Mitochondria are a fundamental component of eukaryotic life, representing much more than just 'the power plants of the cell'. Nevertheless, the current knowledge about their biology (e.g. heredity, biogenesis) and function is largely incomplete, and mostly biased toward a few taxonomic groups. Focusing the research on a small and homogeneous subset of organisms entails the risk of losing a big part of the molecular and functional diversity of mitochondria.
Our work is focused on the Doubly Uniparental Inheritance (DUI) of mitochondria, observed, so far, only in several bivalve species. 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 is localized in somatic tissues, while M-mtDNA is localized in both germ line and soma. Conversely, in females M-mtDNA is degraded (or diluted below detection limits), restoring the homoplasmic condition. There is both molecular and phylogenetic evidence that DUI evolved as a modification of maternal inheritance, thus our research aims at expanding the knowledge 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, DUI represents a unique experimental system for studying mitochondrial heteroplasmy, and two processes that shape genome evolution: genomic conflicts and mito-nuclear coevolution. DUI males are naturally heteroplasmic, therefore the biological functions of mitochondria and their interactions with the nucleus are the unaltered result of evolution. All of this makes DUI a novel and extremely useful model to study mitochondrial biology and evolution.