Sex without crossovers mimics clonal reproduction in Rhynchospora tenuis

Abstract Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes 1 . Although essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy 2 . However, obligate achiasmy in both sexes of a sexual species has not been documented. Here we investigate Rhynchospora tenuis , a flowering plant with the lowest known chromosome number and inverted meiosis 3 . Combining genomics with molecular experiments, we show that R. tenuis undergoes obligate, genome-wide achiasmy in both male and female meiosis. Despite normal early meiotic axis formation, synapsis fails, crossovers are undetectable cytologically and genetically, and univalents persist at metaphase I. Haplotype-specific accumulation of transposable elements generates segregation distortion favouring the transmission of larger, repeat-rich chromosomes. Sexual reproduction is nevertheless retained: fertilization yields viable seeds only when translocation-compatible gametes meet, indicating strong post-meiotic selection against incompatible homozygous combinations. As a result, all surviving offspring are genetically identical, effectively maintaining heterozygosity by sexual reproduction with parental genotype restitution mimicking clonal reproduction. We propose that recombination loss, a low chromosome number, inverted meiosis and selection for compatible gamete combinations together enable faithful segregation and clonal-like inheritance despite sexual reproduction. These findings blur the boundary between sex and clonality, linking genome architecture, recombination loss and transmission bias.

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Journal
Nature
Published
2026-09-16
DOI
https://doi.org/10.1038/s41586-026-11057-7
Primary Topic
Chromosomal and Genetic Variations
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article
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article

Sex without crossovers mimics clonal reproduction in Rhynchospora tenuis

José Antonio Campoy, Duarte D. Figueiredo, André Marques, Korbinian Schneeberger et al.
Nature
Chromosomal and Genetic Variations
article

Sex without crossovers mimics clonal reproduction in Rhynchospora tenuis

José Antonio Campoy, Duarte D. Figueiredo, André Marques, Korbinian Schneeberger, Nafiseh Sargheini, Thiago Nascimento, Thomas Lux, Ulla Neumann, Stefan Steckenborn, Maciej Majka, Ton Timmers, Magdalena Marek, Steven Dreißig, Klaus Mayer, Athul Vijayan, Ursula Pfordt, Gokilavani Thangavel, Meng Zhang, Hequan Sun, Bruno Hüettel, Marco Castellani, Paulo G. Hofstatter, Georgios Tsipas, Andre L. L. Vanzela, Lorraine Deberon, Laura A. Robledillo
article en

Abstract

Abstract Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes 1 . Although essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy 2 . However, obligate achiasmy in both sexes of a sexual species has not been documented. Here we investigate Rhynchospora tenuis , a flowering plant with the lowest known chromosome number and inverted meiosis 3 . Combining genomics with molecular experiments, we show that R. tenuis undergoes obligate, genome-wide achiasmy in both male and female meiosis. Despite normal early meiotic axis formation, synapsis fails, crossovers are undetectable cytologically and genetically, and univalents persist at metaphase I. Haplotype-specific accumulation of transposable elements generates segregation distortion favouring the transmission of larger, repeat-rich chromosomes. Sexual reproduction is nevertheless retained: fertilization yields viable seeds only when translocation-compatible gametes meet, indicating strong post-meiotic selection against incompatible homozygous combinations. As a result, all surviving offspring are genetically identical, effectively maintaining heterozygosity by sexual reproduction with parental genotype restitution mimicking clonal reproduction. We propose that recombination loss, a low chromosome number, inverted meiosis and selection for compatible gamete combinations together enable faithful segregation and clonal-like inheritance despite sexual reproduction. These findings blur the boundary between sex and clonality, linking genome architecture, recombination loss and transmission bias.

Nature
Karlsruhe Institute of Technology (DE), Universidade Estadual de Londrina (BR), Universidade de São Paulo (BR), German Centre for Integrative Biodiversity Research (DE), Helmholtz Zentrum München (DE), Max Planck Institute of Molecular Plant Physiology (DE), Cluster of Excellence on Plant Sciences (DE), Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK) (DE), Max Planck Institute for Plant Breeding Research (DE), Estación Experimental de Aula Dei (ES), Leibniz-Institute for Food Systems Biology at the Technical University of Munich (DE), Institute of Plant Genetics, Polish Academy of Sciences (PL), Heinrich Heine University Düsseldorf (DE), University of York (GB), Technical University of Munich (DE), Xi'an Jiaotong University (CN), Polish Academy of Sciences (PL)
Openalex Percentile: Top 13%
Chromosomal and Genetic Variations
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