Switching a conflicted bacterial DTD-tRNA code is essential for the emergence of mitochondria

Mitochondria emerged through an endosymbiotic event involving a proteobacterium and an archaeal host. However, the process of optimization of cellular processes required for the successful evolution and survival of mitochondria, which integrates components from two evolutionarily distinct ancestors as well as novel eukaryotic elements, is not well understood. We identify two key switches in the translational machinery-one in the discriminator recognition code of a chiral proofreader DTD [D-aminoacyl-transfer RNA (tRNA) deacylase] and the other in mitochondrial tRNA(Gly)-that enable the compatibility between disparate elements essential for survival. Notably, the mito-tRNA(Gly) discriminator element is the only one to switch from pyrimidine to purine during the bacteria-to-mitochondria transition. We capture this code transition in the Jakobida, an early diverging eukaryotic clade bearing the most bacterial-like mito-genome, wherein both discriminator elements are present. This study underscores the need to explore the fundamental integration strategies critical for mitochondrial and eukaryotic evolution.

Automated summary

Mitochondria, formed through an endosymbiotic event, integrated components from two distinct ancestors and novel eukaryotic elements for successful evolution and survival. This study identified two key switches in the translational machinery that enable the compatibility and survival of disparate elements. Additionally, the study revealed a unique code transition in the mito-tRNA(Gly) discriminator element during the bacteria-to-mitochondria transition.