For Quite a Few Chromosomes More: The Origin of Eukaryotes… Review Article

The evolution of eukaryotes addresses an enigmatic question: what are the evolutionary advantages of having a nucleus? The nucleus is traditionally thought to act as protection for DNA, but eukaryotes are more fragile than bacteria. The compartmentalization of the eukaryotic cell might stem from invaginations of the plasma membrane, and I argue that this autogenous origin of the nucleus constituted a selective innovation caused by cellular constraints due to a large genome. The protoeukaryotic nucleus appears to be a physical and chemical solution to the problem of large amounts of DNA in the form of many linear chromosomes. The selective advantages of having a nuclear envelope are to house a large genome in a stabilized structure and to decouple gene translation from transcription. Supporting the karyogenic model, this new hypothesis opens an original perspective to help in understanding the very ancient origin of eukaryotes.