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Unnikrishnan R, Balakrishnan S, Sumod M, Sujanapal P, Balan B, Dev SA. Gender specific SNP markers in Coscinium fenestratum (Gaertn.) Colebr. for resource augmentation. Mol Biol Rep 2024; 51:93. [PMID: 38194000 DOI: 10.1007/s11033-023-09044-6] [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: 02/06/2023] [Accepted: 11/06/2023] [Indexed: 01/10/2024]
Abstract
BACKGROUND Unregulated extraction of highly traded medicinal plant species results in drastic decline of the natural resources and alters viable sex ratio of populations. Conservation and long-term survival of such species, require gender specific restoration programs to ensure reproductive success. However, it is often difficult to differentiate sex of individuals before reaching reproductive maturity. C. fenestratum is one of the medicinally important and overexploited dioecious woody liana, with a reproductive maturity of 15 years. Currently, no information is available to identify sex of C. fenestratum in seedling stage while augmenting the resources. Thus, the current study envisages to utilize transcriptomics approach for gender differentiation which is imperative for undertaking viable resource augmentation programmes. METHODS AND RESULTS Gender specific SNPs with probable role in sexual reproduction/sex determination was located using comparative transcriptomics approach (sampling male and female individuals), alongside gene ontology and annotation. Nine sets of primers were synthesized from 7 transcripts (involved in sexual reproduction/other biological process) containing multiple SNP variants. Out of the nine primer pairs, only one SNP locus with no available information of its role in reproduction, showed consistent and accurate results (males-heterozygous and females-homozygous), in the analyzed 40 matured individuals of known sexes. Thus validated the efficiency of this SNP marker in differentiating male and female individuals. CONCLUSIONS The study could identify SNPs linked to the loci with apparent role in gender differentiation. This SNP marker can be used for early sexing of seedlings for in-situ conservation and resource augmentation of C. fenestratum in Kerala, India.
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Affiliation(s)
- Remya Unnikrishnan
- Forest Genetics and Biotechnology Division, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India
- Cochin University of Science & Technology, Kochi, Kerala, India
| | - Swathi Balakrishnan
- Forest Genetics and Biotechnology Division, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India
- Cochin University of Science & Technology, Kochi, Kerala, India
| | - M Sumod
- Sustainable Forest Management Division, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India
| | - P Sujanapal
- Sustainable Forest Management Division, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India
| | - Bipin Balan
- Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze-Ed. 4, Palermo, 90128, Italy
| | - Suma Arun Dev
- Forest Genetics and Biotechnology Division, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India.
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Zhang GJ, Jia KL, Wang J, Gao WJ, Li SF. Genome-wide analysis of transposable elements and satellite DNA in Humulus scandens, a dioecious plant with XX/XY 1Y 2 chromosomes. FRONTIERS IN PLANT SCIENCE 2023; 14:1230250. [PMID: 37908838 PMCID: PMC10614002 DOI: 10.3389/fpls.2023.1230250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Accepted: 10/04/2023] [Indexed: 11/02/2023]
Abstract
Transposable elements (TEs) and satellite DNAs, two major categories of repetitive sequences, are expected to accumulate in non-recombining genome regions, including sex-linked regions, and contribute to sex chromosome evolution. The dioecious plant, Humulus scandens, can be used for studying the evolution of the XX/XY1Y2 sex chromosomes. In this study, we thoroughly examined the repetitive components of male and female H. scandens using next-generation sequencing data followed by bioinformatics analysis and florescence in situ hybridization (FISH). The H. scandens genome has a high overall repetitive sequence composition, 68.30% in the female and 66.78% in the male genome, with abundant long terminal repeat (LTR) retrotransposons (RTs), including more Ty3/Gypsy than Ty1/Copia elements, particularly two Ty3/Gypsy lineages, Tekay and Retand. Most LTR-RT lineages were found dispersed across the chromosomes, though CRM and Athila elements were predominately found within the centromeres and the pericentromeric regions. The Athila elements also showed clearly higher FISH signal intensities in the Y1 and Y2 chromosomes than in the X or autosomes. Three novel satellite DNAs were specifically distributed in the centromeric and/or telomeric regions, with markedly different distributions on the X, Y1, and Y2 chromosomes. Combined with FISH using satellite DNAs to stain chromosomes during meiotic diakinesis, we determined the synapsis pattern and distinguish pseudoautosomal regions (PARs). The results indicate that the XY1Y2 sex chromosomes of H. scandens might have originated from a centric fission event. This study improves our understanding of the repetitive sequence organization of H. scandens genome and provides a basis for further analysis of their chromosome evolution process.
