Site-and-branch-heterogeneous analyses of an expanded dataset favour mitochondria as sister to known Alphaproteobacteria.
Level 5 - mechanism / opinion, no new human data
Computational phylogenomic modeling (non-clinical basic science)
PubMed 35027725 · doi:10.1038/s41559-021-01638-2
What was done
The authors developed a protein evolution model (MAM60 + GFmix) designed to account for both across-site and across-branch compositional heterogeneity. They applied this model to an expanded dataset consisting of 108 mitochondrial proteins of alphaproteobacterial origin, combined with novel metagenome-assembled genomes recovered from microbial mats, microbialites, and environmental sediments. They compared this approach against conventional site-heterogeneous models applied to compositionally homogenized datasets and examined the distribution of the crista-developing Mic60 protein.
What was found
The abstract reports no specific numerical test statistics, likelihood scores, or confidence values. The MAM60 + GFmix model demonstrated a better fit to the phylogenetic data than standard alternatives and aligned with results from compositionally homogenized datasets. The resulting phylogenies place mitochondria as sister to Alphaproteobacteria (excluding MarineProteo1 and Magnetococcia). Additionally, the presence of ancestral mitofilin-domain-containing Mic60 was identified exclusively in mitochondria and Alphaproteobacteria.
Why it matters
Resolving the position of mitochondria in the tree of life is fundamental to understanding eukaryogenesis and the origin of cellular respiration. This work suggests that longstanding debates may stem from compositional artifacts and positions mitochondria as a sister clade to known Alphaproteobacteria rather than a deeply nested lineage within them.
Limits
The abstract provides no exact quantitative metrics, bootstrap support percentages, or posterior probabilities for the tree topologies. Findings rely heavily on computational models of sequence evolution, which remain vulnerable to deep-time phylogenetic artifacts, missing lineage sampling, and assumptions regarding ancient horizontal gene transfer.
Cited by
- supports Mitochondria are derived from bacteria.