Uniparental mitochondrial inheritance has been suggested to be important for preventing the propagation of selfish cytoplasmic transposable elements that could affect the nuclear genome ( Cosmides and Tooby, 1981 Hoekstra, 2000). Maternal inheritance is brought about by one of many ways, including subjecting paternal mitochondria to (1) sequestration and exclusion ( Yu and Russell, 1992), (2) selective lysosomal degradation via ubiquitination ( Sutovsky et al., 1999, 2000), or (3) simple dilution due to the large size of the female gamete in comparison to the male gamete ( Birky, 1995 Wilson and Xu, 2012). In several eukaryotes, maternal inheritance is the preferred mode of uniparental inheritance.
During meiosis, in contrast to the nuclear genome, mitochondrial genes follow a non-Mendelian pattern of segregation through tightly controlled mechanisms that typically favor uniparental inheritance, or the passing down of mitochondria predominantly from a single parent to the progeny. In addition to this and other important functions, mitochondria carry their own genetic material in the form of mitochondrial DNA (mtDNA) nucleoids. Mitochondria are cellular organelles responsible for the generation of energy-rich adenosine triphosphate molecules in eukaryotic cells. Taken together, we reveal a distinct mechanism that achieves uniparental inheritance by segregation of parental mitochondria. Further, the presence of dynein on an Mcp5 cluster precluded the attachment of mitochondria to the same cluster. We observed that this tethering of parental mitochondria to the poles results in uniparental inheritance of mitochondria, wherein two of the four spores formed subsequently contained mitochondria from one parent and the other spores contained mitochondria from the other parent. Remarkably, mitochondria, and thereby mitochondrial DNA from the parental cells, did not mix upon zygote formation but remained segregated at the poles by attaching to clusters of the anchor protein Mcp5 via its coiled-coil domain. In the isogamous organism fission yeast, we employed high-resolution fluorescence microscopy to visualize mitochondrial inheritance during meiosis by differentially labeling mitochondria of the two parental cells.
During sexual reproduction in eukaryotes, processes such as active degradation and dilution of paternal mitochondria ensure maternal mitochondrial inheritance.