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Affiliation(s)
- Guo-Jun Zhang
- School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, China
- College of Life Sciences, Henan Normal University, Xinxiang, China
| | - Ke-Li Jia
- College of Life Sciences, Henan Normal University, Xinxiang, China
- SanQuan Medical College, Xinxiang Medical University, Xinxiang, China
| | - Jin Wang
- College of Life Sciences, Henan Normal University, Xinxiang, China
| | - Wu-Jun Gao
- College of Life Sciences, Henan Normal University, Xinxiang, China
| | - Shu-Fen Li
- College of Life Sciences, Henan Normal University, Xinxiang, China
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3
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Wu W, Jernstedt J, Mesgaran MB. Comparative floral development in male and female plants of Palmer amaranth (Amaranthus palmeri). AMERICAN JOURNAL OF BOTANY 2023; 110:e16212. [PMID: 37459554 DOI: 10.1002/ajb2.16212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 05/25/2023] [Accepted: 05/25/2023] [Indexed: 08/12/2023]
Abstract
PREMISE Characterizing the developmental processes in the transition from hermaphroditism to unisexuality is crucial for understanding floral evolution. Amaranthus palmeri, one of the most devastating weeds in the United States, is an emerging model system for studying a dioecious breeding system and understanding the biological traits of this invasive weed. The objectives of this study were to characterize phases of flower development in A. palmeri and compare organogenesis of flower development in female and male plants. METHODS Flower buds from male and female plants were dissected for light microscopy. Segments of male and female inflorescences at different stages of development were cut longitudinally and visualized using scanning electron microscopy. RESULTS Pistillate flowers have two to three styles, one ovary with one ovule, and five obtuse tepals. Staminate flowers have five stamens with five acute tepals. Floral development was classified into 10 stages. The distinction between the two flower types became apparent at stage four by the formation of stamen primordia in staminate flowers, which developed female and male reproductive organs initially, as contrasted to pistillate flowers, which produced carpel primordia only. In staminate flowers, the putative carpel primordia changed little in size and remained undeveloped. CONCLUSIONS Timing of inappropriate organ termination varies across the two sexes in A. palmeri. Our study suggests that the evolution of A. palmeri from a cosexual ancestral state to complete dioecy is still in progress since males exhibited transient hermaphroditism and females produced strictly pistillate flowers.
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Affiliation(s)
- Wenzhuo Wu
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Judy Jernstedt
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
| | - Mohsen B Mesgaran
- Department of Plant Sciences, University of California, Davis, 95616, CA, USA
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Garcia S, Janousek B, Pascual-Díaz JP, Renner SS. Sex-chrom v. 2.0: a database of green plant species with sex chromosomes. Chromosoma 2023; 132:55-58. [PMID: 36725728 DOI: 10.1007/s00412-023-00786-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 02/03/2023]
Affiliation(s)
- Sònia Garcia
- Institut Botànic de Barcelona (IBB-CSIC), Passeig del Migdia S/N, 08038, Barcelona, Catalonia, Spain.
