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Oliveira JIN, Cabral-de-Mello DC, Valente GT, Martins C. Transcribing the enigma: the B chromosome as a territory of uncharted RNAs. Genetics 2024; 227:iyae026. [PMID: 38513121 DOI: 10.1093/genetics/iyae026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 02/10/2024] [Indexed: 03/23/2024] Open
Abstract
B chromosomes are supernumerary elements found in several groups of eukaryotes, including fungi, plants, and animals. Typically, these chromosomes either originate from their hosts through errors in meiosis or interspecifically through horizontal transfer. While many B chromosomes are primarily heterochromatic and possess a low number of coding genes, these additional elements are still capable of transcribing sequences and exerting influence on the expression of host genes. How B chromosomes escape elimination and which impacts can be promoted in the cell always intrigued the cytogeneticists. In pursuit of understanding the behavior and functional impacts of these extra elements, cytogenetic studies meet the advances of molecular biology, incorporating various techniques into investigating B chromosomes from a functional perspective. In this review, we present a timeline of studies investigating B chromosomes and RNAs, highlighting the advances and key findings throughout their history. Additionally, we identified which RNA classes are reported in the B chromosomes and emphasized the necessity for further investigation into new perspectives on the B chromosome functions. In this context, we present a phylogenetic tree that illustrates which branches either report B chromosome presence or have functional RNA studies related to B chromosomes. We propose investigating other unexplored RNA classes and conducting functional analysis in conjunction with cytogenetic studies to enhance our understanding of the B chromosome from an RNA perspective.
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Affiliation(s)
| | - Diogo C Cabral-de-Mello
- Departamento de Biologia Geral e Aplicada, Instituto de Biociências, Universidade Estadual Paulista (UNESP), Rio Claro 13506-900, Brazil
| | - Guilherme T Valente
- Applied Biotechnology Laboratory, Clinical Hospital of Botucatu Medical School, Botucatu 18618-687, Brazil
| | - Cesar Martins
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, São Paulo State University (UNESP), Botucatu 18618-689, Brazil
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2
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Asuke S, Horie A, Komatsu K, Mori R, Vy TTP, Inoue Y, Jiang Y, Tatematsu Y, Shimizu M, Tosa Y. Loss of PWT7, Located on a Supernumerary Chromosome, Is Associated with Parasitic Specialization of Pyricularia oryzae on Wheat. Mol Plant Microbe Interact 2023; 36:716-725. [PMID: 37432132 DOI: 10.1094/mpmi-06-23-0078-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Pyricularia oryzae, a blast fungus of gramineous plants, is composed of various host genus-specific pathotypes. The avirulence of an Avena isolate on wheat is conditioned by PWT3 and PWT4. We isolated the third avirulence gene from the Avena isolate and designated it as PWT7. PWT7 was effective as an avirulence gene only at the seedling stage or on leaves. PWT7 homologs were widely distributed in a subpopulation of the Eleusine pathotype and the Lolium pathotype but completely absent in the Triticum pathotype (the wheat blast fungus). The PWT7 homolog found in the Eleusine pathotype was one of the five genes involved in its avirulence on wheat. A comparative analysis of distribution of PWT7 and the other two genes previously identified in the Eleusine pathotype suggested that, in the course of parasitic specialization toward the wheat blast fungus, a common ancestor of the Eleusine, Lolium, Avena, and Triticum pathotypes first lost PWT6, secondly PWT7, and, finally, the function of PWT3. PWT7 or its homologs were located on core chromosomes in Setaria and Eleusine isolates but on supernumerary chromosomes in Lolium and Avena isolates. This is an example of interchromosomal translocations of effector genes between core and supernumerary chromosomes. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Soichiro Asuke
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Akiko Horie
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Kaori Komatsu
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Ryota Mori
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Trinh Thi Phuong Vy
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Yoshihiro Inoue
- Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Yushan Jiang
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Yuna Tatematsu
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Motoki Shimizu
- Iwate Biotechnology Research Center, Kitakami, Iwate 024-0003, Japan
| | - Yukio Tosa
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
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3
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Crane YM, Crane CF, Cambron SE, Springmeyer LJ, Schemerhorn BJ. Molecular characterization of eliminated chromosomes in Hessian fly (Mayetiola destructor (Say)). Chromosome Res 2023; 31:3. [PMID: 36692656 PMCID: PMC9873768 DOI: 10.1007/s10577-023-09718-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 01/05/2023] [Accepted: 01/10/2023] [Indexed: 01/25/2023]
Abstract
Like other cecidomyiid Diptera, Hessian fly has stable S chromosomes and dispensable E chromosomes that are retained only in the germ line. Amplified fragment length polymorphisms (AFLP), suppressive subtractive hybridization (SSH), fluorescent in-situ hybridization (FISH), and sequencing were used to investigate similarities and differences between S and E chromosomes. More than 99.9% of AFLP bands were identical between separated ovary and somatic tissue, but one band was unique to ovary and resembled Worf, a non-LTR retrotransposon. Arrayed clones, derived by SSH of somatic from ovarian DNA, showed no clones that were unique to ovary. FISH with BAC clones revealed a diagnostic banding pattern of BAC positions on both autosomes and both sex chromosomes, and each E chromosome shared a pattern with one of the S chromosomes. Sequencing analysis showed that E chromosomes are nearly identical to S chromosomes, since no sequence could be confirmed to belong only to E chromosomes. There were a few questionably E-specific sequences that are candidates for further investigation. Thus, the E chromosomes appear to be derived from S chromosomes by the acquisition or conversion of sequences that produce the negatively heteropycnotic region around the centromere.
