An analysis of an alternative approach in the evolution of endosymbiosis

Describe the hypothesized steps for the evolution of eukaryotic cells via endosymbiosis.

Biological Reviews 73, — doi The position of highest probability in each tree is shown with the vertical arrow, and the probability for each plastid placement is indicated with the branch thickness see legend. Principles of protein and lipid targeting in secondary symbiogenesis: Euglenoid, dinoflagellate, and sporozoan plastid origins and the eukaryote family tree. Proceedings of the National Academy of Sciences 9, — doi Molecular Biology and Evolution 22, — doi American Naturalist , S—S doi Additionally, blebs would have pushed against one another to create a continuous network of partially enclosed extracellular chambers, over which the cell could exert significant chemical control. The bootstrap values shown in the gray boxes were calculated after the removal of the highly divergent minicircle sequences in the peridinin dinoflagellates. These new trees tend to group the eukaryotes with the crenarchaeotes, specifically with the TACK superphylum of archaea [ 31 ], while at the same time tending to locate the root of the archaea among the euryarchaeotes, sometimes among the methanogens [ 52 ]. Furthermore, only recently, it has been recognized that the invention of eukaryotic specific traits required more metabolic energy per gene than prokaryotes have at their disposal, and that mitochondria afforded eukaryotic cells an orders of magnitude increase in the amount of energy per gene, which finally explains why the origin of eukaryotes corresponds to the origin of mitochondria [ 2 , 34 ]. Current versions of endosymbiotic theory have it that the host was an archaeon an archaebacterium , not a eukaryote.

Phylogeny of Calvin cycle enzymes supports Plantae monophyly. Current Issues in Molecular Biology 7, 57—80 However, this classification scheme is imperfect because it cannot accommodate models that invoke parasitism but not phagotrophy Vesteg et al.

endosymbiosis and eukaryotic cell evolution

Ultrastructure and ecology of Calycomonas ovalis Wulff,Chrysophyceae and its redescription as a testate Rhizopod, Paulinella ovalis N. The probabilities using the one-sided KH test for placing the peridinin plastid clade in three alternate positions are shown in the smaller gray boxes with the arrows.

Removal of the fucoxanthin clade did not, however, change significantly the bootstrap values in the resulting tree unpublished data.

endosymbiotic theory article

The site-by-site likelihoods for these three pools of trees were calculated using the respective data sets and Codeml implemented in PAML V3. However, the chromalveolate hypothesis and the secondary endosymbiosis involving a red alga is the best-supported hypothesis to date based on numerous empirical studies.

It would also permit secretory vesicles to be subjected to additional processing steps before being released into the environment by fusion with the eukaryotic plasma membrane.

An analysis of an alternative approach in the evolution of endosymbiosis

C Placement of the peridinin plastid clade in the taxon ML tree. Rogers, M. Phylogenomic analysis identifies red algal genes of endosymbiotic origin in the chromalveolates. Four chains were run simultaneously, of which three were heated and one was cold, with the initial , cycles trees discarded as the burn-in. That was all he wrote on the possibility of symbiotic plastid origin. Molcular Phylogenetics and Evolution 45, — doi Given the importance of mitochondria to eukaryotic success, it is critical to establish when during eukaryogenesis they were acquired. Moustafa, A.

Isochrysidales, Prymnesiophyceae; Edvardsen et al.

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The Origin of Plastids