| | - Bohuslav Janousek
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65, Brno, Czech Republic
| | - Joan Pere Pascual-Díaz
- Institut Botànic de Barcelona (IBB-CSIC), Passeig del Migdia S/N, 08038, Barcelona, Catalonia, Spain
| | - Susanne S Renner
- Department of Biology, Washington University, Saint Louis, MO, 63130, USA
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Wang Y, Cai X, Zhang Y, Hörandl E, Zhang Z, He L. The male-heterogametic sex determination system on chromosome 15 of Salix triandra and Salix arbutifolia reveals ancestral male heterogamety and subsequent turnover events in the genus Salix. Heredity (Edinb) 2023; 130:122-134. [PMID: 36593355 PMCID: PMC9981616 DOI: 10.1038/s41437-022-00586-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 01/03/2023] Open
Abstract
Dioecious Salix evolved more than 45 million years ago, but have homomorphic sex chromosomes, suggesting that turnover event(s) prevented major differentiation. Sex chromosome turnover events have been inferred in the sister genus Populus. The genus Salix includes two main clades, Salix and Vetrix, with several previously studied Vetrix clade species having female-heterogametic (ZW) or male-heterogametic (XY) sex-determining systems (SDSs) on chromosome 15, while three Salix clade species have XY SDSs on chromosome 7. We here studied two basal taxa of the Vetrix clade, S. arbutifolia and S. triandra using S. purpurea as the reference genome. Analyses of whole genome resequencing data for genome-wide associations (GWAS) with the sexes and genetic differentiation between the sexes (FST values) showed that both species have male heterogamety with a sex-determining locus on chromosome 15, suggesting an early turnover event within the Vetrix clade, perhaps promoted by sexually antagonistic or (and) sex-ratio selection. Changepoint analysis based on FST values identified small sex-linked regions of ~3.33 Mb and ~2.80 Mb in S. arbutifolia and S. triandra, respectively. The SDS of S. arbutifolia was consistent with recent results that used its own genome as reference. Ancestral state reconstruction of SDS suggests that at least two turnover events occurred in Salix.
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Affiliation(s)
- Yi Wang
- Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, China
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China
| | - Xinjie Cai
- College of Forestry, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yue Zhang
- Shenyang Arboretum, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China
| | - Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, Göttingen, Germany
| | - Zhixiang Zhang
- Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, China.
| | - Li He
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China.
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Gutiérrez ML, Rodríguez-González R, Pascual-Díaz JP, Fuentes I, Garcia S. Online Resources Useful for Plant Cytogenetics and Cytogenomics Research. Methods Mol Biol 2023; 2672:549-560. [PMID: 37335499 DOI: 10.1007/978-1-0716-3226-0_33] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
The advancements in research in the field of plant cytogenetics and genomics in recent decades have led to a significant increase in publications. To simplify access to the widely dispersed data, there has been a rise in the number of online databases, repositories, and analytical tools. This chapter presents a comprehensive overview of these resources, which can be beneficial to researchers in these areas. It includes, among others, databases on chromosome numbers, special chromosomes (such as B chromosomes or sex chromosomes), some of which are taxon-specific; genome sizes, cytogenetics; and online applications and tools for genomic analysis and visualization.
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Affiliation(s)
| | | | | | - Inés Fuentes
- Institut Botànic de Barcelona (IBB-CSIC), Barcelona, Catalonia, Spain
| | - Sònia Garcia
- Institut Botànic de Barcelona (IBB-CSIC), Barcelona, Catalonia, Spain.
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He L, Hörandl E. Does polyploidy inhibit sex chromosome evolution in angiosperms? FRONTIERS IN PLANT SCIENCE 2022; 13:976765. [PMID: 36212292 PMCID: PMC9541106 DOI: 10.3389/fpls.2022.976765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 08/24/2022] [Indexed: 06/16/2023]
Abstract
Dioecy is rare in flowering plants (5-6% of species), but is often controlled genetically by sex-linked regions (SLRs). It has so far been unclear whether, polyploidy affects sex chromosome evolution, as it does in animals, though polyploidy is quite common in angiosperms, including in dioecious species. Plants could be different, as, unlike many animal systems, degenerated sex chromosomes, are uncommon in plants. Here we consider sex determination in plants and plant-specific factors, and propose that constraints created at the origin of polyploids limit successful polyploidization of species with SLRs. We consider the most likely case of a polyploid of a dioecious diploid with an established SLR, and discuss the outcome in autopolyploids and allopolyploids. The most stable system possibly has an SLR on just one chromosome, with a strongly dominant genetic factor in the heterogametic sex (e.g., xxxY male in a tetraploid). If recombination occurs with its homolog, this will prevent Y chromosome degeneration. Polyploidy may also allow for reversibility of multiplied Z or X chromosomes into autosomes. Otherwise, low dosage of Y-linked SLRs compared to their multiple homologous x copies may cause loss of reliable sex-determination at higher ploidy levels. We discuss some questions that can be studied using genome sequencing, chromosome level-assemblies, gene expression studies and analysis of loci under selection.