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Affiliation(s)
- Yan M Crane
- USDA Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA.,Department of Entomology, Purdue University, West Lafayette, IN, 47907, USA
| | - Charles F Crane
- USDA Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA.,Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Sue E Cambron
- USDA Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA.,Department of Entomology, Purdue University, West Lafayette, IN, 47907, USA
| | - Lucy J Springmeyer
- USDA Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA
| | - Brandon J Schemerhorn
- USDA Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA. .,Department of Entomology, Purdue University, West Lafayette, IN, 47907, USA.
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4
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Utsunomia R, Vaio M, Ruiz-Ruano FJ. Editorial: Cytogenomics: Structural Organization and Evolution of Genomes. Front Genet 2022; 13:938513. [PMID: 35754797 PMCID: PMC9224753 DOI: 10.3389/fgene.2022.938513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 05/23/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Ricardo Utsunomia
- Department of Genetics, Institute of Biological Sciences and Health, Federal Rural University of Rio de Janeiro, Seropédica, Brazil.,Faculty of Sciences, São Paulo State University, Bauru, Brazil
| | - Magdalena Vaio
- Department of Plant Biology, Faculty of Agronomy, University of the Republic, Montevideo, Uruguay
| | - Francisco J Ruiz-Ruano
- Department of Organismal Biology-Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.,School of Biological Sciences, Norwich Research Park University of East Anglia, Norwich, United Kingdom
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5
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Mari-Ribeiro IP, Scorsim B, Oliveira AVD, Portela-Castro ALDB. Cytogenetic and Molecular Characterization of Oligosarcus pintoi (Characidae): A New Record of Supernumerary Chromosome in this Species. Zebrafish 2022; 19:71-80. [PMID: 35394373 DOI: 10.1089/zeb.2021.0065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The genus Oligosarcus currently comprises 24 valid species distributed in the major river basins of South America. In this group, nine species were cytogenetically investigated, and found to share a diploid number of 50 chromosomes. Despite the conservation of the diploid number, variations in the karyotypic formula, number and position of the nucleolar organizer regions, and longitudinal bands have been described between both species and populations. In this study, we present cytogenetic and molecular data from Oligosarcus pintoi specimens from the Keller River, a tributary of the Ivaí River (Upper Paraná basin), using DNA barcoding and cytogenetic markers (C-band, silver-stained nucleolar organizer regions, and fluorescence in situ hybridization of 18S and 5S rDNA). The genetic inferences reached after analyzing the cytochrome c oxidade subunit 1 gene allowed us to confirm the identity of the individuals with 2n = 50 chromosomes. However, one specimen contained a medium subtelocentric supernumerary chromosome (2n = 51). This is the second record of additional chromosomes in O. pintoi, thereby confirming the existence of a supernumerary chromosome in allopatric populations of this species, a fact that demonstrates an evolutionary path that is divergent from other populations and/or species of Oligosarcus analyzed so far, contributing to the karyotypic diversification of the group.
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Affiliation(s)
- Isabelle Pereira Mari-Ribeiro
- Programa de Pós-graduação em Ciências Biológicas, Universidade Estadual de Maringá, Maringá, Brazil.,Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, Brazil
| | - Bárbara Scorsim
- Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, Brazil.,Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais, Universidade Estadual de Maringá, Maringá, Brazil
| | - Alessandra Valéria de Oliveira
- Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, Brazil.,Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupélia), Universidade Estadual de Maringá, Maringá, Brazil
| | - Ana Luiza de Brito Portela-Castro
- Departamento de Biotecnologia, Genética e Biologia Celular, Universidade Estadual de Maringá, Maringá, Brazil.,Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupélia), Universidade Estadual de Maringá, Maringá, Brazil
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6
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Abstract
Chromosome size and morphology vary within and among species, but little is known about the proximate or ultimate causes of these differences. Cichlid fish species in the tribe Oreochromini share an unusual giant chromosome that is ∼3 times longer than the other chromosomes. This giant chromosome functions as a sex chromosome in some of these species. We test two hypotheses of how this giant sex chromosome may have evolved. The first hypothesis proposes that it evolved by accumulating repetitive elements as recombination was reduced around a dominant sex determination locus, as suggested by canonical models of sex chromosome evolution. An alternative hypothesis is that the giant sex chromosome originated via the fusion of an autosome with a highly repetitive B chromosome, one of which carried a sex determination locus. We test these hypotheses using comparative analysis of chromosome-scale cichlid and teleost genomes. We find that the giant sex chromosome consists of three distinct regions based on patterns of recombination, gene and transposable element content, and synteny to the ancestral autosome. The WZ sex determination locus encompasses the last ∼105 Mb of the 134-Mb giant chromosome. The last 47 Mb of the giant chromosome shares no obvious homology to any ancestral chromosome. Comparisons across 69 teleost genomes reveal that the giant sex chromosome contains unparalleled amounts of endogenous retroviral elements, immunoglobulin genes, and long noncoding RNAs. The results favor the B chromosome fusion hypothesis for the origin of the giant chromosome.
