Endosymbiotic Origins and Differential Losses of Genes in Eukaryotes

Nature have just published a full article concerning an analysis of horizontal (or lateral) gene transfer and how it is different between prokaryotes and eukaryotes [1].  Also, we examined whether eukaryotes experience significant continuous gene gains from prokaryotes over long periods of time, or whether we see evidence for discrete bursts of gene acquisitions.

Hint: We see evidence for the latter.

In the analysis, we looked at almost 1,000,000 genes, their distribution across all of life and their origins.

We find evidence for three major contributions to eukaryotes from prokaryotes - alpha-proteobacteria, cyanobacteria and some kind of archaebacterium.

We also see other linkages between eukaryotes and other prokaryotic groups, but none that are at a level high enough to constitute a significant gene flow.  We hypothesis that these linkages are explained by horizontal gene transfer that occurred pre- and post-symbiotic origin of mitochondria.

With Davide Pisani, we said most of this 9 years ago: see here

What is different here though is that we could carry out a significant within-eukaryotes analysis (we didn't have the genomes a decade ago, nor the computing power, to be honest) and we see that eukaryotes are quite different to prokaryotes in terms of how they generate new functions.  They engage in far, far less horizontal gene transfer with one another.  We are not saying NONE.  We are saying far, far less. We know a lot about HGT in fungi, for example - see here.

What we are saying is that this process has been less important in eukaryotes than prokaryotes.  Probably something that many biologists would have thought was the case - well, we now provide the data.

The next question is - why didn't eukaryotes want to continue doing something (HGT) their progenitors liked to do a lot?


John Archibald has written a News and Views article about this: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature15205.html


1. Ku, C. et al. Endosymbiotic origin and differential loss of eukaryotic genes. Nature (2015). doi:10.1038/nature14963

James McInerney
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