studies on flowering plants due, in part, to the large size of conifer genomes. As a means to accelerate conifer genome research, we constructed a BAC library for the LP genotype 7-56. The LP BAC library consists of 1,824,768 individually-archived clones making it the largest single BAC library constructed to date, has a mean insert size of 96 kb, and affords 7.6X coverage of the 21.7 Gb LP genome. To demonstrate the efficacy of the library in gene isolation, we screened macroarrays with overgos designed from a pine EST anchored on LP chromosome 10. A positive BAC was sequenced and found to contain the expected full-length target gene, several gene-like regions, and both known and novel repeats. Macroarray analysis using the retrotransposon IFG-7 (the most abundant repeat in the sequenced BAC) as a probe indicates that IFG-7 is found in roughly 210,557 copies and constitutes about 5.8% or 1.26 Gb of LP nuclear DNA; this DNA quantity is eight times the Arabidopsis genome. In addition to its use in genome characterization and gene isolation as demonstrated herein, the BAC library should hasten whole genome sequencing of LP via next-generation sequencing strategies/technologies and facilitate improvement of trees through molecular breeding and genetic engineering. The library and associated products are distributed by the Clemson University Genomics Institute (www.genome.clemson.edu).
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22
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Bogunić F, Siljak-Yakovlev S, Muratović E, Ballian D. Different karyotype patterns among allopatric Pinus nigra (Pinaceae) populations revealed by molecular cytogenetics. PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:194-200. [PMID: 21143741 DOI: 10.1111/j.1438-8677.2010.00326.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
To examine variation and taxonomic recognition of Pinus nigra (European black pine) at the intraspecific level, chromosomal distribution of 5S and 18S-5.8S-26S rDNA loci revealed by fluorescent in situ hybridisation (FISH) and fluorochrome banding with chromomycin A(3) and DAPI were analysed among allopatric populations belonging to different subspecies. Despite prevalent opinion on predominantly conserved and homogenous conifer karyotypes, several patterns were observed. Surprisingly, interstitial 18S rDNA loci and DAPI heterochromatin staining after FISH showed variations in distribution and localisation. Three subspecies shared a pattern with nine 18S rDNA loci (ssp. nigra, pallasiana and laricio) while ssp. dalmatica and salzmannii had eight rDNA loci. DAPI banding displayed two patterns, one with a high number of signals (ssp. nigra, pallasiana and dalmatica) and the other with a lower number of signals (ssp. salzmannii and laricio). We conclude that our results cannot provide proof for either classification scheme for the P. nigra complex, but rather demonstrate the variability of different heterochromatin fractions at the intraspecific level.
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Affiliation(s)
- F Bogunić
- Faculty of Forestry, University of Sarajevo, Sarajevo, Bosnia and Herzegovina.
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23
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Kovach A, Wegrzyn JL, Parra G, Holt C, Bruening GE, Loopstra CA, Hartigan J, Yandell M, Langley CH, Korf I, Neale DB. The Pinus taeda genome is characterized by diverse and highly diverged repetitive sequences. BMC Genomics 2010; 11:420. [PMID: 20609256 PMCID: PMC2996948 DOI: 10.1186/1471-2164-11-420] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 07/07/2010] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND In today's age of genomic discovery, no attempt has been made to comprehensively sequence a gymnosperm genome. The largest genus in the coniferous family Pinaceae is Pinus, whose 110-120 species have extremely large genomes (c. 20-40 Gb, 2N = 24). The size and complexity of these genomes have prompted much speculation as to the feasibility of completing a conifer genome sequence. Conifer genomes are reputed to be highly repetitive, but there is little information available on the nature and identity of repetitive units in gymnosperms. The pines have extensive genetic resources, with approximately 329000 ESTs from eleven species and genetic maps in eight species, including a dense genetic map of the twelve linkage groups in Pinus taeda. RESULTS We present here the Sanger sequence and annotation of ten P. taeda BAC clones and Genome Analyzer II whole genome shotgun (WGS) sequences representing 7.5% of the genome. Computational annotation of ten BACs predicts three putative protein-coding genes and at least fifteen likely pseudogenes in nearly one megabase of sequence. We found three conifer-specific LTR retroelements in the BACs, and tentatively identified at least 15 others based on evidence from the distantly related angiosperms. Alignment of WGS sequences to the BACs indicates that 80% of BAC sequences have similar copies (> or = 75% nucleotide identity) elsewhere in the genome, but only 23% have identical copies (99% identity). The three most common repetitive elements in the genome were identified and, when combined, represent less than 5% of the genome. CONCLUSIONS This study indicates that the majority of repeats in the P. taeda genome are 'novel' and will therefore require additional BAC or genomic sequencing for accurate characterization. The pine genome contains a very large number of diverged and probably defunct repetitive elements. This study also provides new evidence that sequencing a pine genome using a WGS approach is a feasible goal.
