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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] [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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Svačina R, Hloušková L, Karafiátová M, Bartoš J. Scoring the number of B chromosomes in Zea mays L. using droplet digital PCR assay. PLANT METHODS 2023; 19:43. [PMID: 37131220 PMCID: PMC10155399 DOI: 10.1186/s13007-023-01019-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 04/21/2023] [Indexed: 05/04/2023]
Abstract
BACKGROUND B chromosomes are classified as dispensable genomic components tolerated by cells, which are transmitted to progeny despite providing no benefit in most cases. They have been observed in over 2800 species of plants, animals and fungi, including numerous maize accessions. As maize is one of the most important crops worldwide, research on the maize B chromosome has been pioneering in the field. The characteristic of the B chromosome is its irregular inheritance. This results in offspring with a different number of B chromosomes compared to the parents. However, the exact number of B chromosomes in the studied plants is a crucial piece of information. Currently, assessing the number of B chromosomes in maize largely depends on cytogenetic analyses, which are laborious and time-consuming. We present an alternative approach based on the droplet digital PCR technique (ddPCR), which is faster, more efficient and provides the results within one day with the same level of accuracy. RESULTS In this study, we report a rapid and straightforward protocol for determining the number of B chromosomes in maize plants. We developed a droplet digital PCR assay using specific primers and a TaqMan probe for the B-chromosome-linked gene and a single-copy reference gene on maize chromosome 1. The performance of the assay was successfully verified by comparison with the results of cytogenetic analyses performed in parallel. CONCLUSIONS The protocol significantly improves the efficiency of B chromosome number assessment in maize compared to cytogenetic approaches. The assay has been developed to target conserved genomic regions and can therefore be applied to a wide range of diverged maize accessions. This universal approach can be modified for chromosome number detection in other species, not only for the B chromosome but also for any other chromosome in aneuploid constitution.
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Affiliation(s)
- Radim Svačina
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Šlechtitelů 31, 779 00, Olomouc, Czech Republic
- Plant Science Program, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
- KAUST Center for Desert Agriculture, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Lucie Hloušková
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Šlechtitelů 31, 779 00, Olomouc, Czech Republic
- Department of Cell Biology and Genetics, Faculty of Science, Palacký University, Šlechtitelů 27, 779 00, Olomouc, Czech Republic
| | - Miroslava Karafiátová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Šlechtitelů 31, 779 00, Olomouc, Czech Republic
| | - Jan Bartoš
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Šlechtitelů 31, 779 00, Olomouc, Czech Republic.
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Rajpal VR, Sharma S, Sehgal D, Sharma P, Wadhwa N, Dhakate P, Chandra A, Thakur RK, Deb S, Rama Rao S, Mir BA, Raina SN. Comprehending the dynamism of B chromosomes in their journey towards becoming unselfish. Front Cell Dev Biol 2023; 10:1072716. [PMID: 36684438 PMCID: PMC9846793 DOI: 10.3389/fcell.2022.1072716] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 12/13/2022] [Indexed: 01/06/2023] Open
Abstract
Investigated for more than a century now, B chromosomes (Bs) research has come a long way from Bs being considered parasitic or neutral to becoming unselfish and bringing benefits to their hosts. B chromosomes exist as accessory chromosomes along with the standard A chromosomes (As) across eukaryotic taxa. Represented singly or in multiple copies, B chromosomes are largely heterochromatic but also contain euchromatic and organellar segments. Although B chromosomes are derived entities, they follow their species-specific evolutionary pattern. B chromosomes fail to pair with the standard chromosomes during meiosis and vary in their number, size, composition and structure across taxa and ensure their successful transmission through non-mendelian mechanisms like mitotic, pre-meiotic, meiotic or post-meiotic drives, unique non-disjunction, self-pairing or even imparting benefits to the host when they lack drive. B chromosomes have been associated with cellular processes like sex determination, pathogenicity, resistance to pathogens, phenotypic effects, and differential gene expression. With the advancements in B-omics research, novel insights have been gleaned on their functions, some of which have been associated with the regulation of gene expression of A chromosomes through increased expression of miRNAs or differential expression of transposable elements located on them. The next-generation sequencing and emerging technologies will further likely unravel the cellular, molecular and functional behaviour of these enigmatic entities. Amidst the extensive fluidity shown by B chromosomes in their structural and functional attributes, we perceive that the existence and survival of B chromosomes in the populations most likely seem to be a trade-off between the drive efficiency and adaptive significance versus their adverse effects on reproduction.
