Sex without crossovers mimics clonal reproduction in the holocentric plant Rhynchospora tenuis Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes. While essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy. However, obligate achiasmy in both sexes of a sexual species has not been previously documented. Here, we investigate the beak-sedge Rhynchospora tenuis, a holocentric plant with the lowest known chromosome number among flowering plants (n = 2) and inverted meiosis. Using chromosome-scale genome assemblies from nine accessions, molecular cytogenetics, immunocytochemistry, high-throughput single-gamete sequencing and whole-genome sequencing of controlled crosses, 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 not detected cytologically or genetically, and univalents persist at metaphase I. Extensive haplotype-specific accumulation of transposable elements (TEs) generates segregation distortion (e.g. meiotic drive), favouring the transmission of larger, TE-rich chromosomes. Remarkably, sexual reproduction is retained with fertilisation producing viable seeds only when translocation-compatible gametes meet, indicating strong post-meiotic selection that eliminates incompatible homozygous combinations. As a result, all surviving offspring are genetically identical to the maternal genotype, effectively restoring heterozygosity each generation and mimicking clonal reproduction. We propose that the combined effects of recombination loss, low chromosome number, holocentricity, inverted meiosis, and selective transmission of longer chromosomes enable faithful segregation and clonal-like inheritance despite sexual reproduction. These findings challenge the boundary between sex and clonality, revealing a unique evolutionary strategy linking genome architecture, recombination loss, and transmission bias. ### Competing Interest Statement The authors have declared no competing interest.

3️⃣ Sex without crossovers mimics clonal reproduction in Rhynchospora tenuis

🌱 An extreme meiotic outcome: faithful segregation without crossovers in a holocentric plant.
🔗 doi.org/10.64898/202...

#Preprint #GenomeEvolution #Meiosis4eva #centromere #Pangenomics

CAD-C reveals centromere pairing and near-perfect alignment of sister chromatids Three-dimensional (3D) genome organization plays a central role in gene regulation, chromatin folding, and genome stability. Although chromosome-conformation capture (3C)-derived methods have revoluti...

Hi all!
We developed CAD-C to map chromatin organization at high res in yeast. It revealed an unexpected tight alignment: nucleosomes covering the same sequence tend to be associated across sister chromatids.

www.biorxiv.org/content/10.6...

#3DGenome #chromatin #Cohesin #centromere

New study in @LSAjournal reveals that CENP-A/H4 octasomes form flexible chromatin intermediates that may guide centromere assembly via CCAN. @uio.no @NCMMnews
#chromatin #centromere #CENP-A #cryo-EM #nucleosome #octasome
www.life-science-alliance.org/content/9/3/...

🧪📌 #Centromere #Evolution

Comparative single-cell and spatial profiling of anti-SSA-positive and anti-centromere-positive Sjögren’s disease reveals common and distinct immune activation and fibroblast-mediated inflammation - N... Sjögren’s disease (SjD) can be split into different subtypes and these may have different molecular profiles. Here the authors compare anti-SSA and anti-centromere autoantibody positive SjD and show u...

www.nature.com/articles/s41...
📖”Comparative single-cell and spatial profiling of anti-SSA-positive and anti-centromere-positive Sjögren’s disease reveals common and distinct immune activation and fibroblast-mediated inflammation”
#Sjogren #SSA #centromere

Complete telomere-to-telomere genomes of cowpea reveal insights into centromere evolution in Phaseoleae. #CowpeaGenome #T2T #genomics #Centromere @biorxivpreprint.bsky.social 🧬 🖥️
www.biorxiv.org/content/10.1...

DNA methylation influences human centromere positioning and function. #DNAmethylation #Centromere @natgenet.nature.com
www.nature.com/articles/s41...

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The dogrose (Rosa canina), the wild rose plant species, has a pentaploid genome with 35 chromosomes. #Canina #Caninameiosis #Cell #Celldivision #Centromere #Dogrose #Meiosis #Pentapoidy
www.scientificeuropean.co.uk/sciences/bio...

It’s happening on the 15th!!

#centrosome, #microtubules, #centromere, #mitosis, #cellbiology

@kaustuvsanyal.bsky.social
@viji-draviam.bsky.social
@spindlebehavior.bsky.social

New preprint from Kelsey Fryer in the lab using ChAR-seq to identify RNAs that are bound to human centromeres. Lots of surprises! #centromere #RNA www.biorxiv.org/content/10.1...

Groundbreaking Discovery: Centromeres Move in Onions, Challenging Established Beliefs Researchers at Okayama University have discovered that centromeres in onions can move, challenging long-held beliefs, while garlic shows the largest centromeres known.

Groundbreaking Discovery: Centromeres Move in Onions, Challenging Established Beliefs #Japan #garlic #Okayama #Okayama_University #centromere

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Our work suggests centromere evolution follows a unique mutational path, dominated by small, local events with massive structural consequences.

