Endosymbiosis and Eukaryotic Cell Evolution

Endosymbiosis and Eukaryotic Cell Evolution

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Endosymbiosis and Eukaryotic Cell Evolution

https://doi.org/10.1016/j.cub.2015.07.055

Understanding the evolution of eukaryotic cellular complexity is one of the grand challenges of modern biology.

The precise nature of the host cell that partnered with this endosymbiont is, however, very much an open question.

how — and how often — plastids moved from one eukaryote to another during algal diversification is vigorously debated.

the transformative role DNA sequencing played in solving early problems in eukaryotic cell evolution, and posing key unanswered questions emerging from the age of comparative genomics.

There are two kinds of cellular life forms on Earth — prokaryotes and eukaryotes. How the latter evolved from the former is a mystery that has intrigued biologists for the better part of a century.

the relationships between bacteria, archaea and eukaryotes are not as clear-cut as once thought.

prokaryotic and eukaryotic genomes are evolutionary mosaics; the phylogenetic signals contained within them are complex, so complex that using genomic data to test competing hypotheses of cell evolution is extremely difficult.

Taxonomic issues aside, the eukaryotic grade of cellular organization must surely have arisen from some sort of ‘simpler’ prokaryotic one, and the question of how eukaryotes first evolved is as relevant today as when Stanier and colleagues first underscored the problem more than 50 years ago. And there is one fact upon which everyone agrees: endosymbiosis, the bringing together of distinct cells, one inside the other, has been an important factor in eukaryotic evolution. Precisely how, how often, and why are the outstanding questions of the day.

At present there is no convincing evidence to support the notion that endosymbiosis played a role in the origin of any cytosolic compartments other than mitochondria and plastids. The challenge now is to come up with testable hypotheses for the autogenous origin of such compartments that are compatible with our understanding of cell biology and genome evolution. There is value in looking back at the history of cell evolution research. There is also a lot to be gained from attempting to divorce oneself from the past while looking forward at cell biological problems with modern data. And there is clearly much about the evolution of the eukaryotic cell that still needs to be worked out. In doing so, we should enjoy the view from both perspectives.