Abstract
BackgroundCattle are bred for, amongst other factors, specific traits, including parasite resistance and adaptation to climate. However, the influence and inheritance of mitochondrial DNA (mtDNA) are not usually considered in breeding programmes. In this study, we analysed the mtDNA profiles of cattle from Victoria (VIC), southern Australia, which is a temperate climate, and the Northern Territory (NT), the northern part of Australia, which has a tropical climate, to determine if the mtDNA profiles of these cattle are indicative of breed and phenotype, and whether these profiles are appropriate for their environments.ResultsA phylogenetic tree of the full mtDNA sequences of different breeds of cattle, which were obtained from the NCBI database, showed that the mtDNA profiles of cattle do not always reflect their phenotype as some cattle with Bos taurus phenotypes had Bos indicus mtDNA, whilst some cattle with Bos indicus phenotypes had Bos taurus mtDNA. Using D-loop sequencing, we were able to contrast the phenotypes and mtDNA profiles from different species of cattle from the 2 distinct cattle breeding regions of Australia. We found that 67 of the 121 cattle with Bos indicus phenotypes from NT (55.4%) had Bos taurus mtDNA. In VIC, 92 of the 225 cattle with Bos taurus phenotypes (40.9%) possessed Bos indicus mtDNA. When focusing on oocytes from cattle with the Bos taurus phenotype in VIC, their respective oocytes with Bos indicus mtDNA had significantly lower levels of mtDNA copy number compared with oocytes possessing Bos taurus mtDNA (P < 0.01). However, embryos derived from oocytes with Bos indicus mtDNA had the same ability to develop to the blastocyst stage and the levels of mtDNA copy number in their blastocysts were similar to blastocysts derived from oocytes harbouring Bos taurus mtDNA. Nevertheless, oocytes originating from the Bos indicus phenotype exhibited lower developmental potential due to low mtDNA copy number when compared with oocytes from cattle with a Bos taurus phenotype.ConclusionsThe phenotype of cattle is not always related to their mtDNA profiles. MtDNA profiles should be considered for breeding programmes as they also influence phenotypic traits and reproductive capacity in terms of oocyte quality.
Highlights
Cattle are bred for, amongst other factors, specific traits, including parasite resistance and adaptation to climate
We have investigated the mitochondrial DNA (mtDNA) genetic profiles of cattle that are located in Victoria (VIC), southern Australia and cattle from the Northern Territory (NT) to determine whether the cattle have the genetics associated with the chromosomal and mitochondrial genomes from their relevant phenotypes
Relationship between breeds of cattle To determine how representative mtDNA haplotypes were of different breeds of cattle, CLC Genomics Workbench version 9.5.1 (CLC Bio, Aarhus, Denmark) was used to align and construct a phylogenetic tree from 56 full mitochondrial genome sequences obtained from the NCBI database
Summary
Cattle are bred for, amongst other factors, specific traits, including parasite resistance and adaptation to climate. Mitochondria play important roles in energy production via the electron transport chain, cell death signalling, and the control of stress responses (reviewed by [1]) Mitochondria have their own genome, mitochondrial DNA (mtDNA) which is maternally inherited [2]. Mitochondrial haplotypes have been shown to predispose individuals to and protect them against a number of diseases and phenotypic traits. They are associated with tolerance to heat [12], longevity [13], fertility and litter size [14], time to pregnancy, and milk and meat quality [15]
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