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Affiliation(s)
- Li He
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China
| | - Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants, University of Göttingen, Göttingen, Germany
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Zhang X, Pan L, Guo W, Li Y, Wang W. A convergent mechanism of sex determination in dioecious plants: Distinct sex-determining genes display converged regulation on floral B-class genes. FRONTIERS IN PLANT SCIENCE 2022; 13:953445. [PMID: 36092432 PMCID: PMC9459113 DOI: 10.3389/fpls.2022.953445] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 06/27/2022] [Indexed: 06/12/2023]
Abstract
Sex determination in dioecious plants has been broadly and progressively studied with the blooming of genome sequencing and editing techniques. This provides us with a great opportunity to explore the evolution and genetic mechanisms underlining the sex-determining system in dioecious plants. In this study, comprehensively reviewing advances in sex-chromosomes, sex-determining genes, and floral MADS-box genes in dioecious plants, we proposed a convergent model that governs plant dioecy across divergent species using a cascade regulation pathway connecting sex-determining genes and MADS-box genes e.g., B-class genes. We believe that this convergent mechanism of sex determination in dioecious plants will shed light on our understanding of gene regulation and evolution of plant dioecy. Perspectives concerning the evolutionary pathway of plant dioecy are also suggested.
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Affiliation(s)
- Xianzhi Zhang
- Department of Horticulture, College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Linsi Pan
- Department of Horticulture, College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Wei Guo
- Department of Horticulture, College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Yongquan Li
- Department of Horticulture, College of Horticulture and Landscape Architecture, Zhongkai University of Agriculture and Engineering, Guangzhou, China
| | - Wencai Wang
- Department of Molecular of Biology, Science and Technology Innovation Center, Guangzhou University of Chinese Medicine, Guangzhou, China
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Al‐Dossary O, Alsubaie B, Kharabian‐Masouleh A, Al‐Mssallem I, Furtado A, Henry RJ. The jojoba genome reveals wide divergence of the sex chromosomes in a dioecious plant. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1283-1294. [PMID: 34570389 PMCID: PMC9293028 DOI: 10.1111/tpj.15509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 09/20/2021] [Indexed: 06/13/2023]
Abstract
Most flowering plants are hermaphrodites, but around 6% of species are dioecious, having separate male and female plants. Sex chromosomes and some sex-specific genes have been reported in plants, but the genome sequences have not been compared. We now report the genome sequence of male and female jojoba (Simmondsia chinensis) plants, revealing a very large difference in the sex chromosomes. The male genome assembly was 832 Mb and the female 822 Mb. This was explained by the large size differences in the Y chromosome (37.6 Mb) compared with the X chromosome (26.9 Mb). Relative to the X chromosome, the Y chromosome had two large insertions each of more than 5 Mb containing more than 400 genes. Many of the genes in the chromosome-specific regions were novel. These male-specific regions included many flowering-related and stress response genes. Smaller insertions found only in the X chromosome totalled 877 kb. The wide divergence of the sex chromosomes suggests a long period of adaptation to diverging sex-specific roles. Male and female plants may have evolved to accommodate factors such as differing reproductive resource allocation requirements under the stress of the desert environment in which the plants are found. The sex-determining regions accumulate genes beneficial to each sex. This has required the evolution of many more novel sex-specific genes than has been reported for other organisms. This suggest that dioecious plants provide a novel source of genes for manipulation of reproductive performance and environmental adaptation in crops.
