Oral Presentation Society for Molecular Biology and Evolution Conference 2016

The early origin of the eukaryotic cell according to the Viral Eukaryogenesis hypothesis: an update in light of recent discoveries (#105)

Philip J L Bell 1
  1. Microbiogen, Lane Cove, NSW, Australia

Acknowledged as one of the most difficult challenges in evolutionary biology, the origin of the eukaryotic cell and the related origin of sex remain unresolved.  The Viral Eukaryogenesis hypothesis proposes the eukaryotes and sex arose because the ‘eukaryotic cell’ is a symbiogenic consortium of three separate organisms: an archaeal ancestor of the eukaryotic cytoplasm, a bacterial ancestor of the mitochondrion, and a viral ancestor of the nucleus.  One radical aspect of this theory is the descent of the nucleus from a virus.  When first published 15 years ago, a pox-like virus was chosen as a nuclear ancestor because they possessed large linear chromosomes, they could replicate in their host’s cytoplasm, and they possessed endogenous mRNA capping genes, a classic eukaryotic signature gene.  Since 2001 science has progressed significantly and giant viruses such as the Mimiviruses and other members of the Megavirales (aka NCLDV viruses) have been discovered.  Like the pox virus and the eukaryotic nucleus, a signature gene of this group are the mRNA capping genes.  The discovery of giant viruses has radically altered the view of viruses as simple small ‘filterable’ entities and with other discoveries has strengthened the possibility that viruses play critical roles in evolution including involvement in eukaryotic origins.  Furthermore, several new phyla of the Archaea have been discovered since 2001, including the Lokiarchaeota which form a monophyletic group with the eukaryotes.  In this talk the Viral Eukaryogenesis hypothesis is reviewed in light of these recent discoveries, and it is argued that the profound scientific discoveries over the last 15 years have lent increased plausibility to the Viral Eukaryogenesis hypothesis.