291: Dated gene duplications show Asgard archaeal host complexity before mitochondrial endosymbiosis

Kay CJ et al., Nature, doi:10.1038/s41586-025-09808-z - Relaxed-clock dating of pre-LECA gene duplications in Asgard archaeal and alphaproteobacterial lineages shows a complex archaeal host with cytoskeleton, endomembrane system and nucleus before mitochondrial acquisition around 2.2 Ga. Key terms: eukaryogenesis, Asgard archaea, mitochondrial endosymbiosis, gene duplication, molecular clock.

Study Highlights:
The study interrogates eukaryogenesis using a time-resolved species tree and a sequential Bayesian relaxed molecular clock applied to 135 gene family trees. Analyses with MCMCTree dated divergence nodes (nFECA 3.05–2.79 Ga, mFECA 2.37–2.13 Ga, LECA 1.80–1.67 Ga) and pre-LECA duplication events of archaeal and bacterial origin. Most archaeal-derived duplications (about 85% of those sampled) were fixed prior to inferred mitochondrial endosymbiosis, with archaeal duplications for actin, tubulin, vesicle trafficking and spliceosomal components dated between ~3.0 and ~2.25 Ga. Functionally, these timings indicate the host lineage had an elaborated cytoskeleton, endomembrane trafficking and nuclear compartmentalization before mitochondrial integration, while alphaproteobacterial duplications cluster near ~2.2 Ga consistent with mitochondrial establishment.

Conclusion:
Gene-duplication dating supports a complexified archaeal host with cytoskeleton, endomembrane system and nucleus preceding mitochondrial endosymbiosis, favoring a late-mitochondrion model of eukaryogenesis.

Music:
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Article title:
Dated gene duplications elucidate the evolutionary assembly of eukaryotes

First author:
Kay CJ

Journal:
Nature, doi:10.1038/s41586-025-09808-z

DOI:
10.1038/s41586-025-09808-z

Reference:
Kay CJ, Spang A, Szöllősi GJ, Pisani D, Williams TA & Donoghue PCJ. Dated gene duplications elucidate the evolutionary assembly of eukaryotes. Nature 650, 129–140 (2026). https://doi.org/10.1038/s41586-025-09808-z

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) - https://creativecommons.org/licenses/by/4.0/

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QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-02-15.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections that describe the eukaryogenesis timeline, gene duplication events, and the CALM model, including specific date ranges and functional system developments (cytoskeleton, endomembrane system, nucleus, mitochondrion).
- transcript topics: Eukaryogenesis timeline and debate (mitochondria early vs late); Relaxed molecular clock and cross-bracing dating approach; Pre-LECA duplications in archaeal origin (cytoskeleton, nucleus, trafficking); Endomembrane system and vesicle trafficking gene duplications; Nuclear components and RNA polymerase duplications; Mitochondrial endosymbiosis timing and alphaproteobacterial duplications

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- Pre-LECA host features (cytoskeleton, endomembrane system, nucleus) existed before mitochondrial endosymbiosis
- nFECA divergence 3.05–2.79 Ga
- mFECA divergence 2.37–2.13 Ga
- LECA divergence 1.80–1.67 Ga
- Alphaproteobacterial duplications associated with mitochondrial endosymbiosis (~2.2 Ga)
- 85% of pre-LECA archaeal-origin duplicates fixed before mitochondrial endosymbiosis

QC result: Pass.