The karyomastigont as an evolutionary seme

Abstract

The problem of eukaryogenesis—the evolutionary mechanism whereby eukaryotic cells evolved from prokaryotes—remains one of the great unsolved mysteries of cell biology, possibly due to the reductionist tendency of most scientists to work only within their subdisciplines. Communication between biologists who conduct research on the nucleus and those working on the cytoskeleton or endomembrane system are sometimes wanting, and yet, all of these quintessentially eukaryotic elements of the cell are interdependent, and are physically associated in many protists as the karyomastigont organellar system: nucleus, one or more basal bodies and flagella, nuclear connector, and Golgi apparatus. Here we suggest a more holistic view of the karyomastigont as not simply an organellar system, but an evolutionary seme, the archaic state of the eukaryotic cell. We also present a scheme whereby the karyomastigont may have dissociated, giving rise in more derived cells to one or more free nuclei and discrete flagellar apparati (akaryomastigonts).