[Eukaryotes origin: a new scenario].
A new scenario of eukaryotes origin is proposed that explains the cytoskeleton genesis, and the genesis of cell nucleus as a "cell within cell" structure. The scenario is based on the peculiarities of spore-forming firmicutes life cycle and structure, unique for prokaryotes. It is supposed that a euryarchaeon cell was engulfed by a "bare" sporangium of an ancient polyendosporogenic and endoskeletal clostridia, bearer of microtubular endospore appendages, in the process of "abortive" forespore engulfment. In the result, a new driving force for cell transitions was formed, associated with compartmentalization of prokaryotic chromosomes. Further recombination of chromosomes induced two transitions: transformation of euryarchaeon into true cell nucleus, and transformation of microtubular endospore appendages into nucleus mitotic apparatus. In-cell reproducing organelles, such as mitochondrion and plastids, appeared later. Forthcoming full-genome studies of endoskeletal firmicutes, bearers of microtubular endospore appendages, and some eukaryotes may help to reveal the mystery of the first true nuclear cell origin.
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D000818:Animals; D002467:Cell Nucleus / Q000502:physiology*; D003599:Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D056890:Eukaryota / Q000254:growth & development* / Q000648:ultrastructure; D005057:Eukaryotic Cells / Q000502:physiology* / Q000648:ultrastructure; D019143:Evolution, Molecular; D008954:Models, Biological