Keys to eukaryality: planctomycetes and ancestral evolution of cellular complexity

Abstract

Read online

Planctomycetes are known to display compartmentalization via internal membranes, thus resemblingeukaryotes. Significantly, the planctomycete Gemmata obscuriglobus has not only a nuclear regionsurrounded by a double-membrane, but is also capable of protein uptake via endocytosis. In order toclearly analyse implications for homology of their characters with eukaryotes, a correctunderstanding of planctomycete structure is an essential starting point. Here we outline the majorfeatures of such structure necessary for assessing the case for or against homology with eukaryotecell complexity. We consider an evolutionary model for cell organization involving reductiveevolution of planctomycetes from a complex protoeukaryote-like LUCA ancestor, and evaluatealternative models for origins of the unique planctomycete cell plan. Overall, the structural andmolecular evidence is not consistent with convergent evolution of eukaryote-like features in abacterium and favours a homologous relationship of planctomycetes and eukaryotes

Keywords

• evolution
• compartmentalization
• cell complexity
• LUCA
• eukaryote evolution
• origin of nucleus