📄 Read the preprint: doi.org/10.1101/2025...
#genomics #bioRxiv #centromere #Arabidopsis

(1/3) 🌏 Join DongAhn Yoo and others, including EBP all-star @erichjarvis.bsky.social, on a journey through the complete #genome sequencing of ape genomes and how these little-understood #genes hidden in the densely packed #telomere and #centromere regions of #chromosomes can untangle ape #evolution!

#Centromere #Aging

"Centromeric transcription & CENP-A/C is epigenetically downregulated in Aging"

H3K9me3⏫ H3K4me2⏬on centromere/pericentromeric DNA
Rescued by p53 siRNA + KDM1A inhibitor➡️⏫genomic stability & mitotic fidelity of aged fibroblast

#MolCell 2025
www.sciencedirect.com/science/arti...

Chromosome mis-segregation triggers cell cycle arrest through a mechanosensitive nuclear envelope checkpoint - Nature Cell Biology Hervé, Scelfo et al. show that chromosome mis-segregation induces mTORC2- and ATR-mediated p53 activation through a mechanosensitive checkpoint at the nuclear envelope triggered by altered heterochrom...

Showcasing this exciting paper from our good friends Fachinetti lab @institutcurie.bsky.social. #Centromere inactivation triggers #senescence: mis-segregated chromosomes deform the nuclear envelope and activate TORC2-ATR. We helped with #cGAS and some key suggestions.
doi.org/10.1038/s415...

Centromere diversity and its evolutionary impacts on plant karyotypes and plant reproduction You have to enable JavaScript in your browser's settings in order to use the eReader.

Happy to share our Tansley insight published in @newphyt.bsky.social
nph.onlinelibrary.wiley.com/doi/epdf/10....

#plantscience #chromosome #centromere #meiosis

Independence of centromeric and pericentromeric chromatin stability on CCAN components The chromatin of the centromere provides the assembly site for the mitotic kinetochore that couples microtubule attachment and force production to chromosome movement in mitosis. The chromatin of the ...

Our latest collaboration with Ron Biggs and John Marko at Northwestern is in the wild. Surprising centromere resistance to deformation even in the absence of most core centromere proteins. With @elinehendrix.bsky.social, Kousik Sundararajan and Mina Sun. #centromere www.biorxiv.org/content/10.1...

Source: https://academic.oup.com/gigascience/article/doi/10.1093/gigascience/giae096/7921171

The telomere-to-telomere (T2T) genome provides insights into the evolution of specialized centromere sequences in sandalwood. #SandalwoodGenome #ChromosomeLevelAssembly #Centromere @gigascience.bsky.social
academic.oup.com/gigascience/...

Turnover of retroelements and satellite DNA drives centromere reorganization over short evolutionary timescales in Drosophila Centromeres reside in rapidly evolving, repeat-rich genomic regions, despite their essential function in chromosome segregation. This study of centromere evolution over short evolutionary timescales i...

Spectacular turnover of centromere sequences in drosophilids. New #PLOSBiology paper from @cecilecourret.bsky.social &co, showing dramatic #centromere reorganization over short evolutionary timescales, churning of retroelements & satellites, etc... plos.io/3CBwHQe

Insight into #centromere formation, suggesting crucial roles for #gypsy #retrotransposons moving into #satelliteDNA -dominated neocentromeres

Looking forward to have a more detailed look 🔍🧬

Repeat-based holocentromeres influence genome architecture and karyotype evolution While most eukaryotes contain single regional centromeres, several plant and animal lineages assemble holocentromeres along the entire chromosome length. The assembly of chromosome-scale holocentric g...

🧵𝐀 𝐭𝐡𝐫𝐞𝐚𝐝 𝐰𝐢𝐭𝐡 𝐟𝐞𝐚𝐭𝐮𝐫𝐞𝐝 𝐥𝐚𝐛 𝐩𝐮𝐛𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬: 🧵

#1️⃣
Hofstatter, Thangavel, Lux et al. 2022 𝘊𝘦𝘭𝘭: 𝗥𝗲𝗽𝗲𝗮𝘁-𝗯𝗮𝘀𝗲𝗱 𝗵𝗼𝗹𝗼𝗰𝗲𝗻𝘁𝗿𝗼𝗺𝗲𝗿𝗲𝘀 𝗶𝗻𝗳𝗹𝘂𝗲𝗻𝗰𝗲 𝗴𝗲𝗻𝗼𝗺𝗲 𝗮𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 𝗮𝗻𝗱 𝗸𝗮𝗿𝘆𝗼𝘁𝘆𝗽𝗲 𝗲𝘃𝗼𝗹𝘂𝘁𝗶𝗼𝗻
www.cell.com/cell/fulltex...
@gokilavani.bsky.social
#PlantSciences #Chromosome #Genomics #Meiosis4eva #Centromere

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