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Affiliation(s)
- Vijay Rani Rajpal
- Department of Botany, Hansraj College, University of Delhi, Delhi, India,*Correspondence: Vijay Rani Rajpal, , ; Soom Nath Raina,
| | - Suman Sharma
- Department of Botany, Ramjas College, University of Delhi, Delhi, India
| | - Deepmala Sehgal
- Syngenta, International Maize and Wheat Improvement Center (CIMMYT), Texcoco, Mexico
| | - Prashansa Sharma
- Department of Botany, Hansraj College, University of Delhi, Delhi, India
| | - Nikita Wadhwa
- University School of Biotechnology, Guru Gobind Singh Indraprastha University, New Delhi, India
| | | | - Atika Chandra
- Department of Botany, Maitreyi College, University of Delhi, New Delhi, India
| | - Rakesh Kr. Thakur
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India
| | - Sohini Deb
- Department of Biotechnology and Bioinformatics, North Eastern Hill University, Shillong, Meghalaya, India
| | - Satyawada Rama Rao
- Department of Biotechnology and Bioinformatics, North Eastern Hill University, Shillong, Meghalaya, India
| | - Bilal Ahmad Mir
- Department of Botany, University of Kashmir, Srinagar, India
| | - Soom Nath Raina
- Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, India,*Correspondence: Vijay Rani Rajpal, , ; Soom Nath Raina,
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Cardoso AL, Venturelli NB, da Cruz I, de Sá Patroni FM, de Moraes D, de Oliveira RA, Benavente R, Martins C. Meiotic behavior, transmission and active genes of B chromosomes in the cichlid Astatotilapia latifasciata: new clues about nature, evolution and maintenance of accessory elements. Mol Genet Genomics 2022; 297:1151-1167. [PMID: 35704117 DOI: 10.1007/s00438-022-01911-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 05/24/2022] [Indexed: 12/23/2022]
Abstract
Supernumerary B chromosomes (Bs) are dispensable genetic elements widespread in eukaryotes and are poorly understood mainly in relation to mechanisms of maintenance and transmission. The cichlid Astatotilapia latifasciata can harbor Bs in a range of 0 (named B -) and 1-2 (named B +). The B in A. latifasciata is rich in several classes of repetitive DNA sequences, contains protein coding genes, and affects hosts in diverse ways, including sex-biased effects. To advance in the knowledge about the mechanisms of maintenance and transmission of B chromosomes in A. latifasciata, here, we studied the meiotic behavior in males and transmission rates of A. latifasciata B chromosome. We also analyzed structurally and functionally the predicted B chromosome copies of the cell cycle genes separin-like, tubb1-like and kif11-like. We identified in the meiotic structure relative to the B chromosome the presence of proteins associated with Synaptonemal Complex organization (SMC3, SYCP1 and SYCP3) and found that the B performs self-pairing. These data suggest that isochromosome formation was a step during B chromosome evolution and this element is in a stage of diversification of the two arms keeping the self-pairing behavior to protect the A chromosome complement of negative effects of recombination. Moreover, we observed no occurrence of B-drive and confirmed the presence of cell cycle genes copies in the B chromosome and their transcription in encephalon, muscle and gonads, which can indicates beneficial effects to hosts and contribute to B maintenance.
