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An unusual type of mitochondrial DNA inheritance in the blue mussel Mytilus
E Zouros1, A Oberhauser Ball, C Saavedra
1Department of Biology, Dalhousie University, Halifax, NS Canada.
Abstract:
In animals, mitochondrial DNA (mtDNA) inheritance is predominantly maternal. In a few cases incidental transmission of paternal mtDNA was observed and estimated to account for only 10(-4)-10(-3) of an individual's mtDNA content. In contrast, biparental inheritance is common in mussels of the genus Mytilus. Here we present direct evidence that sex and mtDNA inheritance are coupled in Mytilus. Females inherit mtDNA only from their mother, but they transmit it to both daughters and sons. Males inherit mtDNA from both parents, but they transmit to sons only the mtDNA they inherited from their father. In pair matings, this mtDNA inheritance pattern is associated with a strong sex-ratio bias. These findings establish a newly discovered type of cytoplasmic DNA transmission. We also present evidence that the phenomenon breaks down in interspecific hybrids.
Insights
Mussels exhibit unique mitochondrial DNA (mtDNA) inheritance, where sex influences transmission. This pattern, unlike typical maternal inheritance in animals, leads to biased sex ratios in offspring.
Area of Science:
- * Genetics
- * Evolutionary Biology
- * Marine Biology
Background:
- * Mitochondrial DNA (mtDNA) is typically maternally inherited in animals, with rare paternal leakage.
- * Biparental mtDNA inheritance is observed in mussels of the genus Mytilus.
- * The mechanisms and implications of paternal mtDNA transmission in Mytilus are not fully understood.
Purpose of the Study:
- * To investigate the direct evidence of sex- and mtDNA inheritance coupling in Mytilus.
- * To elucidate the transmission patterns of mtDNA from parents to offspring in relation to sex.
- * To determine the impact of this unique inheritance on offspring sex ratios and its breakdown in hybrids.
Main Methods:
- * Direct observation and genetic analysis of mtDNA transmission in Mytilus pair matings.
- * Tracking of paternal and maternal mtDNA contributions to both male and female offspring.
- * Comparative analysis of mtDNA inheritance in Mytilus interspecific hybrids.
Main Results:
- * Females transmit mtDNA maternally to both sexes, but only inherit it from their mother.
- * Males inherit mtDNA biparentally but transmit only paternal mtDNA to sons.
- * This coupled inheritance results in significant sex-ratio bias, and the phenomenon is disrupted in interspecific hybrids.
Conclusions:
- * A novel form of cytoplasmic DNA transmission, coupled with sex, has been discovered in Mytilus.
- * This mechanism provides a new understanding of mitochondrial inheritance and its evolutionary implications.
- * The breakdown of this pattern in hybrids suggests specific genetic or molecular incompatibilities.