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Affiliation(s)
- Matthew A Conte
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Frances E Clark
- Department of Biology, University of Maryland, College Park, MD, USA
| | - Reade B Roberts
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - Luohao Xu
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Wenjing Tao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), School of Life Sciences, Southwest University, Chongqing, China
| | - Qi Zhou
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
- MOE Laboratory of Biosystems Homeostasis & Protection, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Deshou Wang
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), School of Life Sciences, Southwest University, Chongqing, China
| | - Thomas D Kocher
- Department of Biology, University of Maryland, College Park, MD, USA
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Melo AS, Cruz GAS, Félix AP, Rocha MF, Loreto V, Moura RC. Wide dispersion of B chromosomes in Rhammatocerus brasiliensis (Orthoptera, Acrididae). Genet Mol Biol 2020; 43:e20190077. [PMID: 32542305 PMCID: PMC7295183 DOI: 10.1590/1678-4685-gmb-2019-0077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 07/16/2019] [Indexed: 01/01/2023] Open
Abstract
The grasshopper Rhammatocerus brasiliensis shows polymorphism of B chromosomes, but the magnitude of B-chromosome occurrence and the factors that may contribute to their dispersion in the species remain unknown thus far. The present study analyzed the occurrence and dispersion of B chromosomes in R. brasiliensis individuals from 21 populations widely distributed in the Brazilian Northeast. The genetic connectivity between 10 populations was verified through analysis of ISSR markers from 200 individuals. Of the 21 populations, 19 presented individuals with one B chromosome, three with two, and one with three B chromosomes. The B chromosome is of medium size and constitutive heterochromatin (CH) located in the pericentromeric region. A variant B chromosome was observed in three populations, similar in size to that of chromosome X, gap and CH, and located in the terminal region. B chromosome frequencies in different populations varied from 0% to 18,8%, mean 8,5%. The wide distribution of the B chromosome is likely a consequence of the positive gene flow among the analyzed populations. B-chromosome occurrence in populations of R. brasiliensis possibly follows the population genetic structure of the species and, owing to the existence of a variant, its origin may not be recent.
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Affiliation(s)
- Adriana S Melo
- Universidade de Pernambuco (UPE), Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, Recife, PE, Brazil
| | - Geyner A S Cruz
- Universidade de Pernambuco (UPE), Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, Recife, PE, Brazil
- Universidade de Pernambuco (UPE), Laboratório de Biodiversidade e Genética Evolutiva, Campus Petrolina, Petrolina, PE, Brazil
| | - Aline P Félix
- Universidade de Pernambuco (UPE), Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, Recife, PE, Brazil
| | - Marília F Rocha
- Universidade de Pernambuco (UPE), Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, Recife, PE, Brazil
| | - Vilma Loreto
- Universidade Federal de Pernambuco (UFPE), Departamento de Genética, Laboratório de Genética Animal e Humana e Citogenética, Recife, PE, Brazil
| | - Rita C Moura
- Universidade de Pernambuco (UPE), Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, Recife, PE, Brazil
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8
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Matsubara K, Yanagida K, Nagai T, Kagami M, Fukami M. De Novo Small Supernumerary Marker Chromosomes Arising From Partial Trisomy Rescue. Front Genet 2020; 11:132. [PMID: 32174976 PMCID: PMC7056893 DOI: 10.3389/fgene.2020.00132] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 02/03/2020] [Indexed: 11/24/2022] Open
Abstract
Small supernumerary marker chromosomes (SMCs) are rare cytogenetic abnormalities. De novo small SMCs, particularly those combined with uniparental disomy (UPD), are assumed to result from incomplete trisomy rescue. Recently, a one-off cellular event designated as chromothripsis was reported as a mechanism for trisomy rescue in micronuclei. This Perspective article aims to highlight a possible association among trisomy rescue, chromothripsis, and SMCs. We propose that chromothripsis-mediated incomplete trisomy rescue in micronuclei underlies various chromosomal rearrangements including SMCs, although other mechanisms such as U-type exchange may also yield SMCs. These assumptions are primarily based on observations of previously reported patients with complex rearrangements and our patient with a small SMC. Given the high frequency of trisomic cells in human preimplantation embryos, chromothripsis-mediated trisomy rescue may be a physiologically important phenomenon. Nevertheless, trisomy rescue has a potential to produce UPD, SMCs, and other chromosomal rearrangements. The concepts of trisomy rescue, chromothripsis, and micronuclei provide novel insights into the mechanism for the maintenance and modification of human chromosomes.
