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A huge shoutout to @jvhooff.bsky.social who poured her soul into this paper, and our co-authors @eelcotromer.bsky.social and Max Raas!

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If you’re into chromosome biology, genome organization, or evolutionary cell biology, give it a read and share your thoughts! 🔗 doi.org/10.1016/j.celrep.2025.115855 #EvoCellBio #Genomics #SMC #LECA #Chromatin

doi.org

Redirecting

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Going deeper, duplications of SMC genes happened before eukaryotes: they trace back to the TACK + Asgard archaeal ancestor. This hints at sophisticated chromosome management in the archaeal lineage that gave rise to eukaryotes. #eukaryogenesis #archaea

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Surprise: condensin II was lost independently >30 times across eukaryote evolution—making it one of the most frequently discarded cellular machineries we know. This highlights major shifts in genome organization throughout eukaryotic history.

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SMC complexes (condensin I/II, cohesin, SMC5/6) are the molecular machines that fold chromosomes. By scanning >1 000 genomes we show LECA already housed all four—pointing to a remarkably sophisticated ancestral eukaryote.

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Laura Eme @lauraeme.bsky.social · 19/06/2025

Excited to share our new paper in @cellreports.bsky.social that reshapes our understanding of chromosome organization's deep evolutionary roots! Our work dives into the origins of the machinery that structures our very genomes. 🔗: doi.org/10.1016/j.ce... #Genomics #Evolution #CellBiology #LECA

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Because it’s done on a computer, some think it doesn’t require expertise and that anyone can do it through button pushing. Just because there are arguments doesn’t mean all arguments have equal value. And in fact, over time, many things in phylogenetics have settled even when they started hot.

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Why it matters 🎯 Helps to place DPANN firmly in the archaeal tree, tidying up a long-standing evolutionary puzzle 💡 Highlights cross-domain gene transfer as a key driver in archaeal innovation 🌱 Opens doors to explore how free‑living ancestors gave rise to symbiotic lifestyles

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4/ We uncovered ancient horizontal gene transfer events from symbiotic bacteria—namely Patescibacteria and Omnitrophota—that likely empowered DPANN’s shift to their unique episymbiotic lifestyles

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3/ Altiarchaeota emerge as the earliest‑diverging branch in DPANN, suggesting an origin from free‑living ancestors

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2/ Key finding: DPANN forms a monophyletic clade within Euryarchaeota, resolving a long-standing debate on their evolutionary placement

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Laura Eme @lauraeme.bsky.social · 25/05/2025

1/ We used 126 conserved proteins across 11 known DPANN phyla, with careful taxon sampling and sophisticated phylogenomic analysis

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Every night should be duck night Chez Gladines ! 😋

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Reposted by Laura Eme

Daniel Tamarit @danieltamarit.bsky.social · 14/05/2025

New vacancy in my team! PhD student position on microbial genome evolution, focusing on the evolutionary principles underlying bacterial genome architecture. Please repost and share with talented MSc students in #evobio, bioinformatics or related :) www.uu.nl/en/organisat... #MEvoSky #MicroSky

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Laura Eme @lauraeme.bsky.social · 12/05/2025

Fair enough, my initial post was hastily worded. And yes, when at least one reviewer defeats the point of peer-review by saying teh authors shouldn’t do more work and the debate should happen in public, that’s not helping anyone.

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Reposted by Laura Eme

Journal of Eukaryotic Microbiology @jeukmicro.bsky.social · 08/05/2025

Check out exciting protist research in JEM! Holly Moeller et al. explore the feeding habits of Mesodinium rubrum and provide a tool for studying its cell biology and photophysiology in their open access paper in our March/April issue! doi.org/10.1111/jeu.... #protistsonsky

The marine ciliate Mesodinium rubrum (bottom right) is famed for its ability to steal chloroplasts and nuclei from red cryptophyte algae in the Teleaulax/Gemingera clade. But even these prey specialists can make "mistakes," ingesting blue-green Hemiselmis pacifica (upper left) and transiently retaining their plastids. Here, a M. rubrum cell points its feeding tentacles (labeled with an anti-centrin antibody, yellow) at an H. pacifica cell. The cryptophyte's flagella and ciliate's cilia (labeled with an anti-tubulin antibody, purple) and nuclei (labeled with DAPI, blue) are visible in this expansion micrograph taken with a Nikon spinning disk confocal microscope. Numerous stolen prey nuclei are visible inside of the M. rubrum cell. See Moeller et al. https://doi.org/10.1111/jeu.13066

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Laura Eme @lauraeme.bsky.social · 09/05/2025

(Unlike you, the authors here do imply that the phylogenetic conclusions were driven by this contamination)

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Laura Eme @lauraeme.bsky.social · 09/05/2025

To be clear, I’m not “defending” these MAGs, and take your point regarding Fig 2c.d I don’t think figure 2a b is proving anything though (see above post). Curious to hear your take on 2a and b if any?

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Reposted by Laura Eme

Laura Eme @lauraeme.bsky.social · 08/05/2025

We must have been super lucky that contamination was all from different lineages to each Njord MAG and yet all from the same clade of unknown Asgard so that Njord form monophyletic groups within Asgards in individual gene trees.

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Laura Eme @lauraeme.bsky.social · 08/05/2025

The clade *is* hard to place. Their fig. 2 shows does not prove contamination. Automatic taxonomic assignments of contigs for long-branching, compositionally biased sequences is going to show this pattern regardless of contamination (in fact, this is why they can't place at all many of the contigs)

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Laura Eme @lauraeme.bsky.social · 08/05/2025

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Andrew Roger @andrewjroger.bsky.social · 14/03/2025

I'm pleased to introduce our new paper rooting the eukaryote Tree of Life (eToL) that resulted from a collaboration led by PhD student Kelsey Williamson and a large group of collaborators doi.org/10.1038/s415...htt

doi.org

A robustly rooted tree of eukaryotes reveals their excavate ancestry - Nature

The root of the eukaryote Tree of Life is estimated from a new, larger dataset of mitochondrial proteins including all known eukaryotic supergroups, showing it lies between two multi-supergroup assemb...

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And there's one called Cantina 😉 Cause Scientists Are Hilarious.

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While I was heavily involved in an early version of this project, the bulk of the work presented here was designed and carried out by the Dalhousie group, and most particularly by brilliant Ph.D. student Kelsey Williamson and @andrewjroger.bsky.social!

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🌍 These findings provide a new framework for studying the origins of key eukaryotic traits: phagocytosis, motility, and mitochondrial function. This also refines our models of eukaryogenesis and the ancestral state of complex life. (7/)

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🤔 Why does this matter? If LECA had an excavate-like morphology—complete with a ventral feeding groove—then our understanding of early eukaryotic evolution must account for widespread secondary losses of this structure in modern lineages. (6/)

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🔎 We tested alternative rooting hypotheses (e.g., roots at Archaeplastida, Discoba, Metamonada) and found that none were as strongly supported as the Opimoda+/Diphoda+ root. The results hold across multiple models, even after controlling for biases. (5/)

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