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ReconstructingMitochondrial Evolution??
What is your definition of amitochondrion??
Morphological DiversityMitochondria as we all know them:
Plasma cellPlasma cell
SuprarenalglandSuprarenalgland
Adrenal cortexAdrenal cortex
Liver cellLiver cell
Mitochondrial Diversity???
Giardia - mitosomeEntamoeba - mitosome
100 nm
50 nm
microsporidian - mitosome
Neocallimastix T. foetusChicken
Reconstructing Evolution
Mitochondrial evolution well established endosymbiotic theory α-proteobacterium - Rickettsia prowazekii
Hydrogenosomal evolution No DNA NOW 2 examples Nyctotherus and Blastocystis (MLO) Several proteins similar to mitochondria
Mitosome evolution No DNA Few proteins identified similar to mitochondria
Origins via Endosymbiosis
facultativeorganism?
Aerobic α-proteobacterium prokaryotegave rise to present day mitochondria.
Are hydrogenosomes and mitosomes ofanaerobic protists derived from the sameproto-mitochondrion?
Evidence for: accumulating evidence forseveral proteins that are currently found inmitochondria -Proteins of Fe-S cluster formation.
Scenario ACommon ancestor
Scenario Bdegenerate mitochondrioninvoke lateral gene transfer fromanaerobic prokaryotes
Current dogma - mitochondria and related organelles arose just once in evolution
Hypotheses for Mito Acquisition
Mitochondrion-related Organelles
2 way to interpret this summary - can you think of both?
Groups with mitochondrial homologues
Hjort et al Phil. Trans. R. Soc. B 2010 365, 713-727
Conversion of MitochondriaHYD
Common ancestor with mitochondria
Independent Origin
HYD
HYD?
a)
b)
2.
1.
α-proteobacterium
? - anaerobic bacterium
Origin of Hydrogenosomes (Mitosomes?)
Organelles - origins and biogenesis
Approaches:
(1) Conduct phylogenetic analyses of similar proteinsHsp70 FdHsp60 Isc subunits
(2) Examine protein targeting to the organellematrix protein targetingmembrane protein targeting
(3) Characterize membrane/translocation componentsThese components could have evolved as the
endosymbiont was converted to organelle. Reveals evolutionary history.
Comparison of Biogenesis
Hsp90Hsp70
Nuclear encoded preproteinssynthesized on cytosolicribosomes.
Kept in a translocation competentform by cytosolic chaperones
Related TOM and TIMcomponents.
Similar energetic requirements Matrix chaperones and
processing protein. Similar targeting complex to the
inner membrane.
Review mitochondrial targeting if thisis unfamiliar.
Translocase of the outer membrane - TOMTranslocase of the inner membrane - TIMMitochondrial processing peptidase - MPP
Protein sorting and targeting signals
Co-translational targeting ofsecretory proteins via the RER