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Affiliation(s)
- Keiko Matsubara
- Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, Japan
| | | | | | - Masayo Kagami
- Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, Japan
| | - Maki Fukami
- Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, Japan
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Cardoso AL, Fantinatti BEDA, Venturelli NB, Carmello BDO, de Oliveira RA, Martins C. Epigenetic DNA Modifications Are Correlated With B Chromosomes and Sex in the Cichlid Astatotilapia latifasciata. Front Genet 2019; 10:324. [PMID: 31031803 PMCID: PMC6474290 DOI: 10.3389/fgene.2019.00324] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 03/22/2019] [Indexed: 12/11/2022] Open
Abstract
Supernumerary B chromosomes are dispensable elements found in several groups of eukaryotes, and their impacts in host organisms are not clear. The cichlid fish Astatotilapia latifasciata presents one or two large metacentric B chromosomes. These elements affect the transcription of several classes of RNAs. Here, we evaluated the epigenetic DNA modification status of B chromosomes using immunocytogenetics and assessed the impact of B chromosome presence on the global contents of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) and the molecular mechanisms underlying these variations. We found that the B chromosome of A. latifasciata has an active pattern of DNA epimarks, and its presence promotes the loss of 5mC in gonads of females with B chromosome (FB+) and promotes the loss of 5hmC in the muscle of males with the B element (MB+). Based on the transcriptional quantification of DNA modification genes (dnmt, tet, and tdg) and their candidate regulators (idh genes, microRNAs, and long non-coding RNAs) and on RNA-protein interaction prediction, we suggest the occurrence of passive demethylation in gonads of FB+ and 5hmC loss by Tet inhibition or by 5hmC oxidation in MB+ muscle. We suggest that these results can also explain the previously reported variations in the transcription levels of several classes of RNA depending on B chromosome presence. The DNA modifications detected here are also influenced by sex. Although the correlation between B chromosomes and sex has been previously reported, it remains unexplained. The B chromosome of A. latifasciata seems to be active and impacts cell physiology in a very complex way, including at the epigenetic level.
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Affiliation(s)
- Adauto Lima Cardoso
- Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
| | - Bruno Evaristo de Almeida Fantinatti
- Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
| | - Natália Bortholazzi Venturelli
- Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
| | - Bianca de Oliveira Carmello
- Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
| | - Rogério Antonio de Oliveira
- Department of Biostatistics, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
| | - Cesar Martins
- Integrative Genomics Laboratory, Department of Morphology, Institute of Biosciences, São Paulo State University - Universidade Estadual Paulista, Botucatu, Brazil
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10
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Milani D, Bardella VB, Ferretti ABSM, Palacios-Gimenez OM, Melo ADS, Moura RC, Loreto V, Song H, Cabral-de-Mello DC. Satellite DNAs Unveil Clues about the Ancestry and Composition of B Chromosomes in Three Grasshopper Species. Genes (Basel) 2018; 9:genes9110523. [PMID: 30373193 PMCID: PMC6265867 DOI: 10.3390/genes9110523] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 10/12/2018] [Accepted: 10/21/2018] [Indexed: 11/16/2022] Open
Abstract
Supernumerary (B) chromosomes are dispensable genomic elements occurring frequently among grasshoppers. Most B chromosomes are enriched with repetitive DNAs, including satellite DNAs (satDNAs) that could be implicated in their evolution. Although studied in some species, the specific ancestry of B chromosomes is difficult to ascertain and it was determined in only a few examples. Here we used bioinformatics and cytogenetics to characterize the composition and putative ancestry of B chromosomes in three grasshopper species, Rhammatocerus brasiliensis, Schistocerca rubiginosa, and Xyleus discoideus angulatus. Using the RepeatExplorer pipeline we searched for the most abundant satDNAs in Illumina sequenced reads, and then we generated probes used in fluorescent in situ hybridization (FISH) to determine chromosomal position. We used this information to infer ancestry and the events that likely occurred at the origin of B chromosomes. We found twelve, nine, and eighteen satDNA families in the genomes of R. brasiliensis, S. rubiginosa, and X. d. angulatus, respectively. Some satDNAs revealed clustered organization on A and B chromosomes varying in number of sites and position along chromosomes. We did not find specific satDNA occurring in the B chromosome. The satDNAs shared among A and B chromosomes support the idea of putative intraspecific ancestry from small autosomes in the three species, i.e., pair S11 in R. brasiliensis, pair S9 in S. rubiginosa, and pair S10 in X. d. angulatus. The possibility of involvement of other chromosomal pairs in B chromosome origin is also hypothesized. Finally, we discussed particular aspects in composition, origin, and evolution of the B chromosome for each species.
