nucleation

LIT-1595: Late acquisition of mitochondria by a host with chimaeric prokaryotic ancestry

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Properties5
StatusActive — read in full 2026-10-27 (NOTE-1240) from the PubMed Central author manuscript (PMC4780264), not the version of record; worth reading as the first proteome-wide test of mitochondrion-early against mitochondrion-late, and for its finding that LECA families sort by origin and cell location (alphaproteobacterial with the mitochondrion, other bacterial with endomembranes, archaeal with the nucleus), with alphaproteobacterial families nearest their prokaryotic relatives (THEORY-1102). Read it knowing that stem length is read as time only under the assumption that rates before and after LECA are proportional; that the alphaproteobacterial difference from other bacteria, on which the chimaeric host turns, is P = 0.044; that stem length also shortens when a closer relative is sampled, as its own Lokiarchaeota control shows; and that it cannot say whether the chimaera came from partners or from gene transfer.
Version2
Tagsendosymbiosis, natural-sciences
Cited as “paper” byNOTE-1240 — Pittis & Gabaldón — Late acquisition of mitochondria by a chimaeric host
Cited as “source” byTHEORY-1102 — On Pittis and Gabaldón's stem-length analysis of the LECA proteome, families of alphaproteobacterial origin and mitochondrial location sit closer to their prokaryotic relatives, after correction for each family's rate, than families of other bacterial origin (P = 0.044), which sit closer than archaeal families, and the authors read this as late acquisition of the mitochondrion by a host whose proteome was already chimaeric, under their stated assumption that rates before and after LECA are correlated, THEORY-1206 — The mitochondrion was acquired late in eukaryogenesis, by a host whose proteome was already chimaeric, with genes from several bacterial sources acquired before it

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Pittis, A. A. & Gabaldón, T. (2016). Late acquisition of mitochondria by a host with chimaeric prokaryotic ancestry. Nature 531(7592): 101–104. doi:10.1038/nature16941.

Key takeaways

From the reading, NOTE-1240.

  • The measure. A family’s stem is the branch from its closest prokaryotic sister to LECA, divided by the family’s median branch length inside eukaryotes. This removes rate only if rates before and after LECA are proportional, which the authors assume.
  • The order. Bacterial families are shorter than archaeal (P = 1.38e-25); alphaproteobacterial families are shortest, and shorter than other bacterial ones at P = 0.044 (THEORY-1102).
  • Origin tracks location. Alphaproteobacterial families go with the mitochondrion and energy production, other bacterial ones with endomembranes, archaeal ones with the nucleus and information processing. Matched comparisons say origin, not function, drives stem length.
  • Controls. Plastid-derived families have shorter stems still, as the later plastid predicts. Adding one Lokiarchaeum genome shortens 30 archaeal stems, which also shows that stem length depends on how close the sampled relative is.
  • What it cannot say. Whether the non-alpha bacterial genes came with partners or by transfer, and anything about when partners became dependent on one another. Its closing claims, that the mitochondrion ended massive transfer and gave “the definitive selective advantage”, are not analysed.

Why this is here

The earlier statement of the mito-late explanation, “cellular complexity preceding mitochondrial acquisition”, which A1 named and did not cite. What it shows is genomic chimaerism before the mitochondrion, not cellular complexity. LIT-1566 continues its mitochondrion-late order by a different method, and departs from it on the bacterial component: it dates most non-alphaproteobacterial duplications after the mitochondrion and argues against serial endosymbiosis. LIT-1561 is said to continue its argument, and Gabaldón is senior author on it; that is unchecked here. Its branch-length method has been disputed. The dispute is not in this paper, but the reading finds where the method is exposed: the assumption of proportional rates, and the dependence of stem length on how close the sampled relative is.

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