Molecular evolution of archaeal, bacterial and organelle genomes.
EMBO Workshop-95.
6-9 OCT 1995. Aronsborg, Balsta, Sweden. Invited presentation.
MITOCHONDRIAL GENOMES AS A UNIQUE WINDOW ON THE EVOLUTIONARY
HISTORY OF THE LOWER EUKARYOTES.
G. Burger*, R.R. Cedergren, B. Golding, M.W. Gray*, B.F. Lang*, C.
Lemieux, T.G. Littlejohn, D. Sankoff, and M. Turmel.
(Presented by *.)
Organelle Genome
Megasequencing Program, Canadian Institute for Advanced Research,
Departement de Biochimie, Universite de Montreal, Montreal, Quebec,
H3C 3J7, Canada.
Relatively little is known about the mitochondrial (mt) DNAs of
protists and lower fungi, although this group contains most of the
phylogenetic diversity of extant eukaryotes. We have initiated a
systematic exploration of mtDNAs from protists and lower fungi in order
to reconstruct the evolutionary history of the mt genome. Organisms for
which we have complete or nearly complete mtDNA sequences include
Prototheca wickerhamii (green alga), Pedinomonas minor (green alga),
Porphyra purpurea (red alga), Rhodomonas salina (cryptomonad alga),
Ochromonas danica (chrysophyte alga), Cafeteria roenbergensis
(bicosoecid zooflagellate), Phytophthora infestans (oomycete
pseudofungus), Acanthamoeba castellanii (rhizopod amoeba), Monosiga
sp. (choanoflagellate), Allomyces macrogynus and Spizellomyces punctatus
(chytridiomycete fungi), Rhizopus stolonifer (zygomycete), Schizophyllum
commune (basidiomycete), Reclinomonas americana and Malawimonas
jakobiformis (jakobid flagellates) and Tetrahymena pyriformis (ciliate
protozoon). Phylogenetic analyses based on multiple protein sequences
provide trees that are in agreement with those produced from nuclear
sequence data but, additionally, establish the topologies of deep branches
that until now had been unresolved with nuclear data. We have found that
(i) oomycetes are most closely related to golden-brown algae
(Ochromonas danica) and their non-photosynthetic relatives, the
stramenopiles (e.g. Cafeteria sp.); (ii) red algae share a common ancestor
with green algae/plants, to the exclusion of cryptomonads; (iii)
chytridiomycetes are an ancient and paraphyletic fungal group, with
Spizellomyces as a basally-diverged genus and Allomyces more derived
and closely related to the zygomycete Rhizopus; and (iv) fungi, animals
and choanoflagellates diverged at about the same time from a common
ancestor to form three independent lineages. Our analysis supports the
hypothesis that mitochondria had a monophyletic origin. [supported by
MRC Canada, FCAR and CGAT].
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