Arnau Sebé Pedrós
ICREA research professor at the Centre for Genomic Regulation (CRG) in Barcelona
What they do
The authors address one of the fundamental problems in biology: understanding the origin of the eukaryotic cell. To do this, they use phylogenetic methods applied to current genome data from eukaryotes, prokaryotes, and giant viruses, with the aim of tracing the origin of different genes associated with typically eukaryotic functions and structures, such as the cytoskeleton, chromatin, and the endomembrane system.
Main message
The most important result is that the study reinforces an idea already suggested in a previous article by Toni Gabaldón: that the mitochondria (the energy factory of the eukaryotic cell) was a relatively late addition. This contradicts a more classical view in which the early acquisition of mitochondria would have been the main driver of the evolution of eukaryotic complexity.
Main Novelty
Beyond dating the origin of mitochondria to symbiosis with an alpha-proteobacterium, the study also suggests that horizontal gene transfer from other bacteria (and from giant viruses) was a key factor in explaining the origin of some eukaryotic genes. In this sense, the work proposes a more complex and gradual view of the origin of the eukaryotic cell, in which different microbial interactions would have contributed to forming the gene repertoire of the first eukaryotes. This is perhaps the most novel message of this article.
Consistency with other recent results
Finally, the results are largely in agreement, regarding the late origin of mitochondria, with two other studies recently published in Nature: Kay et al. 2025 and Tobiasson et al. 2026. The main difference is that here the authors suggest a greater importance of horizontal gene transfer from bacteria and giant viruses.
Overall, I think it's an excellent article, which perfectly exemplifies how massive sequencing and comparative analysis of genomes across the tree of life are transforming our ability to gradually reconstruct the great evolutionary transitions of the past.