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Affiliation(s)
- Diogo Milani
- Instituto de Biociências/IB, Departamento de Biologia, UNESP-Universidade Estadual Paulista, Rio Claro, São Paulo 01049-010, Brazil.
| | - Vanessa B Bardella
- Instituto de Biociências/IB, Departamento de Biologia, UNESP-Universidade Estadual Paulista, Rio Claro, São Paulo 01049-010, Brazil.
| | - Ana B S M Ferretti
- Instituto de Biociências/IB, Departamento de Biologia, UNESP-Universidade Estadual Paulista, Rio Claro, São Paulo 01049-010, Brazil.
| | - Octavio M Palacios-Gimenez
- Instituto de Biociências/IB, Departamento de Biologia, UNESP-Universidade Estadual Paulista, Rio Claro, São Paulo 01049-010, Brazil.
- Department of Evolutionary Biology, Evolutionary Biology Center, Uppsala University, 75236 Uppsala, Sweden.
| | - Adriana de S Melo
- Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, UPE-Universidade de Pernambuco, Recife 50100-130, Pernambuco, Brazil.
| | - Rita C Moura
- Instituto de Ciências Biológicas, Laboratório de Biodiversidade e Genética de Insetos, UPE-Universidade de Pernambuco, Recife 50100-130, Pernambuco, Brazil.
| | - Vilma Loreto
- Centro de Biociências/CB, Departamento de Genética, UFPE-Universidade Federal de Pernambuco, Recife 50670-901, Pernambuco, Brazil.
| | - Hojun Song
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX 77843-2475, USA.
| | - Diogo C Cabral-de-Mello
- Instituto de Biociências/IB, Departamento de Biologia, UNESP-Universidade Estadual Paulista, Rio Claro, São Paulo 01049-010, Brazil.
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11
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Ruban A, Schmutzer T, Scholz U, Houben A. How Next-Generation Sequencing Has Aided Our Understanding of the Sequence Composition and Origin of B Chromosomes. Genes (Basel) 2017; 8:E294. [PMID: 29068386 PMCID: PMC5704207 DOI: 10.3390/genes8110294] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 10/18/2017] [Accepted: 10/24/2017] [Indexed: 12/21/2022] Open
Abstract
Accessory, supernumerary, or-most simply-B chromosomes, are found in many eukaryotic karyotypes. These small chromosomes do not follow the usual pattern of segregation, but rather are transmitted in a higher than expected frequency. As increasingly being demonstrated by next-generation sequencing (NGS), their structure comprises fragments of standard (A) chromosomes, although in some plant species, their sequence also includes contributions from organellar genomes. Transcriptomic analyses of various animal and plant species have revealed that, contrary to what used to be the common belief, some of the B chromosome DNA is protein-encoding. This review summarizes the progress in understanding B chromosome biology enabled by the application of next-generation sequencing technology and state-of-the-art bioinformatics. In particular, a contrast is drawn between a direct sequencing approach and a strategy based on a comparative genomics as alternative routes that can be taken towards the identification of B chromosome sequences.
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Affiliation(s)
- Alevtina Ruban
- Leibniz Institute of Plant Genetics and Crop Plant Research Gatersleben, 06466 Seeland, Germany.
| | - Thomas Schmutzer
- Leibniz Institute of Plant Genetics and Crop Plant Research Gatersleben, 06466 Seeland, Germany.
| | - Uwe Scholz
- Leibniz Institute of Plant Genetics and Crop Plant Research Gatersleben, 06466 Seeland, Germany.
| | - Andreas Houben
- Leibniz Institute of Plant Genetics and Crop Plant Research Gatersleben, 06466 Seeland, Germany.
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Carmello BO, Coan RLB, Cardoso AL, Ramos E, Fantinatti BEA, Marques DF, Oliveira RA, Valente GT, Martins C. The hnRNP Q-like gene is retroinserted into the B chromosomes of the cichlid fish Astatotilapia latifasciata. Chromosome Res 2017; 25:277-290. [PMID: 28776210 DOI: 10.1007/s10577-017-9561-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/12/2017] [Accepted: 07/14/2017] [Indexed: 11/27/2022]
Abstract
B chromosomes are dispensable elements observed in many eukaryotic species, including the African cichlid Astatotilapia latifasciata, which might have one or two B chromosomes. Although there have been many studies focused on the biology of these chromosomes, questions about the evolution, maintenance, and potential effects of these chromosomes remain. Here, we identified a variant form of the hnRNP Q-like gene inserted into the B chromosome of A. latifasciata that is characterized by a high copy number and intron-less structure. The absence of introns and presence of transposable elements with a reverse transcriptase domain flanking hnRNP Q-like sequences suggest that this gene was retroinserted into the B chromosome. RNA-Seq analysis did not show that the B variant retroinserted copies are transcriptionally active. However, RT-qPCR results showed variations in the canonical hnRNP Q-like copy expression levels among exons, tissues, sex, and B presence/absence. Although the patterns of transcription are not well understood, the exons of the B retrocopies were overexpressed, and a bias for female B+ expression was also observed. These results suggest that retroinsertion is an additional and important mechanism contributing to B chromosome formation. Furthermore, these findings indicate a bias towards female differential expression of B chromosome sequences, suggesting that B chromosomes and sex determination are somehow associated in cichlids.
