2026-09-16 マックス・プランク研究所
The Brazilian beak-sedge Rhynchospora tenuis © Maciej Majka
＜関連情報＞
- https://www.mpg.de/26975614/sex-without-the-shuffle-a-plant-that-breaks-the-rules-of-inheritance
- https://www.nature.com/articles/s41586-026-11057-7
Rhynchospora tenuisにおける、組み換えのない有性生殖はクローン繁殖を模倣している Sex without crossovers mimics clonal reproduction in Rhynchospora tenuis
Meng Zhang (张萌), Marco Castellani, Stefan Steckenborn, Maciej Majka, Georgios Tsipas, Thiago Nascimento, Ulla Neumann, Gokilavani Thangavel, Laura A. Robledillo, Thomas Lux, Lorraine Deberón, Ursula Pfordt, José A. Campoy, Athul Vijayan, Ton Timmers, Nafiseh Sargheini, Magdalena Marek, Hequan Sun, Paulo G. Hofstatter, Bruno Huettel, Steven Dreissig, Klaus F. X. Mayer, Duarte D. Figueiredo, André L. L. Vanzela, … André Marques
Nature Published:16 September 2026
DOI:https://doi.org/10.1038/s41586-026-11057-7
Abstract
Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes1. Although essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy2. 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 meiosis3. 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.
