nucleation

THEORY-1203: The host lineage elaborated its cytoskeleton, endomembrane system and nuclear machinery before mitochondrial endosymbiosis began, about 2.2 billion years ago: most pre-LECA duplications in eukaryotic gene families of archaeal origin predate it

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Properties5
StatusProposed
Tagsendosymbiosis, natural-sciences
SourceLIT-1566 — Dated gene duplications elucidate the evolutionary assembly of eukaryotes
ExtendsTHEORY-1099 — On Kay and colleagues' relaxed-clock dating of pre-LECA gene duplications, most duplications in eukaryotic gene families of archaeal origin, including actin, tubulin, vesicle-trafficking and nuclear-targeted families, predate the onset of duplications in genes of alphaproteobacterial origin at about 2.2 billion years ago, which the authors take as the start of mitochondrial endosymbiosis, so the host was elaborating its cytoskeleton, endomembranes and nuclear machinery before the mitochondrion; each date is a maximum age for its paralogues' functions, many intervals reach below 2.2 billion years, and the order of phagocytosis and the mitochondrion is left open
Bears onQUESTION-277 — When formerly autonomous partners come to depend on one another, which of mutual dependence, reproductive cohesion, the distribution of essential functions across genomes, the host's regulatory control and the alignment of selection does each route to dependence bring about, and which of them, alone or together, make the partnership a new evolutionary individual?

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Source

Kay et al. (2026), LIT-1566, read in full in NOTE-1234. The authors conclude that the host elaborated these systems before mitochondrial endosymbiosis, which they align to the onset of duplication in genes of alphaproteobacterial origin.

Where the evidence stands

What the paper shows, and what it does not, is THEORY-1099, Active, which this entry extends: that entry is the reading, this one the thesis. The promote_when above is THEORY-1099’s condition before the twenty-second status review promoted it, carried here unchanged, because it asks what would make the thesis true and not what the paper says.

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