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Affiliation(s)
- Bianca O Carmello
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Rafael L B Coan
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Adauto L Cardoso
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Erica Ramos
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Bruno E A Fantinatti
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Diego F Marques
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Rogério A Oliveira
- Institute of Biosciences, Department of Biostatistics, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Guilherme T Valente
- Institute of Biosciences, Agronomic Science School, Department of Bioprocess and Biotechnology, Sao Paulo State University (UNESP), Botucatu, SP, 18610-307, Brazil
| | - Cesar Martins
- Institute of Biosciences, Department of Morphology, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil.
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Takagui FH, Dias AL, Birindelli JLO, Swarça AC, da Rosa R, Lui RL, Fenocchio AS, Giuliano-Caetano L. First report of B chromosomes in three neotropical thorny catfishes (Siluriformes, Doradidae). Comp Cytogenet 2017; 11:55-64. [PMID: 28919949 PMCID: PMC5599706 DOI: 10.3897/compcytogen.v11i1.10496] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/15/2016] [Indexed: 06/07/2023]
Abstract
The family Doradidae (Siluriformes) is an important group of fishes endemic to freshwater ecosystems in South America. Some cytogenetic studies have been conducted focused on the group; however, there are no reports on the occurrence of B chromosomes for the family. In this paper the chromosomal characteristics of Platydoras armatulus (Valenciennes, 1840), Pterodoras granulosus (Valenciennes, 1821) and Ossancora punctata (Kner, 1855) were investigated through classical cytogenetics approaches. The conventional staining reveals 2n=58 in Platydoras armatulus and Pterodoras granulosus, however with distinct karyotypic formulae, possibly originated by pericentric inversions. In Ossancora punctata a derivate karyotype was described with 2n=66 and predominance of acrocentric chromosomes. The C banding pattern was resolutive in discriminating the three species, being considered an important cytotaxonomic marker. All species showed B chromosomes totally heterochromatic with non-Mendelian segregation during meiosis and low frequencies in mitotic cells. The probably origin of these additional elements was through fragmentations of chromosomes of the standard complement, which occurred recently and independently in these three species. The diploid number observed in Ossancora punctata is an evidence of centric fusions and up to the moment it is the highest diploid number reported for Doradidae.
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Affiliation(s)
- Fábio Hiroshi Takagui
- Laboratory of Animal Cytogenetics; Department of General Biology, CCB, Universidade Estadual de Londrina. Rodovia Celso Garcia Cid, PR 445, km 380, Londrina-Brasil
| | - Ana Lucia Dias
- Laboratory of Animal Cytogenetics; Department of General Biology, CCB, Universidade Estadual de Londrina. Rodovia Celso Garcia Cid, PR 445, km 380, Londrina-Brasil
| | - José Luís Olivan Birindelli
- Museum of Zoology, Department of Animal and Plant Biology, CCB, Universidade Estadual de Londrina. Rodovia Celso Garcia Cid, PR 445, km 380, Londrina-Brasil
| | - Ana Claudia Swarça
- Laboratory of Histology and Genetics; Department of Histology; Center of Biological Sciences (CCB); Universidade Estadual de Londrina (UEL). Londrina-Brasil
| | - Renata da Rosa
- Laboratory of Animal Cytogenetics; Department of General Biology, CCB, Universidade Estadual de Londrina. Rodovia Celso Garcia Cid, PR 445, km 380, Londrina-Brasil
| | - Roberto Laridondo Lui
- Laboratory of Cytogenetics; Center of Biological Sciences and Health: Universidade do Oeste do Paraná, Campus Cascavel. Cascavel - Brasil
| | - Alberto Sergio Fenocchio
- Laboratory of General Cytogenetics; Department of Genetics; Facultad de Ciencias Naturales; Universidad Nacional de Misiones. Posadas- Argentina
| | - Lucia Giuliano-Caetano
- Laboratory of Animal Cytogenetics; Department of General Biology, CCB, Universidade Estadual de Londrina. Rodovia Celso Garcia Cid, PR 445, km 380, Londrina-Brasil
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14
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Clark FE, Conte MA, Ferreira-Bravo IA, Poletto AB, Martins C, Kocher TD. Dynamic Sequence Evolution of a Sex-Associated B Chromosome in Lake Malawi Cichlid Fish. J Hered 2016; 108:53-62. [PMID: 27630131 DOI: 10.1093/jhered/esw059] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 08/26/2016] [Indexed: 12/16/2022] Open
Abstract
