Mitochondrial Genome Evolution

Abstract

Mitochondria are membrane‐enclosed organelles present in most eukaryotic cells that generate most of the cell's adenosine triphosphate (ATP) supply. Derived from a proteobacterial ancestor, mitochondria harbour their own, drastically reduced genome. Starting from a prokaryote‐like ancestral state encoding a complete ribosomal ribonucleic acid (rRNA) operon, a complete set of transfer RNAs (tRNAs) required for translation, and key enzymes of the respiratory chain as well as some ribosomal proteins, the mitogenome has been dramatically restructured and further reduced in many of the eukaryotic lineages. The loss and transfer to the nucleus of mitochondrial genes is a common trend in most phyla, in particular in Metazoa and Alveolata. In extreme, phylogenetically dispersed cases, often associated with parasitic or anaerobic life styles, mitochondria have been transformed to the so‐called mitosomes or hydrogenosomes devoid of their own genetic material. Ancestrally a single circular deoxyribonucleic acid (DNA) , mitogenomes have evolved to complex, fragmented architectures in particular in Euglenozoa. Key Concepts: Mitochondria have an endosymbiotic origin deriving from a proteobacterial ancestor. Various evolutionary mechanisms operate on mitochondrial genomes. Mitochondrial genomes have developed very diverse properties during eukaryote evolution. Mitogenomic gene content declines in most eukaryotic lineages by horizontal transfer to the nuclear genome. Complex idiosyncratic genome organisations have independently evolved in several eukaryotic phyla.

Mitochondrial genome evolution in the Saccharomyces sensu stricto complex

“…In contrast to the higher variability of intergenic and intron regions in MT genomes than in nuclear genomes, coding regions are more conserved in MT genomes than in nuclear genomes of the SSS group, which indicates that the mitochondrial genes underwent stronger purifying selection [ 34 , 35 ]. It is likely that the retained genes in the MT genomes are indispensable for cell respiration [ 36 ] and the high AT content of MT genomes (approximately 80%) restricted mutations of mitochondrial genes [ 37 , 38 ]. Moreover, we speculated that the origin of the aerobic fermentation lifestyle in the SSS group could also be associated with the opposite evolutionary process for coding regions and non-coding regions between MT genomes and nuclear genomes.…”

Chemical synthesis of left arm of Chlamydomonas reinhardtii mitochondrial genome and in vivo functional analysis

“…Considering the unique characteristics of mitochondria, including double-wrapped membranes, unique internal structure, numerous copies, and ultra-small size (0.5–1 μm), challenges are obvious for this specific organelle’s transformation ( Bernt et al, 2013 ; Wu et al, 2020 ). It must be considered that for a long time, mitochondrial transformation was almost impossible, especially in higher plant cells ( Li et al, 2021 ).…”