nucleation

THEORY-1228: A bacterial endosymbiont becomes genetically integrated, an organelle, when host proteins imported into it replace genes it has lost, and this does not require gene transfer from the endosymbiont: in the Paulinella chromatophore and the nitroplast, the two systems with hundreds of imported proteins, the replacing genes are mostly the host's own or come from other bacteria

1 min read

Properties5
StatusProposed
Tagsendosymbiosis, natural-sciences
SourceLIT-1560 — Protein import into bacterial endosymbionts and evolving organelles
ExtendsTHEORY-1100 — On Sørensen and colleagues' review, a bacterial endosymbiont becomes genetically integrated, the authors' mark of an organelle, when nuclear genes whose products are imported into it functionally replace essential genes it has lost, and this does not require gene transfer from the endosymbiont: in the Paulinella chromatophore and the nitroplast, the two systems with hundreds of imported proteins, many of which fill gaps left by lost genes, the imported proteins come mostly from the host's own genes or from other bacteria, and in the nitroplast no gene transfer from the endosymbiont has been found
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

Sørensen, Stiller, Kröninger & Nowack (2025), LIT-1560, read in full in NOTE-1241. The authors conclude: “It is important to note that EGT is not a precondition for the genetic integration of an endosymbiont.”

Where the evidence stands

What the review shows, and what it does not, is THEORY-1100, Active, which this entry extends: that entry is the reading, this one the thesis. The review reports the origin of the imported proteins in summary (“mostly from the host itself”), not counted, and the absence of EGT in the nitroplast is a negative result. The promote_when above is THEORY-1100’s condition before the twenty-third status review promoted it, carried here unchanged, because it asks what would make the thesis true and not what the review says.

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