B chromosomes are extra chromosomes found in many species of plants, animals, and fungi. B chromosomes often manipulate common cellular processes to increase their frequency, sometimes to the detriment of organismal fitness. Here, we characterize B chromosomes in several species of Lake Malawi cichlid fish. Whole genome sequencing of Metriaclima zebra "Boadzulu" individuals revealed blocks of sequence with unusually high sequence coverage, indicative of increased copy number of those sequences. These regions of high sequence coverage were found only in females. SNPs unique to the high copy number sequences permitted the design of specific amplification primers. These primers amplified fragments only in Metriaclima lombardoi individuals that carried a cytologically identified B chromosome (B-carriers), indicating these extra copies are located on the B chromosome. These same primers were used to identify B-carrying individuals in additional species from Lake Malawi. Across 7 species, a total of 43 B-carriers were identified among 323 females. B-carriers were exclusively female; no B chromosomes were observed in the 317 males surveyed from these species. Quantitative analysis of the copy number variation of B-specific sequence blocks suggests that B-carriers possess a single B chromosome, consistent with previous karyotyping of M. lombardoi A single B chromosome in B-carriers is consistent with 2 potential drive mechanisms: one involving nondisjunction and preferential segregation in a mitotic division prior to the germ-line, and the other involving preferential segregation during meiosis I.
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Affiliation(s)
- Frances E Clark
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins)
| | - Matthew A Conte
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins)
| | - Irani A Ferreira-Bravo
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins)
| | - Andreia B Poletto
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins)
| | - Cesar Martins
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins)
| | - Thomas D Kocher
- From the Department of Biology, University of Maryland, College Park, Maryland 20742 (Clark, Conte, and Kocher); Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (Ferreira-Bravo); and Departamento de Morfologia, Instituto de Biociências, UNESP-Universidade Estadual Paulista, Botucatu, SP, Brazil (Poletto and Martins).
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Abstract
UNLABELLED Members of the Fusarium solani species complex (FSSC) are capable of causing disease in many agriculturally important crops. The genomes of some of these fungi include supernumerary chromosomes that are dispensable and encode host-specific virulence factors. In addition to genomics, this review summarizes the known molecular mechanisms utilized by members of the FSSC in establishing disease. TAXONOMY Kingdom Fungi; Phylum Ascomycota; Class Sordariomycetes; Order Hypocreales; Family Nectriaceae; Genus Fusarium. HOST RANGE Members of the FSSC collectively have a very broad host range, and have been subdivided previously into formae speciales. Recent phylogenetic analysis has revealed that formae speciales correspond to biologically and phylogenetically distinct species. DISEASE SYMPTOMS Typically, FSSC causes foot and/or root rot of the infected host plant, and the degree of necrosis correlates with the severity of the disease. Symptoms on above-ground portions of the plant can vary greatly depending on the specific FSSC pathogen and host plant, and the disease may manifest as wilting, stunting and chlorosis or lesions on the stem and/or leaves. CONTROL Implementation of agricultural management practices, such as crop rotation and timing of planting, can reduce the risk of crop loss caused by FSSC. If available, the use of resistant varieties is another means to control disease in the field. USEFUL WEBSITES http://genome.jgi-psf.org/Necha2/Necha2.home.html.
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Affiliation(s)
- Jeffrey J Coleman
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, 36849, USA
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Abstract
Chromatin structure can affect the organization and maintenance of chromosomes. Recent discoveries in several filamentous fungi suggest mechanisms for the clustering and co-regulation of secondary metabolite genes or pathogenicity islands. An extreme case of this may be fungal 'accessory', 'conditionally dispensable', or 'supernumerary' chromosomes that often confer beneficial traits. Fungal supernumerary chromosomes may be derived by similar mechanisms as animal or plant B chromosomes, and we thus propose that this term should be reconsidered to capture the wide variety of fungal accessory chromosomes. In some fungi, both the 'ends' of chromosomes and these 'odd B chromosomes are enriched with a silencing histone modification, H3 lysine 27 trimethylation (H3K27me3), suggesting parallel mechanisms in evolving subtelomeric or B-chromosomal pathogenicity islands and secondary metabolite clusters (SMCs).
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Affiliation(s)
- Jonathan M Galazka
- Department of Biochemistry and Biophysics, Center of Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331, United States
| | - Michael Freitag
- Department of Biochemistry and Biophysics, Center of Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331, United States.
