Evolution of Translation in Mitochondria

Mitochondria arose from bacterial endosymbionts. One of the consequences of the endosymbiosis event was that the ancestral bacterial genome underwent deep transformations, including massive gene transfer to the host nucleus and gene losses and rearrangements. Upon eukaryotic origin, the gene content, size and shape of mitochondrial genomes evolved differently throughout eukaryote’s radiation into many lineages. As a consequence of this phenomenon, the mechanisms for gene expression in mitochondria have also co-evolved and diverged from the ancestral bacterial systems. Mitochondria possess the complete machinery to translate reduced sets of messenger RNAs transcribed in these organelles. Although this machinery retained many features from bacteria, it has also undergone modifications across eukaryote lineages, rendering this process highly specialized and regulated. In this chapter, we summarize and discuss the general characteristics of the mitochondrial translation machinery. We also discuss the current knowledge on mitochondrial translation across different eukaryotic phyla and compare it with its bacterial counterpart to throw light on the evolution of translation in mitochondria.