Proto-mitochondrion

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The proto-mitochondrion is the hypothetical ancestral bacterial endosymbiont from which all mitochondria in eukaryotes are thought to descend, after an episode of symbiogenesis which created the aerobic eukaryotes.

Contents

Phylogeny

The phylogenetic analyses of the few genes that are still encoded in the genomes of modern mitochondria suggest an alphaproteobacterial origin for this endosymbiont, in an ancient episode of symbiogenesis early in the history of the eukaryotes.

Pseudomonadota

ProtomitochondrionMartijn et al 2018

Alphaproteobacteria
Caulobacteridae

Rhodospirillales,Sphingomonadales, Rhodobacteraceae, Hyphomicrobiales, Holosporales, etc

Iodidimonadales
Iodidimonadaceae

Iodidimonas

Protomitochondrion Geiger et al 2023

Magnetococcales, Mariprofundales

Three hypothesized placements of protomitochondrion on the Pseudomonadota tree of life

Although the order Rickettsiales has been proposed as the alphaproteobacterial sister-group of mitochondria, [1] [2] [3] no definitive evidence pinpoints the alphaproteobacterial group from which the proto-mitochondrion emerged, and some contradictory evidence, especially in the early, sparse genome samplings. Martijn et al found mitochondria are a possible sister-group to all other alphaproteobacteria. [4] The phylogenetic tree of the Rickettsidae has been inferred by Ferla et al. from the comparison of 16S + 23S ribosomal RNA sequences. [5] Geiger et alii (2023) propose placing the recently discovered (2016) genus Iodidimonas – found in a sister clade to Rickettsidae: the Caulobacteridae [5] – as the closest free-living relative of mitochondria, as it possesses more metabolic products matching that of mitochondria today, such as cardiolipins and sphingolipids, and important genetic markers such as the COX operon and the bc1 complex (Complex IV and Complex III in mitochondria, respectively). [6]

Metabolism

Gabaldón & Huynen (2003) reconstructed the proteome (the entire set of proteins expressed by a genome) and corresponding metabolism of the proto-mitochondrion by comparing extant alpha-proteobacterial and eukaryotic genomes. They concluded that this organism was an aerobic alpha-proteobacterium respiring lipids, glycerol and other compounds provided by the host. At least 630  gene families derived from this organism can still be found in the 9 eukaryotic genomes analyzed in the study. [7]

See also

References

  1. ↑ Viale, A M; Arakaki, A K (21 March 1994). "The chaperone connection to the origins of the eukaryotic organelles". FEBS Letters. 341 (2–3): 146–151. Bibcode:1994FEBSL.341..146V. doi:10.1016/0014-5793(94)80446-x. PMID   7907991.
  2. ↑ Emelyanov, Victor V (Jul 13, 2001). "Evolutionary relationship of Rickettsiae and mitochondria". FEBS Letters. 501 (1): 11–18. Bibcode:2001FEBSL.501...11E. doi:10.1016/S0014-5793(01)02618-7. PMID   11457448.
  3. ↑ Fitzpatrick, David A. (2006). "Genome phylogenies indicate a meaningful α-proteobacterial phylogeny and support a grouping of the mitochondria with the Rickettsiales". Molecular Biology and Evolution. 23 (1): 74–85. doi:10.1093/molbev/msj009. PMID   16151187.
  4. ↑ Martijn, Joran; Vosseberg, Julian; Guy, Lionel; Offre, Pierre; Ettema, Thijs J. G. (2018). "Deep mitochondrial origin outside the sampled alphaproteobacteria". Nature. 557 (7703): 101–105. Bibcode:2018Natur.557..101M. doi: 10.1038/s41586-018-0059-5 . ISSN   0028-0836. PMID   29695865. S2CID   13740626.
  5. 1 2 Ferla, Matteo P.; Thrash, J. Cameron; Giovannoni, Stephen J.; Patrick, Wayne M. (2013). "New rRNA gene-based phylogenies of the Alphaproteobacteria provide perspective on major groups, mitochondrial ancestry and phylogenetic instability". PLOS ONE. 8 (12) e83383. Bibcode:2013PLoSO...883383F. doi: 10.1371/journal.pone.0083383 . PMC   3859672 . PMID   24349502.
  6. ↑ Geiger, Otto; Sanchez-Flores, Alejandro; Padilla-Gomez, Jonathan; degli Esposti, Mauro (2023). "Multiple approaches of cellular metabolism define the bacterial ancestry of mitochondria". Science Advances. 9 (32) eadh0066. Bibcode:2023SciA....9H..66G. doi:10.1126/sciadv.adh0066. PMC   10411912 . PMID   37556552.
  7. ↑ Gabaldón, Toni; Huynen, Martijn A. (2003). "The proto-mitochondrial metabolism". Science. 301 (5633): 690. doi:10.1126/science.1085463. PMID   12893934. S2CID   28868747.
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