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Affiliation(s)
- Allen Kovach
- Section of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Jill L Wegrzyn
- Department of Plant Sciences, University of California, Davis, CA 95616, USA
| | - Genis Parra
- Genome Center, Division of Biological Sciences, University of California, Davis, CA 95616, USA
| | - Carson Holt
- Eccles Institute of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA
| | - George E Bruening
- Department of Plant Pathology, University of California, Davis, CA 95616, USA
| | - Carol A Loopstra
- Department of Ecological Science and Management, Texas A&M University, College Station, TX 77843, USA
| | - James Hartigan
- Beckman Coulter Genomics (formerly Agencourt Biosciences), Danvers, MA 01923, USA
| | - Mark Yandell
- Eccles Institute of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA
| | - Charles H Langley
- Section of Evolution and Ecology, University of California, Davis, CA 95616, USA
| | - Ian Korf
- Genome Center, Division of Biological Sciences, University of California, Davis, CA 95616, USA
| | - David B Neale
- Department of Plant Sciences, University of California, Davis, CA 95616, USA
- Institute of Forest Genetics, USDA Forest Service, Davis, CA, 95616, USA
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Figueroa DM, Bass HW. A historical and modern perspective on plant cytogenetics. Brief Funct Genomics 2010; 9:95-102. [DOI: 10.1093/bfgp/elp058] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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Khan N, Barba-Gonzalez R, Ramanna MS, Visser RGF, Van Tuyl JM. Construction of chromosomal recombination maps of three genomes of lilies (Lilium) based on GISH analysis. Genome 2009; 52:238-51. [PMID: 19234552 DOI: 10.1139/g08-122] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Chromosomal recombination maps were constructed for three genomes of lily (Lilium) using GISH analyses. For this purpose, the backcross (BC) progenies of two diploid (2n = 2x = 24) interspecific hybrids of lily, viz. Longiflorum x Asiatic (LA) and Oriental x Asiatic (OA), were used. Mostly the BC progenies of LA hybrids consisted of both triploid (2n = 3x = 36) and diploid (2n = 2x = 24) with some aneuploid genotypes and those of OA hybrids consisted of triploid (2n = 3x = 36) and some aneuploid genotypes. In all cases, it was possible to identify the homoeologous recombinant chromosomes as well as accurately count the number of crossover points, which are called "recombination sites". Recombination sites were estimated in the BC progeny of 71 LA and 41 OA genotypes. In the case of BC progenies of LA hybrids, 248 recombination sites were cytologically localized on 12 different chromosomes of each genome (i.e., L and A). Similarly, 116 recombinant sites were localized on the 12 chromosomes each from the BC progenies of OA hybrids (O and A genomes). Cytological maps were constructed on the basis of the percentages of distances (micrometres) of the recombination sites from the centromeres. Since an Asiatic parent was involved in both hybrids, viz. LA and OA, two maps were constructed for the A genome that were indicated as Asiatic (L) and Asiatic (O). The other two maps were Longiflorum (A) and Oriental (A). Remarkably, the recombination sites were highly unevenly distributed among the different chromosomes of all four maps. Because the recombination sites can be unequivocally identified through GISH, they serve as reliable landmarks and pave the way for assigning molecular markers or desirable genes to chromosomes of Lilium and also monitor introgression of alien segments.
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Affiliation(s)
- Nadeem Khan
- Laboratory of Plant Breeding, Wageningen University and Research, P.O. Box 386, Wageningen, 6708PB, The Netherlands
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Morse AM, Peterson DG, Islam-Faridi MN, Smith KE, Magbanua Z, Garcia SA, Kubisiak TL, Amerson HV, Carlson JE, Nelson CD, Davis JM. Evolution of genome size and complexity in Pinus. PLoS One 2009; 4:e4332. [PMID: 19194510 PMCID: PMC2633040 DOI: 10.1371/journal.pone.0004332] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Accepted: 12/24/2008] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Genome evolution in the gymnosperm lineage of seed plants has given rise to many of the most complex and largest plant genomes, however the elements involved are poorly understood. METHODOLOGY/PRINCIPAL FINDINGS Gymny is a previously undescribed retrotransposon family in Pinus that is related to Athila elements in Arabidopsis. Gymny elements are dispersed throughout the modern Pinus genome and occupy a physical space at least the size of the Arabidopsis thaliana genome. In contrast to previously described retroelements in Pinus, the Gymny family was amplified or introduced after the divergence of pine and spruce (Picea). If retrotransposon expansions are responsible for genome size differences within the Pinaceae, as they are in angiosperms, then they have yet to be identified. In contrast, molecular divergence of Gymny retrotransposons together with other families of retrotransposons can account for the large genome complexity of pines along with protein-coding genic DNA, as revealed by massively parallel DNA sequence analysis of Cot fractionated genomic DNA. CONCLUSIONS/SIGNIFICANCE Most of the enormous genome complexity of pines can be explained by divergence of retrotransposons, however the elements responsible for genome size variation are yet to be identified. Genomic resources for Pinus including those reported here should assist in further defining whether and how the roles of retrotransposons differ in the evolution of angiosperm and gymnosperm genomes.
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Affiliation(s)
- Alison M. Morse
- School of Forest Resources and Conservation, University of Florida, Gainesville, Florida, United States of America
| | - Daniel G. Peterson
- Department of Plant and Soil Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
| | - M. Nurul Islam-Faridi
- Southern Institute of Forest Genetics, USDA Forest Service Southern Research Station, Saucier, Mississippi, United States of America
| | - Katherine E. Smith
- Southern Institute of Forest Genetics, USDA Forest Service Southern Research Station, Saucier, Mississippi, United States of America
| | - Zenaida Magbanua
- Department of Plant and Soil Sciences, Mississippi State University, Mississippi State, Mississippi, United States of America
| | - Saul A. Garcia
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Thomas L. Kubisiak
- Southern Institute of Forest Genetics, USDA Forest Service Southern Research Station, Saucier, Mississippi, United States of America
| | - Henry V. Amerson
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina, United States of America
| | - John E. Carlson
- School of Forest Resources, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - C. Dana Nelson
- Southern Institute of Forest Genetics, USDA Forest Service Southern Research Station, Saucier, Mississippi, United States of America
| | - John M. Davis
- School of Forest Resources and Conservation, University of Florida, Gainesville, Florida, United States of America
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Ribeiro T, Barão A, Viegas W, Morais-Cecíli L. Molecular cytogenetics of forest trees. Cytogenet Genome Res 2008; 120:220-7. [DOI: 10.1159/000121070] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2007] [Indexed: 01/03/2023] Open
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