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Marques A, Klemme S, Guerra M, Houben A. Cytomolecular characterization of de novo formed rye B chromosome variants. Mol Cytogenet 2012; 5:34. [PMID: 22800712 PMCID: PMC3541114 DOI: 10.1186/1755-8166-5-34] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 11/23/2022] Open
Abstract
UNLABELLED BACKGROUND B chromosomes (Bs) are dispensable elements which occur in many species including rye (Secale cereale). We determined the organization of B variants to obtain insights into the origin of B polymorphisms in rye. RESULTS The observed B variants were classified according to their morphology and in situ hybridization patterns with the B-specific repeats D1100 and CL11 into (I) long arm iso B, (II) D1100-deficient B and (III) small metacentric B variants. Long arm iso Bs are likely products of a meiotic centromere misdivision and subsequent duplication of the long arm, whereas small B variants are probably generated by chromosome breakage. Some deficient Bs experienced extensive amplification of CL11 repeats. CONCLUSIONS Both the pericentromere and the nondisjunction control region seem to be involved in the generation of rye B chromosome variants. However, due to the loss of the B-specific nondisjuction control region most of the variants generated are not capable to accumulate in a population.
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Affiliation(s)
- André Marques
- Leibniz-Institute of Plant Genetics & Crop Plant Research (IPK), 06466, Gatersleben, Germany
- Laboratory of Plant Cytogenetics and Molecular Biology, Department of Botany, UFPE, Recife, Brazil
| | - Sonja Klemme
- Leibniz-Institute of Plant Genetics & Crop Plant Research (IPK), 06466, Gatersleben, Germany
| | - Marcelo Guerra
- Laboratory of Plant Cytogenetics and Molecular Biology, Department of Botany, UFPE, Recife, Brazil
| | - Andreas Houben
- Leibniz-Institute of Plant Genetics & Crop Plant Research (IPK), 06466, Gatersleben, Germany
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18
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Voltolin TA, Senhorini JA, Foresti F, Bortolozzi J, Porto-Foresti F. Intraspecific crosses resulting in the first occurrence of eight and nine B chromosomes in Prochilodus lineatus (Characiformes, Prochilodontidae). Genet Mol Biol 2011; 34:220-4. [PMID: 21734820 PMCID: PMC3115313 DOI: 10.1590/s1415-47572011005000009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 11/30/2010] [Indexed: 11/22/2022] Open
Abstract
B chromosomes are supernumerary elements present in about 15% of eukaryotic species and are most frequently heterochromatic, behave parasitically, show a transmission rate higher than standard (A) chromosomes, and can provoke harmful effects on carriers. In the current work, Prochilodus lineatus individuals carrying eight and nine B chromosomes were obtained by induced crossing performed involving breeders with different B chromosome numbers in their cells. The high B chromosome numbers found in the offspring were recorded for the first time in this species. The use of cytogenetic techniques applied in the present study revealed that regardless of the increase in number of B chromosomes in the genome of these individuals, those elements did not presented active genes, and showed their normal heterochromatic characteristic.
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Affiliation(s)
- Tatiana Aparecida Voltolin
- Departamento Ciências Biológicas, Faculdade de Ciências, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Bauru, SP, Brazil
| | - José Augusto Senhorini
- Instituto Chico Mendes de Conservação da Biodiversidade, Centro Nacional de Pesquisa e Conservação de Peixes Continentais, Pirassununga, SP, Brazil
| | - Fausto Foresti
- Departamento de Morfologia, Instituto de Biociências, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Botucatu, SP, Brazil
| | - Jehud Bortolozzi
- Departamento Ciências Biológicas, Faculdade de Ciências, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Bauru, SP, Brazil
| | - Fábio Porto-Foresti
- Departamento Ciências Biológicas, Faculdade de Ciências, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Bauru, SP, Brazil
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19
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Abstract
Although evidence for horizontal gene transfer (HGT) in eukaryotes remains largely anecdotal, literature on HGT in fungi suggests that it may have been more important in the evolution of fungi than in other eukaryotes. Still, HGT in fungi has not been widely accepted because the mechanisms by which it may occur are unknown, because it is usually not directly observed but rather implied as an outcome, and because there are often equally plausible alternative explanations. Despite these reservations, HGT has been justifiably invoked for a variety of sequences including plasmids, introns, transposons, genes, gene clusters, and even whole chromosomes. In some instances HGT has also been confirmed under experimental conditions. It is this ability to address the phenomenon in an experimental setting that makes fungi well suited as model systems in which to study the mechanisms and consequences of HGT in eukaryotic organisms.
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Affiliation(s)
- U Liane Rosewich
- USDA-ARS Cereal Disease Laboratory, University of Minnesota, 1551 Lindig Street, St. Paul, Minnesota 55108; e-mail: ,
| | - H Corby Kistler
- USDA-ARS Cereal Disease Laboratory, University of Minnesota, 1551 Lindig Street, St. Paul, Minnesota 55108; e-mail: ,
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