A resourceful genome: updating the functional repertoire and evolutionary role of animal mitochondrial DNAs

• Animal mitochondria are involved in many biological processes besides the production of ATP.
• Some animals show non-standard mitochondrial features: unusual protein-coding gene content and/or mtDNA-encoded proteins with extramitochondrial localization and non-oxidative phosphorylation function.
• These unusual mitochondrial features are good candidate factors affecting mitochondrial transmission or other aspects of mitochondrial biology, and they may have an important role in lineage-specific adaptations and speciation processes.

Recent data from mitochondrial genomics and proteomics research demonstrate the existence of several atypical mitochondrial protein-coding genes (other than the standard set of 13) and the involvement of mtDNA-encoded proteins in functions other than energy production in several animal species including humans. These results are of considerable importance for evolutionary and cellular biology because they indicate that animal mtDNAs have a larger functional repertoire than previously believed. This review summarizes recent studies on animal species with a non-standard mitochondrial functional repertoire and discusses how these genetic novelties represent promising candidates for studying the role of the mitochondrial genome in speciation.