Variations in Hybrid Combinations Lead to Differences in Mitochondrial Inheritance

BackgroundWhile tilapia are the second most farmed group of fish in the world, the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrid is one of the most frequently observed tilapia crosses in China. Based on its conservative nature and maternal inheritance pattern, mitochondrial DNA is often used in kinship analysis. Evidence of paternal inheritance has been noted in some animal species. ResultsThe mitochondrial CoI and Cytb genes, and D-loop gene regions of Oreochromis niloticus and Oreochromis aureus fish were sequenced and aligned to their orthogonal and backcrossed offspring. As evidence of paternal mitochondria DNA inheritance was found, the whole mitochondrial genome was then sequenced. Results showed that in the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrids, certain fish shared 92.88% of the maternal mitochondria genome, and 99.86% with the paternal mitochondria genome. This implied that there was paternal mtDNA inheritance. However, all Oreochromis niloticus (♂) × Oreochromis aureus (♀) hybrids had 100% identical mitochondria genome with their female parent. ConclusionsThe study showed that while paternal mtDNA inheritance occurred in the Oreochromis niloticus (♀) × Oreochromis aureus (♂) hybrid, this did not happen in Oreochromis niloticus (♂) × Oreochromis aureus (♀) offspring. This implies that in hybrid species, different hybridization combinations might provide an explanation for paternal mtDNA inheritance pattern.