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Abstract Detail

Systematics Section/ASPT

Baum, David A. [1], Baum, Buzz [2].

An inside-out origin of the eukaryotic cell.

All existing evolutionary models for the origin of the eukaryotic cell have assumed that the nucleus and endomembrane system arose within the cytoplasm of a prokaryotic cell.  Here we challenge this paradigm by proposing that an ancestral prokaryote, equivalent to the modern day nucleus, constructed an external membranous compartment, homologous to the modern eukaryotic cytoplasm. Our model begins with the extrusion of stable membrane-bound blebs that served to facilitate material exchange with ectosymbiotic proteobacteria that represent progenitors of mitochondria. Blebs were stabilized through the association of nuclear pore proteins within the bleb neck and attached to the outer cell wall by progenitors of LINC complexes. The space between adjacent blebs gave rise to the endoplasmic reticulum (ER), with subsequent bleb fusion events yielding a plasma membrane.  Strikingly, this model explains previously enigmatic aspects of eukaryotic cell biology, including ER continuity, the close association between mitochondria and ER, the site of N-glycosylation in the lumen of nuclear-proximal ER, and the ability of nuclei in syncytia to control their local cytoplasm. Moreover, our model is consistent with recent phylogenetic analyses supporting “eocytes” as sister to Eukarya, and the presence of bacterial lipids in eukaryotes.  Thus, the inside-out model not only provides a new, more-plausible explanation of eukaryotic evolution, but also provides a new predictive framework by which to better understand the dynamic organization of modern eukaryotic cells

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1 - University Of Wisconsin, Department Of Botany, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University College London, Laboratory for Molecular Cell Biology, Gower St., London, WC1E 6BT, UK

Cell Biology.

Presentation Type: Oral Paper:Papers for Sections
Session: 38
Location: Salmon/Snake/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 10:15 AM
Number: 38001
Abstract ID:95
Candidate for Awards:None

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