Institute of General and Experimental Biology, Siberian Branch RAS
670047 Ulan-Ude, ul. Sakhyanovoy, 6
e-mail: ggonch@biol.bscnet.ru
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.