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Affiliation(s)
- Adauto Lima Cardoso
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, SP, 18618-689, Brazil
| | - Natália Bortholazzi Venturelli
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, SP, 18618-689, Brazil
| | - Irene da Cruz
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, 97074, Würzburg, Germany
| | - Fábio Malta de Sá Patroni
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, SP, 18618-689, Brazil
| | - Diogo de Moraes
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, SP, 18618-689, Brazil
| | - Rogério Antonio de Oliveira
- Department of Biostatistics, Plant Biology, Parasitology and Zoology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Ricardo Benavente
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, 97074, Würzburg, Germany
| | - Cesar Martins
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, Sao Paulo State University, UNESP, Botucatu, SP, 18618-689, Brazil.
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Abstract
The supernumerary B chromosome of maize is dispensable, containing no vital genes, and thus is variable in number and presence in lines of maize. In order to be maintained in populations, it has a drive mechanism consisting of nondisjunction at the pollen mitosis that produces the two sperm cells, and then the sperm with the two B chromosomes has a preference for fertilizing the egg as opposed to the central cell in the process of double fertilization. The sequence of the B chromosome coupled with B chromosomal aberrations has localized features involved with nondisjunction and preferential fertilization, which are present at the centromeric region. The predicted genes from the sequence have paralogues dispersed across all A chromosomes and have widely different divergence times suggesting that they have transposed to the B chromosome over evolutionary time followed by degradation or have been co-opted for the selfish functions of the supernumerary chromosome.
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Affiliation(s)
- James A. Birchler
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Hua Yang
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
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The r-X1 deletion induces terminal deficiencies in the maize B chromosome. Chromosome Res 2021; 29:351-360. [PMID: 34480269 DOI: 10.1007/s10577-021-09671-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 08/16/2021] [Accepted: 08/20/2021] [Indexed: 10/20/2022]
Abstract
In addition to causing the nondisjunction of maize B and normal A chromosomes at the second megaspore division during embryo sac development, the r-X1 deletion results in terminal deficiencies (TDs) in various A chromosomal arms, but whether the r-X1 deletion also induces TDs of the maize B chromosome remains unknown. To answer this question, the chromosomal composition in the r-X1-containing progeny of r-X1/R-r female parents carrying two standard B chromosomes was determined. Nine of 104 (8.7%) examined kernels contained a smaller telocentric B chromosome, and one of these (designated Bdef-1) was further identified as a TD with a breakpoint in the third distal heterochromatic region of the B chromosome. Thus, the results indicated that the r-X1 deletion could also induce TDs of the maize B chromosome during megaspore divisions. The Bdef-1 chromosome lacked nondisjunctional behavior, and this behavior was restored by the presence of the B chromosome in the cell. A transmission analysis of the Bdef-1 chromosome revealed that loss of the distal portion of the B chromosome reduced female but not male transmission of the B chromosome. Furthermore, the Bdef-1 chromosome was used to more finely map B-derived miRNA genes on the B chromosome. Our results indicate that the r-X1 deletion results in TDs of the B chromosome in maize, and the r-X1 deletion system can thus be used to generate a series of terminally truncated B chromosomes that may be used to map features of the B chromosome, including genes and properties related to B chromosome functions.
