The Doubly Uniparental Inheritance: a model system for studying evolutionary and functional genomics of mitochondria.

Mitochondria are a fundamental component of the eukaryotic cell, nonetheless, available data on their heredity and biogenesis are largely incomplete. Our research is focused on the Doubly Uniparental Inheritance (DUI) of mitochondria. DUI organisms have two mitochondrial lineages, one transmitted through eggs (F-type), the other through sperm (M-type), whose mtDNAs show up to 50% of amino acid divergence. In DUI species, after amphimixis, the embryo is heteroplasmic for its mtDNA, a status that is eventually maintained only in males, where F-mtDNA localizes in the somatic tissues, while M-mtDNA localizes in both germ line and soma. Conversely, in females M-mtDNA disappears, restoring the homoplasmic condition. There is both molecular and phylogenetic evidence that DUI evolved as a modification of the mechanism of maternal inheritance, typical of all Metazoa. Our work aims at expanding the knowledge we have about DUI to make it a model system for mitochondrial biology. Thanks to its unusual features, DUI can shed light on mitochondrial inheritance and biogenesis and on the relationship between mitochondria and germ line components. Moreover, the DUI male represents an unique experimental system for studying mitochondrial heteroplasmy: the heteroplasmic condition of DUI males is natural, therefore the biological functions and interactions between nucleus and mitochondria are the unaltered result of evolution. Among those interactions, of particular interest is the relationship between two processes that shape genome evolution: genomic conflicts and coevolution between nuclear and mitochondrial genes. There is no biological system more suitable than DUI to study that.