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Affiliation(s)
- Othman Al‐Dossary
- Queensland Alliance for Agriculture and Food InnovationUniversity of QueenslandBrisbane4072Australia
- College of Agriculture and Food SciencesKing Faisal UniversityAl Hofuf36362Saudi Arabia
| | - Bader Alsubaie
- Queensland Alliance for Agriculture and Food InnovationUniversity of QueenslandBrisbane4072Australia
- College of Agriculture and Food SciencesKing Faisal UniversityAl Hofuf36362Saudi Arabia
| | | | - Ibrahim Al‐Mssallem
- College of Agriculture and Food SciencesKing Faisal UniversityAl Hofuf36362Saudi Arabia
| | - Agnelo Furtado
- Queensland Alliance for Agriculture and Food InnovationUniversity of QueenslandBrisbane4072Australia
| | - Robert J. Henry
- Queensland Alliance for Agriculture and Food InnovationUniversity of QueenslandBrisbane4072Australia
- ARC Centre of Excellence for Plant Success in Nature and AgricultureUniversity of QueenslandBrisbane4072Australia
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Prentout D, Stajner N, Cerenak A, Tricou T, Brochier-Armanet C, Jakse J, Käfer J, Marais GAB. Plant genera Cannabis and Humulus share the same pair of well-differentiated sex chromosomes. THE NEW PHYTOLOGIST 2021; 231:1599-1611. [PMID: 33978992 DOI: 10.1111/nph.17456] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
We recently described, in Cannabis sativa, the oldest sex chromosome system documented so far in plants (12-28 Myr old). Based on the estimated age, we predicted that it should be shared by its sister genus Humulus, which is known also to possess XY chromosomes. Here, we used transcriptome sequencing of an F1 family of H. lupulus to identify and study the sex chromosomes in this species using the probabilistic method SEX-DETector. We identified 265 sex-linked genes in H. lupulus, which preferentially mapped to the C. sativa X chromosome. Using phylogenies of sex-linked genes, we showed that a region of the sex chromosomes had already stopped recombining in an ancestor of both species. Furthermore, as in C. sativa, Y-linked gene expression reduction is correlated to the position on the X chromosome, and highly Y degenerated genes showed dosage compensation. We report, for the first time in Angiosperms, a sex chromosome system that is shared by two different genera. Thus, recombination suppression started at least 21-25 Myr ago, and then (either gradually or step-wise) spread to a large part of the sex chromosomes (c. 70%), leading to a degenerated Y chromosome.
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Affiliation(s)
- Djivan Prentout
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, F-69622, France
| | - Natasa Stajner
- Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, Ljubljana, SI-1000, Slovenia
| | - Andreja Cerenak
- Slovenian Institute of Hop Research and Brewing, Cesta Zalskega Tabora 2, Zalec, SI-3310, Slovenia
| | - Theo Tricou
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, F-69622, France
| | - Celine Brochier-Armanet
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, F-69622, France
| | - Jernej Jakse
- Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, Ljubljana, SI-1000, Slovenia
| | - Jos Käfer
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, F-69622, France
| | - Gabriel A B Marais
- Laboratoire de Biométrie et Biologie Evolutive, UMR 5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, F-69622, France
- LEAF- Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, 1349-017, Portugal
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Renner SS, Müller NA. Plant sex chromosomes defy evolutionary models of expanding recombination suppression and genetic degeneration. NATURE PLANTS 2021; 7:392-402. [PMID: 33782581 DOI: 10.1038/s41477-021-00884-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 02/18/2021] [Indexed: 05/17/2023]
Abstract
Hundreds of land plant lineages have independently evolved separate sexes in either gametophytes (dioicy) or sporophytes (dioecy), but 43% of all dioecious angiosperms are found in just 34 entirely dioecious clades, suggesting that their mode of sex determination evolved a long time ago. Here, we review recent insights on the molecular mechanisms that underlie the evolutionary change from individuals that each produce male and female gametes to individuals specializing in the production of just one type of gamete. The canonical model of sex chromosome evolution in plants predicts that two sex-determining genes will become linked in a sex-determining region (SDR), followed by expanding recombination suppression, chromosome differentiation and, ultimately, degeneration. Experimental work, however, is showing that single genes function as master regulators in model systems, such as the liverwort Marchantia and the angiosperms Diospyros and Populus. In Populus, this type of regulatory function has been demonstrated by genome editing. In other systems, including Actinidia, Asparagus and Vitis, two coinherited factors appear to independently regulate female and male function, yet sex chromosome differentiation has remained low. We discuss the best-understood systems and evolutionary pathways to dioecy, and present a meta-analysis of the sizes and ages of SDRs. We propose that limited sexual conflict explains why most SDRs are small and sex chromosomes remain homomorphic. It appears that models of increasing recombination suppression with age do not apply because selection favours mechanisms in which sex determination depends on minimal differences, keeping it surgically precise.
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Affiliation(s)
- Susanne S Renner
- Systematic Botany and Mycology, University of Munich (LMU), Munich, Germany.
| | - Niels A Müller
- Thünen Institute of Forest Genetics, Grosshansdorf, Germany.
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