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Martins C, Jehangir M. A genomic glimpse of B chromosomes in cichlids. Genes Genomics 2021; 43:199-208. [PMID: 33547625 DOI: 10.1007/s13258-021-01049-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 01/11/2021] [Indexed: 01/25/2023]
Abstract
BACKGROUND B chromosomes (Bs) are extra karyotype elements in addition to A chromosomes and are found in all major eukaryotic taxa. Among hundreds of investigated species, cichlid fishes have emerged as an interesting group of model and have contributed to unravel the complex biology of B chromosome. OBJECTIVE We review the current state of knowledge on B chromosome investigation in cichlid fish and discuss the recent genomic advances over gene and sequences hunting on Bs and their impact on the current concept of B chromosomes. RESULTS The Bs of cichlids have been under the subject of classical cytogenetics and high scale DNA, RNA and epigenetics analysis and a list of B chromosome genes and functional sequences has been generated. B chromosomes of cichlids are restricted to females in some species and are enriched with genes, relics of genes, transposable elements and sequences transcribing for many significant biological functions. Diverse potentially functional sequences have been described in the B chromosome of cichlids and could influence important biological characteristics as well seems to affect transcription and epigenetic modifications of the whole genome. CONCLUSION One of the most enigmatic characteristics of Bs in cichlids is their genic content related to cell cycle and chromosome structure, and their influence over sex rates. The relationship of Bs with cell cycle and sex determination looks like to be connected with the drive of the Bs during cell divisions.
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Affiliation(s)
- Cesar Martins
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, São Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil.
| | - Maryam Jehangir
- Department of Structural and Functional Biology, Institute of Biosciences at Botucatu, São Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
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Ahmad SF, Jehangir M, Cardoso AL, Wolf IR, Margarido VP, Cabral-de-Mello DC, O'Neill R, Valente GT, Martins C. B chromosomes of multiple species have intense evolutionary dynamics and accumulated genes related to important biological processes. BMC Genomics 2020; 21:656. [PMID: 32967626 PMCID: PMC7509943 DOI: 10.1186/s12864-020-07072-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 09/14/2020] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND One of the biggest challenges in chromosome biology is to understand the occurrence and complex genetics of the extra, non-essential karyotype elements, commonly known as supernumerary or B chromosomes (Bs). The non-Mendelian inheritance and non-pairing abilities of B chromosomes make them an interesting model for genomics studies, thus bringing to bear different questions about their genetic composition, evolutionary survival, maintenance and functional role inside the cell. This study uncovers these phenomena in multiple species that we considered as representative organisms of both vertebrate and invertebrate models for B chromosome analysis. RESULTS We sequenced the genomes of three animal species including two fishes Astyanax mexicanus and Astyanax correntinus, and a grasshopper Abracris flavolineata, each with and without Bs, and identified their B-localized genes and repeat contents. We detected unique sequences occurring exclusively on Bs and discovered various evolutionary patterns of genomic rearrangements associated to Bs. In situ hybridization and quantitative polymerase chain reactions further validated our genomic approach confirming detection of sequences on Bs. The functional annotation of B sequences showed that the B chromosome comprises regions of gene fragments, novel genes, and intact genes, which encode a diverse set of functions related to important biological processes such as metabolism, morphogenesis, reproduction, transposition, recombination, cell cycle and chromosomes functions which might be important for their evolutionary success. CONCLUSIONS This study reveals the genomic structure, composition and function of Bs, which provide new insights for theories of B chromosome evolution. The selfish behavior of Bs seems to be favored by gained genes/sequences.
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Affiliation(s)
- Syed F Ahmad
- Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Maryam Jehangir
- Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Adauto L Cardoso
- Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Ivan R Wolf
- Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil
| | - Vladimir P Margarido
- Western Paraná State University (UNIOESTE), Center for Biology Science and Health, Cascavel, PR, Brazil
| | - Diogo C Cabral-de-Mello
- Department of General and Applied Biology, Institute of Biosciences, Sao Paulo State University (UNESP), Rio Claro, SP, Brazil
| | - Rachel O'Neill
- Department of Molecular and Cell Biology, University of Connecticut (UCONN), Storrs, CT, USA
- Institute for Systems Genomics, University of Connecticut (UCONN), Storrs, CT, USA
| | - Guilherme T Valente
- Bioprocess and Biotechnology Department, Agronomical Science Faculty, Sao Paulo State University - UNESP, Botucatu, SP, Brazil
| | - Cesar Martins
- Department of Structural and Functional Biology, Institute of Bioscience at Botucatu, Sao Paulo State University (UNESP), Botucatu, SP, 18618-689, Brazil.
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