Challenging Eukaryogenesis: The Story of the Eukaryotic Ancestor

Abstract

As the question of the origins of eukaryotes comes closer to an answer, the interactions between the archaeal ancestor to eukaryotes and environmental, molecular, bacterial, other influences and symbionts have become increasingly relevant. Various studies have pointed towards the Lokiarchaeota as a close archaeal relative to the eukarya. A study by Imachi et al., published in early 2020, was able to decipher the proteome and genome of the Loki and reported an entirely new model for eukaryogenesis due to its findings, thus shifting research of eukaryogenesis away from models focusing on endocytosis and the rapid acquisition of the alphaproteobacteria that would become the mitochondria. Imachi and colleagues proposed that ancestors of the Loki lived symbiotically with other prokaryotes due to its shape, and facilitated molecular transfer between the symbionts as well as the membrane manipulation necessary to allow such transfer, before acquiring a proto-mitochondria over time. This paper will lay out the history of endosymbiosis and the prevailing theory of endocytosis between archaea and alphaproteobacteria, and consolidates the knowns and unknowns up to before the publication of Imachi et al. The findings of their novel study will be discussed, and the knowns and unknowns with respect to these new findings are re-consolidated. The two models of eukaryogenesis are compared and, in moving forward with Imachi and colleagues model, probable areas of research to further validate this approach are discussed, as well as potential usage of research tools of other fields to answer the persistent unknowns of how eukaryotes came to be.